Seanmay1

This isn't for a 3rd gen, but i thought maybe some of you guys would be able to help me out on this.

My uncles truck is a 1990 silverado, 350 TBI. Motor has almost 300K miles and is about wore out. He has a older 350 thats in good shape but wants to keep his TBI. How hard would that be? Do they make a spacer to bolt the Throttle body onto a spreadbore manifold? or a manifold for the 87 and back motors that use the throttle body off the trucks? What other things like sensors and all would we have to switch over? Will the distributor out of a 90 motor work on the old motors?

scribbles

can you elongate the holes and mout the tbi manifold to the older heads?

Seanmay1

I have thought about that, because u can do that on the older intakes to bolt to the newer motors. But i remember seeing somewhere that u couldn't do that with the newer intake to work with the 87 back motors

Fast355

iTrader: (2)

I elongated the 4 center bolt holes in the stock TBI intake from a 350 to fit onto my 1983 305 in my van.

Seanmay1

Well i guess that will work, do you have any pics that show what all u did?

dimented24x7

iTrader: (2)

Once you get the manifold in place on the older motor it'll be clear what needs to be done as on the older heads all the bolt holes are at the same angle. On the newer heads, the angle of the four center bolt holes was changed to provide more clearance for the pushrods that run directly behind the bolts there. You will need to use a dremel or some other tool to cant the top and bottom of each of the holes so the bolts can pass thru them. Also, using angled washers would also be advisable as the bolts will no longer have full contact with the intake manifold. IIRC, the angle needs to be something like ~14.5 deg. The last thing to watch out for is that you dont bend a pushrod with one of the bolts in the center. The bolts get close to them there.

Seanmay1

cool thanks demented and fast355, im sure we can handle that.

90c350

Just get a tbi to carb manifold adapter and you'll save yourself the time and hassle!! One thing to watch for is the flywheel or flexplate. Is it an auto or manual tranny?? You will have to get the right one for the older style crank. Other than that it's pretty much a bolt in. I currently run a 1980 350ci in my 1990 tbi truck. Very easy swap with some very minor details to watch for. Only other thing might be the tuning issue's depending on what cam is in the older engine?? Hope that this helps?

Seanmay1

its a 700R4 tranny, so im sure the flywheel off the older motor will work. Do you happen to have a link to the adapter? I for some dumb reason couldn't find one.

I'm sure we will have to get it tuned but if thats the biggest hassle then I will be happy

va454ss

iTrader: (1)

The 90 454 pickups came with a spreadbore manifold and an adapter for the TBI. There are quite a few around as most of the 454SS guys remove em.

They were also used thru the mid 90's on HD trucks with manual trannies.

Fast355

iTrader: (2)

Alot of marine enignes had the same adapter and even some of them had a 2" bore to square carb flange adapter.

va454ss

iTrader: (1)

Yeah, I recall you posting a pic of one. Did you ever figure out the flow of the injectors?

Fast355

iTrader: (2)

Only that they are bigger than 110# @ 32 psi and came on a 454 engine making 385-405 HP at the prop shaft (similar to SAE NET HP)