4.0 Crank in 2.9?

[ranger_in_danger]

im rebuilding my 2.9 and ive heard that the 4.0 is almost identical to the 2.9 just larger. if you look at the specs they share the same category. so i know with chevys you can put a 400 crank in a 350 to make it a 383. i was wondering if i could put a 4.0 liter crankshaft in my 2.9 block to make it a stroker. plz help.

 

[Sunk]

I think I read somewhere you can do it with a lot of machining. I can't remember where I saw it though.

 

[Sunk]

Check these links out. Apparently the counterweights on the crank will either hit the piston skirts or the pan. Maybe somebody has better info.

http://agnes.goams.com/ford/

http://www.ford-trucks.com/forums/502092-stroking-2-9-with-4-0-crank-mopar-3-3l-pistons-need-info.html

 

[holyford86]

the 4.0 is a bored and stroked 2.9 and to do it they widened the block and increased the deck height.

 

[Will]

If you put a 4.0 crank in a 2.9 you get 3.4 liters. If you put a 4.0 crank in a 4.0 you get--4.0 liters. That's better.

The rods are the same length and the stroke is different. You would need pistons with a shorter compression height (center of pin to top of piston) to keep them from colliding with the heads. That most likely means custom pistons and after all that dough, you still have a smaller motor with smaller ports.

But the 2.9 has larger valves so maybe there would be more merit in trying to fit the 2.9 valves in a 4.0? I have no idea how close that would be to working.

 

[Psychopete]

Although it would be a cool project; but after all the cost, time/effort, etc, I think you'll have an engine that you won't be happy with. For the fraction of the cost, you could swap in a 4.0L/5.0L with a greater aftermarket with plently of room to grow. After all of that, you would have an engine (2.9L) that's meets it's mechanical limits. And how long it would actually last would be questionable. I think the only way to get this engine going good within a somewhat decent budget would be forced induction.

From the looks of the links above, stroking a 2.9L to 4.0L doesn't look feasible. Very cool links, btw!

I was there a while ago, I am actually letting go my plans for a S/C swap, once I found out forged pistons alone would cost $650 for 6. I think I'll get a full roller 5.0L that came with forged pistons from the factory. The S/C kit is going on E-bay soon (hint hint) for cheap (which I was told stock pistons are fine for it's 4-6PSI output, but I was going to get a smaller pulley for it - Eaton blower from 2000ish Nissan Xterra). Also was going to get an aftermarket PCM, etc, the whole 9 yards. If it doesn't sell, hopefully someone with an Xterra needs an extra blower.. Lots more parts, I also have a 10,000 RPM aluminum flywheel for a W/C T-5 conversion for 2.9L/4.0L (probably more for the 4.0L people). I am guessing that it works with the W/C T-4 bellhousing from a 2.8L in a early/mid 80s Mustang. Bucket seats are required.

Pete

 

[ranger_in_danger]

hey thanks for the help guys. ill take those thought into consideration. i my self am automotive sservice technician in school and ive read that when you custom stroke and engine they weld extra metal on to the end of the crank pins and re grind the area to increace the through but not my much but probably just enough in my case.

 

[AllanD]

I just wonder why this question comes up over and over and over...

What exactly is the attraction?

The special machining work can't be easier than simply swapping a 4.0 in...

IS it that people think that they can run their stroked engine on the original management system? because they CAN'T, an engine 20% bigger is going to need specialized tuning.

Plus they throw away the advantages of the 4.0.
the better alternator, accessory drive (serpentine belts rather than V-belts)
The better management system, etc...

It isn't that putting a 4.0 in where a 2.9 has been is all that difficult, it uses
the same y-pipe, motor mounts bellhousing pattern, etc...
There are some electronics issues to be sure, but it's really no more difficult that wiring a stereo (with amp and CD changer) into a vehicle that has no previous audio equipment...

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