502 flywheel question
 

Hi, I'm slowly trying to finish up a motor to put in my boat hopefully in a month. Here's my question, I'm going from a gen IV 454 to a gen VI 502. Can I just go to my local gm dealer and get a flywheel for a 502 and it should work or do I need a different one. If so does anyone know the part #. Thanks

Call 1800runsnew, just bought one from them its a real gm for a forged 502 crank, think it was 240.00 plus 15 to ship it...they stock them. or check out their web site

You need this one
http://www.jegs.com/i/GM+Performance...96987/10002/-1


do not run the old flyweel for the cast cank

P,
You really should not make these comments without knowing for sure.

The MKIV engines use a different flywheel than the MK5 and newer. The balance weight is different because the MK5's have a one pc rear main seal and the crankshaft does not have the counterbalance on the back flange. Also, as was already mentioned, the cast crank and the steel cranks use a different flywheel, also due to balancing differences.

You have to get the correct flywheel for the engine.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Bill K and Rockfish are correct.

Both have helped me and KNOW what they are talking about.

BOTH are respected in the business so listen in learn.

I also hate people giving advise that they have no idea what they are talking about.:eek:

I would order the ones on ROCKFISH link.

Like BALLON I paid $200 X 2 for new ones from 1800.

There's two 168 tooth flywheels for externally balanced big blocks:

3993827 - MkIV

14096987 - GenV and GenVI

Within the same generation engine, it makes no difference if it's a 454 or 502, cast crank or forged.

That's the truth.

THANK YOU

are you guys sure about this? So I can use the flywheel that came off my cast gen 6 454 and put it on my 502?

13 year old thread 252

yes...

is your question about mixing internal external balanced parts ?

Both the motors are gen 6, so I believe they are both externally balanced.

whats the part # on your flywheel

Not sure. It came off my gen 6 454 that had cast internals, and was installed on a new 502 long block, that has forged internals. I don't notice much vibration, but I'm wondering if its ok to leave as is..

Yes but the steel crank uses a different flywheel than the cast crank.. The balance is different. Not much but it is different. It might be enough to affect bearing wear in the long run, especially the rear main. I have the exact specs at the shop in my balancing files.

Im not 100% for sure

The cast crank flywheel is 42 oz-in out of balance. The forged crank one is 42.5 oz-in. The .5 oz-in difference is about the same as 7 grams on a typical big block crank counterweight. Is that enough to cause a noticeable vibration ? Probably not. Is it enough to cause long term bearing wear ? Who knows :) :)

To be honest with you it probably is no worse than your typical Big Block truck engine is from the factory. But those engines lumber along at 1800 rpm most of the time.

Thanks Bill, I appreciate the info. Based on this, I think I'll leave my original flywheel installed as is.
I'm not a mechanic, but it seems to me that the specs are so close that they are almost in the range of manufacturing differences?

Thanks again..

Here’s the GM listing for BBC flywheels:
https://www.chevrolet.com/performanc...els-flexplates

Not sure if that is 100% correct.

This is the same thing that my older GMPP catalog shows :
Thius is from the Pace Performance web site. Dont know why I cant seem to actually put a link to the page:(

14096987 - CPP Big Block Chevy 14" Gen VI Manual Transmission Flywheel 1991-On - For Use With CPP 454 & 502 Crate Engines With Forged Cranks

SKU: 14096987

Description

14" flywheel for 11" clutch.This flywheel is specifically balanced for GMPP 454 and 502 Crate engines with forged steel crankshafts.Do not use on production 454 engines with cast crankshafts.

The first number at the GMPP link is coming up as a smallblock flywheel in the PDF catalogs.
Snip out of 2018 (top) and 2023 (bottom) Chevrolet Performance catalog, flywheels offered then and now.

https://cimg0.ibsrv.net/gimg/www.off...866049fd98.jpg

and none of these specify cast or forged cranks..

I wonder why the Pace Performance site does ? They are one of the biggest GMPP dealers. Ill do some more research tomorrow :) Unless GM superceded them to all being the same but that would be unusual for them to do without changing a part number.

Its interesting. The truth is out there! Lol

Bill K is correct:
Mk 4 external : 33 ounch inch
gen V or 6 with cast crank : 41.7 ounce inch
gen V/ 6 steel crank: 42.5

in your opinion, is it going to cause a problem if I run the flywheel for the cast crank on my forged crank engine?

If I say its ok and it hurts your engine is it going to be my fault :) :) After all its always the machine shop's fault ;) Its kind of hard to feel a vibration in a boat compared to a car. I dont know of anyone who has run it like that long term so its very hard to say. Dont know if an oil analysis would tell you anything or not.

I’ll bet $10 .8 ounce of jb weld will stay put. :) :) he he

IDK, weve never done it BUT I think when you look at PRW , ati, tci, atp etc for aftermarket flex plates they do NOT have listing for gen v/6 cast crank vs forged crank for a flexplate for a hotrod/street car, just the same part #, maybe they split the difference, IDK, Smitty

ATI most certainly does show 2 different ones. Dont know about the others.

Im not sure Bill, ATI shows THIS on their listing
:NOTE 2: Cast crank only - 41.95 oz. in.
NOTE 3 Forged crank only - 42.54 oz. in.
and has a different column then seperate listing for EACH, BUT goes on to assign them the SAME part # : 915541
https://www.atiracing.com/products/f.../flexplate.htm

Interesting. My print catalog shows 915541 is for internal balance. 915552 (forged) and 915553 (cast) are for external balance. I dont see the 552 and 553 in your link.

So, I just downloaded the 2023 catalog and it looks like they have done away with the external balance ones for the Gen 5-6 ??? All they show is the 541 which is internal balance.

I have to call them today and order some damper parts. Ill ask them and see what they say.

Yeah to muddy things up worse, I just looked at ATI again and even though they have those balancing notes mentioning cast crank /forged crank and and both have same part number, it also shows it as INTERNAL balanced like the part # out of your catalog so it way AFU!

Ok, I talked to ATI a few minutes ago and they did away with the flex plates because there was no demand for them. I guess if you think about it any marine application would be a manual trans type flywheel anyway. Most performance and race Big Blocks that I do are pretty much internal balance so there is no need there either. And if you are balancing the assembly anyway I guess it does not really matter which one you use as long as you make note of it for future replacement.