need some expertise here

Hello fella's, I have a question, I would like to get your thoughts. unfortunately I dont know too much about building motors, however I am looking to possibly build a cheap 350 for my 1986 IROC-Z. My question right now is, can I use my current TPI intak manifold off of my stock 305, on a 350? I have been told two conflicting things 1: you CANNOT use a 305 intake manifold due to the heads being slightly different, preventing a proper fit/seal 2: I have read/heard that the intake manifolds ARE interchangeable. Now once and for all, can someone tell me which is right?

yes a 305 and 350 manifold are interchangeable. either use your 305 heads on your 350 block, or find 350 heads that are 86 and older. i think it was in 87 that the 4 center bolts became canted, and your 86 manifold wont work on anything 87 or newer.

ok, pardon my ignorance here, but what is the difference between the 305 and the 350, if you can use the same heads, and block?

cubic inches

well outside of the block there exactly the same the bores are differnt some ppl use teh 305 heads cause they have a small combustion chamber like 57cc or something i dont remember , but its for high compression

actually there 58cc, but ya they'll give ya higher compression on a 350. they dont flow that great, but there good for an average street car.

well, dont know how much money you have to play with or nothin. but if your building the engine from scratch, i suggest a pair of vortec heads and a TPI/Vortec baseplate from SDPC. together they are less than 800 bucks. alot less if you get the heads off a wrecked tahoe or something.

but if you are on a budget, the guys are dead on, 86 and pre-86 heads will work with the intake you have, anything after 87 youll have to get an 87 or newer heads. but vortecs are different in and of themselves, and to run those you need the special intake from SDPC. also, the injectors and perameters of the computer on the 305 are slightly different than those used on the 350, so it might run a bit lean, grab the injectors off a 350, and the chip while youre at it, and put them in and should run fine.

difference between the 350 and 305, as far as the short block, is the bore, and the pistons. the crank, rods, mains, dimentions, mounting points everything is the same. although, one critical point is that the water passages are different, so if you try to bore a 305, with its small 3.736in bore out to a 350, 4.00in bore, you will hit water passages, and ruin the block. so not worth the effort.

Well if I had any any info it was already posted..LOL

ok, i understand now, I think I will prolly just stick to my original idea, and just buy a 350, be it a short block or long block , and just go from there. as far as the computer goes, can the current computer be reprogrammed to accomdate the new motor, or is a new chip necessary, and further more, if I were to get a new chip, would I be further ahead to just get a high performance chip, such as hypertech, Jet powertech?

your computer will work with the 350, but you'll probly get a check engine light for 34 or a lean mixure code 44. it wont really affect performace, it's just annoying. either get a prom from a 350 or get a custom burnt chip.

bingo, the computer you have cannot be programed. the information that you change, and adjust is in the chip. so for the 350 you will want the chip from a 350, or get a custom burned one. although i have heard of the 305 chip running a 350, but id suggest the 350 chip.

while we are on the subject of 350's and computer's, what we would need to be done, as far as the computer is concerned, to install an LS1? just a new chip, or would I need the whole computer?

you'd have to have a pcm and the wiring harness for an LS1

I see, well, how about some opinions. what is the main advantage of installing an LS1 over, say just building a 350? I have read a lot of information on the LS1 swap over the last few days, and it seems like alot of work to do specifically for that engine. how would a built 350, with say a ram jet compare? what would some of you folks do in my situation?

well, they both are pretty respectable engines. the LS1 has prooven its self and you would definately get bad ass points when you popped the hood. i am personally an old school kinda guy, i like the tec of the new stuff, combined with the old school hardware. but the all aluminum LS1 would be much lighter than a regular iron block and headed 350. really the only major advantage i can think of between the two. the old style 350 would definatly be easier. but hit up www.fbodymotorsports.com about the details of installing an LS1, they actually sell a package kit with al the parts you need. and can probly supply the engine and tranny, and harness and all that. they have great prices too. at least while i was down there.