Massive Type IV,
Thanks for your input. I truely do value your opinion. I actually called you last night to get a quote on that very long block... I assume then you give thumbs up to the proposed config for a daily driver.
While I do have some of those parts, I am doing a new bottom end due to an accident. I stopped a very large car with my engine (rear ended...). I have run a 1776 for 2 years with low compression and semi-hemi'ed heads and have not been totally satisfied. It was tough to tune and ran a little warmer than I cared for after 30 minutes on the freeway.
There has been so much talk here from Jake and John and many others about NOT running such low compression and NOT running semi-hemi heads that I want to play with that idea some more.
I love all the input! Thanks to all!
2110 Compression Ratio Suggestions
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James2
- Posts: 3148
- Joined: Fri Mar 16, 2001 12:01 am
2110 Compression Ratio Suggestions
all I can say is I'm running more then what Berg says and my motor still runs.
True, we have 93 octane gas on the east coast.
True, we have 93 octane gas on the east coast.
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JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
2110 Compression Ratio Suggestions
for every Semi Hemi proponent you find, I can find 3 guys that have had problems with it, unsolvable or VERY difficult to iron out.
There are guys that swear by it, and some that swear at it.
Pick ONE guy you trust, follow his advice, and if it doesn't do what he/she says, bust his balls for it.
The worst thing you can do is follow little pieces of advice for 28 different people, that's a sure recipe for a problem.
John
Aircooled.Net inc.
There are guys that swear by it, and some that swear at it.
Pick ONE guy you trust, follow his advice, and if it doesn't do what he/she says, bust his balls for it.
The worst thing you can do is follow little pieces of advice for 28 different people, that's a sure recipe for a problem.
John
Aircooled.Net inc.
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Well,
Here we are again, tossing the Compression ratio BS stories yet again....
All I can say is that anyone who preaches about static compression ratios being the RULES for every engine combo, is stuck in the 1960s.....
When you build engines everyday, like we do, and see the low CR, semi hemi engines run rich and are so unresponsive to jet changes,it gets really old really fast...There is nothing worse than an engine than runs like a sick dog, puffing black smoke and contaminating the oil with fuel in less than 100 miles of driving.
I do NOT believe in super low CR , or the fact that it alone will keep an engine alive longer... LOW CR AND SEMI HEMI have caused me nothing but problems, consistantly.
John C and I as well as few others caught a huge amount of flack when we took a stand against low CR and semi hemi in a VW Trends article a few months back. I could care less, Getting in trouble, while telling my personal experiences is always a ton of fun.
We set our lowest static CR @ 7.7:1, and all the way to 9.5:1 for street engines. The fact is that a properly configured engine can be @ 8.5:1 static, and dynamically can be below 8:1....Run on pump gas too.
Between myself and Brent, about 100 engines/year go through our doors, of those we receive about 2 back for warranty repairs, per year. If higher static CR was that bad, I would be out of business by now..
Our customers never complain about low power, or hotter temps, they drive their cars all the time with no problems..
We build engines (Type I&IV) for 35,000.00 streetable race cars,(not a VW body) consistantly. Most of the drivers of these cars have a 911 attitude, and are not mechanical types, their cars must be right. I feel confident in placing an engine in those cars with over 8.5:1 they last, and their drivers love their zero-60 times below 4 seconds, while lighting up the tires through 3 gears, in their 1200 pound, mid engined rocket.
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
Here we are again, tossing the Compression ratio BS stories yet again....
All I can say is that anyone who preaches about static compression ratios being the RULES for every engine combo, is stuck in the 1960s.....
When you build engines everyday, like we do, and see the low CR, semi hemi engines run rich and are so unresponsive to jet changes,it gets really old really fast...There is nothing worse than an engine than runs like a sick dog, puffing black smoke and contaminating the oil with fuel in less than 100 miles of driving.
I do NOT believe in super low CR , or the fact that it alone will keep an engine alive longer... LOW CR AND SEMI HEMI have caused me nothing but problems, consistantly.
John C and I as well as few others caught a huge amount of flack when we took a stand against low CR and semi hemi in a VW Trends article a few months back. I could care less, Getting in trouble, while telling my personal experiences is always a ton of fun.
We set our lowest static CR @ 7.7:1, and all the way to 9.5:1 for street engines. The fact is that a properly configured engine can be @ 8.5:1 static, and dynamically can be below 8:1....Run on pump gas too.
Between myself and Brent, about 100 engines/year go through our doors, of those we receive about 2 back for warranty repairs, per year. If higher static CR was that bad, I would be out of business by now..
Our customers never complain about low power, or hotter temps, they drive their cars all the time with no problems..
We build engines (Type I&IV) for 35,000.00 streetable race cars,(not a VW body) consistantly. Most of the drivers of these cars have a 911 attitude, and are not mechanical types, their cars must be right. I feel confident in placing an engine in those cars with over 8.5:1 they last, and their drivers love their zero-60 times below 4 seconds, while lighting up the tires through 3 gears, in their 1200 pound, mid engined rocket.
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
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Matt Harris
- Posts: 204
- Joined: Tue Jan 23, 2001 12:01 am
2110 Compression Ratio Suggestions
Good god man, please don't semi-hemi anything!!! It sounds to me like you've already seen the ugly head of the semi-hemi and low c/r in you're own personal engine already so why continue the misery? Semi hemi is THE worst thing you can do to your heads (in context). There is just no benefit at all in doing. It's just a cheap way to lower the c/r with allot of adverse effects. I think that a blanket statement that one MUST run such and such a c/r without consideration of cam timing is absurd. Just talk to people that build engines for a living like Jake Raby, Art Thraen, Dan Lawson, Roger Crawford, among others, they have REAL EXPERIENCE with the semi hemi and absurdly low c/r. Also keep in mind that I don't know of anyone who is currently testing the semi hemi with big cams, big engines, and low c/r with todays fuel at the moment, but there are sure allot of people that base their livelyhoods on engine building and if their customers aren't happy they have no income; yet you don't see them setting c/r at 7:1 or below and semi hemiing heads do you?
I would agree that that cam is too small for your engine. Go with a 109 or Engle 125 or similar. You might think those cams are big for a driver, I don't think they are, and you shouldn't sell yourself short on performance with that size of an engine.
Here's some practical experience with super low compression and my thoughts. I have a 6.6:1 2007cc engine with a 294 degree cam (e-120), 40x37.5 heads, semi hemi cut etc. And from the outset the oil ran a consistent 231 running at 65 mph on a 85 degree day on the 91 freeway in so cal. So I plugged some holes in the tinware and still got 223-225 on a 85 degree day running at 65mph in so cal. Stock geared tranny, stock 165 tires, etc with a stock doghouse cooler and all tinware painted black by me. Needless to say I was pissed about dropping $6500 and going conservative on the c/r and sacrificing power just get an overheating pig! So I had to put an external cooler on it just so I could drive for extended periods and keep things at bay.
And I got the same engine temps whether I was running 37 or 40 degrees of timing so not running enough timing is not an issue. And I didn't assemble it wrong either as Jim Brown had the same exact combo as me to the "T" and had the EXACT same problems with overheating tuning problems. And he is a "tinkerer" and did his best with what he had.
And just to elaborate on the hard to tun issue. I bought an O2 senor and spent over $100 (remember that John) in jets and it still didn't run right. It took Art Thraen, a professional carb tuner/rebuilder, to tune my car while staying at my house on business. Ended up with 135 main, 180 air, 60 idle, 132 idle air corrector, 34 vents and it runs OK.
I also had the heads off after only 5 months of running and you should have seen the massive buildup of carbon in the chamber!! Again, another sign of inefficient running, no vacuum at low rpm! And yes the mixture was right as jetted with a $5000 O2 sensor that reads actual numbers not just lights.
So next time the heads are off, I'm going to 8:1 or 8.2:1 c/r period. I got burned running low low low compression and will never be burned again. I have talked to many professional engine builders and they said they noticed that engines with loose deck, big chambers, and low c/r overheat and are hard to tune. I figure that my engine can't run much hotter with 8:1 c/r and at least I'll get some decent power out of it and have it be more predictable.
Anyways, I just thought you would like to here some personal experience from someone with ultra low c/r and the hemi cut.
So what's the moral? No semi hemi, and set c/r based on cam timing and the rest of the engine as a whole.
BTW I drive my car 45 miles per day from Lakewood to the USC health sciences campus not far from you, to go to Medical School, and if I didn't have my external oil cooler I wouldn't be able to do it. Even still after the drive home in the afternoon, the engine still runs for a second after I turn the key off (not good). This I attribute to the hot running heads and excess carbon buildup (from the semi hemi and low c/r no less). It should shut off right away like when I drive shorter distances. I sure hope you don't semi hemi you're heads and set the c/r at least at 7.8 with the cam you have and more if you go bigger on it. Jake and John both have good recommendations on c/r suggestions. You could also call Art Thraen in SLC at 801-943-1234 to get his take. He runs 8.2:1 (2007cc engine) in his personal street car with a 270/262 @ .050" cam that he drove on the Berg cruise this year from SLC to Denver colorado and his oil ran 10 degrees COOLER than mine the whole time even though I have 6.6:1!!! Real world experience doesn't lie.
------------------
Matt Harris
78 x 90.5
2007cc
1971 Super
I would agree that that cam is too small for your engine. Go with a 109 or Engle 125 or similar. You might think those cams are big for a driver, I don't think they are, and you shouldn't sell yourself short on performance with that size of an engine.
Here's some practical experience with super low compression and my thoughts. I have a 6.6:1 2007cc engine with a 294 degree cam (e-120), 40x37.5 heads, semi hemi cut etc. And from the outset the oil ran a consistent 231 running at 65 mph on a 85 degree day on the 91 freeway in so cal. So I plugged some holes in the tinware and still got 223-225 on a 85 degree day running at 65mph in so cal. Stock geared tranny, stock 165 tires, etc with a stock doghouse cooler and all tinware painted black by me. Needless to say I was pissed about dropping $6500 and going conservative on the c/r and sacrificing power just get an overheating pig! So I had to put an external cooler on it just so I could drive for extended periods and keep things at bay.
And I got the same engine temps whether I was running 37 or 40 degrees of timing so not running enough timing is not an issue. And I didn't assemble it wrong either as Jim Brown had the same exact combo as me to the "T" and had the EXACT same problems with overheating tuning problems. And he is a "tinkerer" and did his best with what he had.
And just to elaborate on the hard to tun issue. I bought an O2 senor and spent over $100 (remember that John) in jets and it still didn't run right. It took Art Thraen, a professional carb tuner/rebuilder, to tune my car while staying at my house on business. Ended up with 135 main, 180 air, 60 idle, 132 idle air corrector, 34 vents and it runs OK.
I also had the heads off after only 5 months of running and you should have seen the massive buildup of carbon in the chamber!! Again, another sign of inefficient running, no vacuum at low rpm! And yes the mixture was right as jetted with a $5000 O2 sensor that reads actual numbers not just lights.
So next time the heads are off, I'm going to 8:1 or 8.2:1 c/r period. I got burned running low low low compression and will never be burned again. I have talked to many professional engine builders and they said they noticed that engines with loose deck, big chambers, and low c/r overheat and are hard to tune. I figure that my engine can't run much hotter with 8:1 c/r and at least I'll get some decent power out of it and have it be more predictable.
Anyways, I just thought you would like to here some personal experience from someone with ultra low c/r and the hemi cut.
So what's the moral? No semi hemi, and set c/r based on cam timing and the rest of the engine as a whole.
BTW I drive my car 45 miles per day from Lakewood to the USC health sciences campus not far from you, to go to Medical School, and if I didn't have my external oil cooler I wouldn't be able to do it. Even still after the drive home in the afternoon, the engine still runs for a second after I turn the key off (not good). This I attribute to the hot running heads and excess carbon buildup (from the semi hemi and low c/r no less). It should shut off right away like when I drive shorter distances. I sure hope you don't semi hemi you're heads and set the c/r at least at 7.8 with the cam you have and more if you go bigger on it. Jake and John both have good recommendations on c/r suggestions. You could also call Art Thraen in SLC at 801-943-1234 to get his take. He runs 8.2:1 (2007cc engine) in his personal street car with a 270/262 @ .050" cam that he drove on the Berg cruise this year from SLC to Denver colorado and his oil ran 10 degrees COOLER than mine the whole time even though I have 6.6:1!!! Real world experience doesn't lie.
------------------
Matt Harris
78 x 90.5
2007cc
1971 Super
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
aaron, you can't rely on seat-of-the-pants opinions that we spout off with over the internet about c.r... you have to be logical.
first off, you can't use dynamic c.r. calculations for octane requirements; they vary tremendously with the slightest change in cam timing, which, in part, means that they are not accurate, because it's nearly impossible to calculate... what you have to use for calculating octane requirements is mostly head design and cylinder pressure.
the best way to do that is to model your engine on what the vw factory did originally... i.e., if you are gonna use a stock head chamber on your motor, set your cylinder pressure around what was designed by the factory... i believe that figure was about 127(?) psi.
numerous engine math tests that i have run recently prove that cam design has a somewhat minor effect at the most on cylinder pressure; on a performance engine, that is more than offset by the increased efficiency of the intake/exhaust, so the end result is an increase in cylinder pressure at higher rpm levels, where the cam comes on.
in other words, radical cams do NOT lower the octane requirements of an engine... sorry if that's a little o.t. for your original question
then take into account that we no longer have the same metals-based octane enhancers that were used in the early '70's... running factory 7.3:1 c.r. on the 87 octane crap we have in california isn't the same thing.
people will tell you that in the late '70's vw claimed that the new way of rating octane meant that the old 91 ron is the same as the 87 octane of today... that may have been somewhat true in the late '70's, but not today.
gasoline formulations have changed radically in just the last 6-10 years; right now i know for a fact that there are at least 15 different formulations in use in america today... some people claim it's more like 40 different types of gas.
another part of the problem today is that the octane rating system we use averages the results of two different testing procedures... but if you drive your engine more like one testing procedure than the other, then the octane figure at the pump may be too low for your driving habits... that can spell disaster for an air-cooled engine, because our head temps are so much hotter than the water-cooled engines in use today... and hotter heads raise the octane requirement drastically.
with regards to semi-hemi heads, there is no one in this or any other internet forum that i know of that has any really significant experience with 'em... try calling steve hollingsworth, i believe he has built 1,000 semi-head motors, he has a shop in phoenix right now.
the other thing to remember about semi-hemi heads is that the entirely redesigned 1999(?) small-block chrysler motors use 'em, so they are not the crap that some people blindly claim... if you look back thru some of these threads, you'll see the link i posted regarding that, pictures and all... and i believe it was kawasaki that also recently used semi-hemi heads on some of their race-winning carbed motorcycles, at c.r.'s of nearly 12:1.
lastly, go find the internet gasoline faq... it lists some octane vs. c.r. requirements for carbed water-cooled engines, so you have something to base your static c.r. off of.
dan
oceanstreetvideo.com
first off, you can't use dynamic c.r. calculations for octane requirements; they vary tremendously with the slightest change in cam timing, which, in part, means that they are not accurate, because it's nearly impossible to calculate... what you have to use for calculating octane requirements is mostly head design and cylinder pressure.
the best way to do that is to model your engine on what the vw factory did originally... i.e., if you are gonna use a stock head chamber on your motor, set your cylinder pressure around what was designed by the factory... i believe that figure was about 127(?) psi.
numerous engine math tests that i have run recently prove that cam design has a somewhat minor effect at the most on cylinder pressure; on a performance engine, that is more than offset by the increased efficiency of the intake/exhaust, so the end result is an increase in cylinder pressure at higher rpm levels, where the cam comes on.
in other words, radical cams do NOT lower the octane requirements of an engine... sorry if that's a little o.t. for your original question
then take into account that we no longer have the same metals-based octane enhancers that were used in the early '70's... running factory 7.3:1 c.r. on the 87 octane crap we have in california isn't the same thing.
people will tell you that in the late '70's vw claimed that the new way of rating octane meant that the old 91 ron is the same as the 87 octane of today... that may have been somewhat true in the late '70's, but not today.
gasoline formulations have changed radically in just the last 6-10 years; right now i know for a fact that there are at least 15 different formulations in use in america today... some people claim it's more like 40 different types of gas.
another part of the problem today is that the octane rating system we use averages the results of two different testing procedures... but if you drive your engine more like one testing procedure than the other, then the octane figure at the pump may be too low for your driving habits... that can spell disaster for an air-cooled engine, because our head temps are so much hotter than the water-cooled engines in use today... and hotter heads raise the octane requirement drastically.
with regards to semi-hemi heads, there is no one in this or any other internet forum that i know of that has any really significant experience with 'em... try calling steve hollingsworth, i believe he has built 1,000 semi-head motors, he has a shop in phoenix right now.
the other thing to remember about semi-hemi heads is that the entirely redesigned 1999(?) small-block chrysler motors use 'em, so they are not the crap that some people blindly claim... if you look back thru some of these threads, you'll see the link i posted regarding that, pictures and all... and i believe it was kawasaki that also recently used semi-hemi heads on some of their race-winning carbed motorcycles, at c.r.'s of nearly 12:1.
lastly, go find the internet gasoline faq... it lists some octane vs. c.r. requirements for carbed water-cooled engines, so you have something to base your static c.r. off of.
dan
oceanstreetvideo.com
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Matt, Thank you for the confession..
I want to add that my new DYNO is one week from being set up, I have a 2017 crying to be tested with 8.5:1 cr and conventional chambers, I plan on rippping the heads off and replacing them with a set of over- springed ppigs that have 66cc semi hemi chambers, and exacting ports and valve sizes, I will drop the CR to 4 levels and try it from there.....My data acquisition program can be attached to posts, so the BS will stop when the flow charts are seen.
I do not pplan on doing further type I testing, as they have been worn out and there are too many gods already in place, my dyno is for our type IV testing..Our type I combinations are street proven and have all been dynoed previously, they are sweet and will not change.
------------------
Jake Raby
Raby's Aircooled Technology www.aircooledtechnology.com
[This message has been edited by MASSIVE TYPE IV (edited 10-21-2001).]
I want to add that my new DYNO is one week from being set up, I have a 2017 crying to be tested with 8.5:1 cr and conventional chambers, I plan on rippping the heads off and replacing them with a set of over- springed ppigs that have 66cc semi hemi chambers, and exacting ports and valve sizes, I will drop the CR to 4 levels and try it from there.....My data acquisition program can be attached to posts, so the BS will stop when the flow charts are seen.
I do not pplan on doing further type I testing, as they have been worn out and there are too many gods already in place, my dyno is for our type IV testing..Our type I combinations are street proven and have all been dynoed previously, they are sweet and will not change.
------------------
Jake Raby
Raby's Aircooled Technology www.aircooledtechnology.com
[This message has been edited by MASSIVE TYPE IV (edited 10-21-2001).]
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Matt Harris
- Posts: 204
- Joined: Tue Jan 23, 2001 12:01 am
2110 Compression Ratio Suggestions
Please let us know when you get done testing those combos!! You will have real world data that none of us have access to that will settle things once and for all. Maybe you could give us some oil temp numbers too?
------------------
Matt Harris
78 x 90.5
2007cc
1971 Super
------------------
Matt Harris
78 x 90.5
2007cc
1971 Super
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
The one main thing I want to see is exhaust tempperatures and their changes with CR..It seems that most low CR engines are still combusting in the exhaust, since there is so little fire to burn the mixture in the chamber, so the exhaust is hot as HELL.
I hooked up my Pyrometer, dual cylinder head temp gauges, oil temp gauges and pressure all this morning, I should have the first engine bolted up in 2 weeks, as I still need to finish some ducting for the carb inlet air, with a sensor installed for accurate readings, and separated from the ambient air of the DYNO cell. We have went to extremes with the installation of this unit.
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
I hooked up my Pyrometer, dual cylinder head temp gauges, oil temp gauges and pressure all this morning, I should have the first engine bolted up in 2 weeks, as I still need to finish some ducting for the carb inlet air, with a sensor installed for accurate readings, and separated from the ambient air of the DYNO cell. We have went to extremes with the installation of this unit.
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
-
danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
it's pretty funny to read how we all try to out-smart the vw factory... even semi-hemi acvw heads are an attempt to improve on an older factory vw head design.
the engineering team at chrysler uses semi-hemi heads with 9:1(?) c.r... but they also have water-cooling, fuel injection, and most importantly, knock sensors controlling the timing, to protect the engine.
so i have to laugh when i read how someone wants to run one of our acvw pig motors on the same c.r. that new cars use... then control the audible knock with fine manual adjustments to the timing... what about the inaudible knock?? duh...
you only have to look at the history of factory c.r. settings to see what your limits are... it's ranged from something like 5.8:1 to 7.3:1, to the 6.6:1 that mexico used for their dual-port motors... that was where gene berg got his low c.r. recommendations in the '80's... kids, he didn't pull those numbers out of a hat.
these days the fuel-injected mex motors run 7.7:1; and guess how they do it? with big-chambered heads! yup, the vw factory is putting more of the combustion cycle in the head... just like with the semi-hemi head.
>>>Semi-hemi just doesn't make sense. The last thing you want is more surface area exposed to the flame front.<<<
maybe one of you "experts" on high c.r. knows enuf about acvw motor building to tell us how many c.c.'s are in the latest dual-port mex heads... and how the c.c. amounts compare to semi-hemi heads, as well as the old stock dual-port heads.
dan
oceanstreetvideo.com
the engineering team at chrysler uses semi-hemi heads with 9:1(?) c.r... but they also have water-cooling, fuel injection, and most importantly, knock sensors controlling the timing, to protect the engine.
so i have to laugh when i read how someone wants to run one of our acvw pig motors on the same c.r. that new cars use... then control the audible knock with fine manual adjustments to the timing... what about the inaudible knock?? duh...
you only have to look at the history of factory c.r. settings to see what your limits are... it's ranged from something like 5.8:1 to 7.3:1, to the 6.6:1 that mexico used for their dual-port motors... that was where gene berg got his low c.r. recommendations in the '80's... kids, he didn't pull those numbers out of a hat.
these days the fuel-injected mex motors run 7.7:1; and guess how they do it? with big-chambered heads! yup, the vw factory is putting more of the combustion cycle in the head... just like with the semi-hemi head.
>>>Semi-hemi just doesn't make sense. The last thing you want is more surface area exposed to the flame front.<<<
maybe one of you "experts" on high c.r. knows enuf about acvw motor building to tell us how many c.c.'s are in the latest dual-port mex heads... and how the c.c. amounts compare to semi-hemi heads, as well as the old stock dual-port heads.
dan
oceanstreetvideo.com
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Dan,
Big chambers, and semi hemi are 2 different things. I use bigger chambers, but just large enough that I can run .050-.060 deck, with no shims, on most stroker engines.
The cc's on those new mexican heads are hard to give a specific answer for, since their quality control keeps them between 54-58cc, which still is not alot. Most of the heads we run have 63 cc, with a conventional chamber.
VW used alot of 7.7:1 CR engines, mostly in type III vehicles, they were stronger than anything else...
Pulling things out of a hat takes alot of skill, and very gullible people listening to it to accomplish...Timing(not ignition timing) is everything.
BTW:
Old school 040 castings have 48- 51cc, according to their exact application, and smog preparedness.
Newer standard 040 units have 50-54cc depending on when they were made
Mex mex heads have the numbers mentioned above, all very inconsistant, even in the same head, from one chamber to another.
Semi Hemi have up to 70+cc, and are dished completely above the spark plug to do so.
My normal heads have from 52-63cc, but not in a hemi style arrangement...
[This message has been edited by MASSIVE TYPE IV (edited 10-21-2001).]
Big chambers, and semi hemi are 2 different things. I use bigger chambers, but just large enough that I can run .050-.060 deck, with no shims, on most stroker engines.
The cc's on those new mexican heads are hard to give a specific answer for, since their quality control keeps them between 54-58cc, which still is not alot. Most of the heads we run have 63 cc, with a conventional chamber.
VW used alot of 7.7:1 CR engines, mostly in type III vehicles, they were stronger than anything else...
Pulling things out of a hat takes alot of skill, and very gullible people listening to it to accomplish...Timing(not ignition timing) is everything.
BTW:
Old school 040 castings have 48- 51cc, according to their exact application, and smog preparedness.
Newer standard 040 units have 50-54cc depending on when they were made
Mex mex heads have the numbers mentioned above, all very inconsistant, even in the same head, from one chamber to another.
Semi Hemi have up to 70+cc, and are dished completely above the spark plug to do so.
My normal heads have from 52-63cc, but not in a hemi style arrangement...
[This message has been edited by MASSIVE TYPE IV (edited 10-21-2001).]
-
danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
>>>The last thing you want is more surface area exposed to the flame front.<<<
>>>Big chambers, and semi hemi are 2 different things.<<<
i agree, jake... steve, when the head cc's are the same, so is the surface area; in other words, it's the chamber design that is the concern.
the semi-hemi head design has been used in chevy 396/375 h.p. engines, ford 427, buick aluminum block v-8's, chrysler 318 and 340 motors, porsche 356 engines, etc... i have enclosed some pics for your perusal.
once you have educated yourself about how predominant semi-hemi head design really is, you begin to understand how fully stupid it is to think that it doesn't work on the acvw.
in the defense of semi-hemi ignorance, i'll agree that the main thing that is different about some of the newer semi-hemi designs is a small squish area adjacent to the chamber... if you semi-hemi out too much of an acvw head, you'll really lessen that squish area next to the top of the jug.
>>>The cc's on those new mexican heads are hard to give a specific answer for, since their quality control keeps them between 54-58cc, which still is not alot. Most of the heads we run have 63 cc, with a conventional chamber.<<<
all of the new design mex heads i'm referring to have cc'd out to within 58-60 cc's, period... i don't know where you are getting those numbers, but nothing would surprise me regarding the quality of mexican parts.
i have never seen an unmodified factory type 1 head with 63 cc's in it.
>>>Old school 040 castings have 48- 51cc, according to their exact application, and smog preparedness.
Newer standard 040 units have 50-54cc depending on when they were made<<<
nice job jake; here is the factory i.d. breakdown as i've seen it:
original "flat" dual-port head: 48-50 cc's.
newer smog "stepped" dual-port head: 50-52 cc's, with about a .060" step cut.
and then there is the new mex heads with their 58-60 cc's... depending on the application, that kind of combustion chamber size would seem to make semi-hemi cutting obsolete... i think the reason you still see the bergs doing it is because they are working off of an old stash of original heads... and there may be something to say for that, when it comes to the actual quality of the old german castings.
dan
oceanstreetvideo.com
>>>Big chambers, and semi hemi are 2 different things.<<<
i agree, jake... steve, when the head cc's are the same, so is the surface area; in other words, it's the chamber design that is the concern.
the semi-hemi head design has been used in chevy 396/375 h.p. engines, ford 427, buick aluminum block v-8's, chrysler 318 and 340 motors, porsche 356 engines, etc... i have enclosed some pics for your perusal.
once you have educated yourself about how predominant semi-hemi head design really is, you begin to understand how fully stupid it is to think that it doesn't work on the acvw.
in the defense of semi-hemi ignorance, i'll agree that the main thing that is different about some of the newer semi-hemi designs is a small squish area adjacent to the chamber... if you semi-hemi out too much of an acvw head, you'll really lessen that squish area next to the top of the jug.
>>>The cc's on those new mexican heads are hard to give a specific answer for, since their quality control keeps them between 54-58cc, which still is not alot. Most of the heads we run have 63 cc, with a conventional chamber.<<<
all of the new design mex heads i'm referring to have cc'd out to within 58-60 cc's, period... i don't know where you are getting those numbers, but nothing would surprise me regarding the quality of mexican parts.
i have never seen an unmodified factory type 1 head with 63 cc's in it.
>>>Old school 040 castings have 48- 51cc, according to their exact application, and smog preparedness.
Newer standard 040 units have 50-54cc depending on when they were made<<<
nice job jake; here is the factory i.d. breakdown as i've seen it:
original "flat" dual-port head: 48-50 cc's.
newer smog "stepped" dual-port head: 50-52 cc's, with about a .060" step cut.
and then there is the new mex heads with their 58-60 cc's... depending on the application, that kind of combustion chamber size would seem to make semi-hemi cutting obsolete... i think the reason you still see the bergs doing it is because they are working off of an old stash of original heads... and there may be something to say for that, when it comes to the actual quality of the old german castings.
dan
oceanstreetvideo.com
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marco the steem engine
- Posts: 176
- Joined: Thu Apr 26, 2001 1:01 am
2110 Compression Ratio Suggestions
So why did vw's last boxer motor have only 18cc in the head and 45cc in the piston with .040thou for deck and 10.5-1 comp?
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
My 63 cc heads are not factory, although they are based on VW castings. The chamber is kept to the same profiles..
As for Semi Hemi working in other engines, I would not know, I don't work on those powerplants, and would come near starvation before doing so to make a $..... The one thing they do not have in common with an aircooled engine is that they cool with water, it takes alot of inefficiencies to make a big difference in a water cooled vehicles engine to make the same changes as it will in an aircooled engine....
All thos numbers on the heads came from my logs, and memory...We do not use those mex heads, so I had to remember back about 3 years..I have not used them since.
When designed, these engines were just like a Geo Metro is today, cheap and not designed to last 500,000 miles, and damn sure not intended to make 200HP.
No matter how it is cut, put on a platter and presented to me, I will never use low CR, (Below 7.7:1) ever again, unless the engine belongs in a bus. We can all argue till we die, and this will never be solved. I do what works for me, and keeps customers from complaining period, and to this point low CR is not been my ally in this war!
As for Semi Hemi working in other engines, I would not know, I don't work on those powerplants, and would come near starvation before doing so to make a $..... The one thing they do not have in common with an aircooled engine is that they cool with water, it takes alot of inefficiencies to make a big difference in a water cooled vehicles engine to make the same changes as it will in an aircooled engine....
All thos numbers on the heads came from my logs, and memory...We do not use those mex heads, so I had to remember back about 3 years..I have not used them since.
When designed, these engines were just like a Geo Metro is today, cheap and not designed to last 500,000 miles, and damn sure not intended to make 200HP.
No matter how it is cut, put on a platter and presented to me, I will never use low CR, (Below 7.7:1) ever again, unless the engine belongs in a bus. We can all argue till we die, and this will never be solved. I do what works for me, and keeps customers from complaining period, and to this point low CR is not been my ally in this war!
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yeahmag
- Posts: 343
- Joined: Wed Jul 11, 2001 12:01 am
2110 Compression Ratio Suggestions
Matt,
I would love to run a 109 cam, but I simply don't have enough in the budget for larger carbs to support that cam. CB sells up to 34mm vents for the Dellorto 36's. Would that be a big enough venturi for that cam/head combo? Or am I mis-understanding the cam/head/carb relationship?
I want to thank everyone for all their opinions!!! Thanks!
-Aaron
I would love to run a 109 cam, but I simply don't have enough in the budget for larger carbs to support that cam. CB sells up to 34mm vents for the Dellorto 36's. Would that be a big enough venturi for that cam/head combo? Or am I mis-understanding the cam/head/carb relationship?
I want to thank everyone for all their opinions!!! Thanks!
-Aaron