I just pulled the flywheel off the '70 350 that was in my '59 and noticed that there was no alignment dowel in the crankshaft flange. Is there supposed to be one? There is a hole in the flange and the flywheel for one. The flywheel is GM part # 3856579, 12 3/4" across and seems kind of light. Thanks. Pat
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Re: crankshaft to flywheel dowel pin
For internally balanced engines like the 350, you could argue that the dowel pin isn't required if the crank is balanced without the flywheel and then the flywheel is neutrally balanced. On the other hand, many shops just drill the flywheel to balance the engine, in that case, the flywheel MUST be properly installed.
If you have the L88 style flywheel, it appears hollowed out on the backside and weighs about 15#. It's a very desirable flywheel with the dirt track guys and typically sells for $50 to $100 in good shape.
Should you add the dowel pin now? If the engine was originally balanced without it, then it will slightly affect the balance, but then again, it's fairly light and is close to the crank centerline... aw heck, I think I would just leave it as is and make sure to lign up the holes!
Good luck,
Mark -
Re: crankshaft to flywheel dowel pin
Pat-----
The only PRODUCTION 55-82 small block that ever was originally fitted with a crankshaft dowel pin was the 400 cid and none of those were ever originally used in Corvettes.
No 1970 350 ever installed in a Corvette used a 12-3/4" flywheel EXCEPT ZR-1. However, a few very low performance 350s during the 69 model year in passenger cars and Chevelles did use a 12-3/4" flywheel. Those were the only ones that I know of, though.
Also, no C1 Corvette ever used a 12-3/4" flywheel. All were 14". A 12-3/4" flywheel does not work with the cast iron and aluminum bellhousings used on C1 Corvettes, so I suppose yours has been converted to a later style bellhousing.
GM CASTING #3856579 is the lightweight 12-3/4" flywheel originally used on 1965 Corvettes with L-78, 1967-69 Corvettes with L-88, and 1970-72 Corvettes with ZR-1. It is still available today under GM PART #14085720.In Appreciation of John HinckleyComment
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Re: crankshaft to flywheel dowel pin
Thanks for the great info guys. The block is a 3970010 dated D202, heads are 3891492, cam is a roller, pistons are domed (200#+ in all eight). The hole in the flywheel and the crank flange line up for a pin but I will leave it out.
Joe, do you have a suggestion for a GM bellhousing? I would like to replace the Lakewood blowproof. Clutch cross-shaft support is bolted to bellhousing and the starter is bolted to block.
Thanks again. PatComment
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Correction
Pat-----
Although this does not pertain to your situation, I will post it in the interest of accuracy. From what I've been able to find out since, it appears that 55-61 Corvette 265s and 283s did use a crankshaft dowel pin. I was not aware of that since I've never really had a whole lot of experience with these engines.
From some reports that I've gotten, it may also be that some small blocks after 1961 also originally used dowel pins regardless of what GM says. I can say, for certain, that I've never seen a 350 (the most widely produced small block, ever) with a dowel pin during the 1969-1985 period. From 1986 on, though, 350s DID get a dowel pin since those engines were externally balanced.
Usually, the need for the dowel pin relates to external balance which is why all 400 cid, 454 cid, and later 350 cid have them. I have no idea why they would have been used on 55-61 small blocks or any other small blocks.In Appreciation of John HinckleyComment
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Re: crankshaft to flywheel dowel pin
if you keep the 12 3/4" flywheel, the 403 cast aluminum bell is cheap and readily available, also I think the 383 cast would work. If you're going back to stock, then look for the stock bell. If you're looking for a 14" flywheel part, the 621 will work with a block mounted starter but costs an arm and a leg, there was a later 1970's part that was similar but I don't recall the number.
Please verify these will work in your application before buying as I don't work with the early cars.
Good luck,
MarkComment
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Re: crankshaft to flywheel dowel pin
Mark-----
All 1967 to 1981 Corvettes with 14" flywheel (which includes 67-68 big blocks except L-88 and all 1969-81 with manual trans except L-88/ZL-1/ZR-1) used bellhousing GM PART #3899621. In addition, all bellhousings with the CASTING number 3899621 are GM PART #3899621 bellhousings.
The other casting number used for some GM PART #3899621 bellhousings, and the one to which I believe you are referring, is GM #464697. This casting was also used for some truck bellhousings which had a different finished part number. The 2 different PART-numbered bellhousings are NOT interchangable, but it's not possible to discern them by the casting number since it's the same for both. This was a VERY stupid thing for GM to do, but they did it.
From about 1977 onward, the bellhousings found on Corvettes with 4 speed may have EITHER the GM #3899621 or the GM #464697 CASTING numbers. But, they're all GM PART #3899621 bellhousings.
I'm sure that this little "foible" has caused a lot of "pain" in the service world and may also have caused some undeserved "pain" on the judging field for 77+ models.In Appreciation of John HinckleyComment
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