Crank differences??

[The S is Silent]

I have looked around, and can't seem to find the answer. What exactly is the difference between the pre-commonblock 2.2 and 2.5 cranks? Is the only thing keeping you from running a 2.5 crank in the 2.2 the deck height?

Are bearing sizes the same between the 2.2 and 2.5 pre-common block cranks?

In essence, could a 2.2 crank be bolted into a 2.5 tall deck block?

[Shel-Game]

A 2.2 crank can be bolted into a 2.5 tall deck. That's the basis for the "long rod" 2.2 that used to be popular for drag racing. I think the 2.5 tall deck blocks are getting harder to find, though.

[The S is Silent]

thanks...i just found the mini-mopar site on it. i was looking into the possibility of doing a long rod engine for increased revs, but a dohc head would be needed to get enough power up top to make it worth it. i was just thinking.

realistically, how much would a longer rod setup increase your rev limit, if you could make power up top to make it worth it?

[turbovanman]

Quote:

Originally Posted by The S is Silent thanks...i just found the mini-mopar site on it. i was looking into the possibility of doing a long rod engine for increased revs, but a dohc head would be needed to get enough power up top to make it worth it. i was just thinking. realistically, how much would a longer rod setup increase your rev limit, if you could make power up top to make it worth it?

Oh god, don't start another thread on 2.2's and 2.5's, lol! Longer stroke would reduce your top end rpm power, 2.2s rev higher and hit harder in the upper rpm range, 2.5's make more bottom end grunt but run out of steam at higher revs. Now a 2.2L crank with longer rods and custom pistons, wonder what that would do?

[The S is Silent]

yeah...that's the point. i'm not beating the 2.2 and 2.5 thread again. i was just wondering if increasing the rod length would increase the ability for the engine to rev higher.

[Glhs60]

There is a great comment on this topic on Garys site by Dave Zelkowsky.

I hope I am not breaking any rules by quoting a bit of what Dave said on Gary Donovans Dodge Garage as it is great reading.



"I've been following this thread and I think it's a poor allocation of resources to concentrate on rod ratio. The amount that it contributes to output is miniscule, if it does contribute at all, compared to the gains to be had in the cylinder head/induction system. In the reference to the V8 gain of 8 HP, what was that as a percentage of total output? If it's less than 2% or so it's probably not even real."

Thanks
Randy

[The S is Silent]

you make a good point. i wasn't really looking into it as a hp gain. it was more of an issue of revs, but its not rod ratio that keeps us from reving, its weight. we have beefy parts, and they physics doesn't like to move them as fast as we want them to move...and i don't mean down a quarter mile track