305 or 350

[Shanker1371]

Ok Recently I bought a new flywheel for my what I though was a 1980 350. The truck the engine came out of was an 86 GMC longhorn with a th350. I am using a 3spd. I went through some trouble because the bolt pattern was off. The last three of the block number is UFC which comes back to an 80 350. However the the flywheel that was on it was externally balanced which wasnt how it was in 1980. So I traded for an 86 flywheel and it matched. I have been told that all 1/2 ton gmc came 305 in 86. The motor has been freshly rebuilt because when I pulled it I found it has almost new everything. This is also what the owner told me. Remember I'm a wrecker driver and I was told this before he knew I was buying it and I fell at the time he had no reason to lie to me. Somebody please help me.

[raycow]

Any 86 or later engine has a one-piece rear seal and takes a flywheel with the small bolt circle. This is a year thing and not a 305/350 difference. You can not tell the year from the STAMPED code. You must look at the casting date on the top rear of the block. As long as you have the heads off, all you have to do is measure the bore to see if you have a 305 or 350. The 350 was definitely an option in 86, so whoever told you otherwise told you wrong.

ay

[Shanker1371]

Somone on this board said he was a dealer in 86 but either way it does have a smaller bolt circle I actually got to drive the truck it was in and it sounded really good no missfire no smoke. I picked it up in a wreck and the owner didnt want to pay to get it out. This being said I wasnt planning on pulling the heads. All i plan to do is a cam swap,intake and carb. I have the motor in right now but I did that so i could move it to my ne house. I plan to pull it out soon and Ill check the back of the block. Thanks