Newbie-build-o-riffic!

[omegatron]

Howdy all! My name is David and I have been tweakin' out for days--turning into weeks on this fantastic site

Been wafting through tons of info and finally think I'm ready to as some semi competent questions:

Here is the skinny
'97 xj nvh block bored +.060 (still up for debate)
12 cw crank
4.2 rods
0630 head w/ diy p-n-p
+99 intake w/ bored tb

And now for the ?'s...pistons...been looking at the speed pro +.060 hypereutectic pistons as well as the federal mogul =.060 speed pro hypereutectic pistons...only difference I could tell was metric vs standard piston rings. Is one better than the other? Availability issues w/ metric or standard rings? Also I could not find the dish volume for those pistons. Also if you guys could have any piston suggestions they would be appreciated...I don't mind spending a little dough ($40/piston) and would like to avoid going over $300 for a set of pistons. Also any qualms about boring +.060? Didn't think there was a real concern till the .080 mark.

As far as block machine work, I was thinking about decking the block to achieve clearance in the range of 0.0 to .01 and going with the 'GQ' method discussed in the long vs short rod topics (using gasket thickness equal to quench value). Trying to hone in the quench between .045 to .055. As far as the SCR and DCR, I live in Denver and don't mind paying for premium fuel, love to go up in altitude and crawl all over the rocky mts. Thinking about mid 10's to 9's for the SCR and 8.5's to 9.5's for the DCR, using the cam to help achieve a more specific value and ratio, as well as dishing pistons if needed to help with the compression. Hopefully with a good quench and high compression, engine potential will be maximized with low potential for 'pinging'.

And the whole cam deal is still eluding me slightly...think I'll get there though... primarily going to be a daily driver, lower rpm range and a lil toque monster....again, suggestions appreciated.

Thanks for all the insight and tips! Really excited to pop my motor cherry Couldn't do it w/o this site!

[tomcat]

federal mogul = speedpro

as for metric vs standard, i went with whatever the spec for my year was, the pistons are exactly the same otherwise.

i went with speedpro, they have lightning bolts on the skirts

[omegatron]

Thanks...what CR should I try to stay under living @ 5280 ft? 10.6 SCR and 9.5 DCR? Any other pistons I should look at? and does any one know the dish volume of the speed pro +.060?

[Cheromaniac]

Speed Pro H802CP and H825CP pistons have a dish volume of ~15cc. I'd advise you to overbore +0.030" so you can leave more cylinder wall thickness for reliability. You'll find these pistons at Summit Racing under part nos. STL-H802CP30 and STL-H825CP30 respectively. It doesn't matter which ones you use as long as you get the correct matching rings (Imperial rings are easier to find).
You could go for a stroker build like this:

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Speed Pro H825CP +0.030" bore pistons
10.3:1 CR
CompCams 68-239-4 218/226 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.035"
Mopar/Victor 0.043" head gasket
0.046" quench height
Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines

[omegatron]

Sweet Cheromaniac...appreciate the info. The vehicle this is going into is a '92 yj, so I think I'll have to use the '92 fuel rail with an adj. FPR located at the fuel rail...correct?

Is it common to use an adj fpr with your adj map upgrade? Does this just allow one to really fine tune the air/fuel mixture?

[Cheromaniac]

Sweet Cheromaniac...appreciate the info. The vehicle this is going into is a '92 yj, so I think I'll have to use the '92 fuel rail with an adj. FPR located at the fuel rail...correct??

Yes.

Is it common to use an adj fpr with your adj map upgrade? Does this just allow one to really fine tune the air/fuel mixture?

You don't need both. Just use one or the other to fine tune the fuelling. You'll need 24lb injectors anyway. I'm using a homebrew MAP adjuster that I have set at 5.2v.

[omegatron]

Just ordered my pistons today WOOOHOOO! Went with the speed pro hyper +.030 and when I was talking with Summit and they told me to use the moly rings as opposed to the more expensive plasma-moly rings....just wondering what people are using for their strokers...

The dude at Summit said that the plasma rings we a little over kill since I wasn't using a turbo, SC, or nitrous. I want to build a reliable and sweet stroker and wouldn't mind paying for a few nicer parts (given that they will be worth the investment).

Pretty much going with Dino's build suggestions above....

Also went with the Cloyes double roller timing chain....who here is degreeing their cam? Is it necessary to invest in a degree wheel or should I trust the manufactures specs?

Thanks for all the help and when I get a few more parts together I'll start a post under the projects section with tons 'o pics...

[YJason]

Speed Pro H802CP and H825CP pistons have a dish volume of ~15cc. I'd advise you to overbore +0.030" so you can leave more cylinder wall thickness for reliability. You'll find these pistons at Summit Racing under part nos. STL-H802CP30 and STL-H825CP30 respectively. It doesn't matter which ones you use as long as you get the correct matching rings (Imperial rings are easier to find).
You could go for a stroker build like this:

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Speed Pro H825CP +0.030" bore pistons
10.3:1 CR
CompCams 68-239-4 218/226 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.035"
Mopar/Victor 0.043" head gasket
0.046" quench height
Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines

This is my engine except I used a felpro gasket and I'm having a little trouble with pinging on 93 octane.

[SilverXJ]

I degree'd my cam in. And I will have to do it a second time. PM me when you are ready for that and I may be able to rent you the necessary tools.

[omegatron]

Thanks Silver XJ...rental would be nice as I know those tools are pricey.

Is everyone using the standard moly piston rings (roughly $40/set) or the plasma-moly ($130/set)?

YJason....what altitude do you live? Do you think I will have the same problem in Denver (5280ft)? What exactly is your dcr? Did you mill your head at all? I might be running a DCR of 8.4 if the combustion chamber increases in volume by roughly 2cc's to 60cc's due to polishing it....

just trying to get an idea of what i can run w/o pricey race fuel, although I do not mind buying 91 octane gas (our highest rated in Denver)...i still might consider trying to lower the CR w/ depending on everyone's input...

[YJason]

I'm only 400ft and I'm not 100% sure on the CR.

[gradon]

I'm using the premium moly set ($70) instead of the standard set ($40).