Building a stoker - please check my numbers

[dan-cj7]

Thanks for reading and helping me with my "recipe". Please excuse the rookie questions.

I'm using a 93 YJ for the block, an '83 4.2 for the crank and rods. My engine guy has told me I need to go 0.030 over on the cylinders and 0.010 under on the bearings.

I'm deciding between the KB229-030 & SP Z677AP30 pistons. One question I have is what is a coated skirt and what is it good for?

The cam will need to be replaced and I was thinking of the comp cam 68-200-4. Keeping the head stock apart from a bit of porting and a polish.

I used the calculator on this site and got a 9.92SCR and 8.67DCR. Here in Australia regular petrol is 91RON. I live at sea level, should I be concerned about pinging?

I don't expect my Jeep to be too high reving and would prefer the low end torque for daily driver duty with the occasional trip to the bush.

Any advice is welcomed.

Cheers,
Dan

[Cheromaniac]

Dan,

91 RON octane is the same as 87 US octane so if you need to run that grade of fuel, you'll need a low compression stroker and I think this recipe should suit your needs:

4.6L Low-buck, low CR "rockcrawler"

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Silvolite UEM-2229 +0.030" bore pistons
Increase piston dish volume to 30cc
8.75:1 CR
CompCams 68-115-4 192/200 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.035"
Mopar/Victor 0.043" head gasket
0.058" quench height
Ford 24lb/hr injectors for '87-'95 engines
240hp @ 4700rpm, 315lbft @ 3000rpm

Oleshot is a member here and he might be able to dish the pistons for you. Some pistons have graphite-coated skirts to reduce friction but not the 2229s.

[dan-cj7]

I've been reading the comp cams website and all the high energy range (the cam you noted) say it's not suited for fuel injection. I will be using the fuel injection from the YJ in my CJ7. Do you run fuel injection?

[Dezertxj88]

Don't worry about that non sense..idk why its listed that way, it just confuses people! It will work 100% fine for you bud..

Alot of people say the comp 68-231-4 is too big for fuel injection.
This guys in a newer 97+ cherokee, which would be even more finicy to a bigger cam. Hes running the comp 68-239-4 which is the biggest they offer I believe.
http://www.youtube.com/watch?v=wEyD8sn-IaA
I love the way that thing sounds..sound like a pissed off tractor!

Oh and thats a 4.0, not a stroker. You'll have no issues turning or running that cam in a stroker.

[SilverXJ]

Don't worry about that non sense..idk why its listed that way, it just confuses people! It will work 100% fine for you bud..

x2

[dan-cj7]

Please help me understand the difference between my piston choices. On one hand I have the Keith Black 2229C the other I have is the Sealed Power Z677AP. Does anyone have any advise as to which one is better for my rebuild? both pistons come in 0.030" over. Pretty much the same dimensions as far as I can tell. Does one brand have a better reputation?

All the design variables seem to revolve around what piston choice I choose in regards to compression then cam selection.

FYI - I am using the stock connecting rods from my 4.2L.

Thanks for your advise,
Dan.

[604rail_king]

each piston has its own CC which can greatly effect your end SCR and DCR. see the list below and enter the CC value in the stroker calculator to finalize your SCR and DCR or setup.

http://www.jeepstrokers.com/forum/viewt ... ?f=34&t=67

Stock 4.0 cast aluminium '87-'93 #83500251, '94-'95 #4773157, '96-'06 #4798329----1.601" 13.1cc
Keith-Black Silvolite (UEM) cast aluminium 2228/2228c----1.581" 11.5cc
Keith-Black Silvolite (UEM) cast aluminium 2229/2229c----1.581" 11.0cc
Keith-Black Silvolite (UEM) hypereutectic 3238hc/3243hc, 3241hc/3242hc----1.592" 13.7cc
Sealed Power (Sterling) hypereutectic H802CP/H825CP----1.592" 15.1cc
Sealed Power (Sterling) cast aluminium 677P/677CP----1.585" 17.5cc
Sealed Power (Sterling) cast aluminium 525P/525CP----1.580" 17.5cc
Keith-Black Silvolite (UEM) forged stroker 944----1.353" 21.7cc NEW
Keith-Black Silvolite (UEM) forged stroker 945----1.353" 11.4cc NEW

[Cheromaniac]

Please help me understand the difference between my piston choices. On one hand I have the Keith Black 2229C the other I have is the Sealed Power Z677AP. Does anyone have any advise as to which one is better for my rebuild? both pistons come in 0.030" over. Pretty much the same dimensions as far as I can tell.

The Z677AP's have a compression height of 1.585" while the 2229's come in at 1.581". We know that the 2229's can be safely dished out to 30cc but I'm not sure you could do the same to the Z677AP's. The 2229's are also cheaper.

[dan-cj7]

Thanks for the replys fellas.

I've ordered up the KB2229c+0.030 pistons with a 68-115-4 comp cam. I will sort out any decking and piston cupping with the enigne builder when they show up at my door. Should be a ripper of an engine when I'm done. Too bad it won't be started for a few years while I restore the rest of my CJ7.

Cheers,
Dan.

[dan-cj7]

A question....

If I am keeping the original computer do I need to be concerned about changing the compression ratio and fuel rates? The engine builder I am using is concerned if I add any compression and fuel rate/injector size I will effect the computer and it won't work. Does the computer "learn" new engine conditions and adjust accordingly? We have not done any decking or dishing yet, we are about to do a mock assembly to see what clearances I have when it is all together.

Some facts about my engine from a '93 YJ
4.6 stoker
original head - lightly ported
68-115-4 comp cam
KB2229c+0.030 pistons
Balanced 4.2 crank.
Original lifters

Thanks for you replys,
Dan.

[SilverXJ]

The computer is fairly forgiving. Increasing compression or adding larger injectors to make up for the displacement increase won't bother the computer much. An overly aggressive cam could cause some small problems for the PCM. My PCM didn't like the Hesco RVOB cam and caused a poor starting condition when cold. However, I also have a 2000 with has a bit more restrictive program as well as the waste spark system.