ORVette

I couldn't take it any longer, so I pulled the heads on my motor the other night to get some measurments and figure out my compression ratio. Stock style dished pistons(about 13cc), .033 piston to deck height, 74.5cc chambers(76cc milled .006), .041 gasket(9.1cc), and 4.040 bore with stock crank for swept volume of 731.2cc.=just as I thought: 8:1! No wonder this thing can't get out of its own way! I called my favorite machine shop and asked if there was anything I could do to solve this for under $300. He said he has a set of newer chev. 350 heads(not vortec) with 64cc chambers that he could rebuild and set me up for about $200. I'm not sure what casting# they are, but he said they have different angled center intake bolt holes and I would have to modify my intake a little to fit them. I figure with these and a thin head gasket I can get up around 9.25:1 if my math is right. I'll post again when I get it all back together and see if it actually works. Wish me luck.

Jughead

I plan to use sportsman 64cc heads on my budget rebuild. You probably are aware of this site but I just found it. http://www.smokemup.com/utilities/ca...sion_ratio.cfm

AlwaysWave

I'd take the time to evaluate those other heads before I committed to them. Hint----Aren't post 86 heads incompatable with pre-86 block?

tnt76vette

Personally, I think that 3.08 rear end is what holding ya back....Your cam is about right for a low comp motor, albeit a bit mild....Just my $.02......Enjoy!!!!!

TNT

With your current set-up you should pick up about 35-45 HP with the increase in compression. Thad :smash:

QuickVet

not that i know of. i have a set of newer heads on my car and have not had a single problem.

Budman68

With 64cc you should only pick up :50 compression, not 1:40. To get to 9:5, you will need 58cc and 110 duration.

Blake-73

I am running a set of 041 cast heads with the big valves and love them. I would suggest either 041 or 186 castings. Both are great heads and much
better that the stock heads in 1973. HP in small-block's comes the heads.
Tell your machine shop to round you up a set of 186 castings and you will
really wake up your 73. If you got a set of headers and a performance intake
you'll be up in the 275-300 HP range.

Blake-73

GTR1999

What is the formula for CR?
Gary

ORVette

Just talked to the machinist and they are casting#14101083 heads from a n '89 5.7L. Thay have 1.94/1.50 valves and were also used on older 285 and 300HP crate motors according to mortec. Smokemup calculator says switching from my current combo to these heads and a thin shim gasket will put me at 9.26:1. (Steve)1979toy did a desktop dyno for my current setup and with the new heads and came up with about a 23 peakHP/TQ increase. I know my cam is a little weak, but it's the same cam spec wise that they use in the Edelbrock Performer crate motors(not RPM). Same lift/dur.@.050, same opening and closing times. We'll have to see when it's all back together, but it looks like a pretty decent increase for $225+gaskets, especally if all you have is $225 to spend! Thanks for the replies.