Jeep Strokers

Hey guys I'm doing an OEM rebuild on a JY motor I just picked up for dirt cheap. Its going to be a daily driver that will see some desert trails. So it will be pretty mild & stock. I plan on a small cam & valvetrain upgrades, .20 or.30 overbore, slight CR increase. The motor was at the machine shop & got honed. But cly. 6 still has scoring. So my .20 or .30 overbore plans are now useful!
If anyone can help me pick the right set of pistons plz? I'm looking for budget .20 or .30 over pistons & rings!
I'd like to have a final CR of 8.8-9.0:1 & run 87oct.!
I might use a Comp 68-231-4 cam kit off Summit Racing! As well as doing intake & exhaust upgrades.

So onto questions:

1. Should I upgrade my valves or would stock be ok?
2. Which pistons should I get? Plz post a part #. (Because I don't understand all the extra info they give you lol)
3. Which headgasket should I use to get my final CR around 8.8-9.0:1? And is that a safe CR on 87oct.
4. Is there another route I should choose for building this mild street motor?

Any thought on these pistons and which would be best? They are both the same price & both are .30 over.
http://www.summitracing.com/parts/SLP-677CP60/

http://www.summitracing.com/parts/FEM-677CP60/

I'm kinda thinking I might try to go .60 over with this motor lol.

Come on guys no one has overbored a stock 4.0?

I like these with the 114 lobe separation, Helps build the low end cylinder pressure the comp stuff loses. These are Bullett cams out of Memphis Excellent quality stuff. I didn't use the timing chain and gears they sent with it, They are not to good of quality. He might give you a lower price if you don't get the timing stuff.

http://www.shop.505performance.com/cate ... egoryId=30

I wouldn't go .060 if you don't need to. You won't get any noticable umph and then if you ever need to do it again you'll need to sonic check it 1st.

I would bore till the cylinders cleaned and rounded, If they ain't round the rings wont seal. The only bad is if somthing happens in a bore after you go 060, chances are good the block will be no good no more. (they ain't worth sleeving in my opinion) I bored mine 060 because that is what it took to clean it up. I have no heating issues or any other negatives. The plus side of 060 is it helps unshroud the valves a little.

bbarrett wrote:I like these with the 114 lobe separation, Helps build the low end cylinder pressure the comp stuff loses. These are Bullett cams out of Memphis Excellent quality stuff. I didn't use the timing chain and gears they sent with it, They are not to good of quality. He might give you a lower price if you don't get the timing stuff.

http://www.shop.505performance.com/cate ... egoryId=30

How long have you been running this 505 bumpstick, do you have any thoughts of whats your
gas milang is' jest off hand ??

IC-944 pistons (21cc dish) can you bring low compression ratio (about a 9.3 to 1, also in Summit racing).
To achieve lower C.R., I think there needs to be machined the pistons, or buy customs pistons.

He's not building a stroker so those won't work. They'll fit but be WAY down in the hole ..........well it would have low compression anyway lol
Check in FAQ for available pistons. Stockers have 13.5cc dishes so get some with 15 or 17cc's and your compression will drop some. Part#'s are in that section. It depends what type you want - cast (cheapest) -hyperutectic(?)(Much better and can get them with coated skirts but cost a little more)

I plan on the hyperutectic pistons with coated skirts. i deffinetly want to get the coated skirts. I'm aware it wears off & such but it does help!
I'm seeing those pistons for like 40 bucks a piece..so 40x6=240 lol. Thats not bas considering I just came from a boosted IS300. To get the stock 2JZ-GTE pistons were 600+ or 400+ for used pistons. so thats fairly cheap too me, plus your putting out 1200-2000 for a good turbo. I'm glad that addiction is over.

4.whoa could I use either of the Keith Black pistons. I want to go .60 over as this is a fun motor & I have another to stroke.
KB Silvolite cast aluminium 2229/2229C----1.581" 11.5cc
KB Silvolite hypereutectic 3241HC/3242HC----1.592" 13.3cc

The way I've always build N/A motors was with flat top or dome pistons. So my idea here is use pistons with the least amount of dish possible and have a slightly thinner headgasket. I'll be porting the head a little if that affects CR at all.
Main goal is broad power band (2800-5000) & most power on 87oct. daily.

If my CR is to high with those I would use these.
Sealed Power hypereutectic H802CP/H825CP----1.592" 15.1cc

Can you help me figure compression ratios here? This is what I can't figure out on my own lol.

Well this is what I've come up with so far.
I'll be using the Mopar(.043) HG. A Comp 68-231-4 cam & Sealed Power H802CP (.60 overbore) unless I can get away with more compression & use Keith Black 3241HC/3242HC (.60 overbore) pistons.
Head & block WILL NOT be decked. They will remain at factory specs!
PLEASE FEEL OUT/CORRECT ANY WRONG OR MISSING NUMBERS!

bore: 3.935
stroke:3.413
combustion camber:58cc (Factory Spec: I don't know if this changes when I change pistons or head gasket?)
deck clearance:.0215 (Factory Spec)
gasket thickness:.043
Piston Ring Height: (Didn't know what to put here?)
Piston to Bore Clearance: (Didn't know what to put here?)
gasket bore:4"
connection rod length:6.123
cam duration: 250*
cam LSA:111
degrees advance/retard:4

With these specs I've come up with:
249.04 CI---4.08L----8.89SCR----7.72DCR----.0645 Quench----52 intake closing valve angel.

Does this sound right? Are my calculations correct? Is 8.89 SCR/7.72 DCR safe on 87oct? Could I use Keith Black 3241HC/3242HC pistons since they have the same compression distance & such?
These would bump my SCR to 9.06 & my DCR to 7.86! Would that be safe on 87oct. I'm 2800-3000ft. ABOVE sea level.


Please guys I really need some help here!

Thats a pretty weak DCR, on my stroker I was able to run 87, in the early summer at 500 ft ASL, and I think it was 8.38, so it should be good. If I were you, I would go with th comp cams 231, solid for bottom end torque and daily driving. Now that I think about it, my quench was around .044 because I had the block decked, but that is irreversible, but it was only $125 so I didn't care.

I just don't want you to build it with a too low of a DCR, step on the gas, and be like, am in 3rd, on no wait I'm in 1st

Ya I'm trying to get my CR as high as possible on 87oct. It just hard when you don't understand it and don't get any adivce.

Thanks to those who have helped though.

You should be good with anywhere between 8-8.5 DCR on pump gas. Around 8 to run 87, 8.5 run premium. 8.5 DCR is really the max you should go for pump gas and then you have to weigh in altitude etc.