2276 vs. 2332 again

[gearheadgreg]

I know, I know. I searched, I've read, and I have talked to a bunch of buddies. So now I am asking opinions here.

I sacrificed the new period build engine for my 1971 Bay Window Bus to my Baja flip project because I got sick and tired of going through bad engines and cases from local purchases. It was a 74x88 (Thick wall) with mild cam and pocked-ported heads, etc. Good little bus engine.

Now, I have fallen into a freshly machined case that has been opened up for 94's (8mm stud inserts, welded behind #3), and all surfaced and line bored correctly, etc. Not clearanced for a stroker, but I have a chance to buy some really inexpensive forged strokers - 82mm w/ VW Journals or an 84mm with Chevy journals. I kinda prefer the 84, because I imagine the clearancing will be about the same, and why not get some more cc's? It will be going in the 71 Bus, so not a race motor and it won't be revved to the moon or anything.

That being the case (ba-dump-ba, pun intended), the system I think I want to put together is 40x35.5 heads, locally ported by a VW machinist/expert that has built lots and lots of very good race and street engines over the years (several I have driven/ridden in). Port job will be with the goal of a very good mid range engine in mind. I intend to use a Norris cam, likely a 336S (gives the option of 1.1 or 1.25 rockers) or possibly a 407S. Carbs are going to be in the region of 40IDF/DRL-44/45s, or DCNFs 40-44. Compression with the decent cam of about 9:1, maybe 9.5:1 given I am at 6500ft altitude. Planning on 5.7" Chevy rods if I go Chevy with the 84 stroke. Would keep the rod rato around 1.7, VW rod of 5.5" would be close to the same with the 82 crank.

Bus already has an 091 trans, so should be at least alright for the increase in power, and while I plan on using the power, and maybe a burnout or two, I am graying and 40 years old, so not 18 and looking to drag race at every stoplight.

So - any red flags or concerns anyone has with the bench build of the motor?

[Marc]

I honestly don't recall how much more clearancing you can expect to do (the simple answer is ~.040" deeper everywhere, but that assumes all other variables being equal - and they never are. "Chev" rods will need less, but the counterweights may still be bigger on the 84 crank, so you'll probably still need to do a good bit of whittlin' on the cam and bearings).
I do not consider 94s to be thick enough for a bus engine. Ask anyone what they think of 87s...then note that 94s are only .007" thicker.
If the case is opened up to 97.25mm already, I'd use AA thickwall 92s which have the same top & bottom registers as 94s, and a wall thickness even greater than TW 88s - the ideal bus jug IMO.
"B" pistons have a compression height that yields a nominal stock piston deck height on an 80.2mm stroke. 84-80.2=3.8, that means 1.9mm (.075") less deck with a stock 5.394" rod. With a 5.7" rod, you'll need cylinder spacers in the ballpark of .380", for a total engine width that's about 3/4" wider than stock...almost certain to need custom, longer pushrods, sheetmetal extensions, and widened exhaust.
5.5" rods on an 84 stroke would yield about the same rod ratio as stockers on 82, which is too low for all but a Bus motor IMO...easier packaging (.400" narrower total), but lower life expectancy.
I'd consider splitting the difference and going with 5.5" on 82 or 5.6" on 84.

[gearheadgreg]

Awesome - thanks for the reply.

Now to be a jerk and argue - (though I honestly really like the thick wall 92 perspective - a lot):

.179" = 92mm thickwall
.177" = 88mm machine-in
.163" = 85.5mm
.148" = 90.5mm
.140" = 94mm
.118" = 92mm thinwall

The bus will be an occassional driver. Will see some hours long drives, and up grades, etc. but not towing loads, etc. more of a weekend fun vehicle. That said, it is a bus, and will get used. My thoughts *were* that a 94mm ID circle with .140" Of material would have more thermal mass than a 90.5 with .148" of material, and more suface area for cooling, etc. but that is just bench/book arguing... I'd be totally happy with a 2180 vs. a 2276, etc. esp if it makes assembly easier and power is within X%.
I've ridden in a thin wall 18355 Westy Bus that was driven hard a lot, and had 60k plus on the motor, with no oil burn or problems, etc. so I am not against thin*er* walls, but don't want to shoot myself in the foot with a ground up build, either. That's why I'm on here asking questions.

The rod length and packaging info is well received. Thanks again.

[Marc]

...I've ridden in a thin wall 18355 Westy Bus that was driven hard a lot, and had 60k plus on the motor, with no oil burn or problems, etc...

Definitely a rarity. Even in a Beetle, classic 92s & early 90.5s typically develop far more blowby than late 90.5s by the time they've got ~25K on them.
Again, almost nobody would advise 87s on a Bus, and they have .134" walls - not to mention a 1641 makes far less power & heat than a 2-liter. You may get away with the 94s, but IMO they aren't the wisest choice for this project. As for the "thermal mass" argument, it's outweighed by the greater tendency for distortion upon heating/cooling the larger the bore. Even in a perfect world where the cooling air supply was consistent all around the jug, the fins aren't uniform - and have four big holes through them
My son ran an 88x82 (1995) in his `73 Baywindow. 40x35.5, Engle W-110, dual 48IDAs, <8:1 (sea level) and it had ample power. With the 002 trans 1st gear wasn't needed until he put on 17" tires to approximate 091 gearing. I'd think you'd be satisfied with a 2180 or 2234.
Dunno if you've built many big Type Is with CW crankshafts, but be sure to provide ample crankcase ventilation - like at least ½" I.D. hoses off both valvecovers.

[gearheadgreg]

Thanks again - I think I will go with the thick walls - it just makes sense for this application like you say, and the only drawback is a few less cc's. I can live with that.

I haven't built any big stroker Type 1's yet - this will be the first. Worked my way through college in a VW-Porsche shop, and saw how important crankase airflow is on the 911 case internals, so I would assume this would be a similar situation, with the counterweights trying to block some of that airflow now.

[gearheadgreg]

Well, I've been talking more and more with some local engine guys. I found out why some of the thin wall 92s worked so well - they had Bud Whitfield cylinder stiffeners on them (machine off top 2 fins, cool cylinder, heat stiffener, slide on, bingo - strong cylinder). I am leaning more towards the thick-walled 2180 all the time. I also got the local guru to offer to do an intake port for me, and I can match to the rest (done lots of porting on the flow bench in the past). [rubbing hands together]

I was thinking long rods might be a good thing for rod ratio, but the amount of additional work it will require, and being for a bus, I might use some stock, or close to stock length rods - 5.394 or maybe up to 5.5 like you were suggesting. Hmm - pretty much like you told me to do. Heh. Thanks again.

I also found out that bus wasn't an 1835 but a 2074. No wonder it spun the tires, while pulling a cycle trailer. Heh.

[Steve Arndt]

...
Bud Whitfield cylinder stiffeners
...

This is called a power sleeve now. Rimco and Pauter do it. It keeps the cylinder from splitting under high boost. Requires taking material out of the head for the power sleeve to fit.

[Marc]

... being for a bus, I might use some stock, or close to stock length rods - 5.394 or maybe up to 5.5...

Definitely ≥5.5 if you go with 84 stroke, but you could get away with ~5.4 on 82.
I doubt that you'd be able to feel much difference in the torque either way, and your heads'll be big enough that it shouldn't be port-limited at "Bus" RPMs even with short rods. It's mostly about the packaging and side-thrust wear, if you want it to last many years it'll be worth the effort to use 5.5s. Most of the time the only significant extra headaches are finding the correct barrel spacers and if longer-than-stock pushrods are needed for good rockerarm geometry...nothing insurmountable, just allow a little extra time for the build.

[gearheadgreg]

OK - I keep going over this in my head, and haven't bought parts yet, to that end.

I am almost reserved to building a 78x92 2074cc engine now. It's easy, minimal clearancing, should be correct width for tin, etc.

I think that the B pistons with 5.5" rods should come out pretty close to on the mark for deck as well. I really want to run as tight a deck as I can safely, with as much compression as I can do with 91 octane. Really want to start ordering parts, but not the wrong ones.

[Marc]

One big variable is the case deck height (distance from crank centerline to cylinder base surface) and when a case is opened up for 94s that's typically significantly less than stock.
For the sake of argument, suppose that with "B" compression-height pistons you'd have ~.035" piston deck height with a 5.394" rod and an 80.2mm stroke. With the 78mm stroke the deck goes up by 1.1mm (half the difference) - that puts you at around .078". 5.5" rods will cause "negative" deck height => the pistons will project beyond the cylinders by ~.028" if the case deck is .020" lower than stock.

Cylinder base spacers and/or copper head gaskets can be used to set your final piston deck/piston-to-head clearance. Personally I wouldn't go lower than .050" piston-to-head with a 92mm bore on an engine which is expected to run for many miles (as the cylinders wear there will be more piston rock, increasing the chances of head contact if you miss a shift someday). You won't know the exact thickness required until you do a mock-up assembly, but it'll be easier if you throw some spacers under the jugs to make the deck simple to measure. Remember that the thickwall 92s use cylinder base spacers/shims made for the 97.25mm diameter of a 94mm jug. I haven't seen any copper headgaskets offered specifically for the thickwall 92s, so you'd need to use the "94" gaskets as well. Personally I wouldn't use headgaskets on an N.A. motor, so I'd be ordering .060" base spacers and hoping they're in the ballpark - I could add another shim to that if needed.

[neil68]

The main problem with the 94's is not so much the cylinder thickness, rather it's the small space that is left between each pair. This reduces the cooling air that is able to blow down between each pair. One of the European forums had some information on this a few years back, showing how the temperatures will be uneven.

I tried 94's in my '69 Westy a few years ago and got 23,000 miles out of them before they started to warp out of spec...even though the temp gauges showed no overheating. The newer Mahle 94's are thicker, but I think the jury is still out as to whether these will work any better in a bus than the old ones. I used some thick-walled Mahle 88's and got 60,000 miles out of them and when I sold the bus, the next owner was still adding to the mileage a couple years later...then lost track of him. Also, would think that 90.5's might be durable and maybe the AA thick 92's?

[Fiatdude]

[quote="neil68"]The main problem with the 94's is not so much the cylinder thickness, rather it's the small space that is left between each pair. This reduces the cooling air that is able to blow down between each pair. One of the European forums had some information on this a few years back, showing how the temperatures will be uneven.
quote]

I've found that cooling air between cylinders is highly overrated



But I had a 2065 in the Fiat and found it to be an excellent size -- especially with about 20 Lbs boost

[Steve Arndt]

Those thing must rattle Fiat, looks like lots of piston to cylinder clearance. How many miles do you have on the ARPM Siamese cylinders?

[Fiatdude]

Hey Steve -- - it is a optical illusion -- custom boost pistons with the rings way down -- not enough miles on it, but have driven it in traffic with no problems, however I am running E85 -- chasing valve train issues right now, pulling the thing apart for a double check and going to change over from the k800's to beehive springs if I can get a handle on retainers and locks --

was kinda being my usual smart ass self -- but notice just how much more fin area are on the barrels compared to stock

[neil68]

The main problem with the 94's is not so much the cylinder thickness, rather it's the small space that is left between each pair. This reduces the cooling air that is able to blow down between each pair. One of the European forums had some information on this a few years back, showing how the temperatures will be uneven.
quote]

I've found that cooling air between cylinders is highly overrated



But I had a 2065 in the Fiat and found it to be an excellent size -- especially with about 20 Lbs boost

I was responding to the earlier posts that mentioned conventional ACVW cylinders such as Mahle (siamese cylinders are obviously an entirely different product, so I'll you and others provide your feedback for his 71 Bus application). Getting back to the 71 Bus, I would not use Mahle 94 kit for those looking for longevity...