Yesterday i pulled my engine out of my IROC. and today I took it apart. Well the guy I bought it from told me that the guy he bought the car from, told him a 350 had been swapped in place of the orginal 305. Well, it turns out the orginal engine was just rebuilt.

I pulled the heads of my engine and looked at the pistons and found there was a 3.75" bore instead of a 4.00". so here is my problem.

I am building a 76 350, that is bored .030 over. and I was going to use my (supposed) L98 heads with the block. Well, i found out I don't have 350 heads, I have 305. I know that the valves are 1.84/1.5, and the combustion chamber is 58cc. Now I know that I would already be running 9.5-9.7:1 compressoin with Speed Pro forged pistons. and now that I have 58 ccs instead of 64, I'm sure I will be in the 10:1 range. Well is there away I can still use these heads and enlarge the combustion chambers so i don't run that much compressoin. I don't know for sure but if I ran 10:1 I prolly wouldn't be able to use pump gas. I don't have the money to get new heads. So I just want to see what you guys would reccomend for me to do. Thanks!!!

Tyler

 

What castings are your 305 heads? I am planning a 350 soon, and am probably gonna use my 305 heads. From what I understand 10:1 is getting on the high side for Iron heads and Regular Gas. But I also read that if you quench is in the correct range .030"-.040" then you should have little problem with detonation and higher compression. I know you can open the chambers up a bit, just make sure none of it is opened up farther than the bore. I believe that 2-3 cc's can be cut out easily.

There is a nice porting and polishing post here, it is about the 416 heads, but the heads you probably have are 081's which are very simular.

 

14102187 is the casting. I'm sure they could handle the 10:1. Its just a matter of dieseling and pinging from pump gas.....I guess I don't really know yet

 

I have used 305 heads on a 350 for higher compression and great low end torque BUT my engine builder strongly recommended that I perform some work on the heads first which I did. Remove all sharp edges and polish the combustion chamber to monimize the chance of detonation. I ended up with 10 to 1 compression, pump gas and 36 degrees of timing with no detonation. Lucky or good, who knows, but it worked that time.

 

187 heads aren't that great for flow, I believe they are off a L03 TBI engine. I would definetly put a lot of porting and polishing in them if you are going to use them, but I would suggest finding different heads. The compression would end up at probably abou 10.4:1 which may be okay with somewhat conservative timing tables and 91 or 93 octane gas.

 

No money for heads?

I'd take a die grinder and unshroud the combustion chambers a bit...60-62 cc should not be difficult. If no die grinder, and no money...and buy high octane gas.

Or go find some 350 heads at a junkyard.

 

well I don't have alot of money I should say. I know off thirdgen resource i could pick up a set of heads for 100 bucks.....so maybe I will do that

 

well, here is what I ran into.....I have had a set of 14102193 heads sitting around that I had ported and polished for my truck that I had.....well i was desperate so I decided to go with the heads, and yeah they worked...so I guess I will see how they turn out.