6 or 8 bolt crank?

Is there a way to tell if my 1967 440 has a 6 or 8 bolt crankshaft without pulling the transmission?

It's a six bolt.

Robert

It would be a 6 bolt if it is the original crank but if the engine has been rebuilt then someone might have stuck an 8 bolt in there. Unlikely, but possible.

I do not know of any easy way to check. You might be able to pull the inspection cover and look up in there with a mirror or a borescope but you can't see much from that angle.

Okay, let's have the numbers do the talking. Total production of 440s was approximately 750,000. They rolled out the door with 6 bolt cranks. There were also 413s from the early '60s through 1965 with a 6 bolt crank. Earlier 413s had an 8 bolt crank that had a long tail and wouldn't work in a later car without modifications. So let's say there were 850,000 6-bolt 3.75" stroke cranks produced.

The Chrysler Hemi was mostly available in Dodges and Plymouths, maybe a half-dozen came out of the factory wrapped in a C-body (my guess). I went through Dodge production numbers with my calculator and starting in 1965 ending with the Super Bee in 1971 I totaled 3,546, including engines only and Super Stock cars. There were some in the other '71 Dodges and all of the '72s. Let's be generous and call that number 400, and it really wasn't that high. So We'll call all of the Dodge Hemis produced at roughly 4,000. Plymouths also got Hemis and I suspect more might have appeared in Plymouths because it was a slightly less expensive line of cars. Plus you had popular models like the Hemi Road Runner. So let's put the number of Hemi Plymouths at 5,000. We have 9,000 total engines that came out of the factory with a 3.75" stroke 8 bolt crank with a regular tail. Let's do the math. 850,000 + 9,000 = 859,000 total cranks. The percentage of cranks that had 8 bolts is 9000/859,000 = 0.105 x 100 = 1.05%.

So just by the numbers there is a 98.95% chance it's a [b]6[/b] bolt crank.

But there's another factor as well and that is the bulk majority of engines are rebuilt by mechanics or small to medium sized shops. None of these types of suppliers would have built a 440 with a crank that the average flexplate or flywheel wouldn't fit on.

So it is without question that your engine has a 6-bolt crank. It would have had to been put in on purpose by some gearhead who would have been building a race car of some sort.

For those who would say, "Yeah, but it might be possible", I would reply that AndyF had much smaller numbers on his cylinder wall thickness report that we all believe, myself included.

I would feel totally confident to tell the OP to go ahead and buy a 6 bolt flywheel or flexplate and if it didn't fit I'd reimburse him plus shipping costs to my place.

R.

Yes, I goofed and fixed the mistake. How embarrassing for me!

Great with math, proofreading, not so much.

Oh, I'm sure he'll be right back to make the correction...

I purchased my 71 Barracuda, found a Sonny Bryant 8 bolt crank in the 440,

I ALWAYS love reading your posts... Informative, entertaining, to the point, what else can I say.

Thanks guys.

One of the things not pointed out on the stock Mopar cranks was that all the stock hemi cranks are 8 bolt and all of them are heavier than the 440 6 bolt due to the rod and pistons weights of the Hemi parts.
My point is if someone had installed a Hemi crank in your motor (there is no gain in doing that ) and did not have it rebalanced the motor would shake itself apart in very little driving time. If they did install a hemi crank and had it rebalanced your good
Mopar sells the non SFI flex plates pretty cheaply . I have a large stack of all of the six (I think there is that many) different flex plate Mopar has used and offered since 1962
One easy way to see if your converter has the large, 7/16x20 bolts is to remove the dust cover and see what size your bolts are, if the are the smaller 5/16 bolts you have a six bolt flexplate
All the hemi motors came with 7/16x20 lugs on the converter and used those size bolts ONLY The early Max Wedge motors also came with the 7/16 bolts and lugs on the converters.
Most of the after market race converters have the larger bolts also