Turbo Crank Part # / 84-85 block .vs. 86-87 block

[RBE17]

Normally I would try to find answers to these questions on gnttype.org. Any help is appreciated.

1) What is the part # for the turbo crank w/ the rolled fillets? What years were these cranks produced?
2) What are the major differences between an 84/85 block .vs. an 86/87 block? How much abuse can each block take?

Thanks,


Steve.

 

[Dwayne]

All 86/87 blocks were 109's. There were 2 different 84/85 blocks. The production 4/5 blocks were weak like the NA 4.1 blocks. You can run 15 or so lbs pretty safely. They would make a great street motor. My dad and I both have split 4.1 production blocks at around 18 lbs. There were also 4/5 turbo blocks. They are just as strong as the 109 blocks. The lifter valley looks kinda rough when compared to the 109 blocks but I have never seen problems with the lifter galley. The main concerns on these blocks is in the bottom end.

If you use an 4/5 turbo block; here are some things to remember:

1. the deck height is a little taller on these blocks. (I decked my block so I can use the 6\7 GM headgaskets)

2. if you use head studs; be sure and order them for the 4/5 block as the length is different than the 6/7.

3. You will have to drill and tap the front of the block for the turbo oil drainback.

I'm not sure of the part numbers that you ask for but I'm sure someone will chime in with them ......good luck

 

[Silver 6]

Buick made changes in the blocks almost every year. The 83 was different from the 84 and then the 85 and then the 86/87(109).

Major changes were to the oil passage drillings in the 83 to the 84 castings which also brought a change of cam bearings. This year Buick also changed the base circle on the cams .030" and made the lifters and push rods each .015 longer to compensate. I found that out because I have a few NOS 83 non-turbo cams and I wante to find out why they were different.

The 84 to the 85 casting change brought the 20 bolt oil pan in place of the 14 bolt.

The 84-86/87 casting(109) change brought the different casting to the lifter valley which most people believe is stronger and holds the entire block more rigid. This block has a pad cast on the lifter valley wall above the timing cover. The pad has a hole drilled in turbo applications and not in N/A (carb) applications. The 109 block also had a slightly lower deck height which was used with a composite head gasket which was thicker and maintained compression ratio without a change to the head chamber or piston dish. The deck on the 109 block has the head bolt threads recessed deeper in the deck and requires a longer head bolt to fit.

No one has been able to find any differences between a "turbo" block and a "N/A" block of the same year. Members of the gnttype site took samples of both blocks and found they were cast of the same mix of cast iron.

The turbo cranks were the same from 78-89 with the minor difference of the 78 having a slightly smaller hole for the balancer bolt.

The N/A 3.8 crank was #1260877.

The turbo 3.8 and N/A 4.1 were #1260873

There were several casting numbers used, but I don't have a listing number for those and they didn't vary between turbo cranks and not. Buick just pulled some castings for the extra rolling and gave the new part number.

 

[cool 84]

Cranks are the same. According to what Duttweiler told me, the main webbing is just as strong in the 84-5 blocks as the later ones. I've always used a girdle so I don't have any input. The biggest difference is the taller deck in which you use the stock steel shim headgaskets which hold better than the later ones anyway. The threads for the head bolt holes come all the way to the deck so it's a good idea to chamfer the holes and use head studs. 84-851/2 use 14 bolt pans. 85.5 use the regular 20 bolt. The 84/5 blocks used a different front cam bearing but when rebuilding just order bearings for the 86-7 if you plan on swapping cams.

From the tests I've seen, there is no such thing as a "turbo" block.