4.3V6 & 700-R4 Changeover

[beenydu]

I have a '71 Deluxe with a whopping 250 and 3 Speed. I have access to a 1990 4.3V6 and 700-R4 and am thinking about putting it in. As you can guess the $3.00+ / gallon is making this idea sound sweeter. Has anyone out there done this or know of someone who has? I would really like some input as to what somebody thinks. Is it possible to use the fuel injection or do I have to buy a new edelbrock and demon to put on top? Thank you in advance for all the help. I reallllllly appreciate it!

[LUV2XCLR8]

Never done it, but I contimplated it w/ my old 70 several times, think it would be

[shifty]

I hear the setup I'm installing will get over 20mpg highway....but it has to do with the 6spd, something about final drive (overdrive) gear being different than the automatic (4l60e?)

[beenydu]

Well, I figured the 1990 S-10 is getting 18-19 mpg average per tank, so I thought it would get somewhat close to that. I really love the idea of cruising at 60mph and turning 1700rpm. Anybody else out there done it yet? If I do it, I will be sure to take pics and document it very well. That way some more folks can save gas and still enjoy to drive the 67-72s.

[beenydu]

Well, I found some great info that I just read through. Here is the link:

http://www.howell-efi.com/technical_...bi_harness.pdf

I will continue to update as I find out info.

[guyryan100]

why not put in the 700r4 behind your 250? The fuel economy will come mostly from the tranny - not the engine. Would be a much easier & cheaper swap...

[beenydu]

Well, I have a bad oil ring on #3 and #5. I have oillish gunk building up on the spark plugs and then they foul out. I have put non-foulers on them and I think it helps some. I have not been impressed with the way it runs even after converting it to HEI. I drove it to work the other day and it cost me roughly $18 to drive 40 miles. So, I have been very impressed with the power the 4.3 makes and the dependability of the fuel injection. Winter is coming and cold starts are not to easy. My biggest concern is getting the wiring right and the computer wired up.

[djracer]

The used 4.3's bring pretty good money I'd sell it and buy a V8! They don't get that good of mileage I would think only 1 or 2 miles better than a V8 and Your truck would have much better resale with a V8!

[djracer]

by the way Troy Brown at howell's is a great guy to work with!

[tnblazerk5]

Originally Posted by beenydu

Well, I figured the 1990 S-10 is getting 18-19 mpg average per tank, so I thought it would get somewhat close to that. I really love the idea of cruising at 60mph and turning 1700rpm. Anybody else out there done it yet? If I do it, I will be sure to take pics and document it very well. That way some more folks can save gas and still enjoy to drive the 67-72s.

i may be wrong ,but i would think that it would get worse gas mpg in the 67-72 than in a s10 cause of the weight of the 67-72 ,i got a 91 s10 4.3 5speed and when i put 800 or more lbs in it ,it drinks the gas and when i pull a 5x10 trailer it drinks gas and in both pulling and stuff in the bed the 4.3 proformance sucks
i to would think the 250 and a 700r or a 4le<? would be better or a stock v8 with a 700 or 4le<? with a 308 or higher gear would get better gas than the 4.3
like i said i may be wrong

[beenydu]

Well, this will be a daily driver, so I think it will serve the purpose. I have a salvaged truck that I will be taking it out of, so it shouldn't be very expensive. I hope it turns out well.

[vtblazer]

Originally Posted by beenydu

I really love the idea of cruising at 60mph and turning 1700rpm.

Having an overdrive will of course lower your highway RPM's but it all depends on what you have for a final drive ratio in the rear axel.

Interesting swap though.
Does the 4.3 have as much HP as an old style six?

[beenydu]

vtblazer - It looks like it will be similar HP. The V6 may have a few more HP. The big advantage is that I am looking forward to a one-piece rear main seal and center bolt valve covers. That = no oil leaks or very slight ones. It doesn't go out as fast as you put it in. Also I love the fuel injection part. I have found some great information about installing the ECM and converting it over. I think it is something that many more people should consider. Insert key, turn, and drive. No cold start stumble or stubborness. I guess I am most impressed becuase I am a computer geek.

[kwmech]

How about a tbi 305, still have the v8 for resale and end up with a reasonable amount of hp and torque, mileage will still be in the high teens

[68 Stepside]

Someone here on the board has done this swap, they have a silver (I think) stepside. From what I recall they were fairly happy, but I think had mentioned it was a little gutless. I just can't recall the members name off the top of my head, sorry.

[vtblazer]

Originally Posted by vtblazer

Having an overdrive will of course lower your highway RPM's but it all depends on what you have for a final drive ratio in the rear axel.

Another consideration is the "shape" of our trucks vs. an S-10 not to mention the shear vehicle weight difference.

An S-10 has at least the beginnings of aerodynamics. Certainly a smaller frontal area.
Pushing a C/10 down the road at highway speeds will take more ponies/gas.

All I'm saying is I wouldn't expect "as good" where MPG is concerned.

I hear what your saying about the other issue's though.