Stroking a 2.5 four cylinder?

[JeepSpeed]

He had a custom crank made, etc, etc, and said the thing put out over 300 hp. From what I gathered, it's in pieces needing to be assmbled and he was looking to get $1500 for it all. It has injectors, header, intake, all that good stuff. I think it even has a custom computer for it. I can try to find out more if you are interested. PM me your phone # and I'll call you.

Yeah, 300hp out of a NA 2.5L (or 2.7, 2.8, 2.9) is a little hard to beleive. Actually, it's pretty much impossible to beleive. If it's anywhere close to true though, that's a great deal.

 

[xjcrawlr]

Yeah, 300hp out of a NA 2.5L (or 2.7, 2.8, 2.9) is a little hard to beleive. Actually, it's pretty much impossible to beleive. If it's anywhere close to true though, that's a great deal.

Why not? I personally know guys with 300hp, 1.8 liter hondas (turbo'ed of course).

Heres an idea.....Olds Quad 4.....185hp box stock, seen dirt track racers get 350hp out of them.

 

[ChicksDigWagons]

Why not? I personally know guys with 300hp, 1.8 liter hondas (turbo'ed of course).

Heres an idea.....Olds Quad 4.....185hp box stock, seen dirt track racers get 350hp out of them.

Sure, with forced induction. There are lots of low displacement high-hp cars out there with turbos and superchargers. He was saying NA.

 

[JeepSpeed]

Sure, with forced induction. There are lots of low displacement high-hp cars out there with turbos and superchargers. He was saying NA.

Thank you. That's why I specified "NA". Sure with enough boost you can make anything powerful. My original post stands. With a Jeep sourced 2.5L, 300 ponies is pretty much completley unbeleivable without boost.

 

[FUNKYTEE5]

Why not start with a motor that has more potential There's a reason why there is not stroker cranks available for the 2.5. The motor is just too small to net good gains from mods. and that's why it's still under 150hp as stated. The only way to make good power with N/A 4cylinders is to rev them higher. With the lack of torque from the lack of displacement, more rpms is about the only route to power gains. Every 4cyl that made good power that I've ever seen made it at 7-8,000rpm and had: multivalve heads, way extensive mods, or variable valve timing. From all of the cash thrown at a custom crank (not to mention custom pistons or shorter rods) for the 2.5, you'll probably be bummed with the outcome. Forced induction or a 4.0 will be a much better place to start

FUNKYTEE5

 

[Eagle]

Why not start with a motor that has more potential There's a reason why there is not stroker cranks available for the 2.5. The motor is just too small to net good gains from mods. and that's why it's still under 150hp as stated. The only way to make good power with N/A 4cylinders is to rev them higher. With the lack of torque from the lack of displacement, more rpms is about the only route to power gains. Every 4cyl that made good power that I've ever seen made it at 7-8,000rpm and had: multivalve heads, way extensive mods, or variable valve timing. From all of the cash thrown at a custom crank (not to mention custom pistons or shorter rods) for the 2.5, you'll probably be bummed with the outcome. Forced induction or a 4.0 will be a much better place to start

FUNKYTEE5

While I agree that BIG power in 4-cylinder engines comes from more sophisticated designs, that is unrelated to why there isn't a stroker crankshaft available for the 2.5L engine. The basic reason is that there isn't enough demand to justify tooling up to mass produce it.

The same holds true for the 4.0L. In the case of the 4.0L we luck out because the 4.0L is a derivative of a previous AMC engine that used the same block aith a longer stroke. Nobody is mass producing stroker cranks for the 4.0L engine. They're just plugging in 4.2L crankshafts. That option doesn't exist for the 2.5L -- disregarding the evolution from carburetor to TBI to MPI, there has only been one basic version of the engine. No alternate displacements from which to borrow parts.

 

[FUNKYTEE5]

I agree, the demand for stroker cranks for the lil 2.5 just isn't there for anyone to justify producing them.

5

 

[HossHoffer]

You're exactly right Eagle. As I stated previously no one that I have contacted is interested in putting the effort and money into engineering a stroker crank. I would be happy to get any more gains from my 4 banger and knowing what gains I got from the 4.6 stroker would think that a 4 banger would put me over the top as far as power needs go. However I don't think there are enough people interested in the maybe 185 hp and 225 ft/lbs torque (rough guesses) to get them interested. I would do it but I love driving Norbert and have saved mucho dinero on cross country trips.

 

[FUNKYTEE5]

At first I thought I found the answer to the stroker 2.5 dilemma, but it was a dud. I thought that AMC 2.5 was still a GM 2.5 derivative. If it was, one could use a 3.0 4cyl Mercruiser (marine) crank 3.6" stroke. But after research, I found that the AMC 2.5 is different after all. If you're willing to swap motors? You could build a killer GM 3.0+ liter 4 cylinder and then use the Novak adapter to mate it to the Ax-15.

FUNKYTEE5

 

[flexj]

A 300hp 2.5????.....ummmmm.....not on gasoline.....200hp maybe....but at a zillion rpm...

Now that you say that, I do remember him saying that they were using alcohol. The compression ratio was way up there so some machining or new pistons would be needed.

Now my interest level is peaked. I'm going to call him and get more details to see if it is bull or real.

 

[Nason]

At first I thought I found the answer to the stroker 2.5 dilemma, but it was a dud. I thought that AMC 2.5 was still a GM 2.5 derivative. If it was, one could use a 3.0 4cyl Mercruiser (marine) crank 3.6" stroke. But after research, I found that the AMC 2.5 is different after all. If you're willing to swap motors? You could build a killer GM 3.0+ liter 4 cylinder and then use the Novak adapter to mate it to the Ax-15.

FUNKYTEE5

You wouldn't even need a Novak adapter.
Take a bellhousing from a 99+ Dakota 2.5 (uses the Jeep 2.5 with the GM 4/narrow V-6 pattern, not the Chrysler) that used an AX-15 transmission.

 

[MudDawg]

There are three things that affect ultimate power output. The amount of fuel/air mixture being pumped, the type of fuel and the combustion efficiency.

On any specific normally aspirated motor you make it pump more by making it bigger (bore/stroke) or by improving it's pumping efficiency and reving it higher. This is hard to do when working with a pushrod engine. Especially when the head was never designed for performance. Or add a blower or turbo to force more volume. Or use fuels such as nitro or Gas/nitrous to increase the combustion pressure.

Pushrod engines are like a wooden club compared to multi valve DOHC engines as far as performance capability goes.