I've currently got a 1981 305 carb'd, and got the opportunity to get a 1990 350 TBI with a blown engine.

Questions for you all now.....

If I take the TBI intake mainfold and drop it on top of my 305, swap over all the sensors and doohickeys from the broken 350, is the ECU going to handle it, or will the different displacement throw it a wonker?

Are ancilliary bracket mounts going to line up, or am I going to be using the plasma cutter and wire feed welder at work a lot?

Cooling system? I think they're compatible, am I right?

The biggest problem is that the 350 block is FUBAR, so I can't just swap my heads over, which is what I originally thought. But now it involves a complete engine swap.

I'd much rather use my current 305 block than have to shell out for a 350 as I'm on a VERY restrictive budget.....

Any questions? ;)

I believe the 350 & 305 TBI motors used different injectors & computer chips.

It will run, but not at optimum levels. If it is a beater, I say go for it. Like jim said, you need a 350 throttle body and prom. I think the tbis unit is the same, but injectors are larger flow for 350. The intake will not just bolt up correctly either. Some people just wallow out the bolt holes to match the old style heads, but a adapter for the top is cheap. Also you have to keep flywheel/ flexplate with the righht motor.

Ok, so what you're saying is that the computer will go all screwy if I tried using the 350's intake and computer on my 305?

So I'd need to go get a 305 computer unit and intake to go on mine? Ugh. Wrecking yards around here are next to useless. And as expensive as buying new.

How bad of a Mickey Mouse effort would it be just to put my carby'd engine in as it sits and hook it up to appropriate wires (elec choke, alt wires, coil power, temp and oil sending units, etc.) so that it works? Would I just have to take the bulb out of the "Check Engine" light and run with it?

I'm trying not to get the wife too pissed off at me with this conversion. The way she looks at it is that the truck works fine now, why do I want to mess with it? Well, honey, it looks like a total wreck and it's about as comfortable as a church pew.......:crazy:

Oops, I think re-reading everything I've got a little confusion going here.

The truck has a 350 with a FUBAR'd block in it now. I'm putting an older (currently) carby'd 305 block and heads in it and planning on using the 350's intake and TBFI on the 305.

Does that explanation change anything?

Sorry for any confusion created.

The intake is not a direct bolt on, it will have to be slightly modfied by opening up the blot holes or you could put a carb to tbi adapter on it. I would say to try to keep thr tbi if possible. It will run and prolly run good, but it will think it is a 350 therefore it will feed too much fuel and such. You will also have to deal with the knock sensor, I don't think there will be a bung for it in you old block. Not a big deal though. The whole computer does not change from 350 to 305, just the prom. Hope this helps.

Thank you, ed. So what you're saying is basically if I take a Dremel tool to the bolt holes it'll fit? If that's the case, I've done worse bodge jobs than that before!! :D

As to the knock sensor, I think I'll just let that hang. I'm not too worried about that.

As to the computer allowing too much fuel in, wouldn't the O2 sensor take car of that? Or is there one on these early edition TBI's? I'm going to be using the 350's exhaust manifolds as well on the 305 (mine are single tailpipe, the Silverado's are dually's).

A dremel to the intake should work, just don't remove any more than needed to get the bolts to work, I think it is only the center 4 bolts, can't remember.

The knock sensor would do fine if attached to a motor mount. Weld a bung to the mount(block side) and it will function almost as good as in the block.

The O2 sensor will only make up for so much, maybe enough, maybe not. The truck will run and the difference might not be noticeable. I have heard it both ways. I have never done it myself without correct parts.

The four center bolts stand more upright than with the older style heads. You will have to elongate these but the bolt head will still not seat all the way down due to the angle. Also the center back bolt on the passenger side will be a tight fit so you may have to modify a wrench to get it tight. And forget about torqueing a couple of them. You have to do it by feel. Your ECM will be fine, but you may have to change your PROM out. Try it and see first to see how it runs. Other than the intake and maybe the PROM it should be a pretty straight forward swap.

Kevin

Thank you Ed and Kevin.

You've given me hope that this won't be quite as much of a bodge job as when I stuffed a Mazda RX-7 rotary into a Chevy LUV 4WD... :lol:

End product won't be nearly as much fun, but the process looks like it will be a lot easier.

Thanks again. I'll keep a running photo diary of the process once I get going on it. Think it might be closer to spring before I get started, though as the temps have dropped a lot in the last week around here.

Well, a little update on my story here. I got the Silverado home and plates on it.

http://www.boomspeed.com/bofh1968/OCUK/truck/90chev2.jpg

I'm beginning to resent Minnesota for its licensing practices. I had to buy the entire 2006's year of tabs only to have it expire again in March of 2007. I bought the tabs on the 16th of Jan 2007. :crazy:


Anyways, I've decided that after 13 years of marriage and my wife running off with the tax return as soon as it hit the bank account was enough. This year I'm claiming it as MINE!!! :metal:

Found a truck in the wrecking yard that the original owner had Chevy put a brand new engine in it. It's a 1991. 1,000 miles later he swerved to miss a deer and flipped it into the ditch, writing it off. The wrecking yard is going to sell me it with a 3 month warranty on it.

So I'm not going to have to dismantle my old 1981 and try and bodge its engine into the Silverado!! :c2:

It's still too cold to do much of anything on the truck. I climbed up into the engine compartment and got it stripped somewhat down today as it actually warmed up ABOVE zero for a change. As soon as I can find my thermal coveralls I'll be climbing under the truck to remove the starter and undo the other 4 tranny-engine bolts. Then I'll be pulling the old engine out in preparation for the new one to go in.

Oh, and a bonus!! I found my remote starter that I bought for my Neon right before I sold it!! I thought I had left it in the trunk and the new owner got a freebie. But aparently I threw it in with a bunch of other stuff and misplaced it out in the nightmare that's my garage. So as soon as I can remain warm long enough to finish the install, I'll be hooking it in. So as soon as I get the new engine all hooked up, I'll have remote start, remote central locking, and remote power windows!!:c2:

So a big step up for me from the old 81 that was manual everything and a non-functioning AM radio!! ;)

a friend of mine had a 89 gmc 4x4 came out with a 350 tbi in it supposedly had a goodwrench crate engine we pulled it out and it was a 305 it ran fine we really did think it was a 350 and it used all the computer and stuff from the 350 over on the 305, we replaced the 305 with a police interceptor 350 out of an older caprice which worked fine i don't think you'd have a problem with using the 350 tbi stuff on the 305

Use the carb intake get a tbi adapter from Trans-dapt. The TBI unit will function fine. Many third gen Camaro owners swap out the stock 55LbHR 305 injectors for the 350
injectors anyway. The ECM will not matter the Basic EEPROM
will work fine. Happy Motoring