Outer Limits 4x4 Board

hey guys,,, after advice, ive got a gq lwb with a 351 ford cleveland v8 the engine is mild and running holley 750 double pumper with a emco gas system, 5 speed with 37''s im getting under 2 kms per litre, 125 kms to 70 litres, ive tried mixtures and settings, & if u take it easy or give it shit makes no difference, any help would be good,, thanks

gq351 wrote:hey guys,,, after advice, ive got a gq lwb with a 351 ford cleveland v8 the engine is mild and running holley 750 double pumper with a emco gas system, 5 speed with 37''s im getting under 2 kms per litre, 125 kms to 70 litres, ive tried mixtures and settings, & if u take it easy or give it shit makes no difference, any help would be good,, thanks

Sounds to me like you're getting about the right mileage for that setup. The things against you are:

1) 351 running a 750 Holley, not a bad motor and probably as economical as the std 6 but with the 750 holley its not the most economical setup; and
2) 37 inch tyres, these are a big part of the problem

Maybe with some shit hot tune up you might get up to 3 or even 4 kms per tank but you've got some work ahead of you to get that.

How are you driving it? If you were flat out everywhere or in low 4 all the time I'd say thats about it.
If you are cruising then you should be able to do 3-4 klms per litre, perhaps up to 5 under ideal circumstances. What are you mixtures at cruise?
Is the economy the same on petrol and lpg?
Where is the vacuum advance hose connected? What is the cruise vacuum, and is there sufficient vacuum at cruise to operate the vacuum advance? What sort of engine compression and camshaft do you have? A 750 double pumper is not the best 4x4 carby, large primaries mean low air speed and poor mixture turbulance at cruise (poor atomization), a 650 vac secondary would be a better option as the petrol mixture control would be better not to mention only one accelerator pump.


Joel

V8 = bad fuel economy
thats the price you pay for 37's and a bit of power

Diff Ratio????
City or Highway
Im running a 355 stroker
Was getting 300k's to 95L city driving easy or worst was 260k's
Highway could get up to around 330 for same litreage
3.9 ratios which suck off road though but the 355 pushes it along great on the road. Playing around with ratios at the moment have 4.11's on my 33's i but I think ideally 4.3 on 35's Still gives the V8 legs

1 i had an emco gas system got rid of it they are rubish,
2 i have been told by gas guys in brisi that holys hate lpg ,dont know why but get a genuin carp from a 4.2 petrol you might find it will run better

PGS 4WD wrote:How are you driving it? If you were flat out everywhere or in low 4 all the time I'd say thats about it.
If you are cruising then you should be able to do 3-4 klms per litre, perhaps up to 5 under ideal circumstances. What are you mixtures at cruise?
Is the economy the same on petrol and lpg?
Where is the vacuum advance hose connected? What is the cruise vacuum, and is there sufficient vacuum at cruise to operate the vacuum advance? What sort of engine compression and camshaft do you have? A 750 double pumper is not the best 4x4 carby, large primaries mean low air speed and poor mixture turbulance at cruise (poor atomization), a 650 vac secondary would be a better option as the petrol mixture control would be better not to mention only one accelerator pump.


Joel

Joel knows his stuff and is quite right.

A 750 even on a 351 V8 is way too big. A vac secondary would be far more efficient. The Volumetric Efficiency figures avoid me at this moment, but definately too big.

thanks guys, my brothers got a fj55 cruiser with a 350 chev getting 4-5 klms per litre running 37s with a holley 650 vac, i mite try his carby 2 see if it makes a difference, cheers jess...

big mick wrote:1 i had an emco gas system got rid of it they are rubish,
2 i have been told by gas guys in brisi that holys hate lpg ,dont know why but get a genuin carp from a 4.2 petrol you might find it will run better

How do you fit a carp from a 4.2 to a 351? I didnt even know the 4.2 come with carps. The closet I knew of a carp to a 4.2 was when you threw the boat anchor into the dam and the carp swam around it!

Guppy?

Ditch the holly, 600 vac sec are thirsty POS's too.. just find a good rochester, these are good carbs when tuned properly, have some issues, but you should be able to get a rebuilt one for what you can sell the holly for.. get it set up properly and no more problems

roughly cfm=CID*max RPM/3456

351*6000/3456=609cfm

650 not 750 is the carb you want for starters, then the mixture and timing set

Joel

I had a 351 Fairmont GXL fitted with 600 vac sec and I was getting 19 mpg...

600 vac sec was recommended back then. It was a good carb .

I had a 351 in a gq with a 600 holley base plate with a 425 impco gas mixer, mild cam, ballance, single plane inlet and i got 30-35 l/100km highway. Thats with 33's and 3.9s performance was only ok.

I changed to a 302, same other gear and I now get 22l/100km highway, the bonus is less $$$ in fuel and more hp, 660km on 145 litres
dynoed at 150kw rear wheels.
straight gass does need a modified distributor and workes really well with MSD 6AL ignition

Had a 383 chev, 650 Vac Sec holley and Gas in the old 60 on 35's with stock gears and got about th same economy as my 12HT auto Sahara......