question about SBC

[Dave]

I am working on replacing the ailing 350

in my 71Z I have found a 1986 350 with the

1 piece rear main seal. I at the moment

have a 75 350 with a TH350 will my flex

plate and balancer work on the 86 engine?

If they don't what fits? The 86 has a flex

plate on it but the flex plate has a large

weight attached to it and the balancer has

been removed. How does this engine differ

from the early 350's?

Dave....

[John Scott]

Hi Dave, A little out of my territory here, but I have a closely related little brother, the 4.3. In '86 chev changed to a one piece seal to reduce leakage. Earlier bolt patterns were 3.58" diam, so they won't fit. 86 and up were 3". You have to use a weighted flywheel or flexplate with these engines. They can be found with either the 12.75" diam or the 14". Then choose the matching starter. The others can help you choose which one fits best into the Z. I can't offer advice on the front damper. I'm running a Fluidamper. It's a good piece, but again I'd check your application. Good luck.

John Scott

[Guest Anonymous]

I dont know... seems that the crank would have to be different to fit a one piece seal. The flywheel mating surface would have to be of smaller diamater and would require an externally balanced flywheel unless the weight has been moved inboard. Good Question

 

Call Summit Racing1-800-230-3030 and ask them about the flywheel and balance they will probably have a part # or will be able to tell you if your parts will interchange.

 

 

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He sent me to get the Jedi

[Mikelly]

The 86 and Newer flywheels are significantly larger in thickness and all of them are counter-balanced. As to the rest of your questions... I don't knw, but someone out there must have installed a later model 305 or 350.....

 

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"I will not be a spectator in the sport of life!"

mjk

[John Scott]

The info. I gave about the bolt patterns comes directly from chevy. You can't fit earlier (85and older) flexplates or flywheels on the newer cranks.(86 up) You can, however put the two piece crank into a one piece block with the adapter offered by chevy. This also holds true for one piece cranks into 2 piece blocks, same adapter. The earlier cranks with the larger diam. bolt pattern are recommended for max effort engines. You are talking a lot of ponies before this would be justified though. Find a Chevy power book for more details.

John Scott

[Dave]

Thanks for the info guys. The engine that

I am looking at is a fresh 1986 350 with

flat top pistons and 202 76cc heads. the

cam in this engine is the 327 350hp hyd.

I figure the compression is 9 to 1 and it

should be about 300hp. I can see that I do

need to use the 86 168 tooth 14" flex plate

but I still don't know if the th350 converter

will bolt up and if my 6" harmonic balancer

will work. I have built all my own engines

in the past but at $450 this is hard to pass

up. it is a quality rebuild that was going

in a RX7 until the guy lost interest in the

project.

 

Dave....

v8-240Z@juno.com

[pparaska]

Man, that is one lazy cam at low rpm (L79 327-350 cam) I had one in a 10:1 327 that was in my 70.5 Camaro when I was in high school (20 years ago, kids and it felt like a 6 cylinder until about 3000 rpm, then it came on like gang busters. Even ate up a GT500 Shelby Mustang to about 90 with that car (3.08 open rear, stock Turbo 400 and converter). This car was not optimized for the cam though. It needed a stall converter and some higher numerical gears.

 

I don't think that cam is a good choice for a 9:1 motor. It has a bunch of overlap. Low BMEP and all that. Cams are cheap though, so you could change it out for less than $100 with lifters.

 

That engine sounds like a good candidate for the iron or aluminum (64cc) Vortec heads. You could raise the compression and get some good flow and torque out of it with those.

 

Regards,

Pete