High Compression 2.0 8v

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Dj lost
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High Compression 2.0 8v

Post by Dj lost »

Hey All,

I have an 8v 2.0L on Carbs, drysump in my racecar (Singleseater)

Performs well, Solid lifter 300 cam etc, but its just not strong enough, down midvaal back straight theres a guy who can reel in a few carlengths,

Ive got my gear ratios so that at the 50board im at 7000rpm. limiter set.

So we have stripped for midseason (4x racemeetings) bearings and rings, and decided to CC the engine,

Compression ratio is currently 10.48:1
Pistons in use is 83mm nural protrude 0.8mm

Ive got a set of AAL pistons, protrude 0.97mm, so if I split a headgasket to make a thicker one, +-2.2mm this will push the CR to 14.27:1

This seems super high, The car currently runs AV Gas and a timing curve to 36deg.

Else if I stack 2x gaskets on top of eachother to have 3.2mm this will bring the CR to 12.59:1

Im looking for advise / suggestions as the car needs to be somewhat reliable, atleast to be near full tilt for 30km at a time, atleast to do 500km before rings/bearings change interval.

My logic says if we up the CR we will up the power...
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panic-mechanic
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Re: High Compression 2.0 8v

Post by panic-mechanic »

If you already have a good head that works just cut it down a bit to get to your 12.5 you want. Much higher tends to eat the Big ends a bit.
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Dj lost
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Re: High Compression 2.0 8v

Post by Dj lost »

So I don't really want to cut head, as heat control, and durability of it being thicker,
Ive seen some guys melt away the waterjackets on their superskimmed heads,

So should 2 headgaskets do the trick?, I do have ARP headStuds. I Generally try to keep oilpressure at 3-4 bar at full tilt, yes it robs me of power, but I feel its safer. The 4 racemeeting BE Bearing change would have to be sooner? Maybe every 3 racemeetings?

12.59:1 im guessing will really help in the power department, I know other guys running close to 14:1 but I dont know how things go for them...(allot of breakages, maybe they run oil pressures too low)

Timing would stay same? or less? and then just rejet a bit?
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Dj lost
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Re: High Compression 2.0 8v

Post by Dj lost »

Otherwise to cut the pistons 1mm so they flush. And still run 2x full headgskets will put us at 11.3:1

Maybe small steps is the way to go?
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'71 Leyland Mini 1000 Stationwagen
'84 Ford Sierra XR6
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'09 VW Citi GTS
'86 VW Citi Sport 1800
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HendrikCTI
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Re: High Compression 2.0 8v

Post by HendrikCTI »

Why 2 head gaskets? Can't you contact Payen or someone else to make a custom thickness gasket?
Is this not going to cause a weak spot where blown head gasket can happen or head gasket failure?
With custom thickness gasket you can start with one and bring it down in thickness by ordering another one later until you get the optimum compression that you want and less work swapping a head gasket for testing.
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panic-mechanic
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Re: High Compression 2.0 8v

Post by panic-mechanic »

two head gaskets are something I really hate. I have never seen the failures you talk of on a skimmed head but each to his own..
Unless you run serious octane you will most likely have to slow the timing slightly.
Try redline racing in the cape - they can make you a thicker gasket to spec.
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merlinvenn27
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Re: High Compression 2.0 8v

Post by merlinvenn27 »

panic-mechanic wrote: Tue Aug 07, 2018 9:02 pm If you already have a good head that works just cut it down a bit to get to your 12.5 you want. Much higher tends to eat the Big ends a bit.
and if you used king racing or acl bearings? Logic tells me they stronger bearings, would they just last longer but suffer the same fate in the long run?
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Re: High Compression 2.0 8v

Post by missioner »

merlinvenn27 wrote:
panic-mechanic wrote: Tue Aug 07, 2018 9:02 pm If you already have a good head that works just cut it down a bit to get to your 12.5 you want. Much higher tends to eat the Big ends a bit.
and if you used king racing or acl bearings? Logic tells me they stronger bearings, would they just last longer but suffer the same fate in the long run?
Yes. Panic has built every type of race engine of VW origin in the past 30 odd years.

If you have to listen to advise, he's the guy to give it.

The label on the box cannot make a bearing stronger, that is a fallacy. Everything is dependant on how the engine is machined and assembled. Better quality bearings are simply that, better quality. They are made to meet higher standards. If the engine builder works to higher standards then better quality parts work better, but a good build will still be good with ordinary parts. Spending a fortune on good parts cannot ever fix a poor quality assembly job.
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