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Drivability Issues. Its a slug that doesnt want to shift
Brutus 1972 F250 Custom Sport Camper Special. 72,000 original miles. /390FE with 2 Barrel 2100 MotorCraft.Carb/ C6 Transmission.
The engine has gone from stalling every 3rd or 4th time I try to start from a dead start to stalling each time I stop. If I very lightly and quickly tap,tap, tap tap the gas pedal JUST SO I can get the truck to move out form a stop. Pretty often I do that tap too hard and it has to then be restarted because it will die. It starts RIGHT back up but wont move out unless I tap, the gas pedal rapidly and lightly again but correctly or it will die again.. It also wants to back fire once rolling on more aggressive acceleration. I have a tendency to have had enough with the trouble getting rolling and want to mash it to punish it for running so weak. That's when it responds by backfiring.
Ive put 6 k miles on it and replaced a bunch of tune up related stuff in that time and have never felt it ran well. Its my first FE engine so Im not sure what to expect. Ive had 302's and 351's, 460's in Mustangs LTD's Linc Continental etc that were responsive. This truck lacks for responsiveness/power..There is a list at the end of this post of stuff Ive done in the order Ive done them.
The transmission has ALSO developed a serious delay in shifting. between 2nd and 3rd gear on most of the shifts in the past week. . .It seems to shift ok if I manually shift the lever. thru the gears.
This truck now gets 5mpg. It has never had what I would call any power. My seriously ugly beater Toyota Tundra with 220K abused miles 3.4 V6 has always been able to smoke this Ford. This F250 is currently incapable of breaking the tires loose.. Its really a lethargic dog. Its gorgeous to look at but runs like poop.
Brutus sat for 5 years before I got it 6k miles ago.. I will be doing a transmission service this week after I have a buddy weld in a drain plug bung on the heavy duty steel replacement transmission pan and the upgraded/reusable LUBE LOCKER transmission pan gasket someone on this forum suggested a ways back when I was getting ready to do a service as purely a maintenance thing.. I have a new filter ready to go also. I am going to try to drain the torque converter also. Ill use type F fluid. The fluid in it is not burnt but it isnt clean either. The truck is parked until I do this transmission service stuff.
Because Im having transmission shifting issues I think I want to also replace the transmission modulator. The one in this truck appears to thread in. Its crusty and rusty looking I cant see any color to know what it is. O'Reilly Auto Parts sells them in Pioneer Brand. The choices are: Black, Yellow,Green stripe and NO STRIPE. The Parts guy said the NO STRIPE was adjustable for the shift points. Dont all the colors have some adjustment? I just use this truck mostly as transportation so whatever is the best stripe color is what I need advice on.
I dont haul or tow anything. Ive been using the beater Toyota to do all the ugly moving stuff Ive recently done. I would like to get this truck to not feel so lethargic. It would be great if I could get back to the 9mpg everyone else "enjoys" which sucks but at least its not 5 like I have been receiving. These past 6 weeks.
I read somewhere that the governor could(also) be a reason the shifts are delayed like they are now. How do I know if the governor is functioning correctly?
Replaced/done in the last 6k miles;
In cab gas tank, fuel pump and its filter. Flushed its fuel lines. New hoses
Local Pro rebuilt carb
New vacuum hoses,(except at the transmission modulator its old but works Ill chuck it when the new modulator get done.
New coolant hoses fan belts
Recharge of A/C.
New Coil, coil and instrument gauge cluster wire harness from Tom's Bronco.
New Hei style distributor Cap, rotor, and 8mm ignition wires. P/O did a Pertronix
New spark plugs
New vacuum choke pull off that sits atop the carb
I run Chevron or Shell Premium gasoline.
Coil Wire/gauge harness
The modulator as it is now engine bay showing distributor cap and wires. He looks great runs sluggishly backfires dies on accel, holds onto trans shifts.
I'm no expert on this; But it has been discussed here. Todays coils need to mounted vertical. As far a the 2100 carbs go I bought my 66 because the guy had been through 3 carbs and just could not get it to run reliably. I changed the intake to a Holley street dominator and a Edelbrock 1406. Well that was 6yrs ago and it hasn't failed a single time.
I'm certainly no expert either but if it's backfiring then maybe check the timing. And I drove mine for 2 years (ran decent but like you I thought it could do better) before realizing a couple plug wires were switched. I had even checked it before but how the middle ones criss-cross I missed it. Also I recently got a vacuum gauge & set the timing. She's running smoother than ever.
Does the stock air cleaner mount on your type of setup?
Originally Posted by Christmas
I'm no expert on this; But it has been discussed here. Todays coils need to mounted vertical. As far a the 2100 carbs go I bought my 66 because the guy had been through 3 carbs and just could not get it to run reliably. I changed the intake to a Holley street dominator and a Edelbrock 1406. Well that was 6yrs ago and it hasn't failed a single time.
Hey there thank you for the reply. Will the factory original air cleaner housing that I have and love the look of fit on to keep that original look? I also have to believe I have not set things up correctly yet. if I do so it should run very close to the performance you enjoy with the mods you have made. Ill look into mounting the coil differently if that is a thing. I have also read that the coil needs to be vertical to level the oil....I also remember there was some brand maybe Moroso that claimed that like a lot of things today it could go "either way" . .
Im gonna drag out the vacuum gauge and timing light
Originally Posted by wjwolfe82
I'm certainly no expert either but if it's backfiring then maybe check the timing. And I drove mine for 2 years (ran decent but like you I thought it could do better) before realizing a couple plug wires were switched. I had even checked it before but how the middle ones criss-cross I missed it. Also I recently got a vacuum gauge & set the timing. She's running smoother than ever.
I just did the wires but copied what was there. So I will verify the positioning of them just to eliminate that. I will also check the timing. Thanks for the reply. I value the extra views like yours that help me along. I think it keeps me from doing things that would cost me money and extra time by considering other's experience. THANKS
Vacuum leaks, bad ignition timing and carb tuning all play a part. What's the idle speed and Vacuum reading at idle?
I have not checked any of that. Idle "sounds" correct. Truck does not ping or the like regarding timing but it is powerless so yes . I have sprayed water looking for vacuum leaks. I replaced every vacuum hose but the modulator hose. I sprayed it yesterday and its old but works. The carb settings Ill also attend to.The old spark plugs looked like they were burning correctly. Thanks for the frank and precise info. Im gonna get my friend who is a wizard at this to stand over my shoulder and point out what to do etc. To put an end to all of this. Any suggestions on the color of stripe for a transmission modulator? Green, Yellow or Black Stripe?
Before checking the timing you still running points in the dist.?
If so what shape are they in? Now the new ones I hear are not great (condenser mostly) but maybe time to change them out.
You need to set the points by dwell but you first set them with a feeler gauge to get them close then use the dwell meter.
Once the points dwell is set you can check the idle speed & timing.
If you need to adjust the timing you may need to readjust the idle speed.
As for the transmission not shifting right you cant do anything with it till the motor is running right.
If the vacuum on the motor is low because the motor is wore out the trans will not have the vacuum needed to shift right.
Just the way I would go about checking & adjusting.
Dave ----
Before checking the timing you still running points in the dist.?
If so what shape are they in? Now the new ones I hear are not great (condenser mostly) but maybe time to change them out.
You need to set the points by dwell but you first set them with a feeler gauge to get them close then use the dwell meter.
Once the points dwell is set you can check the idle speed & timing.
If you need to adjust the timing you may need to readjust the idle speed. This truck came to me with a Pertronix the P/O had installed about 25 years ago. The idle sits a bit high at 720 rpm The timing is at 6degrees btdc. The vacuum gauge says 14 at idle.
As for the transmission not shifting right you cant do anything with it till the motor is running right. I found the transmission fluid low by a quart and a half of another quart. I filled it
If the vacuum on the motor is low because the motor is wore out the trans will not have the vacuum needed to shift right. This engine has 71,000 miles on it now I dont think its close to being worn out. The original owner and I are the only owners this truck has had. Mr Miller drove it once a year as a hunting rig to Utah from San Diego. so he put on 2400 miles doing that each year Then he drove it 2x per month to and from work to keep it active. The past 10 years the truck sat with him only starting it here and there. He was ill a lot during this time. I bought the truck from his daughter when Mr Miller passed away.
Just the way I would go about checking & adjusting.
Dave ----
see above my responses are next to your comments and questions
ADDITIONALLY Im still not sure about the transmission or anything else for that matter. After I messed with everything today, just before dusk I tried to fire the truck up and it wouldnt fire. There was the idea that it wanted to start AS I LET OFF OF THE KEY for just a split second but it wouldnt fire at all while in cranking mode.
Earlier in the day I manipulated the plate the Pertronix sits on to see it wasnt locked up.. Is that something I shouldnt have done? Did I ruin the Pertronix by doing that? I found the vacuum advance not holding any vacuum and I also could blow straight into it so I though I should see if the plate the pertronix sits on would move. Clearly something broke. Before I removed the distributor cap to look inside to see the truck started easily.
It was too late to do anything to see anything more. But it had no spark coming from the coil wire.. I got a group of my neighbors and we pushed it to a parking spot for the night.
Vacuum leaks, bad ignition timing and carb tuning all play a part. What's the idle speed and Vacuum reading at idle?
So I found it to idle at 720 rpm should be 650. Timing is 6 degrees BTDC should be 10-12. Vacuum is LOW 14. hopefully will be 18 when I set the timing. I sprayed alcohol around the carb base and intake to see if there was a vacuum leak and it did not change the idle.
The vacuum advance is junk.I can blow right through it and of course it holds zero vacuum..
I probably broke the pertronix. to see if the plate would move, I moved it. and it moves about a 1/4 inch.
I put everything back in place. When I went to start the truck it wouldnt fire up. When letting off of the key during cranking, it gave me the hint that it was firing for a split second. I pulled the coil ignition wire from the cap and looked for a spark....it had none.
Before daylight left I grabbed 4 neighbors and we pushed the truck to a parking spot for the night. Its my guess I wasnt supposed to move the pertronix and probably broke something.relating to it Everything else looks like it did when I started looking at the engine earlier today
One more fact. I used a timing light that has a tack. I left the light connected the whole day. Did the 13.5 volts it was showing on the led screen feed through the coil and fry the Pertronix you know like leaving the key in the on position and not running the engine?
Last edited by mytoolman; May 27, 2021 at 09:29 AM.
Reason: wondering if timing light left hooked up fried Pertronix
I'm not saying that this is your problem but I have seen several of these old FE intakes where the exhaust crossover burns through due to a stuck heat riser. This creates a hidden vacuum leak inside the intake that you can't see and does not show when spraying around the outside.
Just something to think about if you fix everything else and still are having low vacuum.
Try using a bump stop/piston stop to confirm top dead center - you could be way off on the timing. Are you able to observe the mechanical advance with the timing light? If you are at 12 at idle how much does it increase to at 3500 RPM? How much mechanical advance do you have with the HEI style. With a beat up 2 barrel and good timing my 390/C6 ran great with plenty of power so you have the potential - just some issues. A pertronix unit is very sensitive to the gap between the rotor and the pickup. Check your gap and then try to wobble the distributor shaft side to side. If you can move it, the bushings are shot and the Pertronix will struggle due to the varying gap.
Bogging down, hesitating, stumbling from a dead stop or when accelerating at speed is indicative of a defective accelerator pump and check valve.
This is a long time common problem that affects the Auto-Lite/Motorcraft 2100 series 2V carb. Both these parts come in the carburetor kit that's available from Ford and auto parts stores.
1964/72 C4 & 1966/72 C6 // This is the ONLY modulator valve listed for 1968/72 F100/350 360/390 C6 that threads in.
KLIMESH MOTOR SALES in Calmar IA has 5 = 563-562-3241.
GREEN SALES CO. in Cincinnati OH has 8 = 800-543-4959. --------------------------------------------------------------
When the valve is removed, you have to be careful because it has a shift rod inside that can fall out.
C4AZ-7A380-A .. Throttle Control Valve Rod / 1.677" long / 1/8" diameter / Obsolete
Bogging down, hesitating, stumbling from a dead stop or when accelerating at speed is indicative of a defective accelerator pump and check valve.
This is a long time common problem that affects the Auto-Lite/Motorcraft 2100 series 2V carb. Both these parts come in the carburetor kit that's available from Ford and auto parts stores.
1964/72 C4 & 1966/72 C6 // This is the ONLY modulator valve listed for 1968/72 F100/350 360/390 C6 that threads in.
KLIMESH MOTOR SALES in Calmar IA has 5 = 563-562-3241.
GREEN SALES CO. in Cincinnati OH has 8 = 800-543-4959. --------------------------------------------------------------
When the valve is removed, you have to be careful because it has a shift rod inside that can fall out.
C4AZ-7A380-A .. Throttle Control Valve Rod / 1.677" long / 1/8" diameter / Obsolete
KLIMESH MOTOR SALES has 5.
GREEN SALES CO. has 8.
I left the key in the on position and fried the Pertronix while testing for timing etc.. I had no spark at the coil.
I installed a new set of points and condenser. Dwell is 27. Timing is 10. Rpm is 700. Vacuum is 19.I adjusted the carb watching the vacuum gauge I added a quart and a half of Type F to put it full on the dip stick and test drove the truck. It really runs great. It has really nice get up and go. Im deciding on if Im going to put an electronic ignition back in.
I still have to do something with the bad vacuum advance. Prices for an entire rebuilt distributor are a third more than just purchasing a vacuum advance so Im leaning on buying a rebuilt The truck moves away from a standing stop easily now.Its very responsive. I have never felt it run like it obviously can until yesterday.
thanks . see the update for fixes Ive made in a reply to Number Dummy
Originally Posted by GPatrick
Try using a bump stop/piston stop to confirm top dead center - you could be way off on the timing. Are you able to observe the mechanical advance with the timing light? If you are at 12 at idle how much does it increase to at 3500 RPM? How much mechanical advance do you have with the HEI style. With a beat up 2 barrel and good timing my 390/C6 ran great with plenty of power so you have the potential - just some issues. A pertronix unit is very sensitive to the gap between the rotor and the pickup. Check your gap and then try to wobble the distributor shaft side to side. If you can move it, the bushings are shot and the Pertronix will struggle due to the varying gap.
please see my reply to Number Dummy for the stuff done to get this engine to purr.
