Piston & Cam Selection Help?

[SilverXJ]

My stroker has 8.03:1 and when running I need premium.

[casual]

Can anybody tell me my quench height with this setup?

bore: 3.935 (.60 over)
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* (Comp 68-232-4)
cam LSA:113
degrees advance/retard:3

[SilverXJ]

Quench = deck clearance + head gasket compressed thickness
quench = .0215 + .043
quench = .0645"

Not too bad, but could be better.

[doublins]

You really want your quench tighter than that to be able to generate enough swirl in the combustion chamber to mitigate detonation- this doesn't really happen until the quench gets closer to .045"

With the mopar headgasket having a thickness of 0.043", you pretty much need a zero deck height to get your quench where you want it.

[casual]

ok thanks guys I can't belive I over looked the quench counter on the calculator...

Anyway is this a safe setup for 87oct. at 2500-3000ft above sea level.
Remember this isn't a stroker, just a big bore stocker!
(MOPAR HEAD GASKET)
bore: 3.935 (.60 over)
stroke: 3.413
combustion camber: 58cc (Factory Spec: I don't know if this changes when I change pistons or head gasket?)
deck clearance: .00 (zero deck)
gasket thickness: .043
Piston Ring Height:
Piston to Bore Clearance:
gasket bore: 4"
Dish/Valve Relief: 15.1cc
connection rod length: 6.123
cam duration: 250* (Comp 68-232-4)
cam LSA: 113
degrees advance/retard: 3

I get 9.3:1SCR & 7.92:1DCR

OR
(STOCK HEAD GASKET)
bore: 3.935 (.60 over)
stroke: 3.413
combustion camber: 58cc (Factory Spec: I don't know if this changes when I change pistons or head gasket?)
deck clearance: .00 (zero deck)
gasket thickness: .051
Piston Ring Height:
Piston to Bore Clearance:
gasket bore: 4"
Dish/Valve Relief: 15.1cc
connection rod length: 6.123
cam duration: 250* (Comp 68-232-4)
cam LSA: 113
degrees advance/retard: 3

I get 9.14SCR & 7.79DCR

[NorCalChris]

You really want your quench tighter than that to be able to generate enough swirl in the combustion chamber to mitigate detonation- this doesn't really happen until the quench gets closer to .045"

With the mopar headgasket having a thickness of 0.043", you pretty much need a zero deck height to get your quench where you want it.

X2. You really should have a lower quench. Also over on naxja I thought you stated you wanted good gas mileage(I could be remembering wrong). A higher CR will give you better mpg generally speaking. Youre woried about having too high of CR, but I dont think you are taking into account your elevation. Your in high desert correct?

[4.whoa]

I have a .060 4.0 similar to what your going for. Now I don't know all the specs 'cause it started as an advanced auto reman, but i've redone it (without reboring it) It is .060 but i dont know what pistons were used. the dishes look slightly bigger then stock but i'm not sure exactly.last time at the shop(that i quit using) he said they had 20cc dishes............ they are nowhere near as deep looking as the pics i've seen on here of pistons people have had machined that big. So far the head is not ported, but its had .040 cut from the surface. the block was zero decked last time it was in , i'm running the .043 victor mls hg and the comp 68-231-4 @ 4* advanced. I also notched the bores to help unshroud the valves a little.
the next time i have it apart i'll cc everything so I KNOW but I've had no problems running whatever gas i throw into it. when i know I'll be running it hard i use 91( its only like $2 more per tank here) and it runs great!at the moment it in a 4wd '95 xj with a aw4 and 3.55's on 31's on the highway at 70-73 it gets 19 -21 mpg (depending on terrain) and if i stab it it'll squall the tire (open rear ) In it's former line of duty it was in my '94 xj(see avatar) ax15,2wd,with 4.10's and HOLY COW that was a BLAST!! in that when it had 3.08's on the highway it got about 20 mpg (would've been more but i couldn't keep my foot out of it for long)
Bottom line is I dont think you need to worry as much with a 4.0 about the compression(within reason) as with a stroker.

[casual]

Ya chris I'm in the high desert. Elevation is 2500-3000ft.. (victorville, hesperia, phelan)

I'm tallying up cost & such. And trying to get an idea of power output. If the hp/per $ isn't all that great I may build it to a badass 4.6L & then build my daily driver motor into a 4.8L-4.9L or something!
Now I'm looking at costs & stuff it just seems this is alot of work for minimal gains!

[bbarrett]

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 ??

I have been running it since April of 2010, About 6k miles now, gas mileage has fallen to around 23 highway and 17 city, I believe this to be because of the winter blend fuels.

[Tar2001]

Building my second stroker... Blew up a piston in the first engine after around 20k, overheating most probably, will post some pics very soon.
Anyway, im planning the following setup (will reuse some parts from previous engine):
4cw crank
4.0 long rods
Around 9.5- 9.6 scr
Kb944 30 or 40 overbore (i wouldve prefered to find forged pistons with 1.5mm rings using stovk long rods)
Dekcking the block to get near zero
Good porting job (will post some pics)
Cloyes double roller
Melling HV oil pump
Ceramic coated doug thorley headers
62 mm tb


Now the big question is the cam selection:
1- comp cam 68-231-4 (mopar performance springs and retainers)
2- oem pre-96 cam (+4 deg adv using the cloyes gear)
3- oem 96+ cam (+4 deg adv using the cloyes gear)

I have all 3 cams ready (231 comp still looks in good shape from previous strokr)

I would appreciate some expert advice, how would these 3 compare? Any other suggestions on advance / retard?

[Tar2001]

My previous stroker was a short rod with scr> 10 and dcr > 8.6 quench about 0.053 the porting job had a major mistake as the outer edge of the exhaust port was considerably larger than the throat and larger than the headers diameter. It also had a custom 99+ intake manifold with dual tb with adjustable internal diameter. (wil post some pics after finishing the stroker).

I have to mention here that it's a 2001 xj and the stroker continuously threw misfire codes. Dont know if it was due to the 231 cam. I know that there are mixed opinions about its compatibility with fuel injection.

But my major prob with that engine was hesitation just off idle (which was slightly rough) if u floor it quickly. It would kinda choke and i could even see the rpm needle bearly going down before the engine responded like a monster afterwards. This lack of responsivness was only present off-idle. Holding the rpm slightly above 1000 and then flooring it would cause no problem. But i honestly felt the engine lacked the torque that you'd expect in the low rpm range.
While it pulled much quicker than our 5.2 zj, the zj's low end torque was much better. The zj's low end torque is just much nicer when ur cruising.

Any advice on the cam? Other things to prevent the same results? I am flexible with suggestions since i haven't ordered any parts yet. I need a nice low end torque at least comparable to a 5.2 zj but i also want some hp between 3000 and 5000 rpm.