Trying to figure out the compression on this 350 I'm building for my girlfriends camaro........going to install the ported 305 heads on it today and I need to buy the head gaskets. I was going to go with a factory steel shim to up the compression even more.....but I was wondering since I'm already putting 58 cc chambers on a 350 motor.........wouldn't the compression be near 10:1 already? I was going to use a stock Fel Pro 7733 head gasket from autozone (.041 thickness I think), so what a 58 cc head, plus stock 4 valve relief dished 74 truck 350 pistons and a .041 thick head gasket come out to?? I'm aiming for 10:1 or better.........which is why I'm considering the steel shim gaskets which autozone also sells.

 

http://216.121.161.76/files/EngineCalculator.xls

 

"...4 valve relief ... 350 pistons..." are not dished. Sounds like flat-tops, to me.

Use the thicker gasket, if you don't want to run race gas in it all the time.

(I'm considering a dished-piston 350 short-block to go under my ported WP 305 heads, so I have looked into this a little bit. I figured 9.5:1 with dished & .041" gasket.)

 

Ooo, neat tool! Thanks, ede.

Does anybody off-hand happen to know the deck height and/or the volume of the valve reliefs (in cc's) for a the stock bottom end of a L03?

 

Meant to say dished 4 valve relief.

 

You're not going to like the 305 heads on a 350. They won't flow enough air to produce good HP numbers.

If memory serves me correctly, 4 valve reliefs is around 12cc's.

 

You can download a good working compression calculator demo
from Performance trends.

You can get the dish specs for your pistons by going to the
Keith Black pistons site and looking in the listings for the stock cast replacement Siv-o-lite pistons and finding the one that has the same dish depth and valve reliefs with the same deck height
as your factory pistons.

http://www.performancetrends.com/

http://www.kb-silvolite.com/

 

Well heres some info. I think that chev had two piston designs in 74. One had a 21.1cc dish and the other had a 18cc dish. SO:

Bore = 4.0" -----------------same--same---same
Stroke = 3.48"--------------same--same---same
Head cc's = 58--------------same--same---same
Dish cc's = 21.1--------------18-----21.1 -----18
Deck Height = .025---------same--same---same
H/Gasket Thickness .039--same---.021----.021 =(steelshim)
Comp. Ratio = 8.77 to 1----9.04---9.09----9.38

So, to get 10.0 to 1 or better you will need flat top pistons.

Auggie