SBC 400 swap into a TBI 1989 suburban

[MechroMenace]

To start with my truck is eating coolant slowly but surely and its also quite fat and slow, so my idea for a solution is the sbc 400 sitting to the side of my friends house is mostly complete its missing the crankshaft because it ended up with a rod knock so they took the crankshaft out and it went to a machine shop never to be seen again. they said they sell it to me for 200$ which doesn't seem to bad for a relatively complete motor. But I'm planning on getting another stock crankshaft and I'll be doing a light rebuild on it, I'll get one of those rering kits and freshen it up a bit.

From what I understand thats involved on the swap, I'll have to get a new flywheel because I guess the weight isn't large enough the one in my 89 350. as for the intake it has a carb intake on it so I think I can get a adapter for it and it should be good, but at the same time from what I understand is that the carb and tbi intake are pretty much the same minus the fact that the center bolts are on different angles so I should be able to with a little drill work be able to reuse my tbi intake right? also from what I understand all my accessories should move over no problem either, there may be one or 2 bolt holes that i'll need to drill and tap. other than that everything thing else should bolt on just like it was its original home.

the other thing i'll need to do is possibly the ultimate tbi mods for a little more air flow and an adjustable fuel pressure regulator, and I also need to modify the computer to accept burnt chips so I can tune it a little bit. I've got the moates APU1 so I shouldn't have too much trouble finding or making something that will run it smoothly.

The engine will be going in front of a sm465 with a 205 transfer case and behind that is a couple of 10 bolts axles. so I'm not trying to get a ton of power out of it but I'd like it to be able to get out of its own way and out run a bicyclist. So what are your guys thoughts on this? am I on the right track or is there anything that i'm overlooking?

 

[dyeager535]

The TBI motor uses a one piece rear main seal, flywheel bolt pattern is different in any case. I think it's a step backwards (leaks) to go with the older motors, but for a 400, I don't think there is an option without stroking a 350 or aftermarket block. So moot point if you are fixated on the 400.

Coming from a friend, I assume you can take their word on condition. How many miles are on it? Need to know your expectations from the motor...hard use all the time, rarely driven pleasure vehicle, etc. I would really talk with someone that deals with machine work to find out what it will take, depending on how you are going to use it. I'm kind of OCD when it comes to this stuff, I'd prefer to put it together for longevity.

Add up all the costs. Then see what that is going to cost you vs. a crate motor. A block alone, really saves you nothing. The more parts you can use, the lower your overall rebuild cost, and the more likely it is that a rebuild will be worth it vs. a crate engine.

I know you can make the later bolt pattern intakes fit the earlier heads, just never tried it, it doesn't seem complex however. I'm thinking not using an adapter would make things such as throttle linkage easier.

I don't think there are any accessory bolt issues until you start talking really old (like 60's) small blocks. AFAIK pretty much every head made since then has all the holes drilled and tapped. Not aware of any other mounting differences in regards to the block.

Adjustable fuel pressure regulator is not my ideal solution. If you want to adjust the stock one, it can be done, it just takes a TBI gasket kit since you'll have to take the top of the Throttle body off to get to the regulator to mess with it.

From all I've ever seen, the TBI motors are fairly respectable for what they are, power being subjective, but normally TBI rigs are geared pretty decent, without huge tires it should be able to get moving pretty well. You might gain a fair bit of power if you fix the coolant leak, assuming it's an intake gasket. It took me long enough to find where my coolant was going, pretty sure it's what eventually lowered the oil pressure. My mileage went down significantly too, so obviously there is power being lost.

 

[MechroMenace]

alright sweet, thanks for the abundant information. From what I understand they had recently rebuilt the block before taking it back out of the truck I but they had it in a truck they used for off roading a lot, I can still see some of the cross hatching from when they had the block machined and the pistons have a very light brown coating from oil it definitely looks better than some of the other motors I've taken apart. I'm also not too worried about leaks I mean I can a least replace the 2 piece rear main without removing the engine or transmission.

The main reason though I'm considering the 400 is that I want some more power with out getting a big block because I don't want my gas mileage to go completely out the window. Its also kind of convenient at the moment, right now I'm working two jobs and I don't have a spare car at the moment well I might in a couple of weeks I've almost got my dads cj7 finished but I really don't want to drive it because if I manage to hurt it I'm gonna feel sick. Since the 400 is mostly complete minus the crankshaft all I need to really do is replace the crankshaft and clean it up a bit, I can also swap it in and have it running within a day or two once its ready and I can be back to driving the truck quickly. My other option though is to drive my dad's truck or jeep while I pull the motor out of the Suburban go though replace the head gaskets which I believe is the source of the leak and hope that I don't need to do any machine work to the heads or ill be driving one of my dads vehicles for a few weeks and i really don't like driving other peoples rides because they're generally nicer than mine and I'd feel horrible if I managed to get in an accident with one of them.

i'll also look into adjusting the stock fuel pressure regulator, I thought they welded them in place or something like that so they wouldn't adjust.

It seems like this should be a fairly straight forward swap then, my friend will be back in town in a couple of weeks, i'll get the motor then, and I'll take it apart and post what I find. till then I have a jeep to finish in the mean time.

 

[dyeager535]

There were a couple designs of the fuel pressure regulator, IIRC both can be adjusted however. I used shims (washers) to bump pressure up, but from what I saw, the pump quickly becomes the limitation. The pumps we had, brand new Delco's, wouldn't push more than 14PSI. Last time I looked the '88-95 trucks were still pretty plentiful in the yards, you could always grab an FPR off one of those (or a couple) to play with, so you don't have to take yours down.

You'll need to tune it anyway, so adjusting for the increased fuel pressure won't be a big deal. An EP381 pump would allow you to run as much pressure as needed, and is a direct replacement for the TBI pump.

Tough call with the head gaskets. I'd hate to put them on and find out that isn't the problem, or that they don't seal well. Never having torn down a motor with a rod knock, I have no idea how much damage that causes on the entire reciprocating assembly on that rod. That would probably be my major concern, since it was already running. If that was the only problem at teardown, and it was low mileage, and it didn't cause irreparable damage then I don't see why throwing it back together isn't viable.

I believe Blue85 deals with machining all the time, I'd ask him.