[ChevelleFan70]

I came across an issue last night which caught me off guard -- I bought a new flexplate for my ZZ383 engine. A friend got it for me from the Summit Scratch-n-Dent aisle. It had the correct late-model counter weight on the engine side, but it's a 168-tooth. Apparently, my original one is a 153-tooth. The original is about an inch smaller in diameter. I sized the new one against of my old 400sbc flexplates, and its the same size.

I knew flywheels had different diameters for a 10.5" clutch vs. 11", but never came across this with flexplates.

What factory applications, after '87, would use the larger flexplate, and which ones use the smaller?

-Dave

(mods, not sure if this an engine or trans question, but figured it'd get more visibility here)

 

[BillK]

1988 Camaro 305 or 350 Pretty sure the pioneer Pioneer part number is FRA 160. I can verify for sure on Monday at the shop. I have one sitting there in the box

Its bolted to the engine so it can stay in this forum

 

[dyno jonn]

Might be a good time to go with a PMGR starter instead of a different flexplate.

Chevrolet spec PMGR starters pdf

 

[RICH1965]

I think the 2 piece rear seal is the 168 and the 1 piece rear seal is the 153. Im probably wrong though.

 

[pbcbob]

probably the last years of SBC production in trucks used 168 tooth, cars may have used the 153, the last year for SBC in cars was 1996 I think, there are some headers that need the starter clearance from using the smaller diameter

 

[BillK]

Both sizes were used with both types of crankshafts through the years.

 

[YAV8]

All SBC after 1986 were one piece seal blocks. All used a different flex plate or fly wheel form the one piece to the two piece seal. I have found that most or all truck 350 used the larger flex plate and the 305 used the smaller one. Just get a after market starter and you can use it on the big or small flex plate or fly wheel. Theres only two sizes. Get what you need.

 

[ChevelleFan70]

So I went to Summit this morning to pick up some parts, including a flexplate. I get there, and in the scratch/dent/closeout area, they have at least 5 of the smaller 153 tooth flexplate, SFI rated. But the SFI rating had just expired, so they were $10/ each!! I bought 2. Allstar Performance brand, kinda generic but should be good for my purposes. FWIW, you can't even buy a carwash bucket there for $10 -- they're $12, marked down from 14.99. I also picked up another starter, just in case. Dang it, just realized I forgot to get some knurled bolts.

It's been an oddly good day though -- first the dirt cheap flex plate, then I stopped at Sheetz to fill my Mustang (premium) and all grades were the same price as 87, and then on my way home, was just starting to show a couple fellas my taillights on Mayfield Rd hill (divided highway, 8% uphill grade) as I see a cop.. fuuudddgee... after I slowed down, still prob went past him at 65 in a 45, and he didn't pull out. I went and bought some MegaMillions tickets after that.

-Dave

 

[BillK]

Dave,
Do yourself a favor and take your original flexplate and the new one to someone who does balancing and have them compare them to make sure the new one is the same as your original one. It hasnt been as much of a problem on Chevy stuff but I have seen so many aftermarket external balance flexplates that are nowhere even close to the correct imbalance that is isnt funny. It takes less than 15 minutes to check them.

 

[ChevelleFan70]

Dave,
Do yourself a favor and take your original flexplate and the new one to someone who does balancing and have them compare them to make sure the new one is the same as your original one. It hasnt been as much of a problem on Chevy stuff but I have seen so many aftermarket external balance flexplates that are nowhere even close to the correct imbalance that is isnt funny. It takes less than 15 minutes to check them.

Bill, is that something a standard machine shop can do?

 

[BillK]

Bill, is that something a standard machine shop can do?

Anyone who does crankshaft balancing should be able to do it.

 

[RICH1965]

Were the 168 tooth designed to turn over higher compression engines?