im lookin at these 305 high output heads there 58cc my stock heads on my 350 are 76 CC and i have a 8.5:1 compression ratio would putting on these heads make my compression TOO high?? plz help

 

oh yeh this 350 i have is the 260 hp gm goodwrench one

 

Yes, the compression ratio will be too high, and the engine's volumetric efficiency will drop (how well it breaths.) This isn't a good idea.

 

You would have roughly 10.1 to 1 with the 305 heads. If you run premium fuel and keep the timing conservative you will be fine. Also if you install 1.94 intake valves and port the heads you will not lose any flow and should see a nice gain. I'm not familiar with the cam in that motor. You may have to have the valve guides cut down to handle the lift.

 

10.1 would be a good safe compression i would liek it to be i dont want it any higher than that but im unsure heres the heads im lookin at

 

heres 2nd pic

 

last one i know they would need a cleanin but hey im gettin these at a good price

 

sorry- i dont have anything usefull to add. i was just wondering whats a good price for a used set of heads.

 

how much advanced should the timing be?

 

I ran around 10 base, but advance it until you hear detonation and back off 2 degrees or so.

 

Are you planning on porting these yourself? If so Just go ahead and open up the combustion chambers a little. I had mine opened up a couple cc's while I was having them ported and I run 89 octane without any detonation. I really like mine all I have is the bigger valves and a little bowl work and they work great with my setup. I have an insane amount of low end torque. Also you might want to change your cam while your at it, the cam in that motor is about as weak as you can get.

 

well i was plannin on takin them to a shop and gettin them professionally polished n yeah i was lookin at another cam but i think ima put them in later after i get all my bolt ons first wiit this car i just wanna make around 350 hp n still able to daily drive it around cuz its my only car

 

This guy has absolutely no clue what he is talking about. The ports of the 601 and 416 heads are about the biggest of any stock SBC head ever made, only the 461X and a few older heads had a bigger volume.

Your volumetric effeciency will go way with the increase of compression.

If your worried about the compression ratio being too high just grind alittle out of the combustion chambers to increase volume. You might also want to measure your volume to get 9.5:1. I highly doubt that your 350 is 8.5:1, more like 8.0:1 or 8.2:1.

 

Look on top of the head, where the valve stems and springs are. There will be an eight number code. Post it here so we can tell you what the heads are good for.

 

ok ive decided to cancel the 305 heads im lookin @ some lt1 aluminuim heads now would those fit my 350??

 

Short answer no, long answer

 

hey the 305 numbers are 7936551391

get back me quick !! i have lil time to buy them

 

 

ahh good or bad man?

 

No good. You need 081, 601, or 416.

 

i have a 355 w/-4 cc dished pistons, and a 75.4 cc chamber head, (487x's) and my comp is 9.4:1 and with a set of 58 cc 305 heads would raise my comp to 11.4:1 heres a link to a compression calculator http://www.csgnetwork.com/compcalc.html if this helps you

 

ok thanks guys for ur help just saved me some dough i think ima get these vortecs 64 cc heads that are lookin pretty good