Stroking the 2.9

[nwstal]

I know there are posts about this already but they seem to break down into Swap in a 4L and never amount to any serious Ideas about actually doing it. They are doing it in Europe a lot however but a $2500 3.5 Kit is too much. Since I already have new world heads, and headers and it is more or less a rebuild I have been looking into it in depth and hers What Ive come up with:

Solving the Fuel system problem with a Mega Squirt ECU you can use your stock wiring harness and cut the wires and put them into the right spots on their plug, and you can do whatever you like as far as and engine upgrades even regrinding a cam beyond the Computer application Specs and seeing what is really possible

Block Deck heights 2.9L 8.084 4L 8.858
Strokes 2.9L 2.8346 4L 3.3071
Rod Piston Pin bore ID 2.9L .9450 4L .9432
Valve size:
2.9 Intake 1.78 Exhaust 1.41
4L Intake 1.71 Exhaust 1.36
Both engines use the same Rods 5.1386-5.1413 and Journal diameter 2.152 (minor Clearance differences The 2.9 generally running tighter tolerances)
World Heads have 58cc Chambers
Use these engine Calculators http://www.kb-silvolite.com/calc.php Ive tried others but these seem the most accurate and Its a lot faster than the scratch paper method because to get to the end result it takes about 15 equations

possible option
Normally Aspirated
Block Bored 0.0405-0.0466 to keep .008 to .0019 wall clearance
4L Crank Offset ground .030 Max bearing you can get is .040 so unless you have a brand new crank you are going to lose .010 Cleaning it up ending with a 3.3671 stroke
Rods either 2.9 or 4L
Mopar 4.7L Pistons
Bore (in) 3.700 in.
Bore (mm) 93.980mm
Piston Style Flat top, with no valve reliefs
Piston Material Hypereutectic aluminum
Compression Distance (in) 1.240 in.
Wrist Pin Style Press-fit
Pin Diameter (in) 0.946 in.
Piston Ring Thickness 1.50mm x 1.50mm x 3.00mm

This puts your deck clearance at -0.02045
using .038 Gasket thickness as an estimate
You end up with roughly 9.688:1 compression

If you deck the block to zero deck you get 10.172:1

If you want to use forced induction which Im not and haven't ran the numbers I would chose the 302 5.09 Rods and a custom Forged piston because there are only Cast options available in the correct bore and Compression Height ranges to consider but there your still going to be way under the price of buying a Kit.

The chilton's manual I got some of this from is wrong the 4.0 has 5.74 Rods

 

[rusty70f100]

Sounds interesting. The only reason I can think of to do this, however, would be if you wanted to maintain the 2.9L engines relatively small external dimensions and low weight. Otherwise, as everybody else would say, just build a 4.0L. For example, if you were building a light vehicle with a small engine bay and you wanted to keep the weight down. That, and mileage, would be the advantage a Ford Cologne v6, and 2.9 based motor in particular, would have over what most people swap in, which is a 4.3L Chevy v6 or a 350.

With a 4.0L you can swap between large and small chamber heads, and 3 different pistons (large dish, small dish, and flat top). All without any custom machine work.

 

[nwstal]

Rusty the 2.9 and 4.0 are the same block except The 4.0 has siamesed bores and taller deck. Im actually putting this in my Pinto and dissassembling an 87 full size bronco to put under my Bronco II. If you get into rebuilding the 4.0 you also find out that different years used many different parts and configurations, and it still has most of the problems the 2.9 had. The cologne engines also weighs less than the 2.3 four banger and was in the pinto as a 2.8

There is an error in the chiltons I got that info from the 4.0L has a 5.74 Rod.

And Just to piss the 4.0 crowd off try this one on:
3.4L 208cid
4.0 Block
2.9 Crank
3.8 v6 rods resized to 4.0 Journals
Stock 4.0 Pistons

Sad as it is that engine would probably run the best of the four possible combos it has a Lot better rod ratio and would rev like crazy So for those who say swap in a 4.0 I say swap in a 2.9 crank, in a 2wd Application it would romp all over the 4Liter

 

[rusty70f100]

They are not the same block. The closest analogy I can think of is to compare a 262 chevy to a 400.

Yes, I've rebuilt a 4.0L. I put the SOHC flat top pistons in it, a Comp 422 cam, ported the heads, 26lb/hr injectors, headers, and I ran E85 fuel in it, as it had a compression ratio of just over 11:1. I also zero decked the block. For the valvetrain, I used the recommended Comp springs, and rockers and pushrods off a 2.9L to create an adjustable valvetrain, so I could set the lifter preload. That motor was one heck of a runner; I doubt you could do better with less displacement.

Back to the block. They also widened the pan rail when they went to a 4.0L block. The cam bearing bores are different diameter. The lifter bores on a 4.0L have slots for the roller lifter indexing pins; the 2.9L block does not. They are related, but it's not as close as people think.

All you'd do with your 3.4L is move the torque curve out higher in the RPM range and lower it a bit. You wouldn't gain much of anything in horsepower, it would just occur at a higher RPM. Your horsepower is affected most by the flow through the heads.

I have wondered, how come the Europeans aren't importing 4.0L blocks and cranks from America? Or maybe they are and I haven't heard about it.

 

[nwstal]

Ultimately it really depends on what you want to do with your engine, I think the euro's have in small number swapped in 4.0 but some people build what you have. Morana's overrated you would gain maybe 25-30hp over stock. For all out racing I wouldn't stoke the 2.9 but in a low rpm 6000 max in truck your piston speed stays respectable. It would add torque and a little HP and you wouldn't have to spend 350 bucks on a camshaft. But It can be done inexpensively. In a carbed 2.8 it would be even more acceptable because its not EFI.

 

[bobbywalter]

Rusty the 2.9 and 4.0 are the same block except The 4.0 has siamesed bores and taller deck. Im actually putting this in my Pinto and dissassembling an 87 full size bronco to put under my Bronco II. If you get into rebuilding the 4.0 you also find out that different years used many different parts and configurations, and it still has most of the problems the 2.9 had. The cologne engines also weighs less than the 2.3 four banger and was in the pinto as a 2.8

There is an error in the chiltons I got that info from the 4.0L has a 5.74 Rod.

And Just to piss the 4.0 crowd off try this one on:
3.4L 208cid
4.0 Block
2.9 Crank
3.8 v6 rods resized to 4.0 Journals
Stock 4.0 Pistons

Sad as it is that engine would probably run the best of the four possible combos it has a Lot better rod ratio and would rev like crazy So for those who say swap in a 4.0 I say swap in a 2.9 crank, in a 2wd Application it would romp all over the 4Liter

that was funny

 

[84stealthranger]

Ultimately it really depends on what you want to do with your engine, I think the euro's have in small number swapped in 4.0 but some people build what you have. Morana's overrated you would gain maybe 25-30hp over stock. For all out racing I wouldn't stoke the 2.9 but in a low rpm 6000 max in truck your piston speed stays respectable. It would add torque and a little HP and you wouldn't have to spend 350 bucks on a camshaft. But It can be done inexpensively. In a carbed 2.8 it would be even more acceptable because its not EFI.

so with a 2.8 what could u come up with for getting more power out of it? not looking to race anything or be something its not just looking for more power then it has now.

 

[nwstal]

so with a 2.8 what could u come up with for getting more power out of it? not looking to race anything or be something its not just looking for more power then it has now.

Technically speaking that stroker assembly would fit a 2.8 and if you cross-reference all the data it appears the 2.8 block had a .020 lower deck height already so decking the block may not be required. What I didn't mention which goes with most stroker combinations this isn't a bolt in deal Gotta check Crank clearances possibly have the counterweights turned down, Rods might hit bottom of cylinders, so clearances may need to be ground into the block and such... I have a machine shop that I get a rather good deal with so doing such things isn't that out of the question.

Most of this was aimed at the 4.0L guys who come here and say swap in one of them... I believe anyways that this is the 2.9 forum and If i wanted to swap in the 4L id go their forum and ask them

 

[rusty70f100]

The 4.0 has siamesed bores

No, it doesn't. I have a bare 4.0L block sitting in the garage and I just verified it.

 

[Psychopete]

Have fun with it - experiments like these, you just have to do and learn. A cousin of mine built a SBF stroker with all sorts of mixed and matched parts. While it worked, the engine lasted 20K. I am sure he could have gone back and figured out what went wrong, but lots of metal shavings.

Just easier and cheaper to get more displacement by using an engine that's already built and heavily tested. Plus aftermarket parts are easier to come by (and cheaper in most cases) for 4.0L versus 2.9L, or any SBF or SBC V8. Not to mention the 2.9L has been out of production since '92.

 

[nwstal]

I read somewhere it was siamesed thats why you can only bore it .030 if your lucky, but it must be like the later chrysler 400 blocks with thin wall castings. No matter how you look at it its still a bored out 2.9 with a taller deck.

when building a stroker you have to take into account: rod ratio, rod angle, piston speed, and know what your intending to do with the engine. stroking the 2.9 to keep it together you would have a 5500 redline unless you use all aftermarket parts. The best factory engines typically run between a 1.6-1.7 rod ratio and the highest performers where in the 4"bore 3" stroke range. Some of the longest lasting like the 225 slant six are way off the scale the only way to know is to do it and see what happens. The 383 Chevys run well as do some stroker ford combos.

 

[rusty70f100]

You know "they" say the same thing about the 4.0L; that being that "you can only bore 'em .030"." I think it's just a myth that some screwball on the internet came up with. Here's my findings from a while back, on another forum, of actual cylinder wall thickness of a 4.0L block:

http://www.ford-trucks.com/forums/529041-i-got-me-a-motor-2.html#post4144566

I realize it's off topic (in the 2.9 forum), but I don't see why people don't just bore the 4.0L to 4" bores then use whatever off the shelf 4" piston they feel like.

I realize this proves nothing about the 2.9, but it proves that you never know until you sonic check it.