1986 crate motor

[lanconcj]

I am looking at crate motors. The years range up to 1985 and then from 1987 to higher years. They seem to skip 1986. Is there something different about an 86 oil pan or trans. bolt pattern?

[bradford]

If Im not mistaken, 86 was the year they changed to throttle body injection.
This is also the year of the one piece rear main seal.
There are differences specific to these engines starting with the crank has a different bolt pattern at the back for the flywheel and the bolt in the front where the harmonic balancer is smaller.
Also, some have no mechanical fuel pump provision.
I believe the GM Goodwrench does have the fuel pump provision. I know all of this because I just put a new one in my truck this weekend.

[gchemist]

Trans and bolt pattern are the same. Heads went to center bolt valve covers. 87 and later blocks have provisions for roller cams. Most 87 and later blocks should have provision for a mechanical fuel pump.

86 had one piece seals and outter bolt style valve covers. It was a hybrid motor with parts from two generations.

[Your41Plague12]

Although if you want to run a mechanical fuel pump, I'd do some research first. I had what was originally a TBI motor in my truck at one point and it had no provision for a mechanical fuel pump. The block was solid there, no block plate. So if you want the 1 piece rear main seal, go with an earlier one. You can always add a block plate and run whatever fuel pump you want.

[lanconcj]

Thanks. I am still shopping. I want stock but a hot rod would be fun also.

[motornut]

thought the tbi cams didn't have lobes for stock pumps,thats why solid there

[68c10owner]

As already said, the only real difference from 85-86 is the crankshaft went to 1 piece seal. TBI didnt come out till 87` on the trucks and up to 1986 still had the old style perimeter valve covers and the regualr intake manifold bolt pattern, not the center canted bolt holes. all you have to do is get the 1985 crate engine which will be a 2 piece engine and get a flexplate for a 2 piece seal engine and your good. Just remember that some of the later 80`s 350`s had external balanced flexplates so be carefulle. I put a 93 TBI 350 in my old 75 gmc with a carb and had to get a 93` flexplate because of the external balance.

[Dave Kay]

Reviving this post because I'm in the same boat; have a 1986 LT9 (M) in my 1-TON GMC 2wd pickup that needs to be re-engined.

Looking at GM crates at JEGS and guy says '86 is a transition year and I need to be double sure I order the right engine--- either 2 piece or one piece rear main CS seal.

Short of pulling the engine right now, I thought maybe somebody may know if there are some external clues to help determine 2 piece from 1 piece blocks.

Understood; flex-plate and bolt patterns differ as well as oil pan.

Did GM block ID Wild-Goose-Chase and only thing I came up with was my FRONT PASS-SIDE block # V0702UPY, which is supposedly the date of the block manufacture. Running the UPY part of the code I get:

UPY '86 350 Truck 160hp LT-9 4bbl C/20C30 - that's me!

AND

UPY '90 350 Truck 200hp L-05 TBI ALL MODELS 4x4

Question; any guesses on how reliable this info IS and would it be safe to conclude that these are ONE PIECE RR main CS seal blocks?

Also, I believe that '90's trucks ALL went to TBI/Vortec induction and hence; my stock 4bbl intake will not fit this setup. Has anyone else been caught in this 1986 dilemma? Results?

FWIW: Looking to keep this truck bone-stock 'cause I have to please the Calif Smog Nazi's and anything other than stock will cause miscreants to suffer a thousand cuts.

Also, being as today is Sunday I will give my GM dealer a call tomorrow but experience shows that at times they are not so helpful unless you act like a serious parts buyer... OK, how 'bout an intake manifold gasket for your trouble sir?

[80SPORT]

The 86 was a transition year as mentioned.

1 piece rear seal but old style intake mount..and mech fuel pump.

We used lots of the 86 GM service replacement motors because you would get the 1 pc rear seal....no more rear oil seal leaks ...but could use the old style intake and a mechanical pump.

All you have to do is use the i pc flywheel/flex plate and it fits back to 1955.

The part # in my files is 12568759 for a brand new long block.

[Slonaker]

I have actually done this swap on my '86 several years ago. I bought the cheapest 350 crate motor from Summit, Part Number 10067353 (Jeg's has it with free shipping right now). It says it is for '85 and earlier, and it has the old style 2 piece rear main seal. The only thing I had to do to put it in my '86 was to buy a flexplate intended for an '85. The '86 and up with the one piece rear main seal used a different flexplate. Everything else swapped over with no issues. Even the weird 305 exhaust manifolds that have a different bolt spacing on the bolt closest to the firewall were re-used.

Oh, just remembered I had to buy an adapter from the plumbing dept. at Lowe's to fit the temp gauge sensor into the older block. That was two or three dollars. I tried a correct sized sender from a '70s model, but it made the gauge read wrong.

Slonaker