Eagle forged 6.150" length rods

[flexin91xj]

What pistons should I use if I want to go with Eagle forged 6.150" length rods? Im building my motor for boost so I would like to use a strong forged piston, but what all else do I have to do it so It doesn't cause all kinds of damage?
Im still pretty confused when I look at the stroker recipes and see numbers going with the piston dish volume, mill block deck, quench height, and piston bore.

The Modified "poor man's" stroker is what I am planning to build, but using the eagle forged 6.150" or shorter if they're available instead of stock 4.0 rods and some really strong forged pistons.

"The Modified "poor man's" stroker"
Same as above except Jeep 4.0L 6.125" rods, Keith Black UM-IC944-020 forged pistons, and 0.070" quench height. This is a great stroker build for a mild supercharger/turbo application with up to 6psi of boost. The 4.0L connecting rod/IC944 piston combination offers 155g less reciprocating mass than the 4.2L rod/677P piston combination (1275g vs. 1430g), thereby giving this engine a potentially higher rpm capability than the traditional "poor man's" stroker

Could someone explain each of these numbers and what they are actually doing so I can have a better understanding of what all this does?

Thanks
Jeff

[Cheromaniac]

Here's a simple explanation:

Deck clearance = Block deck height - rod length - stroke/2 - piston height

If you build a modified poor man's stroker using the 4.0L rods (6.125" length) and IC944 pistons (1.353" height) you get:

Deck clearance = 9.453 - 6.125 - 1.948 - 1.353 = 0.027"

With a 0.043" head gasket thickness you're left with a quench of 0.070". If you substitute the 4.0 rods with Eagle 6.15" rods, the deck clearance is reduced to just 0.002" (near zero).
The IC944 pistons would be the perfect height to use with the Eagle 6.15" rods but the problem is that the Eagle rods were designed for full-floating pistons with a pin diameter of 0.912". The IC944 pistons have press-fit pins with a diameter of 0.931" so they'd need to be modified and fitted with a smaller diameter pin to make them work with Eagle rods.

[jeepxj3]

Could the Eagle 6.150" rods be modified to work with the KB IC944 pistons?

Seems like the 0.912" rod end could be bored/enlarged to the 0.931". Is that possible?

[jeepxj3]

I have found 2 sets, NIB never used, $300 and $400. Is that a good deal?

[jsawduste]

No and yes

[nicpaige]

Bulltear pistons come with .927" pins and wire locks. Will they work with the Eagle rods?

[jsawduste]

I would not recommend opening up the Eagle rod to accommodate the 927.

I used pistons from Diamond that had the 912 pin and would recommend this route very highly. They are not going to be 500 bucks though.

That said if you want to sell those rods I`ll be happy to buy them.

[beiwulf]

Jsawduste, was there a reason you went with a .912 pin diameter… structural? If so what pin thickness did you go with?

Seems the bullhead imports there piston blanks and machines them iirc. Not saying they don't have a quality product. Just seems that quite a give negative input on non-USA made products regarding engine build (almost a political topic).

/r
B

[jsawduste]

When I built my 1st stroker back in 2006 the Eagles were not hard to come by.

The factory rods were not held to the tolerances that I felt were satisfactory. Length differences and twist to name a few shortcomings. Since I new from past engine builds that I wanted a.000 deck the higher quality Eagles made it much simpler with consistent overall length.

Since no one had off the shelf pistons at that time I had Diamond make me up a set. Which turned out to utilize the Eagle small end diameter with no questions asked. Figured Diamond knew what thickness the pins needed to be so the engine was built with what Diamond supplied.

I suspect Eagle had their reasons for their diameter over the stock but I`d be guessing as to the reason why.

My disappointment is taking the Eagles from this "old" engine, which has performed very well over the years/miles and effectively making it worthless without making up new pistons based on 4.0 rod length and pin diameter.

Wish I could find another set of Eagles for the next personal build using the Edlebrock head. Which will take advantage of new products and knowledge that has come to the surface over the ensuring years.

The plan is to run an even tighter squish ~.038 so having consistency in rod length is vital. The tighter squish combined with a high DCR/SCR will help maximize what Edlebrock is offering and still run pump fuel with a good safety margin.

Hope this answers your question. Happy to help anyway I can.

[gradon]

I've had a set of the Eagle rods waiting patiently for me on the shelf for over 5 years. I traded a set of recon'd 258 rods and new h825cp pistons for them.

[jsawduste]

I've had a set of the Eagle rods waiting patiently for me on the shelf for over 5 years. I traded a set of recon'd 258 rods and new hc825cp pistons for them.

Promise to give them a good home !!

[gradon]

I will definitely be building another stroker somewhere down the line. I need to find a rustless '94-96 gray metallic 2dr 4x4 4.0 ax15 XJ that I'll swap a 242 in.

[TheGreatMarklar]

According to Eagle, they do not and never have offered a 6.15" rod for the 4.0. I take that to mean that these rods are practically impossible to get, correct?

[Cheromaniac]

According to Eagle, they do not and never have offered a 6.15" rod for the 4.0. I take that to mean that these rods are practically impossible to get, correct?

They were discontinued a very long time ago.

[Russ Pottenger]

According to Eagle, they do not and never have offered a 6.15" rod for the 4.0. I take that to mean that these rods are practically impossible to get, correct?

If you shoot me an email I’d be happy to forward you pricing and information on my stock length 6.125 profiled Steel Bushed Rod.
It’s set up for a .927 pin and can be used with my 4032 forged piston with dish volumes ranging from 12cc to 28cc in 2cc Increments in both .030/4.6 .060/4.7 bore sizes.


Russ Pottenger
Bishop-Buehl Racing Engines
531 N. Lyall Avenue
West Covina, California 91790
Work (626) 967-1000
Cell (626) 673-2203
Email: [email protected]