I Have a 1986 Pontiac Trans Am and tonight it spun a bearing from the sound of the horrible knocking and squeaking noise coming from the motor (although the oil pressure seems fine at 15psi for idle and it isn't throwing a CEL, how is that possible?). Since the motor is done anyway, I was wondering what it would take to swap a 350 in place of the factory TPI 305. If I migrated the 305's TPI to a new engine (which I would want to do to keep the stock look, no carbs or holley sniper here, don't want it), what would it take to make it run well? New ECM/ECU for a 350, new wiring harnesses, and all that stuff, or could the stock computer and wiring be used with a chip tune to upgrade it to the 350? If it's faily easy to do, the 350 with a mild 300ish hp would be perfect. This car is going to be my daily so I don't need anything ridiculously powerful, and I would like it to still run on 87.

 

A replacement L31 350 from jegs is 1800 shipped. Scoggin dickey sells the correct tpi base so you can transfer everything over. You'll need to follow the 305 to 350 thread on here for the rest but its a pretty straight forward swap.

 

Quite simple... the inputs from the sen-sores to the ECM are all consistent and within their normal ranges.

There's no code for "engine makes knocking noises" or "crank broke" or any such thing.

To make a TPI 305 into a TPI 350, you need a 350 (duh... just thought I'd not overlook that), a knock sensor, 22 lb/hr injectors or thereabouts, and a 350 "chip". Same ECCM, same wiring, same mounts, same EVERYTHING. For a stock one anyway. Won't be any 300 HP, most likely; a stock TPI 350 was in the 230 - 240 HP range, and most "rebuilt" 350s won't make even that much, but depending on what you want to do to improve it, you might be able to approach 300. Probably not, but maybe.

Various variations of 350s, such as 60s/70s blocks with 2-pc rear main seal, heads with different intake bolt angles or no accessory bolt holes or intake ports in a different place (L31), will require a few other odds & ends. Heads w/o acc bolt holes should be avoided at all costs.

 

I have a 350 short block from a 99 Silverado to use. 4 bolt main hydraulic roller block that I plan on putting a mild cam and head package in to make the 300 number. Wont be a factory L31 block.

 

A block is a block. That one would be 880 casting. Nothing unusual, spectacular, horrible, or anything else. Pretty ordinary really.

What heads? That's where the gotchas are waiting.

 

If you were here in GA, I have an iron 350 short block, iron stock heads, and a spare 700r4 I’d be willing to give you.

 

Not sure yet what heads and cam I'll be going with yet. I'm going to look for some on Friday at the GM swap meet in Carlisle PA, so if anyone will have any for a good deal, I'll be there