compression ratio stock engine.

[MTT3107]

So, I am replacing the cylinders & pistons on my DP 1600.
Engine is stock, except for dual EMPI epc 34's, and Pertronix SVDS distribuitor.

Today I got the tools for measuring cylinder head cc's and deck height.

When I removed the old cylinders, I noticed that they had shims under the cylinders.

I checked my deck height with and without the shims, without the shim, it 0.062, 0.108 with the shim, which turns out to be a CR of 8.1:1 without the shim, 7.3:1 with the shim.

What CR should I be aiming for on a stock engine ?

[BFB]

So, your combustion chambers are 47cc’s? Aaaand you had cylinder shims on a “stock” 1600?
You don’t have a stock 1600.
_________________
Forced induction can overcome a lot of obsticles that gets in it's way
"You are the Engineer and the Mechanic.  
Build it your way not the way someone else does it. Their way might not work for you." - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
“ The monkey see monkey do mentality seems to run deep in VW people. "Gene Berg said it was so 30 years ago so thats the way it is" “ - bdkw1

[Brian_e]

It's WORSE than a stock engine with all that extra deck and no compression

Pull the oil pump out and see if someone put a different cam in it.

The closer to .045" you can get the better. Ditch the shims 110% for certain.


Brian
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www.type-emotorsports.com

[MTT3107]

OK, BFB, have to back up here a bit :

When I bought this beetle, it was in decent condition, engine ran, but not very well.
After I brought it home, my brother and I started checking the engine, and noticed it had a lot of end play, way more than the 0.003- 0.006 you want.

So we pulled it, and took it a part, found that whoever had put it together. had messed up, and not properly aligned the dowel pin of the No.1 bearing, so over time the crankshaft could move, and actually chafe on the case...

So we got an engine from the junkyard, which had been a fuel injected engine, used the case, crank and rods, from that engine, and the cylinders & pistons, camshaft from my original engine.
Also used the heads from the FI engine, since they were DP's, my original engine was SP.

Had the case line bored and thrust cut, and machined the crankshaft for oversize bearings.

Put it back together with new rings, gaskets, etc.

So, it is kind of a "Frankenengine"..

It ran well enough though.

At the time, it didn't even notice that there were shims under the cylinders, I only noticed that recently, when I took it apart because of low compression on one cylinder.

And, if at the time I had known all what I leaned about VW's and their engines over the last 2 years, I probably wouldn't have bought it....

Live and learn...

[BFB]

I dont see how you didn't notice there were shims under the cylinders ... I mean I can see someone not checking the deck height but shims dont just all evenly stick to cylinders when they're removed & did you not clean up the sealant on the cylinders? I would assume it had some since someone built it with shims which isn't factory.
and correct me if im wrong but I dont believe there's any stock heads that have 47cc chambers, I believe 52 & 58cc were stock sizes.
what was the cam that was in the engine you used the heads & cylinders from?
_________________
Forced induction can overcome a lot of obsticles that gets in it's way
"You are the Engineer and the Mechanic.  
Build it your way not the way someone else does it. Their way might not work for you." - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
“ The monkey see monkey do mentality seems to run deep in VW people. "Gene Berg said it was so 30 years ago so thats the way it is" “ - bdkw1

[Brian_e]

[Alstrup]

No stock head had 58 cc. They were all (1600 heads) approx 52 cc with or without step. The 57-58 cc versions are aftermarket. When we go into aftermarket heads they are all over the place, ranging from stock 52 to 54-55 to 57-58 cc.
Dual port 1300 heads were 47 cc.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[Alstrup]

What Brian said.
No stock head had 58 cc. They were all (1600 heads) approx 52 cc with or without step. The 57-58 cc versions are aftermarket. When we go into aftermarket heads they are all over the place, ranging from stock 52 to 54-55 to 57-58 cc.
Dual port 1300 heads were 47 cc.
_________________
https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[vwracerdave]

I'd run it without the shims at 8.0 CR. Run 89 octane gas in the summer and 87 when it's below 60*F outside.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[MTT3107]

[MTT3107]

OK, engine is back together, and runs well, good power.
As mentioned earlier, in the end, I went without the shims, ended up with 8.0:1 CR.
Measured compression before reinstalling it, 120-130 psi on all cylinders, cold engine.

[mikedjames]

Shims are often fitted by engine builders churning out reconditioned engines.
To reduce customer returns from frying the engines.
So they are deliberately detuned.
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1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[nsracing]

It is a tough crowd here, KY - YOu gotta be able to bite back when they do.

We prefer smaller deck heights for more performance. If all you want is a grocery-getter then keep everything stock. Wanna bump it up a bit-the motor needs to get some trimming. Tighten the decks and chambers. Shoot for numbers you are willing to enjoy -

Enjoy -