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4.5 stroker

16K views 97 replies 35 participants last post by  fordbronco 
#1 ·
Finally have the money to rebuild my 4.0 and well I'm in there I want to add a few more ponies. Looking at getting a 258 crank and rods. Do I need to get new pistons to keep the quench height favorable? Do I need anything else? Is getting .020-.030 bored over pistons worth it?

I want to maintain 87-89 octane

Thanks for the help!
 
#9 ·
Taxes and I'm going to start working with my uncle

I want to make power but I don't want to spend 6% more on fuel :sonicjay:
I already put premium in my car don't want to have to put it in my jeep and its more money to build a stroker requiring 93. I just want a mild stroker

i am currently collecting parts for a stroker, I was hoping this thread didnt get derailed so quickly haha


I am going to use a 258 crank and rods and get 6 over pistons and bore my current motor. I have heard with a mild stroker build you can compensate the computer programming aspect of it with mustange injectors and a adjustable fuel pressure regulator.

Its all french to me.

what machine shop are you using
That sounds correct. Not sure yet about to start collecting parts

Will this be done before Silver Lake?
Yes

I just did this I used a 258 crank and rods with speed pro 4.0 pistons bored 30 over I used a mild crane cam. And mustang 24lb injectors I am still using pump gas. But I have around 1500 in the motor that is all parts and machine work on the block, crank , and head
What octane are you running? How much was the cam?
 
#6 ·
i am currently collecting parts for a stroker, I was hoping this thread didnt get derailed so quickly haha


I am going to use a 258 crank and rods and get 6 over pistons and bore my current motor. I have heard with a mild stroker build you can compensate the computer programming aspect of it with mustange injectors and a adjustable fuel pressure regulator.

Its all french to me.

what machine shop are you using
 
#48 ·
I use a machine shop out in Holly that is called SGB Enterprises. The guy that owns it and does all the machine work there is a great guy. He does all the machine work for all of our shops. He has built several jeep stroker motors. One of them was in a Cherokee of I guy that I work with. It seemed to run well and held together through some abuse!! If you want his number shoot me a PM.
 
#8 ·
I just did this I used a 258 crank and rods with speed pro 4.0 pistons bored 30 over I used a mild crane cam. And mustang 24lb injectors I am still using pump gas. But I have around 1500 in the motor that is all parts and machine work on the block, crank , and head
 
#12 ·
If you dont have to bore the block and can use stock pistons it can b fairly cheap and run on 87 oct fuel.
some 4.0l heads do hot spot in the combustion chamber. Often polishing the head in the top of the combustion chamber around the valves can help. Get it nice and smooth, with out removing too much material. Piston quench height needs to be set correctly for it to run well. Thicker and thinner head gaskets are avialable. U can also shve the head or deck the block if necessary.
 
#17 ·
Pistons aren't the only factor in octane requirements. Cam choice also plays a large part in this (if you're considering a cam swap).
If you have to bore the cylinders, you have to get new pistons anyway. Unless you're buying some custom units, I don't see where something with a little more compression is going to add much (if any) to your build. Add the fact that worse case scenario, you have to deck the block or mill the heads to achieve a flat surface... You may end up with more than you want anyhow.
If you're only going to use this for what you're saying, I can't see how it's worth putting a lot of time/effort into something so you can run fuel that's $.10 cheaper a gallon?
 
#20 ·
i have 200 in a cam and lifters and i am running 93 right now have not tried running 87-89 yet. i have 200 in boring the block, instaling new cam bearings and hot tanking the block. 150 in the head which incudes valve job and decking the head to insure it was straight. 200 in the cank that was turning it to .10 to .10 on main and rod journals and makeing sure it was straight. 80 in injectors from ebay 200 for pistons,rings,and cam bearings. 100 in main and rod bearings and 90 in a oil pump. if u are gonna do a rebuild i would most defintly put new cam bearings in it. if i wereto do it all over again i would save the moiney fro the stroker and just go 5.3 in it. or find a good running 4.0
 
#27 ·
Ya I'm not looking to spend that much. New can bearings even when my motor only has 115k on it?

waste o money

this will be a gigantic turd 10-20hp at the most increase over stock yea no thanks
For $300 more id be ok with 20hp

Cam, here's what i see. You will do this 4.5 Stroker, then when you decide to go to tons (and countless threads), you'll go to a 5.3. Then after you are on tons, you'll want a 6.0. You are wasting your money. Just swap your motor with a low mile 4.0 or rebuild yours. Keep it cheap and simple. You don't need anything bigger than a 4.0.
I may go to a 5.3 eventually but while rebuilding it why not spend $300 or so more to get a little more pep. It will be cheap and simple I'm not as cheap as you
 
#22 ·
Cam, here's what i see. You will do this 4.5 Stroker, then when you decide to go to tons (and countless threads), you'll go to a 5.3. Then after you are on tons, you'll want a 6.0. You are wasting your money. Just swap your motor with a low mile 4.0 or rebuild yours. Keep it cheap and simple. You don't need anything bigger than a 4.0.
 
#31 ·
I need to rebuild it just thinking about making a lil more power while in there

I am running a stroked 4.0.. 4.2 crank and rods .030 over pistons I decked the block and milled the head .010 each, 440 lift custom ground cam and a 99 intake with venom 26 lb. injectors and a 62 mm throttle body with a 1.5 inch spacer.. I have tons of power but I have to run premium in the summer and can run midgrade in the winter.. as far as mileage when I first installed it I was getting 21 mpg on the highway with my ax15 ,3.55 gears and 33s.. and that was with stock throttle body since then I am running 4.10s and 33s now I am only getting 12.5 on the highway with the 62 mm .. its all in a 1991 xj 2door.. if you do build it make sure to watch your numbers I am at 10.5:1 compression ratio and I wish it was lower... but that was my own miscalculation but I would give up the power for anything.. I do most of my climbing barley touching the throttle and on the street I have guys thinking I am running a v8 because of how well it gets up and moves.. I wish you luck on a build
Good to know. Thanks

I have done a huge amount of research on strokers, assembled one and I can tell you there is a lot of misinformation and second hand knowledge out there. There are also a lot of poorly built but still running strokers from what I have gathered. The biggest issue you will have is compression ratio. To get proper quench, you need to mill the deck of the block, which raises CR. Too high of a CR is what necessitates higher octane fuel. Basically you have two options to lower your CR. First is custom pistons, I believe Keith Black makes a set, second is having stock pistons dished deeper. Most people don't dive this deep into the build, build a motor with crappy quench and end up unhappy. If you have questions go to Jeepstrokers.com and start reading...more info there than you can imagine, most of which I've forgotten.
Will my quench and CR be fine with just putting in a 258 crank and rods I don't want to do pistons unless I have to. If I do this will I need special head gaskets?
 
#29 ·
I am running a stroked 4.0.. 4.2 crank and rods .030 over pistons I decked the block and milled the head .010 each, 440 lift custom ground cam and a 99 intake with venom 26 lb. injectors and a 62 mm throttle body with a 1.5 inch spacer.. I have tons of power but I have to run premium in the summer and can run midgrade in the winter.. as far as mileage when I first installed it I was getting 21 mpg on the highway with my ax15 ,3.55 gears and 33s.. and that was with stock throttle body since then I am running 4.10s and 33s now I am only getting 12.5 on the highway with the 62 mm .. its all in a 1991 xj 2door.. if you do build it make sure to watch your numbers I am at 10.5:1 compression ratio and I wish it was lower... but that was my own miscalculation but I would give up the power for anything.. I do most of my climbing barley touching the throttle and on the street I have guys thinking I am running a v8 because of how well it gets up and moves.. I wish you luck on a build
 
#30 ·
I have done a huge amount of research on strokers, assembled one and I can tell you there is a lot of misinformation and second hand knowledge out there. There are also a lot of poorly built but still running strokers from what I have gathered. The biggest issue you will have is compression ratio. To get proper quench, you need to mill the deck of the block, which raises CR. Too high of a CR is what necessitates higher octane fuel. Basically you have two options to lower your CR. First is custom pistons, I believe Keith Black makes a set, second is having stock pistons dished deeper. Most people don't dive this deep into the build, build a motor with crappy quench and end up unhappy. If you have questions go to Jeepstrokers.com and start reading...more info there than you can imagine, most of which I've forgotten.
 
#53 ·
You know nothing Joe

Just do a stock rebulid with a little more bumpstick and spend your cash on the head. The best bang for the buck is head work. Power comes from the head and intake. The more air / fuel you can move = more power. Or save the cash do a stock rebulid and regear your ride.
What would you suggest I do to the head?

Is $300 really what you have/want to spend, or is that just a number you threw out there?
It will be 300-400 dollars for a 258 crank and rods

X1558833558658566

Spend that $300 on a cam and headwork. I run a comp cams extreme 4x4 in my I6 along with a good valve job and love it.

Better yet, cam, get head rebuilt and then gasket match all the intake/ exhaust ports yourself with a $35 grinder set.
Suggest a cam over 258 crank and rods?

I want to see the receipts for this $300 stroker build. I bet he spends $300 before he even gets the old engine out. :sonicjay:
I'm saying $300 for the crank and rods I know the whole rebuild will be more

If you don't feel the need to replace any internal bearings and your motor only has 115k on it why are you rebuilding it at all? Run it till it blows.
I hate it blowing smoke
 
#34 ·
Just do a stock rebulid with a little more bumpstick and spend your cash on the head. The best bang for the buck is head work. Power comes from the head and intake. The more air / fuel you can move = more power. Or save the cash do a stock rebulid and regear your ride.
 
#37 ·
X1558833558658566

Spend that $300 on a cam and headwork. I run a comp cams extreme 4x4 in my I6 along with a good valve job and love it.

Better yet, cam, get head rebuilt and then gasket match all the intake/ exhaust ports yourself with a $35 grinder set.
 
#36 ·
If you have to rebuild your engine, why all the hate against trying to bump the HP a bit?

Picking up someone elses 4.0L seems like a gamble to me, you don't know its history. Stuffing another engine in it seems like a headache, your still left with someone elses engine plus everything behind it might not be up to it.

I have plans to stroke my 4.0L in the future as well, refresh it and get a little more out of it. I hope thread gets back on track....
 
#54 ·
Thank you!

If you think your motor is ready for a rebuild, you should plan on new pistons, rings, and bearings regardless of weather or not you have to bore it out.

I do believe that a stock bore that is properly milled to get quench into spec will have low enough compression to run mid grade at least. Jeepstrokers.com has a compression ratio calculator you can use to figure this out.
I know I need new bearings, oil pump, water pump, rings, gaskets etc. I didn't think id need pistons for sure

I was under the impression that you thought you could build a stroker for $300 on top of the cost of just rebuilding the 4.0
No just for the crank and rods out of a 4.2

I use a machine shop out in Holly that is called SGB Enterprises. The guy that owns it and does all the machine work there is a great guy. He does all the machine work for all of our shops. He has built several jeep stroker motors. One of them was in a Cherokee of I guy that I work with. It seemed to run well and held together through some abuse!! If you want his number shoot me a PM.
I will pm you thanks!

Regardless if the $300 is the whole budget, or on top of the rebuild budget, I'd be tearing the thing apart first to see what I had to work with.
Spending $300 on parts to stroke it won't do a bit of good if you tear it down, realize you need to bore it (requiring pistons/etc.), then can't afford to finish it.
I still don't see the sense in worrying about 87 octane so much. You realize if you put 500 gallons of gas a year in it, if gas is $3.30 for 87 / $3.50 for 93, you'd only spend an extra $100 over the course of 500 gallons.
Just getting a plan I will be tearing it out once its warm

Titan engines offers a complete stoker engine kit (including a machined block and rebuilt head) with all new parts for $2000. All you have to do is assemble it.
That's more than I want to spend but I appreciate it
 
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