Im trying to work out what I need to make my 350 a hi-comp engine. I have a 73 block and a set of 71 re-emission heads. I realize the heads will probably have to be replaced with a set of say 70 hi-comp heads. Has anyone ever done the swap, and if so, what did it take. The reason for the change is I dont like the idea of having to dump in a bottle of octane booster at each fill-up. I am hopping to be able to use the heads I have, but I realize it may be a pipe dream. I currently have a 70 Skylark with the original 350 in it. I bought the car off of an old man who has had it since 1975. No grille, hoods beyond repair(he hit a telephone pole), bumper is tweeked a bit but could be straightend. All in all a good ride though. REALY bad compression in 3 cylinders though. Id rebuild the 70 motor but its the only car I got right now. I have always wanted a GS, but the skylark will do(till I win the lottery). If anyone has any advice for me please let me know.
I'm having a hard time understanding the gist of your post. But, let me take a couple shots in the dark and see if I don't answer your question. '70 non-emission heads will fit on any buick 350 block (70-72 blocks for sure) and they coupled with the 10.2:1 high comp pistons will set your compression right about there; 10.2:1. You can run this kind of compression and get away with filling up with 93 octane at the pump. All 3 of my cars are high-comp motors, and I never have to run octane booster. Your '71 heads are going to be a few CCs larger than a '70 head, and lower compression but more than anything the pistons are what make a difference. It would have to be a high comp motor to have the 10.2 pistons, and being a '73 I highly doubt that. If this didn't answer your question, state the question a little bit clearer and I'm sure someone can help. BTW, where are you located?
Chris is right. The heads won't make hardly any difference in compression. It's the pistons that will give you the jump in compression that you want. If you have 3 bad cyl. on your current motor which you said is a 1970 motor than you will not be able to reuse those pistons which are the high compression ones from the factory. If you want to raise the comp. than you will need to buy a set of 10-1 pistons and install them in your 73 block. You should have the cap screw rods in that 73 block which is a good thing. Buy the ARP blots for those rods and your set to live through what ever power that engine can make. You will want to have your block decked just enough to make the deck square. Don't take a bunch off like .010 or .020 inch. Your piston will still be .030 to .045 in. down the hole which will give you around 9.5 or 9.6 to 1 compression. Perfict for any pump gas 89 octain and up. You don't have to worry about the quench area on a 350 because it doesn't have one. your cumbustion chambers are wide open. If you block off the heat crosovers on the heads you will have a really good set up and I think will be happy with the motor. It should give you good performance. If you want to go crazy than have the heads ported a pick the right cam and torque converter and spend all your cash. Good luck
