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Probably came up B4 But did not see it in a search. They seem like a good head on a strong street motor for the money, but B4 I buy I thought I'd ask, also how much of a compression should I expect from a 119cc chamber (stock #049) to a 115cc chamber?
http://cgi.ebay.com/ebaymotors/BBC-B...d=p3911.c0.m14
They look similar to the ZZ502 heads (made by Edelbrock) in specs. Very good street heads. Great price there IMO.
Compression ratio needs more information.
CR=(D + PV + DC + G + CC) / (PV + DC + G + CC)
CR = Compression Ratio
D = Displacement
PV = Piston Volume
DC = Deck Clearance Volume
G = Gasket Volume
CC = Combustion Chamber Volume
Kitz
Unfortunately, I am not up on those figures (ametuer knowledge base here, I do no head work myself other changing them out or average factory type repairs.)
I do know that it is a blueprinted stock block 454 .030 over, studded 2 bolt mains, forged crank w stock 4.135 rods and .030 over KB HyperT factory replacement pistons (KB202) 8.2 Comp per KB's ratio rating for my engine. All custom balanced, Fresh stock unmodified #049 heads w LS6 springs.
D = Displacement = 461.2
PV = Piston Volume = ?
DC = Deck Clearance Volume = ?
G = Gasket Volume = 9.700
CC = Combustion Chamber Volume = ? Whatever stock #049 heads have depends on who you ask (116 to 119 cc's) and am unable to CC them myself.
049's usually use the 118 cc reference for CC'ing. Displacement figures should be used for one cylinder. worry about swept volume and dome cc's or dish cc's (negative cc's) and it's quite easy to figure.
Remembering that deck height (DC) volume is the volume of area when piston is down in the hole at TDC.
4.135 rods? Go back and refigure your combo and rethink the formula Kitz gave you.
It really is quite simple. We just have to dust of the Math part of the brain to go through this.
Calculators are a God send.
Take a deep breath and it'll work out.
If those heads haven't been butchered through repair work, you should snag 'em.
"deck height (DC) volume is the volume of area when piston is down in the hole at TDC."
How or where do I get that? I have the deck hight - Compression hight = 1.645"",crank to deck distance = 9.8" and my bore = 4.281 and using that 118cc chamber figure. My problem is that a lot of those calculators use different terminoligy's or use some I do not understand.
I probably should take engine math 101 sometime. heh heh .
It's a small number. Just assume the piston tops out 0.005 below the deck. PV depends on whether the pistons are dished, flat, or domed. If you don't know just assume it's 0 and the error won'y be too bad.
Kitz
Using an online calculator I came up with this using figures I had and your help. Sound right?
Enter Cylinder Bore Size 4.281
Enter Piston Stroke Length 4.135
Enter Head Gasket Bore Diameter 4.370
Enter Compressed Head Gasket Thickness 0.039
Enter Combustion Chamber Volume In CCs 118
Enter Piston Dome Volume In CCs, Negative For Dished Pistons +3.0
Enter Piston Deck Clearance, Negative If ABOVE Deck : 0
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Calculated Engine Compression Ratio = 8.828691414199347:1
Total Displacement Volume = 124.58558163463904 cc's
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Using the 115cc head as in the question I came up with-
Calculated Engine Compression Ratio 9.021856376087452:1 Comp.
Total Displacement Volume 121.58558163463904 cc's