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[xjlee]

Hi guys, are any of you running or have had experience with stroking a 4.0? 4.6 - 4.7?
I wondered if anybody had done any relevant work on these engines just to improve the torque/bhp and whether you can actually get a stroker kit in the uk or if its a diy job?
The only reason i ask is i'm busying myself on a '97 xj and the engines in bits, and we were toying with the idea of a polish and porting the head, then it lead to other ideas as the cylinder bore on the problem cylinder looks very sorry for itself:

[Delk]

I have had mine  up and running for about 10 years and I think it is great. The modifications are simple enough and you keep all your original auxiliary pieces and fuel injection. The increase in power is very welcome considering my jeep is running 36"s. Mine appears to be as boom proof as any 4.0 and will happily sit on the motor way all day long, has seen the rev limiter more times then are sensible and has taken repeated overheating in stride because the radiator is blocked with mud.

The only problem I have had is not to do with the stroker conversion. I have a large volume oil pump and this puts to much stress on the dizzy drive gear and it failed once. The 4.0 doesn't need a large volume pump and now that I am back in cold climates the oil pressure can be very excessive when cold. 

You will find some good information on here.
http://www.jeep4.0performance.4mg.com/stroker.html

If you do go with a stroker keep it simple. You can now buy direct fit stroker pistons so the quench and compression are spot on. The easiest version you will need a crank, pistons, larger injectors and possably a voltage regulator for the map sensor.

Strokers don't have the best reputation mainly because some companies in the states putting out expensive poor quality engines or kits. If you go radical with a large cam the engine also suffers from excessive lobe failures. Increasing the cam requires extra spring tension, machining the head or other work and the benefits are not enough in my opinion. A buddy of mine went through three Crane cams and never got more then 5000 miles out of them. No wonder Crane went bust.

The side benefits to the stroker is that it looks stock. No issues with the MOT man or insurance companies. Mine has been registered in three contries now without an issue or question.

Most people will also say to go with a V8 conversion as it supposedly will cost you less. I did the work myself and shopped around for the parts so it cost very little. I couldn't have installed a worn out 1970's carbed V8 for what I spent.

[isle of man]

The last stroker I experienced was in the legs 11 Birmingham!!! 

[wildwood]

 :lol_hitting:Anyone thinking of a Stroker should read Delks link......

Seems over the years magazines have tried to get the most BHP at any cost......... This always resulted in meltdown...

the builder in the link also had probs ......it was with the Crane Cam........made of chocolate.....

Back to original cam and happy days, good power and great mileage......... Maybe now those of us .....including me .... That have been frightened  off by journalists building exploding Strokers ,  can file this link for the future....... Some good stuff there......

Worth keeping as a Birty article....permanent thingy?

[Bulldog67]

A V8 is just ...... well ......... a V8, nuff said really

U can make a mondeo fast if ya want but it aint ever a ferrari

each to their own tho

[JamesH]

I've been halfway through building one for years - got put off by stories of cam death and people making very complex ways to try and avoid it with head work. I have the dreaded Crane cam in place but now might switch to a Mopar one and just get it assembled and in (well maybe in the next 12 months or so).

Delk is yours factory stock cam or one of the Mopar mildly uprated ones?

[Delk]

I am running a mid range Comp cam and so far so good. I and when I build another I will keep the stock cam since it runs fine and has no issues.

My parts
2001 Tj block, free because the jeep sank in a hurricane.
My head came from an early HO Xj because they supposedly flow a bit better. Free from a friend.
12 counter weight crank ground and polished journals. 250 dollars
Silvolite pistons, 400 to 600 dollars i dint remember. They didn't make the stroker specific pistons when I built mine.
Stock rods, free
Comp cam, don't remember the number but I could find out if needed. Don't remember the cost.
2001 curved intake off the same amphibious jeep
Mopar valve springs to match the cam lift
Ford mustang injection valves, I think I paid 100 dollars on eBay for a set of 8. Still have two in the garage.
Home made voltage regulator for the map sensor. 10 dollars at the electric shop and some solder.

Tuning is easy. You have to match the injectors to the increase in power and if need be fine tune with the map sensor. The engine will run fine at low load on the stock injectors because it is in closed loop using the 02 sensor. At full throttle the computer switches to open loop and a pre programmes settings and will run very lean on the stock injectors. The larger Ford injectors I installed matched my setup almost perfectly and I don't even really need the map sensor adjuster.

I have my old engine, a set of Eagle rods (very rare) and a Eaton supercharger sitting in the garage. Some day when I sell the kids I hope to get a set of custom forged pistons and build a boosted stroker.

[Delk]

Bulldog you would at least like the paint job on my engine. It received two lovely coats of BBQ matt black.

[xjlee]

So you can build a stroker with different pistons and rods AND keep the standard cam?
Like i said we wouldn't want a stupid engine that needed constant tlc but a bit of extra torque seems appealing.
Is it difficult to do with regards tuning up?

[Bulldog67]

Bulldog you would at least like the paint job on my engine. It received two lovely coats of BBQ matt black.

 

[Delk]

For tuning you are only concerned with high output when the computer is in open loop. Low end, closed loop the ECU will sort itself out. The biggest concern is running lean and causing excessive heat or detonation.

You have roughly three options
1. Go Conservative and install extra large injectors to ensure you are running rich. This will sacrifice a few HP, burn a bit more fuel at wide open throttle but the engine will be safe.

2. Home testing with a proper wide band O2 meter and adjust with fuel pressure or MAP sensor voltage adjuster. A narrow band meter is cheaper but not as accurate.

3. Book some time on a rolling road and adjust away.

I did my initial adjustments with a narrow band sensor and hedged slightly on the rich side. A few months later I picked up a nice wide band unit but have never got around to installing it. Its just to shinny to go in a muddy jeep and the engine is still running fine years later.

Pistons are around 500 USD for a set in the states.
http://www.summitracing.com/parts/uem-ic944-020

http://www.kb-silvolite.com/icon/icon.php?action=details&P_id=543