Rebuilt 350 - Abysmal Fuel Econ

[Irishman999]

Well gentlemen, I guess the old saying is true:

If it's got **** or wheels, it's going to cause you trouble.

Sorry, I couldn't resist .........

Here in mining country it goes "If its got **** or tracks, its going to cause you trouble".

 

[Irishman999]

I'm going to pick up a new pump hopefully this weekend if spare change allows.
As much as I've been advised to pick up an electric pump, I still want to stick with the tried and proven mechanical pump.

Wondering if I should go pump and eventual regulator - or pump only.

I must have been completely oblivious - OR, I was idling fine and leaving a trail of fumes in my wake. Of course, the big area of second-guessing and confusion was poor econ on the old 6 and a rebuilt qjet prior to. Maybe that 6 was just tired.

Either way, I'm still going to do some other underhood cleanup/checking other components.


I'll keep results posted.

I dont know how familiar you are with carbs but the tabs on a float level are just little tiny fragile pieces of stamped steel or brass. Even with really low pressure the plunger can be shoved up into that tab and adjust the float for you, especially if the fuel has no where to go besides through that feed hole under the plunger.

I did the same thing to A 81 Nissan truck I had for a while in high school. This again strengthens my theory that its ALWAYS THE DUMB ****. Truck would shut off while driving, I would check power to the pump when it would shut off because Nissan conveniently mounted a electric pump right on the frame rail even on a 81 with a carburetor! Of coarse it had power when it shut off or started stumbling so at 17 years old I got a stronger fuel pump. I drove it 20 miles to school but I could tell it was flooding BAD. Even worse was it still shutting off completely.

Turns out, the ground wire going to the frame was the entire reason for the repair in the first place.... could have been fixed in 5 minutes with some emery cloth and a wrench. The stronger fuel pump bent the floats and flooded the engine.

Also just recently, someone in my circle of friends was working on another friends Mustang for a few extra bucks. The guy is a complete ****** moron, instead of diagnosing the problem he dropped an Edelbrock 1406 on this 289 because he confirmed it ran great on a small block Chevy. Car would not start easily at all, you had to hold your foot to the floor to get it to start and even then it was horribly rich. Another buddy of mine went over and re set the Floats and suddenly the car runs perfect.

I am willing to bet adjusting the floats down a little will fix your issue.

 

[Nalanthi]

...it usually IS the dumb ****.
The worst part is when you do something that you personally deem epic and then are totally defeated for a few weeks on the smallest of things.

I just need to get up off my ass - but with 9 hours a day in the mill, and STILL being over 90 degrees when I get home sullies my mood to do much of anything outside. With a three day weekend coming up, I'll check pressure and re-adjust the floats.

 

[Nalanthi]

Here's what I have to report currently:

Fuel pressure checked out at around 5.6-5.7 @ idle. The floats were still within spec, but I bent them a bit anyway, and adjusted the accel pump to its shortest stroke.
I misspoke earlier when I stated that I was two stages leaner. I am actually three stages leaner (12%).
I jacked the rear and checked - nothing binding. I did find that I had a drum that was all but destroyed and wasn't functional, to which I removed for the time being until I pick up new parts and a new line. I was able to verify 3.55 gears as well, so I take it that 31x10.50s shouldn't be economy killers.

I ran a short trip down the road to run an errand and noticed that I am still getting rich bouts now that I have been paying attention. I actually decided to open her up all the way for the first time and noticed that around 4500RPMs @ WOT, I'm creating a noticeable cloud of oil. I'm starting to think once more that I built a trash block considering that I found three oil-fouled plugs last weekend.

Lastly, I have not yet verified economy until I drive it for a few days.

Looking for confirmation based on my rekindled doubts: Scrap the engine and go with a different one - or is it worth the continued troubleshooting? The supposed healthy readings I keep getting from testing over and over again don't seem to match my performance.

 

[MadOgre]

Here's what I have to report currently:

Fuel pressure checked out at around 5.6-5.7 @ idle. The floats were still within spec, but I bent them a bit anyway, and adjusted the accel pump to its shortest stroke.
I misspoke earlier when I stated that I was two stages leaner. I am actually three stages leaner (12%).
I jacked the rear and checked - nothing binding. I did find that I had a drum that was all but destroyed and wasn't functional, to which I removed for the time being until I pick up new parts and a new line. I was able to verify 3.55 gears as well, so I take it that 31x10.50s shouldn't be economy killers.

I ran a short trip down the road to run an errand and noticed that I am still getting rich bouts now that I have been paying attention. I actually decided to open her up all the way for the first time and noticed that around 4500RPMs @ WOT, I'm creating a noticeable cloud of oil. I'm starting to think once more that I built a trash block considering that I found three oil-fouled plugs last weekend.

Lastly, I have not yet verified economy until I drive it for a few days.

Looking for confirmation based on my rekindled doubts: Scrap the engine and go with a different one - or is it worth the continued troubleshooting? The supposed healthy readings I keep getting from testing over and over again don't seem to match my performance.

Rich mixture can cause fouled plugs.

If you have compression and your not loosing oil ? why trash the block ?

Lack of ignition can cause fouled plugs.

Dead plugs can cause fouled plugs.

Did you clean up everything around those headers ?

Boiled gas is not gonna help your carb issues.

 

[Nalanthi]

Yessir.
I made sure that the fuel line was routed WAY away from that lower rad hose.

The plug wires - I rerouted those, but did not meticulously bind them (yet). I've decided that I'm going to pick up new wires and will pretty 'em up when I do.

What is your suggestion for the oil-fouled plugs in 3, 4, and 5 - clean or replace?


I'm going to do a compression re-check on those cylinders when I get a chance, because I may very well be burning a bit of oil - but only occasionally at WOT.
The reason I keep bringing this all up is because my "by the books" friend keeps reiterating "man - you should have had that block checked out. I bet you're egged out on a few cylinders." despite the fact that it was exceptionally clean for its age.

 

[MadOgre]

pull each plug out and verify that they fire.

 

[MadOgre]

Yessir.
I made sure that the fuel line was routed WAY away from that lower rad hose.

The plug wires - I rerouted those, but did not meticulously bind them (yet). I've decided that I'm going to pick up new wires and will pretty 'em up when I do.

What is your suggestion for the oil-fouled plugs in 3, 4, and 5 - clean or replace?


I'm going to do a compression re-check on those cylinders when I get a chance.

You made sure the fuel line was routed away from those headers right ?

 

[MadOgre]

Yessir.
I made sure that the fuel line was routed WAY away from that lower rad hose.

The plug wires - I rerouted those, but did not meticulously bind them (yet). I've decided that I'm going to pick up new wires and will pretty 'em up when I do.

What is your suggestion for the oil-fouled plugs in 3, 4, and 5 - clean or replace?


I'm going to do a compression re-check on those cylinders when I get a chance, because I may very well be burning a bit of oil - but only occasionally at WOT.
The reason I keep bringing this all up is because my "by the books" friend keeps reiterating "man - you should have had that block checked out. I bet you're egged out on a few cylinders." despite the fact that it was exceptionally clean for its age.

What was your process in rebuilding this thing ? Did you take it to a machine shop ? or just new bearings and gaskets ?

 

[MadOgre]

Yessir.
I made sure that the fuel line was routed WAY away from that lower rad hose.

The plug wires - I rerouted those, but did not meticulously bind them (yet). I've decided that I'm going to pick up new wires and will pretty 'em up when I do.

What is your suggestion for the oil-fouled plugs in 3, 4, and 5 - clean or replace?


I'm going to do a compression re-check on those cylinders when I get a chance, because I may very well be burning a bit of oil - but only occasionally at WOT.
The reason I keep bringing this all up is because my "by the books" friend keeps reiterating "man - you should have had that block checked out. I bet you're egged out on a few cylinders." despite the fact that it was exceptionally clean for its age.

A slight egg shape should be accommodated for by the rings once they wear in.

 

[Nalanthi]

What was your process in rebuilding this thing ? Did you take it to a machine shop ? or just new bearings and gaskets ?

No machinework was done.

The engine was pulled as running from a 72 el camino because the owner wanted to up the ante and go to a 454.
The cylinders were like mirrors and the block was nice and clean.

I did all new bearings and gaskets, valves and seals... a few peripheral upgrades like the double roller, high flow oil pump, and flat pistons. I otherwise built this thing by the books.

 

[MadOgre]

No machinework was done.

The engine was pulled as running from a 72 el camino because the owner wanted to up the ante and go to a 454.
The cylinders were like mirrors and the block was nice and clean.

I did all new bearings and gaskets, valves and seals... a few peripheral upgrades like the double roller, high flow oil pump, and flat pistons. I otherwise built this thing by the books.

You bottle brushed or blade honed it ?

 

[farmerchris]

how many miles do you have on the engine now,did you use moly or iron rings,full break-in with iron rings can take up to 500 miles to fully seat in and quit using oil.usually moly ring will seat after about 100 miles,not always.most rings in rebuilt kits are moly for that reason.
also how you refinished the bore can affect seat time of the rings.usually crosshatched finish preferred.

 

[MadOgre]

how many miles do you have on the engine now,did you use moly or iron rings,full break-in with iron rings can take up to 500 miles to fully seat in and quit using oil.usually moly ring will seat after about 100 miles,not always.most rings in rebuilt kits are moly for that reason.
also how you refinished the bore can affect seat time of the rings.usually crosshatched finish preferred.

Yep the cylinder hone job can have a lot to do with the rings seating properly, or even whether they seat at all.

 

[MadOgre]

Im thinking this was a high mileage engine if the cylinder walls were like mirrors, and probably would have benefitted a great deal from being machine honed at the least if not an over bore.

Worst case scenario you have to disassemble the whole thing take it to the machine shop and have it cleaned up and then put it back together.

A better scenario is you just have to keep driving it till the rings seat. No Idling !