2F crankshaft in a 3FE?

[Moby]

I know that a 2FE can be built by combining a 2F short block and a 3FE head. I'm wondering if anyone has looked at the possibility of stroking a 3FE short block by using a 2F crank to gain more stroke than can be had by offset grinding the 3FE crank.

Let's assume that custom pistons, rods or both would be needed to get the piston height correct at TDC in the 3FE block and that block clearancing for the longer stroke would also be needed. How about other potential issues like the bearings and caps, front and rear seals, oil pump/pickup interference, timing gears, front cover issues... Anyone know of anything that would make this a no go?

Why go through this trouble? I doubt a 2F block under my 3FE head would pass a visual smog inspection and I'd like to gain as much displacement as possible if I'm going to rebuild my 3FE.

 

[Mark W]

I seriously doubt that you would run into a smog equipment inspector who would recognoze the difference in the blocks. Very Seriously doubt it.

Without measuring and spending some time trying to figure out if there are any workarounds, I don't think that you could fit the crank with rods/pistons short enough to fit the deck height. I just finished a 2F and did a 3FE a couple of weeks ago. IIRC, the bearings are of significantly different sizes. I shouldbe able to recall for sure, but right now I can't.

I remember thinking along these same lines a while back. Back when it occured to me I realized it was pretty much a non-starter.


Mark...

 

[FJ40Jim]

No problem

Not a problem.

2F stroke= 101.6mm
3F = 95mm
stroke difference= 6.6mm
compression height difference= 3.3mm

A set of custom pistons w/ pins moved up 3.3, or
A set of custom rods that are 3.3mm shorter
is all that is required.

Call any one of several custom engine parts suppliers and have them hog a set of slightly shorter rods or pistons out of billet. They will happily do the work and take your money.

That being said, a fuel injected chevy might be a cheaper swap.

 

[Moby]

Mark/Jim,
Thanks, I appreciate the input from both of you. This is part of my ongoing internal debate over whether I want to do a 5.3 vortec swap for my quickly dying 3FE or have some fun with a tricked out 3FE (which has already been rebuilt once with poor results). Not so much a cost issue more of a do I really want to deal with a non stock powertrain (does the increase in power and marginally better fuel economy justify the hassles of dealing with a custom installation long term). I'm really on the fence but fortunately I don't have to rush into a decision.

If I rebuild the 3FE I'm already planning on custom forged JE pistons (they quoted ~$900 for a set of six) so if moving the pin really is all that is needed this might actually be worth it (I don't think offset grinding the 3FE crank is worth the money). I'll put this on the back burner as something to investigate if I decide to stick with the 3FE.

 

[agent orange]

Is the deck height different between a 2f and a 3f? If you really want a super 3f i would think that starting with a 2f short block might be a better bet. You could offset grind the 2f crank to put a stock pistion at zero deck . Do you really think a smog inspector would come close to telling the difference between a 2f block and a 3f block? Can you even tell the difference between the blocks by looking at the outside?

Its nice to see how much custom pistons run, ive always wondered. Maybe you could figure out how low you could go on the compression height without the piston pin getting into the ringlands, and then offset grind the crank to bring the piston to zero deck with that combo. That would be sweeeeeet.

 

[FJ40Jim]

The 3F block is shorter than 2F, 233mm vs. 289mm.
The 3F rod is shorter, 148mm vs 190.5mm.

 

[agent orange]

Damn, why did toyota go to such a tall piston on the 3f? Long rods are good things...

 

[alkaline747trio]

I think the pistons are about the same in size, although the skirt may be longer. It IS the longer/shorter rods that make the difference. 289-233=56mm so the rod should be 56mm shorter 190.5-148=42.5, 13.5mm longer pistons (if there aren't any other variables I missed, and my math is fixed) isn't that much taller.

 

[agent orange]

Ya das true. Nice mathematics.

 

[FJ40Jim]

Tall piston?

The 3F piston is significantly shorter. 71.5mm vs 95.7mm.

 

[agent orange]

Jim, is that overall height or compression height? Im assuming overall.

What is the difference in compression height between the two?

 

[alkaline747trio]

Ya das true. Nice mathematics.

Hehe, you got me on that one, next time I'm in a rush I'll not make a post with math in it.

 

[agent orange]

Hehe, you got me on that one, next time I'm in a rush I'll not make a post with math in it.

Haha, i didnt realize it was wrong, i was actually saying way to actually run the numbers not make a dumb post like me. Although im still a little confused as to why the piston isnt way in the hole on a 3f, i guess i should ponder some time when im not in the middle of studying for a test.... or, goofing off on this sight when im supposed to be studying i guess .

 

[alkaline747trio]

I know the feeling, cept my test was today and I dang sure bombed it. Oh well, it's an AP class, I can't expect to ace it. I think I was actually burned out from math, counting pipe all afternoon was a headache.

 

[alkaline747trio]

I wonder if it's all that much work to put a 2F crank/piston/rod assembly in a 3F block, then all the accessories wouldn't have to be reworked.

 

[Mark W]

I wonder if it's all that much work to put a 2F crank/piston/rod assembly in a 3F block, then all the accessories wouldn't have to be reworked.

You *might* be able to put it in. If you don't mind the pistons sticking out of the top.


Mark...

 

[Moby]

You can't change the stroke of your engine and keep the same block height without changing the rod or piston length.

 

[agent orange]

You can't change the stroke of your engine and keep the same block height without changing the rod or piston length.

You can if the piston is in the hole with the stock setup enough that the difference in stroke wont put the piston sticking out beyond the deck. Not that you cant do that in certain circumstances too.

 

[bigbrowndog]

Does the extra 200ccs make much difference? I thought Toyota shortened the stroke to make the 3F more balanced, revable and responsive to throttle control.

 

[Mark W]

IIRC the shortened the stroke to drop the displacement to skirt below a 4.0+ liter tax penalty.

200 CCs won';t make enough difference to matter. The longer stroke and rod of the 2f will make more torque for any given downward push on the piston from the burning fuel. The lighter rotating assembly and shorter stroke of the 3F will make for greater rpm cpability and a quicker revving motor.

If you have a 2F shortblock and a 3FE head and accesories... Build a 2/3FE. If you have a complete 3FE... Build it instead. Sacrificing a good 2F and a good 3FE to make one motor is not worth it.


Mark...