bore and stroke of the 2.

[88gt]

How big of a bore will the 2.9 take? and how much stroke will it take?
stock is 3.66inch(92.96mm) bore
stroke2.83inch

 

[IMenriched]

My block is .04 oversize...no isssues.
can't say about increasing the stroke.... the 4.0 seem a bunch more adaptable.
someone else may have gone this route...if memory serves correct, that end in a very unhappy engine

 

[88gt]

where did you go for .04 pistons and what type are they? did you get new rods, if so where?

 

[Hahnsb2]

A bored and stroked 2.9 is a 4.0, strongly consider the swap before trying to make the 2.9 into something it can't be.

 

[88gt]

well, just curious about the stroke, but i am goin to do a tear down and rebuild of the motor within the next year. im a machinist so machineing the block and whatever else i decide is nothing for me to do. have access to everything that is neccessary. the main thing is that it will need to be bored out albeit so im mainly concerned about getin pistons to fit the bill.

 

[IMenriched]

where did you go for .04 pistons and what type are they? did you get new rods, if so where?

The machine shop that did the machine work also ordered the OH kit. .04 over pistions wasn't a issue to get, thinking they could go to .06 over if needed. They checked the rods and were fine, so they weren't ordered...but did go with a mild cam. sorry can't come up with the brand , but remember they were a recognized name brand.

again it maybe worth looking into a 4.0 swapp...they are far more proformance up grades available

 

[88gt]

fer finding the pistons, i guess that a call to summit will be in order when the time comes

as for knowing that a 4.0 can be a better base for performance, i know that, but i'm not looking for a super performance motor, just to hop it up a little. i don't have the budget for a crazy build up. just gonna portmatch everything, and refresh the bottom end of the motor.

 

[Psychopete]

Just bore for new cylinder walls, not for HP, that's what stroker kits are for (but they don't make one and custom forged pistons cost around $650 for 6).

Other people have installed 2.8L flat top pistons, that would jump up the CR. But you will probably have to run premium, and you might have issues with detonation. Search around, it's been covered here before.

You'd definitely want to measure the CR and check valve to piston clearance though. That's the cheapest thing I can think of, that and get an aggressive cam, but then you have engine management (computer) that's not going to be real happy and a truck engine that's more like a car engine (like mine ).

MAF conversion is possible and would adapt better than the stock computer that you probably already have. What would be really cool is to look into adapting the Duraspark 2.8L distributor on the 2.9L and fab a carb adapter for the lower intake manifold. It's says it's possible in the 2.8L/2.9L/4.0L OHV book by Sven Pruett, but no one on this board has had a successful story about it. He didn't go into great detail about it either, but the dizzy gears would need swapped for sure. I am swapping a 5.0L V8 and have no intentions of doing anything else with this engine, or else I'd be tempted to try it myself (any donations? parts/money? ).

Other internal parts can cause the engine to turd out, like soft valve springs, worn timing chain, and non-internal - worn sensors, and etc. So just a rebuild might give you the hop up you want, granted that it's pretty through. Even regearing the rear end...

Pete

 

[rickcdewitt]

the pruett book says .040 is the max overbore but he recommends .020the later 2.9 has the same rod and main bearings as the 4.0l but i don't think the 2.9l block is wide enough for the 4.0l crank.and as said you'll get more and it'll cost less to do a 4.0l swap.why not freshen up a dime a dozen 4.0l at your shop instead?

 

[AllanD]

Boring a 2.9 is like boring a 302.

Boring a 2.9 (177cid) gets you to 179 or 180cid
Boring a 302 gets you to 306-ish.

No matter how much you bore a 302 it's never going to be a 351

Ditto for boring a 2.9 it's never going to make it into a 4.0.

the 4.0 has bigger bore longer stroke and higher block decks.
And on top of that is a better intake and better cylinder heads.

For what you are proposing on doing to a 2.9 (just a basic "bore & rebuild) you can probably buy several RUNNING 4.0 engines

 

[88gt]

i don't want a 4.0. the gas milage is better with my 2.9, just was curious about the potentials of the 2.9. nothing more than pure curiosity. if i were to go for a bigger motor, it will be a 302. but im content with my 2.9 and when it needs a rebuild, like a stated earlier, im a machinist, maching the motor is not a problema nd won't cost me nothing except the 250 bucks for a rebuild kit. i just want ot refresh the motor and keep on keepin on.

 

[IDontCare]

RPM machine has what you want. in whatever sizes you need up it .06 bore. engine kits from 472 to 519 bucks. comes with everything but a oil pan gasket. i got the economy kit myself for the cast rings. the other one comes with different rings. expect a 5 to 10 business day wait before it gets to your door...

 

[88gt]

yea, i have their site bookmarked. when the time comes, they'll be getting some of my hard earned cash!!!

 

[AllanD]

i don't want a 4.0. the gas milage is better with my 2.9, just was curious about the potentials of the 2.9. nothing more than pure curiosity. if i were to go for a bigger motor, it will be a 302. but im content with my 2.9 and when it needs a rebuild, like a stated earlier, im a machinist, maching the motor is not a problema nd won't cost me nothing except the 250 bucks for a rebuild kit. i just want ot refresh the motor and keep on keepin on.

I don't agree that your concern over mileage is grounded in truth

I gotta be honest though I could get PEAK mileage of just over 26mpg with my 2.9 I only did it three or four times.
Generally I drove harder and burned more gas.

On the other hand when I needed to do something hard, towing hauling a load etc the 2.9 turned into a pig.
Hell I once managed to get 12mpg with it.

I have yet to get as bad as 16 with the 4.0.
So yeah it burns more gas out on the highway,
but it's minimum mileage is actually better.

The thing is I am VERY used to my truck (having almost 400,000 miles
in it) and drive the same way I have for over a decade and the 4.0 just doesn't have to work very hard to do the same things.

Just average "knocking around" my 4.0 generally gets 20-ish
And while I could get 21mpg in the same driving wiht the 2.9
I usually didn't

Think of it this way, I spend the bulk of my time during local driving either climbing some 4mile long 12% grade or coasting down such a grade.
the 4.0 climbs those grades relatively easily at 2700rpm
in 4th gear, the 2.9 would do those grades at the same speed, but running at ~4000rpm in 3rd.

For practical purposes I usually backed out of it on the 2.9 and climbed the hills at 3500rpm and a lower road speed.
which engine do you think burns less fuel?

The 4.0 basically goes anywhere I wanna go in 4th at 2600-2700rpm., of course in 3rd revving it out it'll climb those came hills at 85mph while the 2.9 had to struggle to do them at 72mph,
my best effort with the 2.9 on one particular hill... with the 4.0 I actually have to lift to take one corner near the top...

Hey, and that's all with the 4.10 gears I installed to make the 2.9 happy, I'm about to switch to 3.73's



AD

 

[88gt]

Thats interesting knowlege to have thankyou. For my needs, the 2.9 serves good. i have a 99 ranger that i do hauling with. it has a 3.0, but it gets the job done. my 88 ranger already has 3.73 gears in it because it is a ranger gt, stock from the factory. I don;t ever recall having to go downt o third to get up a nasty hill where i am in south-central virginia and i do have a 45 mile round trip drive for work.

But oin the other hand there...you have a 4 wheel drive, where as i have a 2 wheel drive. my truck is considerably lighter and the grades down here are hell occasionally, but you have to look for them. usually they are just rolling hills which can be conquered in overdrive. I really don't need the power capabilities of the 4.0 in this truck. wish i had bought my 99 with the 4.0, but the 3.0 does the job. if i need more power, my folks have a excursioin witha diesel i can use, or friends of the family have a f250 w/v10. so i have plenty of options.