426 Hemi Question

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boosted

boosted

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A friend and I was talking cars and he told me that he knew of a guy who put a 440 crank in a 426 hemi block with rods and used Hemi pistons. He said the motor ran fine and that the pistons was originally 13 to one and with this change it lowered it down to like 10 to 1. I have a hard time believing that this can be done so I am asking you .. The experts and why if you have any idea people do this? He may have been just messing with me.... So what say you all?
 
He would have needed to add a lot of mallory metal in order to get the crank and rods to balance out. Back in the day you would want to start with a the heavier 6 pac crank in order to use less mallory because Mallory is expensive to start with.
 
Don't forget the 8 bolt flex plate/flywheel required also. Once re-balanced to work.
 
boosted said:
A friend and I was talking cars and he told me that he knew of a guy who put a 440 crank in a 426 hemi block with rods and used Hemi pistons. He said the motor ran fine and that the pistons was originally 13 to one and with this change it lowered it down to like 10 to 1. I have a hard time believing that this can be done so I am asking you .. The experts and why if you have any idea people do this? He may have been just messing with me.... So what say you all?
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Don't know why you would change crank shafts, they are both the same stroke
 
oldkimmer said:
I believe the HEMI rod is 6.86. And the 440 rod is 6.76. .100 thou shorter. So 2 points less compression. Kim
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And there should have been a wrist pin diameter encountered. being that the 440 is 1.094' and the Hemi is 1.031' diameter.
 
If he used the hemi rods and pistons as you indicated, in a hemi block, then this is way less than amazing. Actually no big deal, other than the fact that it would be expensive to balance. Actually the compression would not change at all, unless of course you are saying that he used 440 (RB) rods in a hemi.
 
I asked him last night and he said he used 440 rods. This was because he did not have a hemi crankshaft. At least that is what I was told...
 
boosted said:
I asked him last night and he said he used 440 rods. This was because he did not have a hemi crankshaft.
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So, that would definately change the compression dramatically, as others have said. Your suspicions are correct about this fishy story tho. Although dimensionally the 440 crank and the hemi crank are the same, with the differences only being the 6 or 8 bolt flexplate flange, you really have to wonder why anyone would go to the trouble. Who would go to the trouble to build an underperforming engine as such? And did this gem get properly balanced, or just bolted together and pedalled??
 
So then at least he had to change the bushings in the 440 rods. What did he use for bushings. If he says he didn’t have to change them, u have ur answer. Have everything balanced. Ask him if he had it balanced or if he figured it was close enough. And if he ran it that way. Lol. Kim
 
Seems kind of janky. He said it was a cheaper way of having a hemi with streetable compression and pump gas. What is the max comp with 93 octa e?
 
Interesting. Sounds like an inexpensive way to avoid burning racing gas. Since 440 rods are lighter than Hemi rods, and pistons weigh the same, it sounds like it may work with the 440 external balance stuff. A Hemi crank probably costs a bazillion dollars, if you can find a used one.

That brings up a question. Since a Hemi is internally balanced, and has heavier rods, why did Chrysler go to external balancing when they put 6 pack rods in the 440's?
 
pt70 said:
Interesting. Sounds like an inexpensive way to avoid burning racing gas. Since 440 rods are lighter than Hemi rods, and pistons weigh the same, it sounds like it may work with the 440 external balance stuff. A Hemi crank probably costs a bazillion dollars, if you can find a used one.

That brings up a question. Since a Hemi is internally balanced, and has heavier rods, why did Chrysler go to external balancing when they put 6 pack rods in the 440's?
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The original TRW hemi pistons were quite a bit heavier than 440 pistons !!
 
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