JP manifold swap article

[dingo151]

Hey, guys

Has anyone seen the article in Jp thats labeled "4.0 myths and legends"? In the article they state that swapping a 2000+ intake manifold is a waste of time/money unless you have a head thats been worked over because the head won't flow enough air. I was wondering if this also applied to our stroker motors and what RPM do the stock heads tap out as far as CFM?

Opinions?


Dean

[Plechtan]

The 2000 plus manifold seems to ge good for about 10 HP. Just look at the specs of a 2000 xj vs a 98.

[Cheromaniac]

I gained 1.9rwhp and 4.5rwtq with my '01 XJ manifold swap. Torque was increased by an average of about 5lbft from off-idle to 3500rpm, with smaller gains from 3500rpm to 4700rpm. Above 4700rpm it dropped slightly.
You could say I blew the myth that the '99+ intake produces 10+hp gains right out of the water.

[dingo151]

So riddle me this? Would you go to the work of the swap if you had to do it again? I'm at that stage of my build and I'm wondering if I need to go buy some brackets and get after it or just run the stock 96 intake.


Dean

[gradon]

I'm of the opinion that every bit helps and being as the swap should be less than $100(I paid $26 for the mani and it bolts right up to the 96-98 ps setup), it is worth it. I was able to modify the setup on the 94 to work for an additional $25 for a longer belt(I reworked the tensioner to pull in the opposite direction). It is clearly a better design that provides equal length runners and smooth turns(not those right angles that 1,2,5,6 have on the earlier ones).

[Cheromaniac]

So riddle me this? Would you go to the work of the swap if you had to do it again? I'm at that stage of my build and I'm wondering if I need to go buy some brackets and get after it or just run the stock 96 intake.

Yeah, definitely still worth it IMO 'cause I also gained ~1mpg and throttle response is even sharper (as if it wasn't sharp already!). Overall it's made the Jeep even nicer to drive.

[1bolt]

Dino's findings are very close to what Engine Analyzer Pro predicted, maybe damn near idenitcal when you realize that Dino's numbers are from a chassis dyno which includes drivetrain losses. there's a thread about it here, if the earlier HO heads like the 7120 and 0630 heads intake ports and exhaust ports were as good as the 0331 head the intake would make more power than is does. The main benefit of that intake is improved low end torque. and better average horse power (not peak hp). Still on a dollars per power scale $50-100 is a smokin' deal.

And hey because we're talking about JEEPS here not Drag Race cars; Throttle response and improved low torque are WAY more useful in a Jeep than a "mythical" 10 horse power at 4800 RPM's would be. I mean is it a "MYTH" because it doesn't give the amount of horsepower that some people pulled out their asses a few years ago and plastered all over the web? Yeah, sure. On the other hand is it a "myth" that JP magazine has uncovered as being a useless mod? No I haven't seen the article but it sounds like JP is steering their users wrong and creating their own myth...

If the factory had wanted it to improve peak HORSE POWER (AKA improved Torque higher in the RPM range) with that intake they would have made the runners shorter not longer. The 2000+ has 11.5" runners, somewhere around 6" would be ideal for peak hp numbers on a 4.0+ sized engine and factory cam, the older manifolds were 8 to 9.5" (Renix to HO).

As always, making power is about how SYSTEMS interact with each other, the 0331 system (head and both manifolds) has better intake ports, smaller more efficient exhaust ports that actually improve power in the useable RPM range, longer intake runners (more inertia ramming at lower RPM's) longer and smaller exhaust runners (better scavenging at lower RPM's)... If the first couple years of them weren't crack prone we'd all be taking this for granted by now.

[dingo151]

I would have to agree. Sometimes it seems like the only thing that you hear about is Horsepower. Which I would readily admit rates at the bottom of the scale of importance in my reasons for building a stroker. My uncle told me one time the "horsepower is secondary because it's the torque that does the work" and that's really what I'm after is an engine that pulls! If the manifold adds torque at the bottom end of the RPM range then that's the kind of mod I'm looking for

[1bolt]

It's the perfect compliment to an RV cam