Going dead at 80 mph

[Stanglover]

I used the standard ole clamps. Is that a gear clamp? Also I just used regular hose I so far haven’t used corn gas.

+1 on no "corn gas", it eats rubber for lunch. A "gear clamp" is one that has the worm screw engaged in slots on the band, usually tightened with a screw driver. They are my pet peeve for sure and I only use them where appropriate or non critical places.

 

[kcmash]

If your Pertronix is the III, they have an on board rev limiter. Do you possibly have a rev limiter set too low?

I did not see what RPM you are failing at, but if you have 4:25 or higher gear you may be reaching the 4k range at 80 mph. If the Pertronix has a rev limiter that is set too low, it could be causing a problem like that.

 

[ROCKET70]

Petronix has adjustable rev limiter. Maybe it's set too low and I also had years ago one that was defective and it would cut out on me.
Just a thought!

 

[Stanglover]

If you do have a PIII, perhaps install a PII which is more reliable IMO. The PIII has good electronics, just poor mechanical design, which is a shame.
However, if you do have a PIII, for sure check the rev limiter setting. If not that, check for excessive movement in the plates. This is for the Ford mode only by the way.

 

[Tommyt]

I have installed a tach so now I can monitor my rpm range. I’ve also made great improvement with a simple fix. I reseated my factory look plug wires in the distributor. I couldn’t see or feel a problem but one or more must have been unseated. I’ve hit 90 mph without a miss.
The engine turns very high rpm I was close to 3500 at top speed(90) if I cruise at 3k I’m in the 70s mph.
I only lose power on our biggest mountain now. I was convinced I was tip-top I drove app. 45-50 miles with no problem. So I gave her the mountain test. The failure felt different she didn’t give up she was either rich or lean I think I’m real close.
I thank everyone for ideas and input. Future plans are get rid of gear clamps and all new hose front to back. Also not ruling out having damaged my petronix which a 2.

 

[Stanglover]

I have installed a tach so now I can monitor my rpm range. I’ve also made great improvement with a simple fix. I reseated my factory look plug wires in the distributor. I couldn’t see or feel a problem but one or more must have been unseated. I’ve hit 90 mph without a miss.
The engine turns very high rpm I was close to 3500 at top speed(90) if I cruise at 3k I’m in the 70s mph.
I only lose power on our biggest mountain now. I was convinced I was tip-top I drove app. 45-50 miles with no problem. So I gave her the mountain test. The failure felt different she didn’t give up she was either rich or lean I think I’m real close.
I thank everyone for ideas and input. Future plans are get rid of gear clamps and all new hose front to back. Also not ruling out having damaged my petronix which a 2.

Awesome! Sounds like you have pretty much solved the issue. Little things can and do, cause BIG problems that are hard to find sometimes.
On your PII, make sure the ground wire is connected and tight, as well as the coil nuts. Also make sure you have a full 12 V powering it. Again, little things.
Glad you're losing those "gear clamps"!!
Keep us posted on progress.

 

[Tommyt]

Well it only took two years to finally correct my going dead at top end. I tried everything from coil, 12 volts on the coil, power valve, jets, add electric fuel pump, blow out the fuel lines, then thought plug wire, or maybe cam and springs were doing it. Once I didn’t have a plug wire seated so that day I had two problems, reseating the wire had me back to one.
The vacuum canister.
The canister was hooked up when I bought the car so I left it. I got a bracket and mounted it and left it in the circuit.
The miss started getting worse I looked at the clear fuel filter it looked clean. When I undid it a white color was in the gas. Replaced filter car only run for a minute then run out of gas. So dropped tank and found full of white stuff. At first I thought sugar but when I looked at vent inlet on top of tank it was full of white stalagmites. I pulled the canister and the charcoal was mush and very wet. I blew in one tube and white junk came out on the top.
I removed canister disassembled, removed charcoal, drilled 3 large holes in bottom reinstalled. Looks factory breathes like a champion runner. Car is a killer on top end now.

 

[Tommyt]

+1 on no "corn gas", it eats rubber for lunch. A "gear clamp" is one that has the worm screw engaged in slots on the band, usually tightened with a screw driver. They are my pet peeve for sure and I only use them where appropriate or non critical places.

When I replaced all rubber hoses I used fuel clamps. Much better thanks

 

[Stanglover]

When I replaced all rubber hoses I used fuel clamps. Much better thanks

Tommy, WTF is that white gunk? Is it the result of ethanol or just water in the gas.
Anyway, glad you found the problem and hopefully fixed it for good. If you get issues again, you know now where to start.
Also glad you used proper fuel line and fuel line clamps. Not only do they look better, but they work better too.

 

[mrgmhale]

Well it only took two years to finally correct my going dead at top end. I tried everything from coil, 12 volts on the coil, power valve, jets, add electric fuel pump, blow out the fuel lines, then thought plug wire, or maybe cam and springs were doing it. Once I didn’t have a plug wire seated so that day I had two problems, reseating the wire had me back to one.
The vacuum canister.
The canister was hooked up when I bought the car so I left it. I got a bracket and mounted it and left it in the circuit.
The miss started getting worse I looked at the clear fuel filter it looked clean. When I undid it a white color was in the gas. Replaced filter car only run for a minute then run out of gas. So dropped tank and found full of white stuff. At first I thought sugar but when I looked at vent inlet on top of tank it was full of white stalagmites. I pulled the canister and the charcoal was mush and very wet. I blew in one tube and white junk came out on the top.
I removed canister disassembled, removed charcoal, drilled 3 large holes in bottom reinstalled. Looks factory breathes like a champion runner. Car is a killer on top end now.

Thank you for your findings. I make a point of only using non-ethanol gasoline, despite it only having 90 octane. I have heard a few too many horror stories re: what ethanol does to these vintage Mustang fuel systems.

 

[mjseakan]

@Tommyt was it the vacuum canister for the air conditioner and such or the fuel vapor canister that's between the gas tank and the air cleaner?
Mike

 

[Tommyt]

Fuel vapor canister was at fault. The charcoal was deteriorating kinda like mush.

 

[Tommyt]

Tommy, WTF is that white gunk? Is it the result of ethanol or just water in the gas.
Anyway, glad you found the problem and hopefully fixed it for good. If you get issues again, you know now where to start.
Also glad you used proper fuel line and fuel line clamps. Not only do they look better, but they work better too.

The charcoal from the fuel canister made that mess. I have never put corn gas in this car. The charcoal was mush when I blew on the hose white junk came out top of canister. At the vent entrance to gas tank white junk growing on it. Removed all charcoal drilled out bottom of canister nothing but clean air now. Gas is clean runs like a champ now.

 

[Tommyt]

Thank you for your findings. I make a point of only using non-ethanol gasoline, despite it only having 90 octane. I have heard a few too many horror stories re: what ethanol does to these vintage Mustang fuel systems.

I haven’t ever ran corn gas. We have very good real gas here. Gas is white reminds me of Amoco in the 70s.

 

[Tommyt]

Tommy, WTF is that white gunk? Is it the result of ethanol or just water in the gas.
Anyway, glad you found the problem and hopefully fixed it for good. If you get issues again, you know now where to start.
Also glad you used proper fuel line and fuel line clamps. Not only do they look better, but they work better too.

That white junk came from fuel canister. Charcoal broke down from being wet. Turned to mush and made white junk. Only found out by blowing on line from canister made white junk come out large hole in middle of canister.

 

[mjlan]

Glad you got it sorted!

 

[Stanglover]

That white junk came from fuel canister. Charcoal broke down from being wet. Turned to mush and made white junk. Only found out by blowing on line from canister made white junk come out large hole in middle of canister.

That's actually good info Tommy, thanks. I would actually be surprised if any of these 50 year old fuel evap canisters actually work now. Maybe time to just make em look pretty and leave it at that.
Glad you got to the bottom of the problem.

 

[Tommyt]

Thanks me too. Mine looks functional but nothing but air inside it now.

 

[mrgmhale]

It looks like a lot of us (me included) appreciate your sharing the info re: the fuel evaporative canister having caused some of your problems. Moreover, it looks like ethanol and/or water in the fuel was also involved. The ethanol tends to absorb water, so it could have been a combination of factors involving the ethanol fuel.

In our area the only non-ethanol gasoline we have has a mere 90 octane. It leaves me having to run our vintage pony car engines at 6 degrees BTDC, instead of moving the timing to 12 degrees, where they begin to liven up. I prefer to run a little on the detuned side with non-ethanol fuel as opposed to running higher octane with ethanol. I have seen, and heard, too much about the adverse impact of ethanol on these older engines and fuel systems.

 

[Stanglover]

It looks like a lot of us (med included) appreciate your sharing the info reK the fuel evaporative canister having caused some of your problems. Moreover, it looks like ethanol and/or water in the fuel was also involved. The ethanol tends to absorb water, so it could have been a combination of factors involving the ethanol fuel.

In our area the only non-ethanol gasoline we have has a mere 90 octane. It leaves me having to run our vintage pony car engines at 6 degrees BTDC, instead of moving the timing to 12 degrees, where they begin to liven up. I prefer to run a little on the detuned side with non-ethanol fuel as opposed to running higher octane with ethanol. I haved seen, and heard, too much about the adverse impact of ethanol on these older engines and fuel systems.

Just curious, but I run non-ethanol 91 oct. gas on an engine with 9.8:1 compression, timing at 14 degrees initial with 20 degrees crank (10L slot) with zero spark knock even if at times I do have to run with ethanol gas. I did have considerable knock issues before with an earlier 11:1 rebuild, with 6 to 8 degrees initial timing with 30 degrees on the crank (15L slot). The cam is a Melling MTF 2, so just a mild cam. IF and I do mean IF, I could get 94 non ethanol still, I might have been ok with the 11:1 motor. Other issues meant I could take the opportunity to install 13cc dish top pistons and be able to run 91 fuel.
What I'm getting at is, if I can run with similar octane, ethanol or not, why do you feel it necessary to drop your initial timing to only 6 degrees? To be fair, my factory Autolite distributor has been changed by welding and recutting the original 15L slot to a 10L plus I use 1 heavy spring and 1 Mr.Gasket 925D set to give the timing all in around 2800 rpm. It pulls like a train.
Don't get me wrong, I'm not being critical of your choice, just trying to understand more for my own furtherment of knowledge.