Good idea to Stroke?

[OverTheHillsATTW]

Well my 89 Renix is at about 151k and at 200k I'm looking at a rebuild. Would I be better off doing a stock rebuild or follow a couple of the stroker options on the internet. I found one to my likeing. Cheap and easy for me to get the parts aswell.

4.5L
~ Jeep 4.2L 3.895" stroke crank
~ Jeep 4.2L 5.875" rods
~ Speed Pro 677P standard bore pistons
~ 9.05:1 CR
~ Stock 4.0 HO camshaft
~ Stock HO cylinder head
~ Stock 0.051" head gasket
~ 0.097" quench height
~ 2.25" exhaust
~ Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines

226hp @ 4600rpm, 304lbft @ 2000rpm

 

[seanyb505]

If you want to, go fo it. Lots of people go that route for power so if its what you want then do it.

 

[Dr. Dyno]

I wrote that recipe a long time ago and I've modified it since:

4.5L "Poor man's" simple stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Sealed Power 677CP standard bore pistons
9.2:1 CR
Stock 4.0 camshaft
Ported HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.088" quench height
Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines
247hp @ 4900rpm, 300lbft @ 3500rpm

Since your engine has a high mileage, I'd suggest at least a +0.020" overbore which would make the displacement 4563cc (like mine). You could reuse your Renix head and port it. You'll end up with about 10hp less than with a ported HO head but torque would be similar.
My stroker is exactly like the above but with a +0.020" overbore. With homebrew CAI, modified 65mm TB, taper bored 65mm to 62mm TB spacer, modified Borla header with 3" outlet, custom 3" downpipe, 2.5" cat-back, dual electric fans, Ford 24lb injectors, MAP adjuster set at 5.1v, and stock computer, my 5-speed '92 XJ put down 200hp@4750rpm and 254lbft@3530rpm at the rear wheels.

 

[wolfpackjeeper]

it is ALWAYS a good idea to stroke

 

[OverTheHillsATTW]

I like that... it's always a good idea to stroke. haha.
I have a spare HO engine from a 91. So i'm thinking either this winter or next summer. I just need to talk to the machine shop guys.
Thanks for the update Dr. Dyno.

 

[spoon_racer]

What about a balance and blueprint? I know a guy who builds classic Pontiacs and has one with a MONSTER. This monster can run 10K rpm! All that power and all that torque with that long of an rpm range. You can imagine quite the deal. I hear him from miles on the highway haha. What say you all about the same procedure on my 4.o HO? I don't expect teh results he has but as far as power and efficiency is it worth it vs other options when this one starts to go? Right now it has about 190K so I am trying to get some options together. All highway miles but still.

 

[wolfpackjeeper]

balance and blueprint still will not carry you much above 6k on a 4.o

 

[JJacobs]

What about a balance and blueprint? I know a guy who builds classic Pontiacs and has one with a MONSTER. This monster can run 10K rpm! All that power and all that torque with that long of an rpm range. You can imagine quite the deal. I hear him from miles on the highway haha. What say you all about the same procedure on my 4.o HO? I don't expect teh results he has but as far as power and efficiency is it worth it vs other options when this one starts to go? Right now it has about 190K so I am trying to get some options together. All highway miles but still.

I call BS on that. 10k rpm, on what engine?

 

[alex22]

10K isnt all that bad. If you have an ultralight valve train, strong springs and enough piston to valve clearance. Also, how long is it at 10K? Some of the engines we work on see 14K+ on a missed shift on road race coarses. They will survive that a few times as long as the valve springs are swaped out for fresh ones before the next race. When valve springs are operated at too high of a frequency it permanently damages them.
The Pontiac monster, which I am assumeing is a drag race car, most likely does not make much power below 3K and launches somewheres around 6K. Which leaves it only a 4K rpm operating range with a narrow power band.

~Alex

 

[wolfpackjeeper]

10k on a big inch v8 monster motor isnt bad. On a 4.0 it will never happen.

 

[JJacobs]

NHRA Pro Stock engines run 9000 rpm. 500 cid, built for revs only, not much down low. A Pontiac V-8 turning 10000 rpm is absurd unless everything internal is titanium and aluminum- and even then it probably ain't happening.

Sticking with :bs:

 

[BBeach]

I call BS on that. 10k rpm, on what engine?

x2. I once caught a fish and it was >==========================:> big!

 

[Shavenyak]

10K on a light valvetrain short stroke V8 is doable. Hell, there were guys building destroked 302/289s to spin 10K decades ago.

 

[wolfpackjeeper]

My stock LS1 turns 6k without a problem. Motors can be built to do anything

 

[BBeach]

The M3's new V8 goes to 8200 or 8300 rpm. Of course that thing's pretty decked out....and sexy.

 

[wolfpackjeeper]

that v8 is stupid, abomination, horrible. Should have stuck with the line six like BMW's are known for.

I really dont care, but my buddy is a BMW enthusiast and it pisses him off a lot

 

[alex22]

I haven't heard much about the new BMW V8. Care to enlighten us?
The problem with the BMW I6 is that they crack, and when they do, nobody makes a new cylinder head for them. I have seen quite a few with severe cracks so I had to tell the customer we could not help him. luckly he was able to find another used one that did pressure test good.

~Alex

 

[wolfpackjeeper]

nah, i was just spouting off. My friend really does hate them though, I think it is more from him wanting to see a new generation of turbo l6's in those cars than a small v8. I dont blame him, even with the potential to crack it was a pretty good engine. kinda like the 4.2 l6 in the older jaguars

 

[alex22]

Back to the question at hand. If you have the opritunity to build a stroker its kinda silly to build anything less. I would try to tighten up the quench on your build. a quench that large is almost not worth mentioning, The tighter the quench the better it will burn the fuel resulting in better power and better mileage. I'm shooting for a zero deck on my stroker.

~Alex

 

[gradon]

x2 on shooting for a zero deck on the stroker (<.010"). Anyhow after the stroker project, I will be saving up to buy a 95-98 m3(I've wanted one for 13 years now). You can bet that the newest m3 is still the real deal. If you want to get the I-6, get the twin-turbo 335 and you'll be able to boost that to 400hp&ft/lbs with a few grand in mods.