2110 Compression Ratio Suggestions

yeahmag · Post by **yeahmag** » Thu Oct 18, 2001 3:26 pm

There has been so much talk out there about heads and C/R that I feel lost. I am building a new bottom end after my accident and am looking for suggestions for a daily driver. Current proposed specs:

82 x 90.5
WebCam 119 .422 lift, 276 duration, 240 @ .050
40 x 35.5 heads mild porting and polishing
Dual Dellorto 36s with 30 to 34mm Venturis (still researching).

Any suggestions on compression ratio? Semi-hemi cut? I called Gene Berg and got a quote for heads and they are still recommending STRONGLY the semi-hemi heads with a low 7.1:1 CR for todays gas. Again, this will be a daily driver.

Thanks.

-Aaron

Steve Arndt · Post by **Steve Arndt** » Thu Oct 18, 2001 4:15 pm

That is a VERY mild cam.
Standard unshrouded and cleaned up chambers are what you should use. Do not use Semi-hemi. 8:1 sounds perfect to me.
I'm running 9.4:1 in my 2276.
Semi-hemi just doesn't make sense. The last thing you want is more surface area exposed to the flame front. It is completely backwards.
Steve

<BLOCKQUOTE>quote:<HR>Originally posted by yeahmag:
There has been so much talk out there about heads and C/R that I feel lost. I am building a new bottom end after my accident and am looking for suggestions for a daily driver. Current proposed specs:

82 x 90.5
WebCam 119 .422 lift, 276 duration, 240 @ .050
40 x 35.5 heads mild porting and polishing
Dual Dellorto 36s with 30 to 34mm Venturis (still researching).

Any suggestions on compression ratio? Semi-hemi cut? I called Gene Berg and got a quote for heads and they are still recommending STRONGLY the semi-hemi heads with a low 7.1:1 CR for todays gas. Again, this will be a daily driver.

Thanks.

-Aaron<HR></BLOCKQUOTE>

[This message has been edited by Steve Arndt (edited 10-18-2001).]

[This message has been edited by Steve Arndt (edited 10-18-2001).]

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Oct 19, 2001 12:47 am

Compression is your friend...

Static CR means nothiing, except a standard...Dynamic CR is what the key is... *:1 works well with a Web 119, it is the base for one of my custom grinds and I like 7.9-8.3:1, but it won't sustain more than about 8.4 to stay cool....BTW, my engine combo close to yours with 8:1 static, is a whopping 7.4:1 dynamic in the analyzer, the math don't lie.

Bent · Post by **Bent** » Fri Oct 19, 2001 6:24 am

Semi Hemi works well with mild cams and low comp ratio, also beats huge deck hieghts.
with std or mild cam 7.0:1 is fine.
Ben

Muffler Mike · Post by **Muffler Mike** » Fri Oct 19, 2001 1:26 pm

since i am more of a performance guy,
has any one actually did a side by side test between large deck and then lower deck and semi-hemi??????????????
some times i think aloud and wonder if having the larger deck may assist in actually creating better turbulance as it come up to squish (squeeze out from the flat part of the head and piston into the chamber) and make a better atomized enviroment.
its been a long time since i have read my tech book but what was the real reason for the semi-hemi? was it to make better hp with the low compression or was it made to create low compression with out changing the stock width of the motor?

Makes me wonder weather i was loosing or gaining with my .150 deck that i run.

------------------
Muffler Mike
www.MufflerMike.com

[This message has been edited by Muffler Mike (edited 10-19-2001).]

yeahmag · Post by **yeahmag** » Fri Oct 19, 2001 1:56 pm

In Gene Berg's writtings he stated that he gained HP with the semi-hemi'ed heads and low compression. I have no way to verify that this was the case with my engine. It certainly ran well for a low compression, mild 1776 (7.0:1 CR), but I also experienced most of the down sides of the semi-hemi that people talk about too... Tough to tune, have to run tons of advance, ran warm (but who knows there - now that its cool in LA I was running 180's vs 220's F). The entire engine was designed around the low compression - semi-hemi'ed heads. It would be really cool to have some test data from someone other than the Berg's.

JohnConnolly · Post by **JohnConnolly** » Fri Oct 19, 2001 2:48 pm

Minor criticism; just stating "our testing has indicated blankety blank" means NOTHING. Where's the lab book? We need to see the "tests", how they were done, under what conditions, compared to what? A proper lab book means we can duplicate the tests.

Not slamming Berg, I don't have a "lab book" of results (they might, but where are they for inspection?), I only have my experience with engines, over a long period of time. I read the Blue Book, and for about 5 years considered it the Bible of VW Performance Info. It was only after having problems that were "unfixable" that I started to question the "wisdom" in that book.

I have seen engines that INCREASED their incidence of detonation as compression was REDUCED (deck increased). I can only attribute that to the reduction of squish in the chamber that resulted from the increased deck. Basic thermodynamics says that you'll get a cooler running engine as you increase compression, PROVIDED you keep the ignition advance correct (need less advance with more compression, so when you up the compression, you need to back off on the timing), and provided that you don't detonate (BOOM). Under 7:1 is ridiculous IMO, and an engine like that will run forever because it's not making any frickin' power. This is just MY opinion.

If a comparison was to be done, you could use the same cam, and same heads (with or without SH), you would just need to re-jet the carbs, AND re-set the ignition advance curve (it's ridiculous to assume that a higher compression engine will use the same advance curve as a lower compression engine, yet "everyone" puts a 009 on the engine and times it to 30-32 degrees full advance. WTF?).

John
Aircooled.Net Inc.

yeahmag · Post by **yeahmag** » Fri Oct 19, 2001 3:53 pm

John,

Your answers rule! I'm sure we all love to hear things like thermodynamics and real world testing in answers vs. speculation and spewing some one else's words back as an answer. I wish I had the money, resources, and time to run those tests myself. I am so damn curious about this...

To follow on Muffler Mike's heels - What additionally would be cool, is to test a high compression (8.0:1 and above) semi-hemi motor vs. a standard head. Just thinking out loud...

Muffler Mike · Post by **Muffler Mike** » Fri Oct 19, 2001 4:24 pm

<BLOCKQUOTE>quote:<HR>Originally posted by yeahmag:
John,

Your answers rule! I'm sure we all love to hear things like thermodynamics and real world testing in answers vs. speculation and spewing some one else's words back as an answer. I wish I had the money, resources, and time to run those tests myself. I am so damn curious about this...

To follow on Muffler Mike's heels - What additionally would be cool, is to test a high compression (8.0:1 and above) semi-hemi motor vs. a standard head. Just thinking out loud...<HR></BLOCKQUOTE>

yea if i had money to burn and could buy another set of heads, that would have been fun to take my 8.6:1 .150 deck and turn it into a .045 deck and hog out the chamber to a 69cc to match the compression.
The what if's.
if i win the lotto, i will do that. Well if i win the lotto, i might try my hands at NHRA Pro Stock

------------------
Muffler Mike
www.MufflerMike.com

[This message has been edited by Muffler Mike (edited 10-19-2001).]

James2 · Post by **James2** » Fri Oct 19, 2001 4:29 pm

7.6-1 with that cam.

That engine is a waste with such a small cam.
Run the web 109 and 8.5-1.

Steve Arndt · Post by **Steve Arndt** » Fri Oct 19, 2001 4:33 pm

<BLOCKQUOTE>quote:<HR>Originally posted by JohnConnolly:
, yet "everyone" puts a 009 on the engine and times it to 30-32 degrees full advance. WTF?).

John
Aircooled.Net Inc.<HR></BLOCKQUOTE>

I don't!!

yeahmag · Post by **yeahmag** » Fri Oct 19, 2001 4:33 pm

James,

Any experience with this cam on a daily driver?

I drive about 35 miles everyday in hot So. Cal. 25 of those miles are highway. It seems to me (and I am no expert) that cam is pretty big for a commuter machine.

Thanks - Aaron

yeahmag · Post by **yeahmag** » Fri Oct 19, 2001 4:36 pm

Speaking of timing... With this style motor and a 009 (which is what I will financially be limited to for a LONG while), does the old start at 28 and advance until you ping and then back off 2-4 degrees still apply?

-Aaron

4Barrel Darryl · Post by **4Barrel Darryl** » Sat Oct 20, 2001 12:10 am

GENE BERG IS ALL YOU NEED. The set up you posted will work great w/ Semi-Hemi heads. You already have those pieces? If so, why change everything now?

You said it yourself: "DAILY DRIVER"

James2 · Post by **James2** » Sat Oct 20, 2001 12:18 am

No, I got one ready to go in my car based on on fiends car with the same cam in a 1776.It has a slightly soft bottom, but in your larger motor the stroke should more then make up for that, especially if you run some CR.

I'm running a engle 110 now, which is slightly larger then the cam your planning on, in a 1776 and it's a pussy cat. It pulls from about 1200 rpm with no bucking.

I'm running 7.6 -1 CR with no pinging or over heating in Mid state GA. I plan on going to 8.5 with the larger cam soon.