ww okrasa heads chamber

[bdub475]

Does anybody know rhe chamber volume of these heads? Also am I suppised to run the copper head gaskets with these heads?

[bdub475]

Ok I called them and was told that the chamber volume is approximately 45cc. The stock heads are 45-47. The add for the ww kit says that the compression with their heads is 7.5:1. How is that? With my math all things being equal otherthan a 2 cc smaller chamber how is the CR 7.5:1? I'm getting 6.9:1 a 40cc would be needed for a 7.5:1. I'm I missing something?

[Sharig1979]

How did you calculate your CR? How did they calculate CR for their add? Depending on the formula it can be done with as few as 3 measurements and as many as 5 measurements and more for other types of engines.

I'm not questioning what you've done or what your number is and I'm not defending their 7.5:1 claim but I can't say from what you have provided that all things are equal to say something that was claimed is not true. This could be a case of the advertised CR was based on specs that do not match your engine.
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[Mr. Motorhead]

Maybe they are assuming you'll also be using their 69.5mm stroker crank as well. Compression with a stock stroke crank is fairly low. If you use 40hp pistons (.040" taller) you could get about 7:1 compression with a stock stroke crank and that chamber size.
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[splitpile]

[slalombuggy]

Here's CBs engine calculator. Plug in your numbers and go

http://cbperformance.com/enginecalc.html

brad

[sgmalt46]

you would need 0.010 deck to get 7.5? im going to fly cut mine to get 8.5 or so.

[bdub475]

I called ww to get the chamber volume, witch he said was 45cc. He then told me that the heads bolted to a stock stroke engine should produce 7.5:1 compression. I used CB's compression calculator to get the 6.9:1. Stock stroke of 64mm stock bore of 77 deck height of .050 and stock chamber volume of 47 and it comes out to 6.6:1. 2cc less in chamber volume doesn't bring the compression to 7.5:1 it brings it to 6.9:1. I mean using all stock figures other than the chamber size it doesn't add up to what ww is advertising. They couldn't possibly know what the CR would be with a stroker crank because they don't know how much you would shim the barrels nor would he suggest an amount to him them.

[Kjell Roar]

Bengt H took his original 36hp heads down 3 mm, and got 37cc in the heads (with a little work in the chambers). With 1 mm deck height he got 8.2:1, if I remember right.

1" = 25,4 mm


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