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351 C Timing?

5K views 18 replies 8 participants last post by  thefonz 
#1 ·
Just want to run this by you all. I bought a 79 f-150 with 351 C.
I went to pick it up and it started fine (really quick, barely turned over and was running) we idled it for a while and shut it off after it was warmed up. We went to start it again and it kept back firing into carb. After messing with it we backed dist off 1 tooth. It started up just fine ran well. The guy I bought it from has been working on it beacuse he went to start it up and it was doing the same thing. I'm not sure what he may have done but he started it up and was going to test drive it and it stalled out and backfired through the carb again. Could there be a timing problem, there are new timing gears and chain in it already.
He told me that he set the #1 to TDC on Exaust stroke isn't it supposed to be on compression stroke?

Does anyone have any ideas or suggestions?
 
#3 ·
If I remember correctly it starts fine when cold. (Truck is 100 miles from here)
So I agree about the 180 out. Only reason I mentioned it is because he said he set it to exaust stroke not compression stroke.

Could it be cracked dist cap or rotor problem?

When we worked on it a few weels ago we did have to take out dist and move it back 1 tooth then it ran fine.

Is it possibly a vaccum problem; does it even have vaccum advance?
 
#5 ·
landscaperluke said:
Just an update...
The engine doesnt start at all. cold nor hot.
The timing seems to be off because he said that it pops and wants to fire but just wont; it fires back thru carb ect.

Sounds like it could in fact be out 180 now that I know its not running at all.
Sounds like it's time to start from scratch , and make sure the leads are added in the correct rotation.
 
#8 ·
I talked to the previous owner today and he said that he could not find timing marks, and that he set #1 pist at TDC on exhaust stroke not compression. It is in fact 180 deg off. It ran really well a couple weeks ago (after new timing chain and gears were installed) The dist. is original to the engine. The dist was reinstalled too advanced and he has been trying to adjust it and had lost the timing by mistake. We are changing dist cap and rotor because it has been acting like there could be a moisture problem inside cap as well. No doubt could it use a bit of a tune up anyway.

I had a similar problem on a 302 a couple of years ago and the symptoms are the same. Turned out it was 180 deg off too. I finally got the help of my father in law to feel for the compression stroke, and it has run well ever since so I'm hoping for a similar outcome......
 
#11 ·
It ran fine after the timing chain and gears were changed. The dist was too far advanced. So we removed dist backed off 1 tooth ran decent; still acting a little funny though like there was moisture in cap. The guy took the dist out and started from scratch only he set #1 at TDC on EXAUST stroke. Now its doing just like you said belching flame out carb, ect...

Im going to work on it Monday (it is a 2 hr drive just to go work on it) Ill know more then. Thanks for your replies thus far.
 
#12 ·
want to fix the timing? Pull the dizzy out, fine #1 on cap, slide rotor on, line it up roughly with #1, set timing to tdc, turn until 6deg btdc and advance 2 or 4 degrees for timing chain slop. Should run like a champ.

EDIT: didn't see the last post, but i left that there incase anyone needs it.
 
#13 ·
Another Update:
I never got to travel to go work on the truck this past Monday but the previous owner got it running. After tinkering with it for some time he found that there was a major space between the carb and where it mounts causing a crazy mixture of fuel and air. After fixing that problem he set the timing an thats that. I dont quite understand exactly hor the Carb problem would affect it but it obviously was a problem. Now it runs like a champ. Thanks to all for your help and insight.

"landscaperluke"
 
#14 ·
Well bad news again.
I went down to pick up the truck and wouldnt start. We set the timing and then got it to start an run for maybe a minute or so. We tried to restart it and it wouldn't. So we backed off the dist 2 teeth and it started and ran again for a little bit maybe a minute. It seems like it is throwing itself off time. The adapter ring on the dist is cracked allowing it to rock and the cap is not fitting on the adapter very well. You can actually see the cap/adapter cup moving as you turn over the engine. Also, with cap off I can turn the rotor (shaft and all) about the same distance as between two contacts on dist cap. We are going to try another dist this week. hopefully this will help.

Has anyone heard of this problem????
(note: the gear on the dist. doesn't seem to be in too bad of shape. Teeth may be slightly rounded but not terrible. Im not sure on the condition of the retainer which prevents the gear from riding above the camshaft gear though.)
 
#16 ·
as the gear teeth get worn they get sharp at the outer edges. rounded? it is hard to see from here but i'd suspect the broken roll pin if it is the correct distributor gear at all? it might drag on broken egdes enough to turn the dizzy for a while, then when the engine shuts off the reverse kick of shutting down moves the gear on the shaft again and you're out of time.
 
#17 ·
I think you are correct. I agree that it has to be a problem with the distributor itself.
There is supposed to be a rebuilt one put in this week... if the weather cooperates. Hopefully that will do the trick.
It has been well below zero degrees (f) for about a week now. Not good weather for working on vehicles especially with no garage.

Was also wondering if the stator in the dist. is not lined up correctly with the armature, will that cause a "developmental" timing problem like this one?
 
#18 ·
u definately want the number 1 piston on the compression stroke, if it is on the exhaust stoke it will run like a hairy goat as u no doubt found out. As to the not finding timing marks i think they need 2 get their eyes checked all cars have timing marks they have 2. wen all that has been done and u have the BASE timing set up an done u jus gota figure out how much u want the timing advanced.
 
#19 ·
79xdfalcon said:
u definately want the number 1 piston on the compression stroke, if it is on the exhaust stoke it will run like a hairy goat as u no doubt found out. As to the not finding timing marks i think they need 2 get their eyes checked all cars have timing marks they have 2. wen all that has been done and u have the BASE timing set up an done u jus gota figure out how much u want the timing advanced.

Are you sure about that?
 
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