Question for 85-87 Owners with 4.3L 262ci V6's

[jrblanke]

I recently acquired an 85 chevy with a factory v6/4 barrel. My truck has a 700R4 and a 3.08 rear end. It looks like the factory rating for that engine is 155 horse power and 230 ft lbs of torque. I really like the fact that it is different from the 305's I see in most trucks, but I feel like the 3.08 does not complement the 700R4 very well and the truck would be more efficient with a 3.42 or 3.73.

I would like to know what fuel economy people are getting as well as what transmission/rear axle ratio you have. I would also like to know how much you like your combination. If you don't like it, what would you change about it?

I am not interested in swapping in a V8 at this time and am more interested in hearing about gearing and transmissions.


Thanks!

[tard01]

I am not fully qualified to answer your question, so i simply provide this in case you've never seen it.

http://www.summitracing.com/expertad...tio-calculator

[Keith Seymore]

Mine is the 4.3L TBI, MY6 manual overdrive with a 3.73 gear.

I get about 20 - 22 mpg and wouldn't change a thing.

Strike that: I wouldn't mind an additional deeper low gear for launching while trailering. Other than that, I wouldn't change a thing.

K

[INSIDIOUS '86]

The my6 has a .7o overdrive correct?
If so his 700r4 should have great first gear for launch with a load
I have 3:73 gears in mine and no overdrive. I love them since I'm going for performance and once I have an overdrive then I think they would be perfect. I think the basic increase is 2-300 rpm every step in gear change. 308s are nice and 3:42 seem to be a real good blend the 3:73 will kill you a little more on the highway but the lock up feature on the overdrive helps that
Make sure your lock up works
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[Keith Seymore]

MY6 = .73 in 4th.

K

[INSIDIOUS '86]

Alright so pretty much the same as a 700r4.
Posted via Mobile Device

[Keith Seymore]

Yes - although you would get some additional torque multiplication from the torque convertor with the 700R4, which you would not get with a manual trans.

So the tip of the hand goes to the auto for launch, in this case.

K

[J Knight]

Did any of the 85-87 V6's come with a TH400 tranny?

[Keith Seymore]

Yes -

For '87, in an R20 at 6400 or 7200 lb GVW.

'85 and '86 have a couple C10's in the 4800/5200 GVW ratings but do not have the corresponding C20 applications.



K

[jrblanke]

Very interesting information! This is what I was looking for.

Does anyone know where I can find a torque curve graph for the 80's 4.3? Or at the very least the RPM's where it made max torque and HP? That information would help me to decide if I wanted to change the rear axle or not.

[Keith Seymore]

I have a hard copy of the Info packet for the '87 pickup at my desk; I keep flipping back to that as you ask questions:

http://www.gmheritagecenter.com/gm-h...tion-kits.html

I didn't find a graph, but did see a reference that the '87 TBI V6 was rated at 160 HP (SAE net) at 4000 rpm, and 235 lb-ft torque at 2400 rpm.

K

[C-10 simplex]

This seems like a really good combination. It would also be interesting to see what kind of E.T. it could produce as well.

[Keith Seymore]

Originally Posted by C-10 simplex

This seems like a really good combination. It would also be interesting to see what kind of E.T. it could produce as well.

I could probably find that out....

(...heh heh....)

K

[C-10 simplex]

Please do.

[Keith Seymore]

It'll have to be in the spring when the local tracks open back up.

K

[buffle]

I have an 87 sbfs 4.3 and 400 turbo. It`s a great truck except in the winter , this combo puts out so much torque you can`t go anywhere.

[C-10 simplex]

Originally Posted by Keith Seymore

It'll have to be in the spring when the local tracks open back up.

K

Thanks in advance. There are many who think the engine is "too small"/underpowered etc. But as you've proven with towing, apparently it IS capable(with the right gears).

i'm mainly interested for the mpg. Right now 16-17 with a 305/350 just isn't quite good enough. While 20 would make it acceptable considering the size of the truck.

[DREAMER1]

My '85 GMC came with the standard 4.3. That's what I know for sure. It also came with the thicker rotors. It currently has a t400. Question is did it come with the 400? Or was it installed by PO?
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[Keith Seymore]

Originally Posted by DREAMER1

My '85 GMC came with the standard 4.3. That's what I know for sure. It also came with the thicker rotors. It currently has a t400. Question is did it come with the 400? Or was it installed by PO?
Posted via Mobile Device

Do you still have the SPID label in the glovebox? That should show which trans it came with

- or -

depending on how badly you want to know: you can send your VIN and $50 to the GM Heritage Center archive and they will send you the invoice for your specific truck.

http://www.gmmediaarchive.com/

K

[jrblanke]

What kind of fuel are you guys running in your 4.3's?

The previous owner of my truck said that the engine would not run on modern fuel containing ethenol. I kind of thought that was bologna. It looks like the 85 4.3L is 9.3:1 compression ratio. So perhaps it runs best on something higher than 87 octane.

I have not put gas in it since I got the truck last Thursday.

[DREAMER1]

Thanx Keith for the help
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[Pyrotechnic]

I've noticed that on new trucks, the 4.3L actually gets WORSE gas mileage than the 4.8 and 5.3 V8's according to the window sticker. I found it a bit odd, considering that a smaller motor should do better.

Then I drove one and realized they give the V6 a pretty bad rear gear, probably the same one that comes standard with the V8's. The V8's get better mileage because they have more grunt to move the truck with that awful gear ratio. The V6 just has to suffer though it.

Give these V6 trucks a better gear ratio and I bet the gas mileage and towing capacity would go up. I bet they would drive pretty nice as well. Though I'm sure they cripple them with a high gear so the V8 will feel better on a test drive and you lay down the extra cash at the dealership.

Same concept with the V6 Mustangs. Manual trans cars got a 2.73 gear, so first and reverse were really crummy. Though I'm sure the rear gear helped cruise RPM's to some extent, the fact is it would have been a fun car to drive with a 3.55 gear. Ford would rather have to you buy the more expensive GT if you want fun, so the V6 is set up as cheap/economic/utilitarian option.

This way, the V8 buying customers stay that way and the V6 is there for people who want to spend as little as possible and don't care about power. Giving people a cheap V6 that gets better gas mileage than the V8 and feels somewhat close in power could hurt V8 sales and lose a lot of money.

[MalibuSSwagon]

Sales is onw reason. Its kind of odd that GM is still using the 4.3L V6 when the SBC's were phased out over a decade ago. I guess all the R+D dollars for the truck engine line are spent on the V8's

[66redw/white]

i had an 02 blazer that had the fuel injected 4.3 v6 and an auto trans and when it was stock it was an absolute dog. 15mpg around town no power at all. i changed the gears up to 373 and did a few mods to the engine and after the dyno tune i was gettin 18-19mpg city and upwards of 21mpg on the hwy. sounded alot better too. i know its a fuel injection motor vs tbi? but that was my experience

[66redw/white]

heres the truck

270 cam + tune blazer - YouTube