Engine Guru Question

[englewoodcowboy]

I have an 87 BII that my son and I are doing a frame off restoration. I swapped the running gear from a 4.0 Ranger into the vehicle with a 3.73 limited slipand added a 4" lift. I am planning to run 32" tires. I had the 2.9L rebuilt at a local machine shop to freshen it up, a full rebuild was completed to include the new style better heads and it was bored .30 over. I have ceramic headers to go on it and thats about it for performance. What would you recommend doing or what do you think I should expect out of this vehicle. I also have an 88 Ranger 2.9 (155K on the odo) that is stock and auto, I'm content with how it scoots and was wondering if the BII will run a lil better.

 

[PetesPonies]

I have built lots of engines over the years. So I figured I'd answer your post and see what you needed. Well, I'm a bit confused as to what you really are asking. You seem to have a plan and followed through . . what is it you are wanting? I mean you say you are happy with how the "other" 2.9 runs. If it is a 2wd, and your BII is 4wd, you can expect a slight different in feel and acceleration. But it will be close. You engine is speed density, so you can't do radical things to it. A fresh engine, efficient exhaust, good ignition parts is going to leave you with a reliable ride. Is that all you are after?

 

[4x4junkie]

Your post is a little confusing... I'm going to assume you mean "swapped in the running gear from a 4.0L Ranger minus the engine" and that it still has it's 2.9L you spoke of being rebuilt.

If that's the case, it's going to be pretty doggy with 3.73 gears and 32s... However if you were to get 4.56 gears for it (4.88s would probably be even better), it should scoot along quite well then.
2.9s do need some RPM to make any decent power.

 

[superds]

I have a 90 Ranger with 2.9L/3.73s and 32" tires. It does good around town but could use some more power at highway speeds. Around 75-80 mph it's at that akward place in the rpm range where 4th gear puts it up around 3000 rpm (higher than I'd like to cruise long distance at) and 5th gear puts it closer to 2000 rpm where it has trouble making enough power to push the vehicle through the air, especially with any sort of head wind.

Probably not what you're asking but just thought I'd let you know what my experience is with a similar setup.

 

[PetesPonies]

See what you have done when you added the 32" tires is take the effective final ratio down from 3.73 to about 3.20. That's close to the 3.08 I want in my BII, but I have a V8. So with the smaller engine, it needs a bit more gear to run "peppy". Add to that the fact that you added some unsprung weight in the larger tires and you are turning the extra 4wd pieces and it just gets worse If you added some 4.56 gears, you would be back to about where the 3.73s were ( in final ratio) with stock size tires.

 

[superds]

Oh, I'm not complaining at all and I understand the effect on my overall gear ratio. I just decided to keep it like it is after I put bigger tires on because I rarely drive it on the highway and I knew when (if ever) i got around to doing the v8 swap in it that that would be the gear ratio i would want, similar to how you have your bii set up. The engine would pur at around 2300 rpm doing 80 down the interstate and should yield some decent fuel economy doing it. But for a 2.9 it's too much tire/not enough gearing for highway speeds.

 

[englewoodcowboy]

I guess I could have been a little clearer but y'all pretty much got what I was looking for. The B2 stock gears were 3:45 so I was hoping for it to be close to stock with the 3:73 and 32" tires. As long as it will get around town ok I think we will manage with what we have. As soon asi get it finished I have my 73 bronco to get in, it will be a full Restomod. Anyone going to Townsend, TN next month for the Bronco Super Celebration?