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externally balanced 89 Chevy flywheel interchangeability

General engine tech -- Drag Racing to Circle Track

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Belgian1979
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externally balanced 89 Chevy flywheel interchangeability

Post by Belgian1979 »

This is about a block I found which could fit my purpose, however it's a one piece rear seal Gen 1 sbc. So the crank is externally balanced. It also has a flex plate. Would an off the shelf flywheel for a one piece rear seal block work with these or does the crank need to be rebalanced in that case (with the flywheel)?
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BillK »

If the flywheel is for a 1 pc seal block it should be fine. None of them are perfect but they are all supposed to be within the factory tolerance which is fairly broad. By the way, the crank is only externally balanced in the rear. The front is still neutral balance like most other small blocks.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by ProPower engines »

BillK wrote: Thu Apr 29, 2021 2:35 pm If the flywheel is for a 1 pc seal block it should be fine. None of them are perfect but they are all supposed to be within the factory tolerance which is fairly broad. By the way, the crank is only externally balanced in the rear. The front is still neutral balance like most other small blocks.
Flywheel balance can be hit and miss for these engines. the 305 and 350 engines whine they use the same flywheel by design the balancing is slightly different amounts.
I just ordered a steel replacement flywheel for a customer and although the company says it is the same a factory I suggested to re balance or at least compare the two flywheels and balance if needed but customer said not it should be fine But it was off by lots as it shook. When checked the difference was 253 grams.

Customer is always right.......right =D> =D> :lol:

You can also use an adapter to install a 2 piece seal crank into a 1 piece seal block.
They work very well but they do not tell you that a line up tool is required for this.
It is just a piece of tubing about 8-10 inches long machined to 2.4464" OD on the one end and to the seal housing bore 2.7770" diameter on the other to align the adapter to the center of the main bore.

That way it holds the adapter centered on the block inline with the seal bore on the adapter. I have used many of them to use older rotating assemblies in the later blocks which seem easier to locate these days saving the cost of a crank and balance and a replacement flywheel...
If the core block came with an auto trans type of flex plate at least compare the factory balance to the flywheel you want to use.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by rebelyell »

Belgian1979 wrote: Thu Apr 29, 2021 2:10 pm This is about a block I found which could fit my purpose, however it's a one piece rear seal Gen 1 sbc. So the crank is externally balanced. It also has a flex plate. Would an off the shelf flywheel for a one piece rear seal block work with these or does the crank need to be rebalanced in that case (with the flywheel)?
For your "pass the test purpose", Don't buy a "performance" 1 pc rms flywheel ... instead, buy a "replacement-type" flywheel for an 87-up truck, firebird, camaro or vette Gen I sbc with same size 153T or 168T to fit your existing starter. Pioneer or LuK has what you need for small money ... it'll be cast iron ... and more likely to match OE balance that a race/performance piece.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BillK »

ProPower engines wrote: Thu Apr 29, 2021 8:25 pmWhen checked the difference was 253 grams.
I have to ask . . . . what flywheel part number was it that was off that much ?????? I have probably balanced at least a hundred 1pc seal assemblies with all sorts of different flywheels and flexplates and have never had one off more than 10-15 grams. I have also matched a few aftermarket wheels to a stock GM one I keep just for that purpose and have never had one be very far off either. For it to be off 235 grams it must have been the wrong part number or misboxed.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BillK »

BG,
I know you are in Belgium and not sure what resources you have as far as balance shops but if you want to be absolutely sure when you get your new flywheel have it checked against the flexplate that came with the engine. It takes less than 15 minutes to check it and see if it is the same or not.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by ProPower engines »

It was a pro comp flywheel that was supposed to be stock balance weight.
Turns out is was not. It was drilled opposite to the bolt on weight and after calculating the missing weight by measuring the hole depths and size I figured roughly 248 Gr.

Turns out it was 235 Gr.. the extra drilled area on the other side of the weight would have made what was to be a neutral balance even worse if the weight was removed. It was not neutral with the weight off but way worse with it on.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by Bill Chase »

Not sure if it is true or not, but have always been lead to believe the 87-96 corvettes were balanced to a slightly better standard from the factory. Makes sense when the few flexplates i have seen from them had additional holes drilled in them and they were removed from 100% stock c4 corvettes. When compared to the same from a truck of the same era that did not have additional balance holes drilled.

Be mindful all these engines from the factory were typically rpm limited to 6000 (corvette l98) trucks typically were lower rpm. so if any high rpm use is planned it is probably best to have the entire rotating assembly balanced.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by Belgian1979 »

It's about a used but good 1989 corvette engine long block which someone has here (unfortunately I bought the heads to refurbish my replacement engine already, but ok). I read in some places the intake bolt pattern may be different on these (TPI-engine). Is that correct. If so, I still may the cast heads I bought.
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Re: externally balanced 89 Chevy flywheel interchangeability

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Bill Chase wrote: Sat May 01, 2021 7:48 am Not sure if it is true or not, but have always been lead to believe the 87-96 corvettes were balanced to a slightly better standard from the factory. Makes sense when the few flexplates i have seen from them had additional holes drilled in them and they were removed from 100% stock c4 corvettes. When compared to the same from a truck of the same era that did not have additional balance holes drilled.
I've always herd corvette engines/parts were finished/built/assembled at the corvette plant and had much better quality overall.

DV once said something like a SBC engine out of balance will run just fine but it'll shake more. Of course not talking extreme rpm apps n so on
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BOOT »

Belgian1979 wrote: Sun May 02, 2021 2:49 am It's about a used but good 1989 corvette engine long block which someone has here (unfortunately I bought the heads to refurbish my replacement engine already, but ok). I read in some places the intake bolt pattern may be different on these (TPI-engine). Is that correct. If so, I still may the cast heads I bought.
TPI thidgen camaros and firebirds changed the heads/intake bolt pattern around 87/88 but C4 corvettes bolt pattern stayed the same from the cast iron TPI 1985 & half of 1986 heads to the half of 1986 to 1991 aluminum 128 & then 113 heads, also the vette tpi base is different from either thirdgen base I think. The alum head vettes didn't have the exhaust passages in the heads, so no need for it in the intake if I rem right. There are other TPI intake section differences but we don't need to go into that.

Your 1989 donor engine should have 113 alum heads and if I rem right your trying to put together a stock horsepower swap inspection engine or something like that. C4 vettes were underrated a bit in HP, those heads are better than the 882's that a basic low hp 79 came with and I think came on early crate ZZ engines, so take that in mind when building the engine.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by Schurkey »

I bought a Vortec 5.7L shortblock from a Treasure Yard as the basis for building a replacement engine for my beater pickup.

The Vortec was pulled due to a "rod knock". Once the engine was removed, they discovered that the flexplate was broken into two pieces--there was a full-circle crack surrounding the holes for the bolts that hold it to the crankshaft. The crack was irregular enough that the center didn't fall out of the rest of the flexplate, but the center could be moved around a little bit. I believe this to be a common occurrence with the one-piece rear main flexplates.

I bought two replacement flexplates--both aftermarket, one "new", one of them "unused" from a private party. Both of them had offset weights that didn't look like the OEM flexplate.

They went to my favorite machine shop, where he compared them to an OEM flexplate. One was so heavy at the offset weight he had to drill it in several places. The other was so light he had to weld to it. Both were a balancing disaster in stock form.

I don't know what the actual offset weight for these one-piece-seal cranks is supposed to be in inch-ounces or whatever. I just know that both my aftermarket flexplates were nowhere close to an OEM flexplate.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BillK »

Schurkey wrote: Mon May 03, 2021 5:03 pm
I don't know what the actual offset weight for these one-piece-seal cranks is supposed to be in inch-ounces or whatever. I just know that both my aftermarket flexplates were nowhere close to an OEM flexplate.
Do you remember what brand they were ? I have been using Pioneer ones and they all have checked about as close as possible to a stock GM one I keep here for reference.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by Belgian1979 »

BillK wrote: Tue May 04, 2021 6:46 am
Schurkey wrote: Mon May 03, 2021 5:03 pm
I don't know what the actual offset weight for these one-piece-seal cranks is supposed to be in inch-ounces or whatever. I just know that both my aftermarket flexplates were nowhere close to an OEM flexplate.
Do you remember what brand they were ? I have been using Pioneer ones and they all have checked about as close as possible to a stock GM one I keep here for reference.
Good to know Bill, I was contemplating of buying a Pioneer unit.
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Re: externally balanced 89 Chevy flywheel interchangeability

Post by BOOT »

Schurkey wrote: Mon May 03, 2021 5:03 pm I don't know what the actual offset weight for these one-piece-seal cranks is supposed to be in inch-ounces or whatever. I just know that both my aftermarket flexplates were nowhere close to an OEM flexplate.

As ask by another, ditto what brands?
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