flywheel question- one piece seal vs. two piece seal.

[crossy]

Hey guys I have a bit of a problem solver question here. I'm trying to install a 1979 350 in place of 1986 engine. the 86 engine had the one piece rear main seal. the truck is a stick shift truck and has the 13.5" dia. flywheel in it. the 86 flywheel will not fit the back of the 79 engine. the bolt pattern is totally different and and the center hole on the 86 flywheeel is smaller in diameter than the back of the 79 crank. I thought i could just get the crank hole bored out on the 86 flywheel, but the bolt pattern is different also.
QUESTION is simply this. can i just install the 85 and earlier style flywheel ?? the truck has the hydraulic clutch. I was pretty sure the trucks started using the hydraulic clutch BEFORE they went to one piece main seals so this should just be a simple swap right???
At the present time i dont have an early flywheel here(usually do), but i want to be sure before i purchase one somwhere.

thanx , crossy.

[Slonaker]

I'm not sure if this helps or not, since I have an automatic, but I used a flexplate for an '85 when I changed my one piece rear main 305 for a 2 piece 350. The Autozone website lists a hydraulic slave cylinder for both '85 and '86, and they have the same part numbers. That implies that they were both hydraulic clutches. They list two different flywheel part numbers for '85 and '86, so it sounds as though you could just use the '85 flywheel with the new engine.

Slonaker

[oldpurple]

This is a bit of a off topic post but I'm hoping someone might see this and know. I'm sort of doing the opposite of you, I'm replacing the '79 350 in my truck with an '85 305 and I'm wondering if I will run into this problem?

Or is it just '86+ cranks that are one piece seal and therefore different?

Sorry for the hijack

[Srubydo1986]

last i hear the 87 up was different casue of the fuel injection. but if you need any picture i have a 86 manual pressure plate that i get get a pic of one new and the other is old ones from an 83 the had a 327 and the other out of my 86 that was a 305.


let me know if you need pictures but im not to shure of the questiion tho.

[crossy]

It is indeed an 86 up issue . I know 85's weres not part of this problem. the only thing you will encounter is dipstick issues. It's harder to cure the dipstick issue if you are going the way i am because of the stupid upswept exhaust manifolds they started using in 82.
I think the 86 up flywheel bolts MAY?? be a diferent size too. crossy

[jimfulco]

http://www.sdparts.com/catalog/trans...mallBlock.aspx shows what GM currently offers for stick-shift small-blocks. Sounds to me like you need to get one from a pre-'86 vehicle that has the same diameter and presssure-plate bolt pattern as the one you're replacing.

If you're going yard-shopping, beware that flywheels from some (not all) 292's have bigger bolt holes (1/2") than the rest (7/16"). Also, some of the 14"-diameter flywheels were drilled for the smaller 10.4" pressure plates.

[Slonaker]

Originally Posted by oldpurple

This is a bit of a off topic post but I'm hoping someone might see this and know. I'm sort of doing the opposite of you, I'm replacing the '79 350 in my truck with an '85 305 and I'm wondering if I will run into this problem?

Or is it just '86+ cranks that are one piece seal and therefore different?

Sorry for the hijack

The '86 and up crankshafts are the one that are different, so you shouldn't have a problem with that.

The problem I see you possibly having will be with the exhaust manifolds and dipstick. The 305 heads use a different bolt pattern some or maybe all of the time. You know how a couple of the exhaust manifold gaskets in the set always have a space for two different bolt holes? That's the issue. The spacing is different.

Look at the double bolt holes on the number 8 cylinder in the photo below. It is drilled for both.

http://www.lowcostengines.com/images/10067353.jpg

Your best solution, IMO, is to use the exhaust manifolds from the '85 305 so that you won't have manifold or dipstick issues. I assume headers would avoid the whole issue, but I don't know for sure. I don't own anything with headers, and never have.

Slonaker

[oldpurple]

Originally Posted by Slonaker

The '86 and up crankshafts are the one that are different, so you shouldn't have a problem with that.

The problem I see you possibly having will be with the exhaust manifolds and dipstick. The 305 heads use a different bolt pattern some or maybe all of the time. You know how a couple of the exhaust manifold gaskets in the set always have a space for two different bolt holes? That's the issue. The spacing is different.

Look at the double bolt holes on the number 8 cylinder in the photo below. It is drilled for both.

http://www.lowcostengines.com/images/10067353.jpg

Your best solution, IMO, is to use the exhaust manifolds from the '85 305 so that you won't have manifold or dipstick issues. I assume headers would avoid the whole issue, but I don't know for sure. I don't own anything with headers, and never have.

Slonaker

I will definitely be checking this out when both engines are out, they do have different manifolds now but I'm not sure about the holes in the heads, and with different manifolds I assume that requires a different dipstick? I was hoping to use the current truck manifolds that go downwards just so the exhaust would bolt up, but If I have to use the upward ones I'm sure I've got enough exhaust pipe between both vehicles that I can rig something up that will work.

[crossy]

if you change to the early manifolds you have to change your headpipe. the dipstick problem MAY or may not be there depending on which side of the engine it is on. the problem stems from location in the Oil pan itself so using the 85 manifolds will not solve the problem.
I THOUGHT by 79 they had changed location to the same as an 85 though. check it out first.
headers make it go away:-)

[Slonaker]

Originally Posted by crossy

the problem stems from location in the Oil pan itself so using the 85 manifolds will not solve the problem.

Why not? He is using the '85 engine in an older truck. Not the other way around...

Slonaker

[crossy]

sorry, guys but i have swapped WAY TOO MANY engines and manifolds to remember which way is which. i merely said CHECK IT OUT before you commit. you can do it while the engine is still on the ground or stand.
I only have one stock chevy small block truck here right now and it's an 81 and I've said many times DO NOT use an 81 to compare anything because they are a cross over year and MANY parts are similar to 1980 NOT 1982. crossy

[Pyrotechnic]

I remember when I switched to a Vortec block, the old starter would not work with the new flexplate for some reason. I didn't not have time to mess with making comparisons and figuring out if there was a difference in teeth or diameter. Just something to keep in mind though.