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To stroke or not to stroke??

X

xj bmx

NAXJA Forum User
Location
Detroit, MI.
So, with around 230k on my stock 4.0 she is finaly showing signs of age with puffs of smoke here and there.

I've been researching strokers for a wile now and getting weary of building one instead of just getting it factory rebuilt. Most of my concerns come from write ups saying things must be done and othrs haveing no mention of such things. One of them is the fuel pump or regulator.

My question is, can I just use stock everything (head,valve train, timeing stuff, pistons) with 4.2 rods, crank and new camshaft but just mill the block down to keep it from blowing up? Or do I need the different pistons some places say?

I'm ok with running higher octane since its a not a dd.

Another fear is disappointment, most people that did the swap ive read seem to be let down tho not saying it.
 
If all you're doing is stroking it and not boring it, you could probably use the stock pistons. But then you'll probably be disappointed as just simply putting in a longer stroke crankshaft won't make nearly as much difference as doing it all together.
 
If you are rebuilding, you will be boring, so you will need new pistons anyway. I love my stroker. It has around 100K on it and still running strong. I run the H802CP .060 over pistons with the stock 4.2L crank and rods. They cost pretty close to what stock pistons cost. I decked the block 0.025. This, along with a thin MOPAR copper head gasket puts the quench height right in the sweet spot and I can run the cheapest regular gas without ping. The cam is the biggest investment. For what we do a good low rpm cam is really where it is at. While a stock cam will work, the cam really makes a ton of difference. The dual rate cam I run was from Crane and is no longer available.

UPDATE: I just found a site that still has the Crane cam I run and the price is cheap.

http://crane.carshopinc.com/product_info.php/products_id/16375/753901
 
i really like my stroker. but i did mine fast and didnt get it done the way i really wanted to. ihave to run 93 octane or it pings really bad. had a cam in it but it wore a lube out so i put in the stock h/o cam.
 
Dougs stroker was impressive at the Crawl.
If I was going to rebuild a 4.0, I'd spend the money and stroke it.
 
old_man said:
If you are rebuilding, you will be boring, so you will need new pistons anyway. http://crane.carshopinc.com/product_info.php/products_id/16375/753901
Click to expand...

Well ya, "stock" meaning not using a dished style piston to help the quench? is it? .

The deal is the block and rotating assembly have 2k miles on it(so he said) with a .020 overbore and if i found this to be true (if thats possible) i was thinking i could just get the 4.2 crank and rods and reassemble as a normal rebuild.

Another thing i just read (on here actually) the guys recipe for a stroker he says that a .040 overbore is better for cooling, but that sorta goes against another write up that says a Undersquare motor, does better at making low end power so i would assume less bore would be better for what we do?

bmx1315
What did you do for yours? And do you ride? or is the BMX a coincidence? I really dont mind using the higher octane but if its to bad i dont want to risk a batch of bad gas killing the motor.
 
xj bmx said:
Well ya, "stock" meaning not using a dished style piston to help the quench? is it? .

The deal is the block and rotating assembly have 2k miles on it(so he said) with a .020 overbore and if i found this to be true (if thats possible) i was thinking i could just get the 4.2 crank and rods and reassemble as a normal rebuild.
Click to expand...
wait, your motor has 2k on the block/rings and is puffing smoke?
 
xj bmx said:
Well ya, "stock" meaning not using a dished style piston to help the quench? is it? .

The deal is the block and rotating assembly have 2k miles on it(so he said) with a .020 overbore and if i found this to be true (if thats possible) i was thinking i could just get the 4.2 crank and rods and reassemble as a normal rebuild.

Another thing i just read (on here actually) the guys recipe for a stroker he says that a .040 overbore is better for cooling, but that sorta goes against another write up that says a Undersquare motor, does better at making low end power so i would assume less bore would be better for what we do?

bmx1315
What did you do for yours? And do you ride? or is the BMX a coincidence? I really dont mind using the higher octane but if its to bad i dont want to risk a batch of bad gas killing the motor.
Click to expand...

I've been building motors for over 45 years, so I have some minor amount of experience. You should not just increase the stroke without boring it. There will be a considerable amount of wear in the inside of the cylinder. The new piston will then travel over a worn portion of cylinder, the have to bump up and then run on a brand new unworn portion of the cylinder. This is a recipe for a broken ring.

As for balancing, it is nice but unnecessary on a low rpm stroker. It may make it a bit smoother running, but if you are going to balance then you should cc the heads and runners as well as port match the head to the exhaust, and not just any exhaust, but a well designed and rpm matched header.

For most people, they need to get the most bang for the buck. It falls back to the old 80/20 rule. You can get 80% of the benefits for 20% of the effort/cash. The last 20% will cost you the 80% of the money.
 
Occasional puffs of smoke? Maybe you need some new valve stem seals.
 
tomcat said:
wait, your motor has 2k on the block/rings and is puffing smoke?
Click to expand...

Haha no sorry, my current motor with 230ishk is puffing, I'm buying a block and assembly to build with "2k"

old_man said:
I've been building motors for over 45 years, so I have some minor amount of experience. You should not just increase the stroke without boring it. There will be a considerable amount of wear in the inside of the cylinder. The new piston will then travel over a worn portion of cylinder, the have to bump up and then run on a brand new unworn portion of the cylinder. This is a recipe for a broken ring.

For most people, they need to get the most bang for the buck. It falls back to the old 80/20 rule. You can get 80% of the benefits for 20% of the effort/cash. The last 20% will cost you the 80% of the money.
Click to expand...

I never thought about the unworn wall issue thank you, and as for the 80/20 that is verry true haha.
 
Last edited:
The stroker was the first engine I built. I built it in May 08 and now have about 30K on it. I thrash it regularly and it takes it and keeps on putting out. There is plenty of power and you can build a more radical stroker if you want more power(like the 4.9 roller I'm building with my brother the next 2 months)--no want whatever or jealousy of the v8 builds going on. The only SUV that has put mine in its place is our big brother srt8(he did let off on a slow sweeping turn that mine stuck to:). Mine has proven itself to stockish 5.0/4.6 stangs, 3.0/4.0 jags, 3.0 bmws, wrxs(non-stis of course), 5.7 hemi chargers/300ms, 3.5l nissans/infinitis, Range Rovers(haven't gone up against the Sport yet), and more(the smaller fish aren't worth mentioning). As said, you have to overbore, even if a mild .020". Parts can't be too clean, you can't use too much assembly lube, triple check bolt torques, triple check the timing chain setup, and triple check the distributor setup(so many issues w/ these). Take your time and enjoy the process--you'll have plenty of fun after.
 
old_man said:
as well as port match the head to the exhaust, and not just any exhaust, but a well designed and rpm matched header.
Click to expand...
That would open the exhaust ports up too much. All the aftermarket headers have ports that are much bigger than the port on the head. Plus, you want at least a smaller port on the head to prevent exhaust gas reversion. However, port matching the intake manifold to the head would be a good idea.
 
xj bmx said:
Well ya, "stock" meaning not using a dished style piston to help the quench? is it? .

The deal is the block and rotating assembly have 2k miles on it(so he said) with a .020 overbore and if i found this to be true (if thats possible) i was thinking i could just get the 4.2 crank and rods and reassemble as a normal rebuild.

Another thing i just read (on here actually) the guys recipe for a stroker he says that a .040 overbore is better for cooling, but that sorta goes against another write up that says a Undersquare motor, does better at making low end power so i would assume less bore would be better for what we do?

bmx1315
What did you do for yours? And do you ride? or is the BMX a coincidence? I really dont mind using the higher octane but if its to bad i dont want to risk a batch of bad gas killing the motor.
Click to expand...



i'm pretty much running 4.2 crank and rods and bored .040 over, 99+ intake.
i used to ride.now i work tomuch and just really got out of it.
 
Nothing else?I know you said cam, no injectors or things? Hmm this is for sure helping me decide to stroke.

Maby we could get a sticky on currently running strokers and what was done?

Thank you guys for not beeing like another Jeep related forum I was on and only answering questions that are about lifts or tires.
 
Talyn said:
That would open the exhaust ports up too much. All the aftermarket headers have ports that are much bigger than the port on the head. Plus, you want at least a smaller port on the head to prevent exhaust gas reversion. However, port matching the intake manifold to the head would be a good idea.
Click to expand...


You know what guys? I caught a bunch of crap on one or more forums when I suggested matching both intake and exhaust ports to the gasket when putting the HO into my Renix. Heard all the warnings about reversion and large losses of torque etc. I did it anyway and the Jeep runs great. I ran the idea past my buddy who worked in Jeep engineering when I was service manager at a Jeep dealer when the 4.0 was new. He told me that the head guys weren't working with the manifold guys and never bothered to match the ports. So, some of the engineers did an experiment and match ported a 4.0 and ran it on the dyno. They picked up power. He explained to me why the exhaust ports were smaller and got even smaller in the late models: to heat up the catalytic converters sooner...........
 
xj bmx said:
Nothing else?I know you said cam, no injectors or things? Hmm this is for sure helping me decide to stroke.

Maby we could get a sticky on currently running strokers and what was done?

Thank you guys for not beeing like another Jeep related forum I was on and only answering questions that are about lifts or tires.
Click to expand...

shortxjdougs stroker ran like crap on 24# injectors. So much so that he fouled out a set of plugs and had to change them on the trail before it would start again. He swapped some stock 19# jobbies in at the campground and wheeled the snot out of it the next day. The Renix ECU is very adaptive, it's very loosely bound by it's fuel mappings. It will pulse 19# injectors long enough to make the mixture right as long as it's not a crazy build.
I think Doug told me it was a 12 weight 4.2 crank, some stockish pistons and a cam.
 
cruiser54 said:
You know what guys? I caught a bunch of crap on one or more forums when I suggested matching both intake and exhaust ports to the gasket when putting the HO into my Renix. Heard all the warnings about reversion and large losses of torque etc. I did it anyway and the Jeep runs great. I ran the idea past my buddy who worked in Jeep engineering when I was service manager at a Jeep dealer when the 4.0 was new. He told me that the head guys weren't working with the manifold guys and never bothered to match the ports. So, some of the engineers did an experiment and match ported a 4.0 and ran it on the dyno. They picked up power. He explained to me why the exhaust ports were smaller and got even smaller in the late models: to heat up the catalytic converters sooner...........
Click to expand...

Matching the ports eliminates turbulence and increases flow and there is no reason NOT to do it.
 
xj bmx said:
Nothing else?I know you said cam, no injectors or things? Hmm this is for sure helping me decide to stroke.

Maby we could get a sticky on currently running strokers and what was done?
Click to expand...

You should make your way over to jeepstrokers.com

Every subject on strokers has been covered here, its a great place to get started and edumacate yerself to more advanced topics.
 
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