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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics> How to increase 262cid (4.3) v6 mpg?
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Topic Review (Newest First)
12-16-2018 08:26 PM
BogiesAnnex1
Quote:
Originally Posted by Oldsm View Post
Are underdrive pulleys just waste of money?

How about holley sniper? It is only east way to drive with moderate mpg or can it give good mpg? Example with vortrc heads and cam.
The Sniper is a high pressure TBI, like the GM TBI you have it is targeted at replacing carburetors, like any TBI or carburetor for that matter equity in cylinder to cylinder fuel distribution is a problem, so the mixture ratio is set so the leanest running cylinder is correct so these are never as good as port injection as that eliminates the weird things that happen to mixtures between the device and the valve.

Under drive pulleys are intended for high flow coolant pumps that deliver more flow per RPM so don't need to spin so fast. They also tend to result in low alternator output as it spins to slowly. Here again for a stock coolant pump, they just don't consume much engine power till you get the engine constantly at or above 4000 RPM. The pump uses fractional to onesie, twosie horsepower in its normal operating range, once again the resultant savings, if any, make it hard to justify the cost except in the minds of advertising executives.

Unfortunately magic fuel burn savings just aren't there against the cost of chasing them. You may end up at the pump spending 48 Euros on a fill up instead of 50, but the 2 Euros saved against the cost of the modifications to get them takes a long time to recover. Been there, done that; as before I retired I did a lot of driving and really worked on getting fuel burn down. As in San Diego to Newport Beach 160 miles each day; Snoqualmie to either to Auburn, Everett, Kent, Renton, or Seattle every day those are from 60 to 100 miles a day. When my friends and I opened our shop in Smohomish I ran parts between there and the machine shop in Centralia that's 240 miles on I-5 at least once a day, so yeah I know about big gas bills.

I know many crazies that pursue high mileaging to the edge of sanity, it can be done but it ain't comfortable and in many cases plain unsafe. I had a neighbor in Snoqualmie a few decades ago, he put a Fisher carburetor on his Dodge van. The Fisher lacked a power enrichment circuit which if you live in flat country and keep an egg between your boot and the accelerator you're OK, but you can't get into nor out of Snoqualmie without some steep and long grades. His fuel savings soon cost a piston, but that was state of the art back in the 1970's, today we have much better engineering with fuel injection so that isn't likely to happen but the cost of the technology is rather large compared to a Fisher carburetor.

Bogie
12-16-2018 04:25 PM
Oldsm Are underdrive pulleys just waste of money?

How about holley sniper? It is only east way to drive with moderate mpg or can it give good mpg? Example with vortrc heads and cam.
12-15-2018 07:37 PM
BogiesAnnex1
Quote:
Originally Posted by Oldsm View Post
Port injection like vortec engines?

Ive read and heard much of stories vortec engines bad mileage compared tbi. Yes they have more power and newer injection system. I dont know?
The Vortec L30 and L31(305 and 350) add about 20 degrees of cam timing, a better combustion chamber than the previous LO3 and LO5 engines, then top them off with a really dumb design of a port injection system, in reality there was little if any gain in emissions or mileage but the rated horsepower went up by 50 and with a little tweaking of the programming could add a 25 to 35 more without a cam change.

The older passenger car V8, TPI system is much better where each injector is working independently from a fuel rail instead of a common main set supplying pressure fuel to a pop off valve at the port which is a shared concept with the 4.3 starting with its late 1995 production. These systems for the V6 and V8 can be modified to use the older TBI injectors, but you still have to bring all the supporting systems which a quite different from what you currently have.

From a hotrodder so point of view these TPI injectors could run off your TBI computer with some driver circuit added as the impedance is different between the 2 TBI injectors and the 6 TPI injectors which if not corrected will eventually "LUCAS" the driver circuit. This would just require a high pressure fuel pump of about 40 psi and a suitable bypassing regulator. The remaining systems of your truck would not be disturbed. But this is still a fair size engineering effort just not a horrifically expensive one.

Bogie
12-15-2018 03:20 PM
Oldsm Port injection like vortec engines?

Ive read and heard much of stories vortec engines bad mileage compared tbi. Yes they have more power and newer injection system. I dont know?
12-15-2018 03:15 PM
BogiesAnnex1 By in large there is nothing that will improve fuel mileage that is cost effective. These trucks were originally designed to meet USA fuel mileage standards and for what there are are pretty well optimized in engine, transmission, and driveline design.

The swirl port heads are designed to maximize the power and mileage of the Throttle Body Injection (TBI) Performance heads would increase power but that comes at the cost of mileage, same holds for a cam swap, more cam timing, more lift, less LSA all increase power but at the cost of mileage.

Exhaust headers and duals will improve power and mileage a little but really need the engine to be used at higher RPMs to see this as you have to get into the zone where the existing system is overworked, so unless you go to Germany to drive the Autoban then there will not a lot of difference to be seen.

The biggest change to this engine would be to install port injection of the 1996 and up models. That along with a 4L60E transmission which has better shift profile than the 700R4 due to it being computer controlled. However, the cost involved for these items and a entirely new fuel system, wire harnesses, computers, and other miscellaneous support parts and systems in great likelihood can never be recovered by the mileage improvement within the vehicles useful lifetime.

Bogie
12-15-2018 01:23 PM
Oldsm Will underdrive pulleys help? Example crank pulley and water pump.


I got shorty headers now but need to make new pipes from headers to back.
03-21-2018 08:36 AM
BuzzLOL Most V6 owners like their V6... but... we're hotrodders!

Yes, a little more lost HP recovered...

Unfortunately, to make the V6, they didn't chop off the front or rear cylinder... they chopped out #5/#6 !!! Of course, with some work/welding/bending, the V8 headers could still be adapted... or buy some V6 headers...
https://www.ebay.com/itm/Chevy-S10-G...-/232699039835 These were prolly made in Asia so maybe you could intercept a set before they come to USA...
.
03-21-2018 07:59 AM
Oldsm Heh canada...

What i had readed, allways in north america nobody likes v6 and all are swapping it to v8 <img src="https://www.hotrodders.com/forum/images/smilies/biggrin.gif" border="0" alt="" title="big smile" class="inlineimg" />

And headers give extra hp too?
Does 305/350 headers fit if i cut 4th exhaust pipe off and blank it down?
03-21-2018 07:23 AM
BuzzLOL
Quote:
Originally Posted by Oldsm View Post
Im from Finland, europe.

How much tbi swirl port heads can safely mill? Nobody knows in my country.

Yes it has wind resistance but truck is not heavy, 4000lbs.

E85 fuel is one option but it must work with 95 octane too.

Can tbi stock ecm hold headers? I have heard that cam swap is too much and you need reprogramming.

Engine is fine and mpg is not poor, just thinking So no engine swap.
Welcome to this Canadian website from an American/USA... LOL!

Usually mill until close to valve seat...

Weight hurts city driving MPG... wind resistance hurts open highway MPG...

E85 needs high compression ratio to be efficient... but gasoline needs lower compression ratio to avoid pinging... so hard to build to efficiently use both...

Engine prolly run slightly leaner with headers, improving MPG... A 'MPG cam' prolly wouldn't upset the ECM like a 'high HP cam' would.

Engine swap was just exploring all or most options...
.
03-20-2018 03:44 PM
joe_padavano
Quote:
Originally Posted by Gearhead Poppa View Post
cold air intake will help
The truck already has a cold air intake. That corrugated duct from the air cleaner is routed to a cold air source at the inner fender.

03-20-2018 03:11 PM
Gearhead Poppa cold air intake will help
03-20-2018 12:55 PM
Oldsm Im from Finland, europe.

How much tbi swirl port heads can safely mill? Nobody knows in my country.

Yes it has wind resistance but truck is not heavy, 4000lbs.


E85 fuel is one option but it must work with 95 octane too.

Can tbi stock ecm hold headers? I have heard that cam swap is too much and you need reprogramming.


Engine is fine and mpg is not poor, just thinking So no engine swap.
03-20-2018 12:28 PM
BuzzLOL Where are you located?

You'll have trouble improving on the MPG... you're pushing something with the wind resistance of a brick...

Milling the heads might help a little bit, but require higher octane gasoline to prevent pinging...

Vortec heads with Fast Burn combustion chambers would prolly help some... if it doesn't already have them...

Headers and freer flowing exhaust system may help a little...

Porting or spacer will prolly slow air flow and hurt MPG... but increase peak HP...

We like the 4.3L V6 in the USA... but this is a more is always better hotrodders website...

We also like TBI and swirl port heads for their intended purpose of everyday trucking torque use...

A diesel engine would help the most... or a direct injected gasoline V6...
03-20-2018 12:15 PM
Oldsm
How to increase 262cid (4.3) v6 mpg?

I have 1992 c1500 with 4.3 v6 tbi and th700.

It works nice and its not thristy. 19-21mpg even -25 celcius winter.

But if we go greedy... How about milling heads or porting? Tbi spacer?

I know in the usa v6 is nothing and tbi with swirl port heads is poor, but i dont have money for ls swap.


Or if anybody isnt improved mileage, thats good answer too.


Or what is lowest that i can get? Normal cruise style (not granpha).

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