My boss purchased an Edelbrock motor from someone about 10 years back that he says is a ZZ4 that was rated 430 hp. While all of this info is in question as I don't have access to records, what I do know and the questions I have are below.

FACTS:

- The block number is 10248880 (a ZZ4 is 10243880 according to the sticky and my research). The number on this block ending in 8880 instead of 3880 is not listed in the sticky.

- The block has a one piece rear main seal.

- The flexplate that is on the motor has a weight on it.

- He wants to swap to a TKO-500.

- He currently has a TKO-500 and the following parts as recommended by Summit when he initially told them it was a ZZ4 motor: LAK-15020 bellhousing, RAM-1508 flywheel, RAM-98730HD clutch.

QUESTIONS:

- I need to know if these will work and, if not, what we should return and then buy that will work for the swap.

- Any information you can give me about this block would be helpful (may be a Mexican block according to my research but I'm not positive on what to believe anymore).

I guess this flywheel he purchased doesn't have a weight on it and is what sparked the question as to whether they are the right parts for this swap.

Thanks for your help as this has been a frustrating project. I'm not much of a tech guy and I have very little info verified along with none of these parts in front of me; I'm only getting bits and pieces of info as I go, so I'm sure many of you know how this goes...

 

First and foremost, the flywheel must be for a one piece rear main seal crank. The flywheel won't have an extra weight on it as the flywheel itself will be machined for the counter balance. You can't bolt a two piece rear main flywheel to a one piece crank, it just won't fit. The clutch disk needs to fit the trans shaft (spline count and diameter) and match with the clutch pressure plate which must then bolt to the flywheel. I believe the TKO has the same bolt pattern and input shaft length as a Muncie trans so a standard bellhousing or comparable Lakewood will work. The only other piece that may come into question may be the starter. The mount bolt pattern is different for a small diameter clutch setup (10.5") and a large diameter clutch setup (11"). IF the auto flexplate and the manual flywheel are the same diameter then the starter will work as is. If changing from small to large diameter or vice versa, you either need a new starter or need to swap the starter nose end (mount end) for the correct one. Hope this helps!

P.S. Are you sure that number in the casting is an 8 and not a 3? When GM went to the LS format for their main motor in production (cars and trucks), they ceased production here in the states and moved all GEN I production to Mexico, so you assessment that this block may be from Mexico is correct, but then again, all GEN I motors are made in Mexico since the early 2000s.

 

Thanks for the info. The flywheel is for a one piece rear main seal and RAM is telling me that if the block is to ZZ4 spec and the balance wasn't modified, we need part 1509 instead of 1508. 1509 is for externally balanced 350 ZZ4 motors and 1508 is for internally balanced.

That's fine except that I'm still not sure if this block is ZZ4 spec since I can't find much info about that block number 10248880. I do see other people mention that number on other forums so I don't think he's reading it wrong; I just can't seem to find much concrete info about it in relation to the ZZ4 or directly from any GM block number listings.

If someone can confirm that blocks with this number are ZZ4 spec then I'd say we're all set and we'll just return flywheel 1508 for 1509. But I'm also really curious as to why this block number is not listed anywhere except for some people saying they have ones with this number on it.

If I get a chance to see the motor I will obviously double check the number just to make sure.

 

A "3" can easily be mistaken for an "8" in those casting numbers. And not surprising that others have done it as well. Don't fret over it. If it's one-piece rear main seal, the rest of the block information won't tell you anything about the rotating assembly, anyway.

I really hate it when people mix terms for "internal" and "external" balance. If it's to ZZ4 specs, it should be "internal" balance (meaning the flywheel is offset weighted, just like the flexplate is, to take the place of the weight that was external to the rear main seal on two-piece rear main seal SBC cranks, and has a neutral-balanced damper on the front end). If it's one-piece rear main seal and external balanced, that should mean it's a 3.75" stroke and needs a weighted damper on the front end.

Any idea what damper it has/needs?