'90s Chevy Truck Performance...

I have been poking around on this site all morning, looks like you have quite a community built here. I like it.

I have also been reading about the problem of repetitive posts, and I am afraid I am about to become part of that problem.

My truck:
’95 350, TBI, automatic, 2WD, 3.42 rear end, Black, extended cab, 54,000 miles

I do a LOT of towing with this truck and in it’s current configuration it does not do so well… 6 MPG lugging in OD or screaming in Drive.

I am looking to go to Vortec heads from a ’96-98 Truck. Probably will do a cam upgrade as well. Holley intake and throttle body base, stock injectiors. Ditch the EGR and cats and go with a true dual exhaust.

If any of you have experience with these mods and would be willing to share it I would greatly appreciate it. Headers, intakes, Cams, TBI mods, Fuel pressure, valve springs, Chips, etc…

I know, I know, my biggest problem is the 3.42s. SO, before I do the Vortec swap…I am going to install some 3.73’s for the rear. Have any of you changed the gearing in your 93-95 GM truck? I understand that it confuses the computer controlled speedometer and possibly the transmission. Do any of you have a recommendation to remedy this besides spending $500 to send the CPU to GM to be reprogrammed?

Are all ring and pinions created equal? Some say Richmond gears are the best. Others say they are a “performance gear” and are loud and only good for 40,000 miles. Yukon is another company I am looking at. Anyone have experience with Precision?

Suggestions of a TBI board I could join?

Thanks in advance!

Jay
www.cyclezoo.com


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your saying you get like 6mpg, but with those upgrades your not gonna get better gas mileage you will be more so losing it. since you do alot of towing i would be upgrading more so your rear and you also say you wanna get a 4.3 vortec engine. if your gonna upgrade your engine to something more fuel better and better power, i would honestly say get a Diesel Engine they provide ALOT of torque which helps you ALOT when it comes to towing, Diesel engines aren't that hard to find and too find one to replace a Chevy small block 350 is pretty easy. ill look around and give you some websites if you would like.

I have done everything any anything you can think of to my '91. You have an electronically controlled transmission, so changing the gears will throw off the speedometer than that will throw off the transmission. The good news is there is a relatively cheap fix for this. The DRAC module is where the calibration is so you can either get one out of a truck that has the gears you want, have yours calibrated, or calibrate yours yourself. Do a search online to find out how to do it yourself. My '91 has the calibration in the speedometer and that was a pain, but yours is not in the speedometer.

I swapped my TBI engine for a Vortec engine when I got a rod knock. It was a good swap but really expensive. You need the special intake manifold to bolt to the new heads and keep the TBI and a special EGR setup with the tube and drivers manifold (or header) from the 96-99 trucks. Changing the heads also requires you to have the MEMCAL (chip in the computer) recalibrated. You can do a mail order tune but I am hear to tell you they are crap. I sent mine back several times and finally gave up and bought all the stuff to do it myself. This was a learning experience and required several hundred more dollars and hundreds of hours of reading/tuning to get it right. One thing after another needed to be upgraded to get the TBI to work the heads and cam I chose. First was the TBI which now didn't flow enough air so I upgraded to a 454 TBI (STAY AWAY FROM THE OLDER HOLLEY UNITS). Then with the larger injectors it idled rough and I couldn't tune it down without starving it for fuel at wide open throttle. That led me to buy a vacuum referenced fuel pressure regulator to give more pressure as the load increased.

I don't tow anything with this truck, but in the end I still wasn't happy with the power so I built a 400 and switched to a carb. This was the best thing I did for me.

I don't know what the weight is of what you tow but the 350 isn't the best for towing. Your mileage will always suck and gets even worse with a big block. I have a diesel for towing and that works very nicely. 6MPG is really bad though. I almost wonder if you have another problem somewhere besides your gearing. Fuel pressure maybe, I don't know. My Dad has a 1-ton crew cab dually, with a carbureted 454, cam for towing, pocket ported heads and 4.56 gears that gets 6MPG towing a 42' box trailer with two racecars inside. Getting the same mileage with a 350 doesn't sound right.

Don't tow in OD with a 700R4. I think you will be surprised at how much better it will be with gears, but you may even consider running with 4.11's or even 4.56's.

huh? you dont tow in OD, but then tell him to get gears that will make him need to use OD

do you know what the actual RPMs are in drive at hwy speed?
he is correct, about not towing in OD, I would try and avoid that

how big are the back tires?

It's not going to be ideal but it sounds like he is towing a lot of weight for a 350. Reving it up will get it more in the power band.

oh crud, i just realized the original post was in 2003

LOL.....funny stuff....

First, your 700R-4 is not built to tow in OD. Having it built to do so is possible, but not if you're too cheap for speedo recal.
Second, doing 65 MPH with 3.42:1 gears, and not in OD, is nowhere near "screaming" RPM.
If you're going to do a gear swap, go right to 4.10:1. That way your engine will be in it's torque curve when towing in Drive.
Those Vortec heads do make great power as the RPM climbs, but you seem to be wanting more low-RPM torque. If so, then forget the Vortecs, your swirl ports are better below 3000 RPM.