Another 4.6 Build

[Geo.]

First I would like to thank Muad'Dib for the site & all the regulars (I would name them, but I am afraid I would leave some one out) for all the time, effort and knowledge contributed to this forum and the Stroker list before.

I have been lurking and learning for over a year now and am finally starting to put together my own stroker. It will be for a 95% trail rig with an auto, so torque at low rpm for big tires (40") is my goal.

Parts on hand:
91 4.0 block & head
re-conditioned 258 rods
silvolite 2229c pistons
comp cams 68-231-4 & lifters
Mopar 5249464 springs
Mopar .043 head gasket (set)

I was hoping to take the block and head in for machining next week and looking for help on a few things. I am going to have the pistons dished, I would like to end up with 30cc's but have read that 24 cc's may be the safe limit. Anybody have any experience with this?

If 24cc is the max and I deck the block .035 and the head .010 I end up with 9.25 SCR and 8.378 DCR and a quench height of .0575 if I have used the calculator right. Is this too high for pump gas? The alternative is to take less off the block but this increases the quench.

Assuming I do deck the block and head I need shorter push rods or adjustable rockers, correct? If I chose adjustable rockers, I need a valve cover spacer?

Or should I wait to see how the KB 944's work out and start again?

[gradon]

You'll be able to run on pump gas, so a low-mid 20cc dish will be fine. My SCR--10:1, DCR--8.54:1 with the H825cp30(15.5cc dish, block decked .028", head shaved .004")and I have been using 93 w/o pinging(haven't tried 91 or 89 yet). Make sure you get details on the gasket set--I thought I was getting the Mopar Performance/Victor Reinz HG set and it turned out to be a Fel-Pro set with the .051" HG and crappy cork gaskets.

[Flash]

Hmmm Well you already have the piston, but if it's not a problem to Buy another set(KB) and you have the time to wait for the info to come out. than, this would be the better plan, in my opinion, as there is several plus's to the new KB "stroker pistons
1- you will get a better quench for a set or same compression ratio, then with other store bought or stock pistons (4.0L)
2- with the longer 4.0L rod, the piston skirt, or bottom side of the piston won't poke out the bottom of the cylinder wall a BDC.
3- Wellllll,...... 3 hasn't been proven yet. but if the piston sets some were close to .010 below deck that is said,(even .020 wouldn't be Bad) and the compression come out right......You wouldn't need push rod or adj rocker arm.......well New rocker arm is highly recommended if the cam is changed. But new stock ones, may be all you need, if you don't need to deck the block to get a respectable Quench.........................But, then again, there has been good success with the silvo's dish in the 24+ cc and the shorter 258 rods.....................


Flash

P.S. WELCOME A BOARD!!!!

[Geo.]

Thanks for input, guys.

Gradon, I saw that in your thread and ordered a separate hg with the kit to ensure at least one .043, thanks for the heads up.

Flash, I was thinking the same thing, but if you have to deck the block and deal with different push rod length anyways, then the only advantage is the longer rod, right? I think I am going to go ahead as planned with the silvo's as I have another jeep that could use rebuild in next year or so. Maybe one of each?

Is there a source for custom push rods? Gotta be cheaper than the adjustable rollers and valve cover spacer route.

[John]

You will find that info furnished by gradon in the FAQ section. Some good sources for pushrods of about any length we would need.
John

[Geo.]

Doh!

I swear I have read every post on this board and saw reference to the FAQ but never noticed it til now. Too much good stuff here.

Thanks.

[John]

Too much.. this site is just getting warmed up.
John

[gradon]

That it is.

[Geo.]

Not sure if this is old news or not but I e-mailed KB and asked min. recommended crown thickness as I wanted to increase the dish in my 2229's. Their tech guy said 1.9" minimum thickness, this is great news for me as I thought .3" was the limit. I am fairly sure that at least 30cc is possible based on my low tech ruler and straight edge measurements. Taking parts in on Fri., we'll see if the machine shop says.

[John]

2229's ok to 1.9" dish minimum thickness at KB technical Department. We have another nugget. Flash can you add that to our piston faq's
John

[Flash]

2229's ok to 1.9" dish minimum thickness at KB technical Department. We have another nugget. Flash can you add that to our piston faq's
John

Done.

One question, what is the stock Piston Dish or depth.........or am i miss understanding this?


Flash

[Geo.]

The stock dish is .1 according to the KB website. This gives a 11.5cc volume according to the piston FAQ.

I measured one of my pistons and came up with 3.07" over all height less 2.6" from bottom of skirt to bottom of crown at thinnest point less .1 for the existing dish leaves .37" by my admittedly rough measuring.

.37" less min. recommended thickness of .19 = an additional .18" of dish. So 1.8 x 11.5 + 11.5 = 32.2cc

This will allow me to deck the block .045, which makes the SCR 9.1 and DCR about 8.1 with a quench of .0475".

Do I have the math right? This is looking pretty good to me.

[Geo.]

Oops, I just noticed that I had the min. thickness @ 1.9" instead of .19". You might want to change that in the piston FAQ, sorry.

[Flash]

Oops, I just noticed that I had the min. thickness @ 1.9" instead of .19". You might want to change that in the piston FAQ, sorry.

Done, and now it make sense

Flash

[gradon]

tsk-tsk