CJ7 stroker build...questions?..KB944...quench??

[Cheromaniac]

I'm not going to spoon feed you everything I found out the hard way over the years.

Here's an idea for you. Write a book and sell it. You'd enrich yourself financially and enrich the Jeep world at the same time with your valuable knowledge and experience instead of carrying it with you to your grave.

It's pretty obvious that you have no intention of actually helping increase the body of knowledge here. It's a shame too. I was hoping we could benefit from your alleged expertise.

x1,000,001

Go build a few engines, and learn the "why".

OK. Let's all quit our jobs to become professional engine builders so we can learn why. Great idea.

[Bodo]

It's really too bad that you choose to be negative and adversarial. If you're not here to help others and share your knowledge, what is your game?

Insults and Innuendo and lulz?

[noFreeTime]

I emailed Rick Mudge, he worked at Chrysler JTE (Jeep-Truck engineering)for 20 years in the flow lab. He worked on the 0331 head design. Here is a copy of the Email:

Rick:

Have you ever heard of installing the pistons in a 4.0 180 deg out? A guy on one of the boards claims that this increases torque 10% and that Chrysler (jeep) knew about it, but did not do it because of piston slap noise when cold. he also claims that all of the race motors were built this way.


Is this guy full of crap or is he on to something?

Thanks

Peter Lechtanski

Rick Mudge Wrote:

The answer is YES and NO! The stock JEEP pistons had a pin offset about .060" so the piston slap noise (when cold) is reduced. TRUE!
Turning the pistons around will reduce friction and gain some power BUT, the dish is moved off the chamber and the squish area is reduced. We had pistons having the dish in the stock location but using ZERO offset pins. This produced the best power by keeping the dish orientation correct and eliminating the friction of the offset pins. But, turning a stock piston 180 will increase power, YES! NOW, the biggest noise problem wasn't piston slap but cylinder miss fires. Inconsistent spark light off at low engine speeds, like idle. We tried pin offsets as high as .125" and saw NO improvement in noise, it was miss fires causing the noise. Low charge motion (swirl/tumble) at idle and just off idle, bad spark plugs, cylinder to cylinder distribution all contributed to the miss fires.

While I don't doubt Rick Mudge's experience or credentials I think there may be more to this. According to Jeep Engines 3rd edition (published by Chrysler) installing the pistons 180* does increase torque. The only downside listed is increased noise.

Both quotes are from the chapter on the 4.0L.

Page 153, Second paragraph of the Piston Race Preparation section:
Factory pistons have the pin offset to reduce piston slap. By reversing the offset (reversing the piston), you can reduce engine friction.

Page 157, First paragraph of the Offset Pins section:
It's commonly known that you can turn pistons around. The piston, when originally made, had an offset pin. This offset pin makes the engine run quieter. By reversing the piston (the arrow on the top of the piston now points to the rear of the engine instead of the front [stock] installation position), you reverse the centerline placement of the pin. This makes the engine noisier, but will also produce a little more torque.

[yuppiexj]

I don't know about you but a FREE power adder at the cost of cold piston slap noise is an epic WIN in my book.

Even 1 HP or ft/lb for no added effort or cost, why not, I mean you're going to install those pistons anyway right?

(don't drink and post.... or do and include a disclaimer)