new to the 4.0, any help with figuring out a setup?

[CSXRT4]

Hey all, ive been doing a bunch of research on the 4.0 lately for my build. I originally wanted to go with a turbo setup on a 4.0l engine with megasquirt, revving it to ~6500 as the 4.0l has a short enough stroke to rev it considerably higher than its stock rev limit. But then I found out about the crank/cam harmonic issues that the engine suffers and if I am going to be confined to 5300rpm I may as well have the longest stroke I can get. So now my interest has been drawn to doing a stroker, more specifically a 4.6L as I dont feel like going crazy with over-boring and offset grinding. So now I need to know the limits of the 4.0 internals. I am confident that the 4.2 crankshaft is quite strong, I was wondering what is the highest torque/hp levels that the 4.0/4.2 rods have been taken too? Also what is the highest power level the stock pistons have been taken too(this isnt as important as I will probably be getting a set of forged)? I would like to run the eagle rods as im sure they could take a lot of abuse but the problem is I would like to run ~8.0:1 compression and that would require a huge dish or a higher pin height which I dont even know is available.


So to recap, the main questions I guess I have are

1: What is the torque/power limit of the stock rods?

2: What is the torque/power limit of the stock pistons?

3: How would I get an 8.0:1 compression ratio with a 4.2l crank and eagle rods?

4: Has anybody figured out or cured the cam/crank harmonic issue at ~5500rpm?

Thanks

[Cheromaniac]

I don't think anyone knows the answers to your first two questions but I can tell you that I haven't heard of any 4.0L or 4.2L rod failures in any strokers (N/A and forced induction). The stock pistons are pretty strong and the rare failures are most often caused by detonation or if the engine runs lean on nitrous.
Your answer to question 3 is custom forged pistons with a large cc dish.
The answer to question 4 is no.

[Biggrnjeep97]

1: What is the torque/power limit of the stock rods?

2: What is the torque/power limit of the stock pistons?

3: How would I get an 8.0:1 compression ratio with a 4.2l crank and eagle rods?

4: Has anybody figured out or cured the cam/crank harmonic issue at ~5500rpm?

1: Everyone will tell you different. A deburred/shotpeened rod should have the ability to take on a force inducted 4.7L. Case in point; to the tune of 400hp-> http://www.pirate4x4.com/forum/showthread.php?t=614289

2: A silvolite 677p will handle an N/A 4.7; not a question. That being said, there is a "super-textbook" way and a "Budget" way to build a stroker. I, personally, would use KB944/945's and not make the piston the "weak link" nor the limiting factor, cause down the road you may want a supercharger/turbo/nitrous/whatever.

3: Play with the stroker calculator. Dont limit yourself to 8.0 CR. CR=Combustion Efficiency. 9.0-9.5 CR is a nice area to aim for, IMO. I will recieve flack for saying this but Eagle products are junk made in china with LOOSE tolerances that your engine and wallet cannot afford. Effective paper weights. Ineffective engine parts.

4: I, personally, have never taken a 4.0/4.5/4.7 past 5500. So ive never had the luxury of meeting this harmonic issue head on. I believe Plechtan would be the one to ask.
-Will

[CSXRT4]

Ok, I did some calculations with the stroker calculator. To get a CR of 7.8:1 using the 4.0l pistons and 4.2l rods, I would need a 38cc dish and the quench distance would be increased to .03". The largest dish I have seen anybody mention is 30cc, I am worried that 38cc may not be obtainable without compromising the integrity of the top of the piston. Have you guys heard of anybody with as large a dish as 38cc? As a last resort I guess I could get a custom pin height piston but I would rather not have to spend a ton of money on that.

What is the most power/torque you guys have heard of anybody making with the 4.0?

[lafrad]

Why are you looking to go to such a low compression ratio? the "nice" part about building a motor like this, is the fact that you can put a LOT of attention to detail in the build. get all the cyls consistant... cleanup the head, ports, valves, etc... you can run a higher-than-factory compression ratio on 87 octane pump gas by careful and well thought out assembly... NO PROBLEM.

[CSXRT4]

I want the low compression ratio because I am building the engine to be turbocharged. I guess my first post is worded kind of odd, I want to do the a turbo setup along with the stroker

[Plechtan]

4: Has anybody figured out or cured the cam/crank harmonic issue at ~5500rpm?

4: I, personally, have never taken a 4.0/4.5/4.7 past 5500. So ive never had the luxury of meeting this harmonic issue head on. I believe Plechtan would be the one to ask.
-Will

I have run my engine up to 7,000 rpm , but had lubrication problems. Six Pac runs his sand drag Jeep up to 7,000 rpm on every run. He has crank harmonic issues that cause his timing chain to strech. He can tell when it is getting loose because his et's start to drop. The Hill dagster would rev over 8,000 rpm, but they used a hrmonic ballacer from a Big Block Chevy to try and control things. They has timing chain issues as well.

On the bonneville truck we use a gear drive forthe cam, 12 cw crank, and a ATI ballancer.

Several threads on the board talk about this , i believe one is called "Max rpm of a Jeep engine" Read on

http://www.jeepstrokers.com/forum/viewt ... 4347#p4347

http://www.jeepstrokers.com/forum/viewt ... 53&start=0

[Plechtan]

I want the low compression ratio because I am building the engine to be turbocharged. I guess my first post is worded kind of odd, I want to do the a turbo setup along with the stroker

Check out Turbo Tom's build 450hp build here http://www.jeepstrokers.com/forum/viewt ... ?f=5&t=530 You could probably PM Tom if you have questions.


****Edit****

Here is a link to the YJ & Cory 400hp turbo street build. http://www.pirate4x4.com/forum/showthread.php?t=614289 He used Hesco 8:1 turbo pistons, these would be a good choice over getting custom pistons made. Hesco put allot of R&D into them.