The Stovebolt Site Forums The Shop Area The HiPo Shop Differences between -86 and 87-95 small blocks

This isn't technically a pre-'73 question, but I hope someone can help anyways.

I have a '89 Suburban with a blown TBI 350 engine (cracked head led to valve seat rattling around in the cylinder). I have a good '85 350 that I can use to put into the Suburban. I know the heads and intake manifolds changed, but I'm not clear on any other changes. Right now I plan to get a new head, and use the good '89 head and intake on the '85 350. But I need to make sure the '89 accessories will bolt up to the '85 block. Time and budget is a little tight, which is why I would like to avoid a new/rebuilt engine or rebuilding the '89.

If I remember correctly, the main issue between the early and late was they changed the angle of the middle 4 bolts on the intake manifold. The block should be the same. Do a quick visual to verify.

Cheap quick fix:

you got to grind out the center 4 bolt's to make it work or you have too put 350 EFI head's on your old carbbed block. . .

proper fix later:

other wise Jeg's offer's and intake for both swap's EFI to carb and Carb to EFI. . .

Imagine that another 350 fail's. . .< boat anchor :hammering:

Mike

The flywheel is different. You must use a 85 on back flywheel. The 86 up has a counter weight on it.

86 up has the smaller crank flange for a one-piece seal. Also, center bolt valve covers became standard. Mounting points and bosses are the same from Generation 1 and 2 small blocks. LT1's (Gen 2) have reverse flow cooling.

I personally would look for a 94+ SBC in a truck and grab the Vortec heads and pick up a new intake.

Of if you are in a quick pinch, toss in the carb'd 350, pick up a holley fuel pressure regulator with return and plumb that to the carb. Then wire a relay to power the Distributor and to back-feed the TBI fuel pump through the priming lead as the computer will want to shut down the fuel pump without a valid tach signal. The TBI pump is a 1-bar (15psi) fuel pump.

The Vortec-head (L31) 350 started in '96 and ran thru '98 in the trucks and '99 in Tahoes and Suburbans. '88-'95 used TBI with the low performance TBI heads. The difference is also, as stated earlier, different flexplate and balancer, and a one piece rear main seal.

A great upgrade is a set of Vortec heads, a GM or Edelbrock TBI vortec intake, Edelbrock shorty header & y-pipe kit (made a big difference on mine), and a little more cam (since you're going that far into it), like this:
HYDRAULIC-Great in throttle body, crossfire or carbureted engine and 305 TPI.

Hyd. Hyd. 1000 to 5000
12-249-4 XE249H
lift .434 .444
dur - 249 260, at .050 - 206 212
centerline - 112°

That would make a killer torquey street engine, and running it up on my computer dyno shows about 324 hp at 4500 and 423 ft lbs of torque at 3000-3500, and 421 ft lbs of torque at 2000.

I had an 89 Suburban 2500 with a TBI 350, and was going to do this to mine, but ended up selling it to a friend of mine (it had rust issues) and got my 04 Suburban 2500 with the 8100 BB and 4.10s. Good luck with it.

Thanks Scott, the mounting points is what I really wanted to know. If all the mounting points are the same, I think I'll get a Holley TBI intake for the 85 and stick it in. Down the road I'll probably get a Vortec top end.

Also, it's mated to a Turbo 400, any issues, such as the flywheel counter-weight, that I need to be concerned with using an automatic? The 85 had a 700R4 slushbox on it.

You will have to use the older flexplate. Make shure the flexplate will bolt up to the converter before you put it in. If not you can drill it to fit.

This is the week I here a 24K Trans Am running prior to being
parted out. The engine is the LS1 5.7 Alum, with 4L60E trans.
The idea is to place it in the 53 Chev Panel. There are
a couple of early trucks with this setup albeit very top notch
restos. The pic's show the engine compartment width being
small with the steering column knuckled off very high up
to reach the box or Mustang II setup.
Would this be a problem? I also noticed the inner fenders
are modified for the air con and alternator.
Looks a lot tougher than older small blocks for install.

Sorry, hooked on to the wrong post.

Presently converting an 87 TBI 350 to a carb engine. Have a Wieand 4 Bbl manifold with the correct center bolt angles, and a Edlebrock 600cfm carb. plan to use a standard HEI ignition, and probably swap the 87 pulleys, which have both v belts and serpentine belts, to an all v-belt arrangement to match the alt, A/C, PS, belts, presently on the 350 in my 68 GMC.

ANYWAY, my question is this: The 87 engine has a 165 tooth stock flywheel, and was originally hooked up to a 700R4. Are there any fitment issues connecting that engine, with that flywheel to the TH300 that's already in the truck?