Jeep 4.2 Stroker High Performnce Build

Hi all, im new to this forum and i have a question about building my 4.2 liter amc engine. I do alot of off road 4x4 racing and the jeeps not fast enough. i was looking to build a high performance 4.5 stroker. my questions are, can i get a custom high lift "roller" cam? High performance rods? and high compression pistons?
Any ideas?
 

80broncoman

VIP Member
Staff member
Not sure if anyone has done a roller cam in a 4.0 block or not. if so that will probibilty be where the biggest chunk on money goes if it you find one.
I am unsure about the different rods as well.
I do know people make pistons though.
What is your HP/Torque @ what RPM goal on this engine?
planning on EFI or Carb??
 
id like to make around 400hp. its going to be a full out race motor. rpms can go as high as it can handle. not sure what the cranks good till.
 

DaGr8Tim

Well-known member
Check out jeepstrokers.com.

I found a 258 that I was going to stroke my 4.0 to 4.6. Then the guy turned around and offered me a deal for the whole Jeep, and I jumped on it.
 

BIG 6 farmer

Well-known member
Seems one popular upgrade on a AMC 258, is to bolt on a Cyl. Head off of a newer 4.0 Jeep. Even better to use the later version. another bonus is, you get rid of the plastic Valve cover mess.
 

DaGr8Tim

Well-known member
BIG 6 farmer":297tbkvg said:
Seems one popular upgrade on a AMC 258, is to bolt on a Cyl. Head off of a newer 4.0 Jeep. Even better to use the later version. another bonus is, you get rid of the plastic Valve cover mess.

Another popular way is to throw a 258 intake on a 4.0 and convert it to carb. If it were me, I'd go that route and stroke the 4.0 out to 4.6.
 

BIG 6 farmer

Well-known member
?? is, Does a performance Intake for a 258 fit on a 4.0 Head? Seems i read that using the later 4.0 Cyl. Head, is quite an improvement over the old 258 Head. Also thought they liked to fit a 258 Crankshaft in a 4.0 Block, to get a 4.5? Stroker. Problem with building a Stroker Engine, is it gets very expensive too fast. ( unless your talking a V8 Chevy, or some Fords). Going from a 4.0 or 4.2 (258). To a 4.5, or 4.6, isnt much of a gain for the money needed to get it done. My guess for a build, would be an overbored 258. With a late 4.0 Cyl. Head, Good Intake & Carb. Header. Im sure you can still get a lot of performance Flat Tappet Cams for a 258. Maybe somebody makes Roller Cam Kit? If they do, im sure the price is outa sight ! :bang: Building an AMC is like building a Mopar, twice the price. Look on sites & Forums for 4.0-4.2 jeep Engine Builds. :nod:
 

DaGr8Tim

Well-known member
BIG 6 farmer":132yl0w7 said:
?? is, Does a performance Intake for a 258 fit on a 4.0 Head? Seems i read that using the later 4.0 Cyl. Head, is quite an improvement over the old 258 Head. Also thought they liked to fit a 258 Crankshaft in a 4.0 Block, to get a 4.5? Stroker. Problem with building a Stroker Engine, is it gets very expensive too fast. ( unless your talking a V8 Chevy, or some Fords). Going from a 4.0 or 4.2 (258). To a 4.5, or 4.6, isnt much of a gain for the money needed to get it done. My guess for a build, would be an overbored 258. With a late 4.0 Cyl. Head, Good Intake & Carb. Header. Im sure you can still get a lot of performance Flat Tappet Cams for a 258. Maybe somebody makes Roller Cam Kit? If they do, im sure the price is outa sight ! :bang: Building an AMC is like building a Mopar, twice the price. Look on sites & Forums for 4.0-4.2 jeep Engine Builds. :nod:

From what I understand, you can use a 258 intake on a 4.0 head if you use an aftermarket header.
 

Ford 6-4u

New member
HESCO JEEP PRODUCT sells a aluminum head for the six cylinder jeep. This head flows 260 cfm at 28 inches "according to Stan Weiss site". This should get you 400 HP around 7000 rpm with a 258=6 cylinder, "depending on VE." 4550 piston feet per minute is a lot for any jeep. BUT POSSIBLE. Use the best of everything. I spun a 4 main bearing Ford 6 on the El Mirage lake bed at 4300 piston feet per minute for five years. Only problem was a occasional loose fly wheel. Go for it and keep us informed!
 
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