A Week Long Restoration turning into a Summer Time Adventure! 86 XLT Lariat Explorer

[Jake Papageorge]

When I joined this forum some weeks ago, I had just taken possession of my deceased father in laws 85 F150 XLT Lariat Explorer. This truck has the VIN H 351 HO (what a joke!) 4V carb with a C6 trans and 3.50 gears. Someone had done a real number on the 4180 that was on there so rather than trying to unpackage what some other lain-brain did, I just took out a new 1850 600 CFM carb and put it on there. I made the necessary adjustments to maintain all of the OEM vacuum controlled emissions controls except, of course, the evaporative emissions hook up on the float bowels. I also blocked down the EGR because I simply cannot find a suitable replacement EGR valve for a reasonable price anywhere. Pretty much everything else is there and it all works!

What is my point, you ask?

I know this thing is a one and a half ton vehicle. This being said, I do not expect it to get great fuel economy, HOWEVER, this thing is unquestionable the biggest fuel pig of ANY old F truck or Bronco I have EVER owned!

It has less than 50K on the odometer and the WORST cylinder only has about 12% blow by and all with plenty of compression!

It is certainly not over-carbureted, nor is it running rich by any stretch of the imagination! The EGR deletion alone would not account for the mileage this thing is getting.

What is the mileage? A whopping 8 MPG.

Ok, I get it! a 3 speed, with 3.50 gears spinning 3K down the freeway in a 6K lb. truck is not going to get the mileage of a MINI Cooper, but I sure don't think double digit mileage is unreasonable to expect! Or is it?

It has been so long since I owned one of these things. I know the ethanol content makes anything use more fuel, but holy cow!

Just want to get an idea what kind of fuel economy others with a SIMILAR POWERTRAIN are getting! Personally, I know people with 460 equipped bullnose trucks that get better mileage, but of course, a 460 works a lot less to move a 6K lb. chunk of steel and cast iron!

[85lebaront2]

Ok, a couple of items to look at, the distributor, it has two advance systems a mechanical (RPM operated) and a vacuum (ported or manifold source).

Mechanical - with the cap off the distributor, take the rotor and turn it counterclockwise, if it doesn't move, take the rotor off and put some penetrating oil down the hole in the advance mechanism. let it soak and continue until it moves and snaps back.

Vacuum - engine running, se if the line going to the distributor has vacuum, if not, increase the rpm until it does. If you cannot get a vacuum signal, find a source (on the manifold if necessary) and try connecting it, rpm should increase, if not, the vacuum advance may be bad.

Those are the two most likely issues, third would be, does it have a catalytic converter? If so is it possibly clogged?

Fuel economy, 1986 F350 6400lb crew cab dually, 3.55 gear and C6 got me a solid 10 mpg except towing a 35 ft 10K 5th wheel, then 8 was normal. Since converting to MAF/SEFI and E4OD, since I have very low compression using E7TE heads on a carbureted short block, max of 12.5 running 70-75 on interstates.

[ArdWrknTrk]

Ok, a couple of items to look at, the distributor, it has two advance systems a mechanical (RPM operated) and a vacuum (ported or manifold source).

Mechanical - with the cap off the distributor, take the rotor and turn it counterclockwise, if it doesn't move, take the rotor off and put some penetrating oil down the hole in the advance mechanism. let it soak and continue until it moves and snaps back.

Vacuum - engine running, se if the line going to the distributor has vacuum, if not, increase the rpm until it does. If you cannot get a vacuum signal, find a source (on the manifold if necessary) and try connecting it, rpm should increase, if not, the vacuum advance may be bad.

Those are the two most likely issues, third would be, does it have a catalytic converter? If so is it possibly clogged?

Fuel economy, 1986 F350 6400lb crew cab dually, 3.55 gear and C6 got me a solid 10 mpg except towing a 35 ft 10K 5th wheel, then 8 was normal. Since converting to MAF/SEFI and E4OD, since I have very low compression using E7TE heads on a carbureted short block, max of 12.5 running 70-75 on interstates.

A 150 would have come with a cat, Bill.

It's only 8,600 gvw and above that were exempt from converters.

But Jake seems to think that a 150 is a 1 1/2 ton payload vehicle. And that is definitely not the case.

150's are generally 1/2 ton trucks, 250's 3/4 ton rated and 350's rated at 1 ton.

Exceptions for the 250 HD's with eight lug axles.

Ron (Reamer) had a problem with his pickup being gutless a few years back and I suggested he disconnect the cat in the first few posts of that thread.

Fortunately he finally found it, but I think it caused him a lot of frustration.

[85lebaront2]

A 150 would have come with a cat, Bill.

It's only 8,600 gvw and above that were exempt from converters.

But Jake seems to think that a 150 is a 1 1/2 ton payload vehicle. And that is definitely not the case.

150's are generally 1/2 ton trucks, 250's 3/4 ton rated and 350's rated at 1 ton.

Exceptions for the 250 HD's with eight lug axles.

Ron (Reamer) had a problem with his pickup being gutless a few years back and I suggested he disconnect the cat in the first few posts of that thread.

Fortunately he finally found it, but I think it caused him a lot of frustration.

Jim, I knew it would have come with one, my question was is it there and if so could it be clogged. I was also of the impression that the 351 HO was in the F250s through 1987, then dropped. AllData is interesting, they show the 351 4 barrel in both light duty (with cats) and medium duty (no cats).

We are also talking about a 36 year old truck that who knows exactly what has been done to it over the years.

[ArdWrknTrk]

Jim, I knew it would have come with one, my question was is it there and if so could it be clogged. I was also of the impression that the 351 HO was in the F250s through 1987, then dropped. AllData is interesting, they show the 351 4 barrel in both light duty (with cats) and medium duty (no cats).

We are also talking about a 36 year old truck that who knows exactly what has been done to it over the years.

The 351 HO was definitely available in the F-250 over 8,600 gvw for '87.

There were no carbs on pickups for the '88 model year.

 

[mat in tn]

Jim, I knew it would have come with one, my question was is it there and if so could it be clogged. I was also of the impression that the 351 HO was in the F250s through 1987, then dropped. AllData is interesting, they show the 351 4 barrel in both light duty (with cats) and medium duty (no cats).

We are also talking about a 36 year old truck that who knows exactly what has been done to it over the years.

there is a lot going on here. condition is part of it. tuning is part of it. driving style/ load demand is part of it.

50k miles? that's extremely low for a 40 yo truck and very unlikely. five-digit odometers reset every 100k and can rollover numerous times. this has misled many in the past and many salesmen have misled buyers with it also. unknowingly, I'm sure.

I only bring this up because my experience leads me to change timing chains at 150k on average due to stretched chains allowing the valve timing to retard many degrees although seemingly running fine. this WILL cause a loss in power and therefore you will use more throttle and push it more to get the same work done. this involves all of the three things I mentioned at first.

[Jake Papageorge]

A 150 would have come with a cat, Bill.

It's only 8,600 gvw and above that were exempt from converters.

But Jake seems to think that a 150 is a 1 1/2 ton payload vehicle. And that is definitely not the case.

150's are generally 1/2 ton trucks, 250's 3/4 ton rated and 350's rated at 1 ton.

Exceptions for the 250 HD's with eight lug axles.

Ron (Reamer) had a problem with his pickup being gutless a few years back and I suggested he disconnect the cat in the first few posts of that thread.

Fortunately he finally found it, but I think it caused him a lot of frustration.

No, not 1.5 ton payload....it is a 6000 lb truck!

[Jake Papageorge]

Ok, a couple of items to look at, the distributor, it has two advance systems a mechanical (RPM operated) and a vacuum (ported or manifold source).

Mechanical - with the cap off the distributor, take the rotor and turn it counterclockwise, if it doesn't move, take the rotor off and put some penetrating oil down the hole in the advance mechanism. let it soak and continue until it moves and snaps back.

Vacuum - engine running, se if the line going to the distributor has vacuum, if not, increase the rpm until it does. If you cannot get a vacuum signal, find a source (on the manifold if necessary) and try connecting it, rpm should increase, if not, the vacuum advance may be bad.

Those are the two most likely issues, third would be, does it have a catalytic converter? If so is it possibly clogged?

Fuel economy, 1986 F350 6400lb crew cab dually, 3.55 gear and C6 got me a solid 10 mpg except towing a 35 ft 10K 5th wheel, then 8 was normal. Since converting to MAF/SEFI and E4OD, since I have very low compression using E7TE heads on a carbureted short block, max of 12.5 running 70-75 on interstates.

Both vacuum advance (12 degrees @14"hg) and mechanical 13 degrees at 1750) advance are working properly. and With of initial set at 10, it has 35 degrees of total timing. No issues there.

Cats have been hollowed out.

I would be thrilled if this thing got 10mpg! Just for the hell of it, I am going to rebuild that 4180. I personally HATE those things, but hey, ya never know! I always wondered if the 2 stage power valve from a 4180 would work properly in a 4160.

 

[Jake Papageorge]

there is a lot going on here. condition is part of it. tuning is part of it. driving style/ load demand is part of it.

50k miles? that's extremely low for a 40 yo truck and very unlikely. five-digit odometers reset every 100k and can rollover numerous times. this has misled many in the past and many salesmen have misled buyers with it also. unknowingly, I'm sure.

I only bring this up because my experience leads me to change timing chains at 150k on average due to stretched chains allowing the valve timing to retard many degrees although seemingly running fine. this WILL cause a loss in power and therefore you will use more throttle and push it more to get the same work done. this involves all of the three things I mentioned at first.

Just FYI, I am the 2nd owner and the mileage is 100% actual!

[Machspeed]

I have the same engine, trans, and gearing, though I think it's 3:55, not 3:50. My truck is also 4x4. I bought it new and at first it got "okay" fuel mileage....14-15 mpg. As time past, that fuel mileage went to 8 mpg. Fed up with the crappy fuel mileage and poor performance, I pulled all the emission garbage off of it and added an Edelbrock 600CFM carb and intake. Also put a set of headers on it with true dual exhaust. Not only was the fuel mileage markedly improved, so was the performance.