My head CCs r 64 so that gives me 8.9:1 on my 78x90.5.....at 0 deck....Whats your thoughts on a 0 deck???
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Fredy-
55 bug-
63 bug-
Head CCs
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Marc
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Head CCs
You have to allow enough clearance for deflection and piston rock. If you're talking about the use of copper head gaskets to give piston-to-head clearance, like in last month's DB&HVW, that's another subject. The justification seems to be that they'll be more forgiving if there are imperfections at the cylinder-to-head sealing surface or if the installed height of the barrels doesn't exactly match. Looking at all the problems Type IV engines have with head gaskets, I'd rather correct the problems than use headgaskets to mask them. Opinions will vary, of course.
.040" is considered the minimum safe piston-to-head clearance by most builders, and generally you want to keep it as low as possible for better combustion, but bear in mind that the bigger the bore the less clearance there'll be at the edges of the pistons when they rock. If you're building this engine to stay together for a while it'd be wise to run no less than .045" (personally I'd go .055").
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"For every complex problem, there is a solution that is simple, neat, and wrong." --H.L. Mencken
`67, 69, `77 Beetles, `73 II (Type I engine), `86 Audi 5000s, etc. etc.
Independent VW specialist shop manager/unit repairman 1978-1991
.040" is considered the minimum safe piston-to-head clearance by most builders, and generally you want to keep it as low as possible for better combustion, but bear in mind that the bigger the bore the less clearance there'll be at the edges of the pistons when they rock. If you're building this engine to stay together for a while it'd be wise to run no less than .045" (personally I'd go .055").
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"For every complex problem, there is a solution that is simple, neat, and wrong." --H.L. Mencken
`67, 69, `77 Beetles, `73 II (Type I engine), `86 Audi 5000s, etc. etc.
Independent VW specialist shop manager/unit repairman 1978-1991
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James2
- Posts: 3148
- Joined: Fri Mar 16, 2001 12:01 am
Head CCs
You need to allow room for the crank to flex and also the rod and piston to stretch. If you run 0 deck, the piston will hit the head.
I wanted to run the min deck possible in my engine, which led me to ask many questions and do much research. The min deck depends on how strong the crank and rods are and also what stress is put on them. more rpms= more stress. So higher rpms need more deck.
If you have a stock stroke motor, built with quality components and the rpm is held under 6500, then .035 is the min deck.
If you run over 6500 rpm add .005
If it runs over 8000, then you don't ned my advice.
If you run a quality stoker crank add .005
If it's cast add .010
If you run stock rods that have been clearanced for a stroker, you should add .010.
in your case, the min deck would be .050 if you running clearanced rods and keep it under 6500 rpm. If your running a quality aftermarket rod you could run .045.
If you're running clearanced rods and a cast crank, the min deck would be.055 and redline should be 5500 rpm.
These numbers are just what i've come up with, so use with your own caution! It be wise to run an extra .005 in any case. As mentioned above, the larger pistons rocks more in the bore. This could be a problem, especially at higher rpms or later in the engines service life.
But be clear, deck hieghts under .060 do make more power because of the increased squish. my reseach says it will burn cleaner and cooler.
I wanted to run the min deck possible in my engine, which led me to ask many questions and do much research. The min deck depends on how strong the crank and rods are and also what stress is put on them. more rpms= more stress. So higher rpms need more deck.
If you have a stock stroke motor, built with quality components and the rpm is held under 6500, then .035 is the min deck.
If you run over 6500 rpm add .005
If it runs over 8000, then you don't ned my advice.
If you run a quality stoker crank add .005
If it's cast add .010
If you run stock rods that have been clearanced for a stroker, you should add .010.
in your case, the min deck would be .050 if you running clearanced rods and keep it under 6500 rpm. If your running a quality aftermarket rod you could run .045.
If you're running clearanced rods and a cast crank, the min deck would be.055 and redline should be 5500 rpm.
These numbers are just what i've come up with, so use with your own caution! It be wise to run an extra .005 in any case. As mentioned above, the larger pistons rocks more in the bore. This could be a problem, especially at higher rpms or later in the engines service life.
But be clear, deck hieghts under .060 do make more power because of the increased squish. my reseach says it will burn cleaner and cooler.