I am in the planning stages of my next Hemi build and not really happy with any of the shelf pistons that are available and was wondering why I don't see any 4.15 stroke/7.1 rod piston choices out there. It would seem like a nice package with a compression height of 1.55" and the extra clearance of the 2.2 chevy big end size and .990 pin. Are there any disadvantages out there running this stroke and rod combination?

My goal is to have a really strong street/strip combo but nothing crazy. This will be used on an older Mopar mega block and want to retain the stock internal oil pickup and is my only build constraint.

Allan G.

If I was you, I would have that crankshaft rod journals offset ground down to 2.200 to increase the stroke to 4.250 or even 4.300 stroke and use the 7.1 BB Chevy H beam racing type rods with a custom set of pistons
You will need to grind around .030 to .060 off of the oil pump pickup boss in the block to clear the rod cap depending on which brand rods you use and the stroke increase you:: work:
I've used that combination on many B, RB and 426 street hemi builds with no issues at all
IHTHs

It is also amazing to me the few choices available. I am shopping for a 528 4.5 bore assembly, and all of them want to use the short rods as you have found, and full size crank journals and 1.031 pins for everything from 556 on down to a 472...I am like, are you kidding me? From a 572 to 605 they offer the other cranks, rods, and pistons with the small journals and long rods, probably because its the only way it fits in the block.

I was going to use a billet Ohio crank, but all of them use full size rod journals. Seems like a whole niche in strokers is missing for G2 Hemi's utilizing the smaller journal cranks....Very few options as far as a kit....I hate piecing everything together. inevitably, somthing won't match up right.

Molnar has 2.200 journal cranks.

I'm in the initial planning stages now and do not have the crank and rods yet. I figure I'm going to need custom pistons anyway because the shelf stuff, even with the 6.86 rod doesn't give me what I want for compression. So basically everything is up in the air for consideration.
I was wondering if a 4.25 stroke with a 2.2 pin would clear the oil pump pickup. I was afraid to ask that question directly with the fear of the typical response of doing a google search or something. It would seem at least that the 4.25 stroke with a 2.2 pin shouldn't give up any clearance.....

I would most likely use Molnar crank and rods for this combo.

AG....

Last engine I built used Molnar 7.1” rods with standard rod journals, 4.15” crank and Milodon road race pan and pickup. Didn’t have to touch the boss at the pickup tube.

Correction - I didn’t grind but it appears to have a factory cleanup. New block out of the box. Very slight cleanup.

I never see a shelf piston that makes me happy. Just call Ray Barton and tell him what you want and he will have Diamond make them. And I have a set that I don't need if you want them. Might save you a little money.

K1 sells 4.150, 4.250, 4.375, and 4.500 with 2.200 rod journals.

I put the 4.500 version in my 572.
Seemed like a pretty nice piece to me and the local shop who checked it out and balanced it.
I would buy another one.

PS Campbell Enterprises was super easy to work with.

Edit:

Here is a corrected link:


https://www.campbellenterprises.com/426-hemi-crankshaft/k1-426-hemi-crank-stroker-crank.php

The rods in that link are Mopar width. Most 2.200" Mopar cranks are Chevy width. Be aware of what you need before ordering. I find it more universal to use Chevy width rods when going to 2.20" rod journals.

What’s even worse is no one makes a shelf stock .030 piston for 4.5 bore. These blocks been out over 20 years, they don’t wear out?

Again, if there was a shelf piston it would have too big of ring grooves, etc. And who has driven one enough to need .030" over? This isn't the old days. If you need an oversize piston (and I have before) you just figure out how much over you need, and call Ray Barton and he will tell Diamond to make what you need. I wouldn't be going .030" over when .005" over will probably clean it up.

This guy's engine dropped a valve and damaged the cylinder wall so we had to go .030" over.

I should probably crawl back under my rock and stop posting, but try this link instead.

https://www.campbellenterprises.com/426-hemi-crankshaft/k1-426-hemi-crank-stroker-crank.php

Sorry for the previous error, looks like I copied the wrong tab.

The old 4.150 stroke cranks are a bit outta date these days!

Most folks are going 4.250 stroker 2.200 Chevy journal since the early 2000’s.

7.100 rods are cheap as chips and plenty of pistons from 440 Source.
Standard oil pipe pick-up and 512 cubes, coolio...

Me thinks 440 Source does not sell hemi parts

I will look....Not sure a standard forged crank is strong enough for what I want to do. Was looking at Ohio Cranks Billet deals...

How much power are you wanting to make?

1500hp is what I am building to......Probably make less , but not much...

Not a engineer or metallurgist. Get into a discussion on forged vs billet components, with them. 4340 forged is the strongest way to approach a high stressed part like a crankshaft. Crower is one of a few that has a forging die for 8 counter weigh mopar crank.. You have to have a die to forge a crank.. They all start as a billet piece of steel. You can make any thing billet that's why they are popular. Upper level billet cranks are made from EN30B material. A higher level of material strength because i needs to be to tolerate its lack of twisting strength. 1500hp.Good 4340 crank, no worries. My 2 cents.