Tweet
I GM P/N 3991469 the correct flywheel for my 66 L72? It appears correct from the description, but I didn't know if there was another part more accurate. It is listed for internally balanced applications on BBC. Just curious if this is a GM built part or aftermarket since GM lists it in their performance parts catalog and they have been pulling in other suppliers lately for these items. I bought an oil pump for a small block application through GM and while fine, it was made by Melling vs the original GM manufacture, and they of course had much more markup than if bought through aftermarket sources....thx!....Craig
-
-
Re: Correct Flywheel for my 66 427/425
for more snap in acceleration i would use flywheel #14085720, but it takes a different starter nose piece and clutch diameter. -
Re: Correct Flywheel for my 66 427/425
john hit the nail on the head. the smaller flywheel he refers to is similiar to that used by GM on the 65 396's and the L-88 in 67 thru 69. Lighter flywheel-clutch/press plate make for quicker High RPM attainment.Comment
-
JOHN WHO?? *NM*
Comment
-
Re: Correct Flywheel for my 66 427/425
Mike and Clem-----
I believe that changing to the 12-3/4" flywheel mentioned also requires changing to a '383' or '403' bellhousing. As desribed, the starter also needs to be changed. All 1966 Corvettes with 427 used the '444' bellhousing which is designed for use with a 14" flywheel. While the 12-3/4" flywheel will fit within this bellhousing, I don't think that the starter geometry will work properly.In Appreciation of John HinckleyComment
-
Re: Correct Flywheel for my 66 427/425
Craig-----
GM #3991469 is the correct SERVICE part number for the flywheel required for your application. It's not the part used in PRODUCTION, though. The original part number was GM #3889694. That part number was changed several times until it finally ended up 3991469 in 1982 or 1983. It's been 3991469 ever since. The 3991469 is dual-drilled to accept either a 10.4" or 11" clutch. The 3889694 was drilled only for the 11" clutch. The 3889694 usually carried GM casting #3789733. The GM #3991469 may carry this same casting number, casting #3973458, or other casting numbers.In Appreciation of John HinckleyComment
-
Re: Correct Flywheel for my 66 427/425
joe going to the larger diameter fly wheel from a small one could cause a starter interference with the bell housing but i would think going the other way that it would fit. all my engines used the scatterproff bellhousing so i can not say for sure.Comment
-
Re: JOHN WHO??
sorry clem, meant you, not a john. Must have posted that before first coffee this AM. regards, mikeComment
-
Re: Correct Flywheel for my 66 427/425
------I have done the light L88 flywheel assembly many times for performance gains on big blocks and it does work well.You are correct about the bellhousing.But the starter just needs the different snout.This modification works better the stouter the gear!........Bill SComment
-
Re: Correct Flywheel for my 66 427/425
Bill, Joe, Clem, and Mike - thx all for the input. My 66 427/425 still had the original 444 bellhousing, and I have the correct dated starter (I don't remember offhand but I seem to recall 4365 for the last 4 digits). I am aware of the different noses on starters, as I recall the other nose is aluminum and not cast iron, and the bolt patter is straight not staggered. This would probably look wrong visually for judging if I get to that stage. The engine is set up stone stock as I build it back, other than 0.030 over, GM dimple 7/16" rods with ARP prowave bolts, and a 7115 forging 427 crank. My rear end is a 3.36 in the car, I guess the light flywheel would let it wind quicker. I may be able to use the flywheel in the car, I still have to pull the 68 427/435 engine to replace with my correct 942 block/858 heads, the original 5069 intake and 3247 Holley are still there...I guess someone blew the original engine.
Thx Joe for the casting numbers, I will check on the flywheel next time I crawl under. I was toying with buying a new one, my complete rotating assembly is balanced now, but the shop will balance the flywheel, clutch pressure plate, and harmonic balancer as part of my original balance job cost. I have heard pros and cons about balancing the damper, any thoughts? Should I just assume GM did OK on that, or take it in with the rest? Also, for clutch, si LUK the way to go for replacement (again, no clue about condition of what's in there now, my guess is original GM, but who knows, it's been apart obviously)...thx!...CraigComment
-
Re: Correct Flywheel for my 66 427/425
Bill - are you saying the original 444 housing will work correctly or not with the smaller flywheel, I would think so unless the starter nose change causes an issue with the casting shape. With my 336 gears, the change may be less evident that a deeper 411 set for acceleration...I don't know yet if the gears in my transmission are M20 or M21 gears.....CraigComment
-
Re: Correct Flywheel for my 66 427/425
just don't drill the damper ring too deep when balancing to prevent weakening the outer ring. i always used several shallow drilled holes rather than one deep one.Comment
-
Re: Correct Flywheel for my 66 427/425
Thx Clem. I would think it should be very close already if not right on from GM....If I buy a brand new one, but I guess it can't hurt to take it along for the balance since it is "free" at this point (translation- included in my original $180 balance fee that is already paid)...thx!....CraigComment
Comment