Beating a dead horse!

[FlexdXJ]

I know this has been thrown around all the time but i am thinking of doing a stroker. I ended up here looking at stroker setups: http://www.jeep4.0performance.4mg.com/stroker.html

Here is the setup i liked the most

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Jeep 4.0L 3.875" standard bore pistons
9.7:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Stock 0.051" head gasket
0.081" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
266hp @ 4950rpm, 322lbft @ 3500rpm

It seems like a good mix of power and economy as a matter of fact more than i need but thats ok for me and it won't need to be bored. This will be down the road a ways i'm just starting to do my research and this may be completely different than what i end up with. Since mine is a 97 i can run a 49psi FPR instead of an adjustable. Would I need to run premium gas with this setup? Will i be able to retain the stock computer?

 

[Talyn]

Get your quench tighter. .081" quench is useless. You stock computer will be fine you may just need larger injectors and a piggy back. There is no absolute as to what gas you can run with what DCR.

 

[FlexdXJ]

ok so i am assuming that quench is the deck height+ head gasket thickness? I was reading your thread ans yours was somewhere around .045 right?

 

[Talyn]

Yes, but deck height isn't really the correct term. Deck clearance is the correct term, but I think you have the general idea. The distance from the highest flat spot on the piston to the flat spot on the head. The tighter the quench the more resistance to pre detonation and better burn. Of course you will be upping the compression a bit, but in theory that shouldn't matter in terms of what octane you can run as the tighter quench reduces pre detonation.

In my build I shot for .045". However, due to difference in piston rod lengths it varies between cylinders on my build.

My previous stroker was similar to your build. While I could run stock injectors at WOT it would run very lean. I used an Apexi SAFCII to add fuel at WOT. I also tried the upgraded injectors, Ford Cobra XR3E, using those it ran rich but I was able to adjust it out. Ideally I don't think its possible to put a stroker in with out some kind of piggy back fuel management.

Check out jeepstrokers.com too.

 

[FlexdXJ]

Yes, but deck height isn't really the correct term. Deck clearance is the correct term, but I think you have the general idea. The distance from the highest flat spot on the piston to the flat spot on the head. The tighter the quench the more resistance to pre detonation and better burn. Of course you will be upping the compression a bit, but in theory that shouldn't matter in terms of what octane you can run as the tighter quench reduces pre detonation.

In my build I shot for .045". However, due to difference in piston rod lengths it varies between cylinders on my build.

My previous stroker was similar to your build. While I could run stock injectors at WOT it would run very lean. I used an Apexi SAFCII to add fuel at WOT. I also tried the upgraded injectors, Ford Cobra XR3E, using those it ran rich but I was able to adjust it out. Ideally I don't think its possible to put a stroker in with out some kind of piggy back fuel management.

Check out jeepstrokers.com too.

Thanks man i have a lot to learn i will definately spend some time over on jeepstrokers. If i end up heading to Christiansburg i'll shoot you a PM before i go and maybe I could come check out that Jeep! I may try to come in June or July not sure yet!

 

[cal]

If you're going to spend the money, pony up another $500, get the KB pistons and use 4.0 rods.

its easier to get the quench in spec, and the forged pistons will handle 9.7:1 with abuse better than the OEM style cast ones will.

Also, the 231 cam is a little mild for a stroked motor. You might consider stepping up to the 235, or you won't have any top end -at all-, but that means doing aftermarket valve springs too as it lifts a bit higher (comp cams would tell you that you have to do the valve springs either way, OEM springs do not have the seat pressure Comp wants to see).

 

[Talyn]

You will need after market springs any how with the 231.

 

[cal]

You will need after market springs any how with the 231.

Really? they told me it was a stock replacement, and shouldnt require any further mod's. I'll trust you on this one.

 

[Talyn]

I just checked the 68-231-4 on comp's website and it does say that stock springs can't be used. I don't recall the reason at this point, but they either can't handle the lift or they are too weak at 80 lbs seat load. It isn't a stock replacement cam. I remember reading that one person used stock springs.. but they didn't last long.

 

[Dr. Dyno]

I know this has been thrown around all the time but i am thinking of doing a stroker. I ended up here looking at stroker setups: http://www.jeep4.0performance.4mg.com/stroker.html

Here is the setup i liked the most

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Jeep 4.0L 3.875" standard bore pistons
9.7:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Stock 0.051" head gasket
0.081" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
266hp @ 4950rpm, 322lbft @ 3500rpm

It seems like a good mix of power and economy as a matter of fact more than i need but thats ok for me and it won't need to be bored. This will be down the road a ways i'm just starting to do my research and this may be completely different than what i end up with. Since mine is a 97 i can run a 49psi FPR instead of an adjustable. Would I need to run premium gas with this setup? Will i be able to retain the stock computer?

That's my site and the recipe you quoted is really for a low mileage 4.0 that definitely won't need reboring. Since yours is a '97 and probably will need a rebore, I'd suggest this:

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith-Black Silvolite UEM-KB944 +0.030" bore forged pistons
9.5:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.020"
Mopar/Victor 0.043" head gasket
0.051" quench height
Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
Stock computer
89 (winter) or 91 (summer) octane gas

 

[FlexdXJ]

That's my site and the recipe you quoted is really for a low mileage 4.0 that definitely won't need reboring. Since yours is a '97 and probably will need a rebore, I'd suggest this:

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith-Black Silvolite UEM-KB944 +0.030" bore forged pistons
9.5:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.020"
Mopar/Victor 0.043" head gasket
0.051" quench height
Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
Stock computer
89 (winter) or 91 (summer) octane gas

Cool man! Thanks for the advice. is that around the same HP and torque range?

 

[jeepinwi]

The stroker that Dr Dyno recommended will make about the same horsepower and torque. I've run my stroker for about 28k miles on mid grade gas, and it runs great. Compression Ratio is 9.4:1 and quench is about .090". I've always heard that a tighter quench is preferred, but I've never had an issue with mine. When I assembled mine, I cleaned up the compression chambers so there were no rough edges or high spots. Any sharp points get hot quicker and promote predetonation...not a good thing.

Also, my stroker is in my 99 XJ running 25 lb Mustang Cobra injectors and stock computer. It runs great, but I do think it could be improved upon with a piggyback computer.

 

[Darky]

Subscribed as a stroker is in my future.

 

[FlexdXJ]

Subscribed as a stroker is in my future.

Yeah seems like we got a few stroker gurus chiming in on my thread. I Need to be schooled on the stroker info! :yelclap:

 

[Gascan340]

Can someone give on information on this piggyback computer?

 

[FlexdXJ]

Can someone give on information on this piggyback computer?

X2 I'm assuming they are talking about fuel management . :dunno:

 

[FlexdXJ]

What do you stroker guys think of Golen or Titan strokers? I've heard some horror stories about titan but not much about Golen.

 

[Gascan340]

yeah fuel management but is seems that for most it is not needed for stroker

 

[FlexdXJ]

yeah fuel management but is seems that for most it is not needed for stroker

Yeah i think it just depends on how the engine is set up. I hope to run one without a piggyback but hell who knows i may have to. But first i need things to pick up at work so i can afford the aforementioned stroker! :tears:

 

[Talyn]

What do you stroker guys think of Golen or Titan strokers? I've heard some horror stories about titan but not much about Golen.

Titan is Titanic crap. Golen is decent stuff.