ok, tell me this is a dumb idea, or show me how to make it

[kowboydmac]

I've got so many questions but basically, here's the summary;

I want to run a 4.6 stroker with a remote mount turbo pushing about 5-7 lbs of boost.

I'll be searching as much as I can to find info to make this work over the coming year

[kowboydmac]

Do I absolutely have to go forged even if I want to stay at a relatively low boost?

I think they hypers would hold up to what I want, but at the same time I don't want to have to buy them twice.

I've got a great running 4.0 that I'll be swapping in/out but should I get an extra head to mill and toy around with?

[4.whoa]

The hyper's should hold up- if you keep the boost down, however its hard to resist turning it up after you get used to it when you know there's more on the table. Guess it depends how much restraint you have. Are you stroking the current motor or a 2nd one? If you're getting a 2nd, just get 1 with a head.

[kowboydmac]

Yeah I know about the temptation stuff lol but really this is a Jeep not a racecar (Plus Ive had my eyes on a 300zx with a twin turbo setup wayyy down the road)

I dont want to have much down time with my jeep and im planning on building up a high pinion dana 30 and dana 44a with a truss, both with 4.56 gears to turn 33" tires.

im comfortable trying out the hypers to keep this a realistically priced project

ok, so im also confused on whats the best head, if there is, to use?

Also need help with compression ratio. I know 7 lbs isnt much boost, and im parlaying my build off of the ;

4.6L low-buck stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Speed Pro H825CP +0.030" bore pistons
9.6:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.081" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
264hp @ 4900rpm, 324lbft @ 3500rpm

my problem is I'll most likely need a turbo friendly cam, and IDK if 9.6:1 is still too high even for low boost. my preference would be 8.5:1

[4.whoa]

There are people on here that know WAY more than me about cams, but I do know you don't want much overlap or it'll bleed the boost off.
You will need bigger injectors then 24# with the boost.
The 7120 is the most used head here & It flows well. The 0331 "tupy" head probibaly flows the best stock and has the best exh ports for sure, but IIRC you should use both the int and exh manifolds matched to it.

[kowboydmac]

ok so looks like i may be in for a deal for a machined crank and rods... 320 shipped. Kind of more than I wanted to pay but slim pickens and machining a crank would be similar priced anyway from what I can tell.

Got a Cam conversation going on with Kevin from Schneider cams. Looks like I'll be getting a regrind for about 120 bucks, but I have to find a Cam since I'm not pulling apart my 4.0 already in the ZJ

Also thinking about the Sealed Power hyper pistons, gotta keep my cost down and I don't think I'll be rev'ing high enough to really justify the extra 260 bucks for KB forged pistons. I'll definitely do my homework to make sure everything is tuned appropriately.

About to order an electronic copy of "Jeep I6 Power Manual" hopefully that gets me going in the right direction of how to appropriately build up this motor.

Long way to go, but I'm definitely not rushing this cause the 4.0 in the ZJ is running great, just has a little overheating issue so I'm swapping out the fuel pump and Thermostat this coming week sometime (I Dont drive often, and with the cold, it barely gets up to temp by the time I reach my local destination)

[kowboydmac]

There are people on here that know WAY more than me about cams, but I do know you don't want much overlap or it'll bleed the boost off.
You will need bigger injectors then 24# with the boost.
The 7120 is the most used head here & It flows well. The 0331 "tupy" head probibaly flows the best stock and has the best exh ports for sure, but IIRC you should use both the int and exh manifolds matched to it.

If I go for something around 40 lb injectors, would I be able to use them on my stock motor? Just curious what would happen, if I'd run rich or if the computer would limit how much fuel they'd spit out.

Actually, I'm getting a bit overwhelmed and confused about how to run my fuel system since I have a 98 Grand Cherokee with OBDII. What's my best bet for making sure I'm tuned right? Guessing I'd start with the wideband o2 sensor, then a piggy back? Not sure how piggy back's work since I've never physically used one.

[SilverXJ]

ok so looks like i may be in for a deal for a machined crank and rods... 320 shipped.

You can get a new Scat crank for $400 or less.

Looks like I'll be getting a regrind for about 120 bucks, but I have to find a Cam since I'm not pulling apart my 4.0 already in the ZJ

You can get a new cam for less. IIRC my Isky was like $90

I don't think I'll be rev'ing high enough to really justify the extra 260 bucks for KB forged pistons. I'll definitely do my homework to make sure everything is tuned appropriately.

How high you run the RPM has nothign to do with forged pistons.

About to order an electronic copy of "Jeep I6 Power Manual" hopefully that gets me going in the right direction of how to appropriately build up this motor.

URL for that? Not familar with that book.

Long way to go, but I'm definitely not rushing this cause the 4.0 in the ZJ is running great, just has a little overheating issue so I'm swapping out the fuel pump and Thermostat this coming week sometime (I Dont drive often, and with the cold, it barely gets up to temp by the time I reach my local destination)[/quote]

If I go for something around 40 lb injectors, would I be able to use them on my stock motor?

No way in hell. The PCM would throw a fit.

[4.whoa]

I agree. Get a new cam. If you go used, you really need the cam gear its mated to. If not its a potential problem.
The forged pistons are to handle the heat from high boost / comp / nos.
There are calculators on the net to help pick inj sizes, but you need to know what to put in them. I've never messed with them for a boosted engine.

[SilverXJ]

If you go used, you really need the cam gear its mated to.

How so? I've never heard of this. The cam gear doesn't develop a wear pattern on the cam.

[4.whoa]

I had it happen to me. A crane cam that was 2 yrs old or so. I put it in a fresher shortblock. I was in a hurry,so i put it in with the wrong flywheel(renix ) and one of the codes it threw was cam sensor. I swapped the whole dizzy (came with a new gear and i didnt think anything about it@ the time )Of course it wasnt bad, but i didnt yet know that. Anyway it ran for about 3 - 4 mos (not a dd just a toy) and then shredded the cam / dizzy gears ( in the middle of an intersection no less ) I didnt hold on to the old stuff, but those gears were TOAST !

[SilverXJ]

ohh.. the distributor gear. I've heard of that before. I thought you were talking about the timing cam gear.

[kowboydmac]

ok so looks like i may be in for a deal for a machined crank and rods... 320 shipped.

You can get a new Scat crank for $400 or less.

Looks like I'll be getting a regrind for about 120 bucks, but I have to find a Cam since I'm not pulling apart my 4.0 already in the ZJ

You can get a new cam for less. IIRC my Isky was like $90

I don't think I'll be rev'ing high enough to really justify the extra 260 bucks for KB forged pistons. I'll definitely do my homework to make sure everything is tuned appropriately.

How high you run the RPM has nothign to do with forged pistons.

About to order an electronic copy of "Jeep I6 Power Manual" hopefully that gets me going in the right direction of how to appropriately build up this motor.

URL for that? Not familar with that book.

Long way to go, but I'm definitely not rushing this cause the 4.0 in the ZJ is running great, just has a little overheating issue so I'm swapping out the fuel pump and Thermostat this coming week sometime (I Dont drive often, and with the cold, it barely gets up to temp by the time I reach my local destination)

If I go for something around 40 lb injectors, would I be able to use them on my stock motor?

No way in hell. The PCM would throw a fit.[/quote]


Silver, man, I read your thread and to be honest, I kind of want to avoid the Isky cam.

I mention high rev'ving cause usually high RPM's means more heat.

A re machined crank and rods for 320 is still a better deal than 400 for just a crank.

The book isn't a book, it's just an online thing he has going on.. Can't remember who referred me to the Yahoo group... I've emailed the guy back and forth and he seems to know a ton of stuff. groups.yahoo.com/group/JeepPower

[kowboydmac]

I agree. Get a new cam. If you go used, you really need the cam gear its mated to. If not its a potential problem.
The forged pistons are to handle the heat from high boost / comp / nos.
There are calculators on the net to help pick inj sizes, but you need to know what to put in them. I've never messed with them for a boosted engine.

Uhhh.. wouldnt a new cam be just as liable without a cam gear thing? Not trying to be a butthead, I'm new to all this, but neither a new cam or a cam out of the same block would have that gear I presume.

Schneider cams isn't a new company or anything, they've been around a long time

[4.whoa]

I'm not sure how much you know about vehicles, but parts that constantly "rub" each other develop wear patterns. Most commonly known among "car guys" are axle ring & pinion gears for this ,but cams & dist gears also do it.
Now not everyone agrees about it, however it CAN cause a problem. Not every gear/time of course , but some used stuff is worn more than others. I'm just saying so you are aware 'cause it would suck to put that $ into a used cam and have it shread itself and I hate when that crap happens.
Also with a new cam a new dist SHOULD be used. ( Yeah, yeah, some have gotten away without it , but for what- $10 why chance it?)