Are the flywheel bolts for a '57 7/16" X .680" and also the same for a '77 flexplate?
Also, are they around 120,000 - 130,000 psi?
Thanks!
Steve
Also, are they around 120,000 - 130,000 psi?
Thanks!
Steve
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Re: Flywheel Bolts
Steven,
I believe manual transmission cars require a longer bolt. I purchased mine from GM, not expensive..
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Re: Flywheel Bolts
Steve-----
First of all, the flywheel and flexplate bolts are definitely NOT the same.
The flywheel bolts are of 7/16-20 X 1" (although they might actually measure slightly different than that). They are of GM-300M material (SAE grade 8; 6 radial lines) and 150,000PSI. They are phosphate-finished. They are GM #839756.
The flexplate bolts are of 7/16-20 X 0.70" (although they might actually measure slightly different than that). I believe they are of either GM 300M OR GM-290M material (5 radial lines) and about and about 150,000 or 130,000 PSI. They are GM #3727207.
I would not use either of the above, though. I'd use ARP bolts.In Appreciation of John HinckleyComment
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Re: Flywheel Bolts
Thanks Guys!! I have used ARP on all internal applications before and prefer them, too.
SteveComment
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Re: Flywheel Bolts
Todd-----
ARP (or, Automotive Racing Products) is an aftermarket supplier of extremely high quality fasteners. They're just about the best on the market and are widely used in racing circles. I use them pretty much exclusively for critical, high strength internal engine applications. Most external engine fastener applications are not so critical, so I usually use original type fasteners for those.
The other thing about ARP fasteners is that they are usually not all that expensive, even for their highest grade of fasteners.
By the way, there are fasteners out there that are superior to ARP. However, they are WAY, WAY expensive and are primarily used for exotic racing engines (like Indy Car, Formula One, etc.) or aviation. These are overkill for any street application. ARP are actually overkill, too, but given their relatively reasonable price, it's worth the "insurance".
In Appreciation of John HinckleyComment
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Re: Flywheel Bolts
Saw this thread and started looking in one of my stashes of flywheel/flex plate bolts and found a some with 5 grade lines and some wth 6 grade lines. This was the same for both the flywheels and the flex plates.
I wonder if this might have been a High Performance/higher horspower rating. specific?
What I mean is this...Did a 6 cylinder flex plate/flywheel use the same as a 8 cylinder flex plate/flywheel? Think about it this is a way to save a few pennies on each car and when you produced them in the hunderds of thousands it could add up.
The first photo is of Flywheel bolts, second of flex plate bolts and third is to show the difference in length and all the flywheel bolts have a small shoulder.
RichComment
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Re: Flywheel Bolts
Todd------
By the way, you don't want to buy these fasteners directly from ARP. They're a lot more expensive that way since, while many manufacturers do sell their product direct, they don't want to "undercut" their distributors, so they only sell at list or "jobber" prices.
Purchase ARP fasteners from sources like Summit Racing or Performance Auto Warehouse.In Appreciation of John HinckleyComment
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Re: Flywheel Bolts
Rich------
I can find no indication that different bolts were used for different engine applications. From what I can find, the same bolts were used for 6 cylinder applications as for 8 cylinder and regardless of horsepower.
It is possible that in PRODUCTION different bolts were used for the reasons you suggested. I greatly doubt it, though.
As I mentioned previously, I have found differing material grade specs for the 3727207 bolts--either GM 290M (5 lines) or GM-300M (6 lines). That's confirmed by your examples. So, I suspect they were made both ways. What may have happened was that some bolt manufacturers decided that it would be more expensive to manufacture the "oddball" GM-290M bolts and, so, just made them from the more common 300M material grade as a "free upgrade". That may have been acceptable to GM either under the original specs for the bolts or through some other sort of approval process.
I have no information that the flywheel bolts were ever of anything other than GM-300M material grade but, apparently, they were per your examples.
GM-290M is a very oddball material grade. In fact, you virtually never see any non-GM fasteners of this grade (i.e. 5 lines). There were very few fasteners used on Corvettes that were of GM-290M. However, there was one application that was virtually always, if not absolutely always, of GM-290M. Do you know what it is?In Appreciation of John HinckleyComment
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Re: Flywheel Bolts
OH! O! OH! Mr Kotter I know this one (said in my best Arnold Horseshack impersination)
Outer Leaf spring bolts....
What do I win????Comment
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Re: Flywheel Bolts
I am aware that brake lining and clutch facing rivets were upgraded from other than what was ordered by a manufacturer who sometimes supplied GM and other retailers. In the mid 70's when I was a production supervisor in a brake and clutch manufacturing facility we had a couple of different specs, including shear, for attachment of linings to shoes/plates. Since we could save warehouse floor space, chance for assembly error and minimize cost through standardization we ordered and used the highest requested spec. rivet for all applications. I assume that happens in a numberof industries.
SteveComment
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Re: Flywheel Bolts
Also note that you can't use just any old Grade 8 bolt for flywheels (or pressure plates); those applications are "specials", with a precise diameter-sized plain shank under the head to register the flywheel to the crank (and the pressure plate to the flywheel). Do NOT use a full-threaded bolt for either application.Comment
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