engine problem at high speed

[finmad]

So I accelerate through second into third and up to 55-60 in third, all seems fine, no misses or hesitation. about a mile of this and then it starts... sounds like engine "knock" it is kind of a pinging sound. It is definitely motor related as I can make it worse by giving it more gas. Once this starts, I start to loose power slowly at first then worse and worse until it starts backfiring and I am slowed down to 2nd gear speed. I can shift it into second and as long as I don't floor it I can get along at a higher rpm in second. The minute I shift it back into third same thing. I can pull over stop the truck keep it running with the throttle knob and choke. let it sit for a minute or so and then start off again. It gets up to speed fine and then the knock starts and it does it all over again.

 

Theories????

 

[Jeff Balazs]

Timing may be off a bit.

[Don Coatney]

I agree, timing is too far advanced.

[Plymouthy Adams]

I am thinking you may be starving for fuel after a bit of running as you HAVE to use the throttle and choke to keep it running...do a fuel delivery test...also check to se if your gas cap is properly vented and there are no leaks in the delivery line to the pump and at worse case scenario..you could have a piece of trash that is partial obstructing the jet in the carb and when it sits without any venturi effect as seen when running..it falls to the bottom of the float bowl and could repeat this action again later....

 

as for the pinging noise...not so sure if the timing is high but you're leaning out at that speed and will cause a pinging regardless of timing being dead on the money...

[Jerry Roberts]

Are you using Champion spark plugs ?  My truck acted like that and I think that I was loosing compression between the porcelain and the steel base on the plugs . Another brand of plugs and the problem was solved . 

[finmad]

I agree, timing is too far advanced.

 

 

Timing may be off a bit.

 

So I went to see if I could rotate the distributor and it is frozen all the way turned to the right. The cap clips are not very tight though and the cap can be rotated either way 1/4 turn. I don't know if that is right. I would think the cap should not rotate.

[finmad]

I am thinking you may be starving for fuel after a bit of running as you HAVE to use the throttle and choke to keep it running...do a fuel delivery test...also check to se if your gas cap is properly vented and there are no leaks in the delivery line to the pump and at worse case scenario..you could have a piece of trash that is partial obstructing the jet in the carb and when it sits without any venturi effect as seen when running..it falls to the bottom of the float bowl and could repeat this action again later....

 

as for the pinging noise...not so sure if the timing is high but you're leaning out at that speed and will cause a pinging regardless of timing being dead on the money...

 

I kind of thought this way myself. I wonder if the fuel pump is weak and can't keep up with the carb at high speed. If I am draining down the bowl and it is not being replenished fast enough. This would make sense that it runs fine at low speed and half throttle, then when I am at full throttle for an amount of time, it drains down the bowl. How do you do a pump check to see if it is putting out enough fuel?

[finmad]

Are you using Champion spark plugs ?  My truck acted like that and I think that I was loosing compression between the porcelain and the steel base on the plugs . Another brand of plugs and the problem was solved . 

 

I am using champion and I noticed some blow by at the seat of the plugs, I cleaned the head surface and tightened them down well. Then on the next start up I put some water in the valleys and noticed 4 and 6 still had some blow by, I torqued them down again and it seemed to be good. You think there could be blow by at the porcelain? what plugs do you use now?

[Don Coatney]

So I went to see if I could rotate the distributor and it is frozen all the way turned to the right. The cap clips are not very tight though and the cap can be rotated either way 1/4 turn. I don't know if that is right. I would think the cap should not rotate.

The cap should not move. There is a "key" as pictured that fits into a slot in the distributor preventing the cap from moving. If the cap moves this will alter the timing.

 

[Merle Coggins]

So I accelerate through second into third and up to 55-60 in third, all seems fine, no misses or hesitation. about a mile of this and then it starts... sounds like engine "knock" it is kind of a pinging sound. It is definitely motor related as I can make it worse by giving it more gas. Once this starts, I start to loose power slowly at first then worse and worse until it starts backfiring and I am slowed down to 2nd gear speed. I can shift it into second and as long as I don't floor it I can get along at a higher rpm in second. The minute I shift it back into third same thing. I can pull over stop the truck keep it running with the throttle knob and choke. let it sit for a minute or so and then start off again. It gets up to speed fine and then the knock starts and it does it all over again.

 

Theories????

 

I've experienced a similar issue with my truck this year that finally manifested into a stranded situation. Maybe you've read my thread on the topic. Anyway, I seem to have found that my valve clearance was way too tight on a few valves and I believe this was creating my problem. Under heavy loads the high exhaust temperature was expanding the valves enough to remove all clearance and they wouldn't seat. This would cause the loss of power and backfiring issue. Once it cooled down sufficiently all would be good again.

 

I suggest you check your valve clearance. It is certainly something I will be checking more often.

 

Merle

[finmad]

The cap should not move. There is a "key" as pictured that fits into a slot in the distributor preventing the cap from moving. If the cap moves this will alter the timing.

 

 

Don, you are right on. I had a new cap and rotor in the garage and decided "Let's replace those and see what happens". The old cap the keyway was all kinds of worn away and the rotor it self was super loose on the shaft, I could rotate it 1/4 inch either way with out the shaft moving. Put the new rotor on and swapped the wires to the new cap. It fit in the keyway snug and tight. I took the truck down the street, I don't have time to go for a long ride, but it is much improved already. hopefully this takes care of my timing issue. Amazing what a little tune up will do....  I am still suspicious of a low fuel issue, so I will see if that problem rears its head again.

[Jerry Roberts]

I am using champion and I noticed some blow by at the seat of the plugs, I cleaned the head surface and tightened them down well. Then on the next start up I put some water in the valleys and noticed 4 and 6 still had some blow by, I torqued them down again and it seemed to be good. You think there could be blow by at the porcelain? what plugs do you use now?

 I am using AC Delco R45 . Purchased at Oreillys Auto Parts . I think the R stands for resistor , I have a radio . These plugs that I have now work fine . Do I think that there could be blow by at the porcelain ?  My plugs were a little dark there ,,, from carbon ? But as the problem occurred at speed , so there is no way to know for sure . I do know that I threw away those Champion plugs even though they were brand new . 

[finmad]

I got it out today for a ride and it is still happening. One more piece of info, I noticed the temp gauge also shoots up when the knocking starts. I was able to get it to settle down this time without pulling over. I lowered the speed got it back into third and then just babied the throttle. the knocking went away and I was ok after about 2 minutes. I am now thinking it is leaning out because of being starved of fuel. If the engine started running lean would you see an almost immediate jump in temp??

[Jeff Balazs]

You need to start by verifying that the timing is in the correct range. Until you know it is for sure you will just be chasing phantoms.

 

Jeff

[Dave72dt]

With the replacement of the cap and rotor, you are probably getting more consistent timing but it still may not be correct timing.   Yes, it can rise rapidly if leaned out.  Merle believed his initial problem with valve clearance may have contributed to similar symptoms.  Do the timing and do the fuel pump flow tests first.  That eliminates 2 of the most likely possibilities and they are the easy ones to check.  Then you can move on to other possibilities that may require more in depth work.

[Merle Coggins]

Yes, I highly recommend checking your valve clearance if it hasn't been done in a while. What you describe is very similar to what my truck would do. Mine would take longer, and I would have to be pushing pretty hard, but it would pop, fart, and run very poorly until it cooled down again. I found a few valve clearances to be VERY tight.

[Fernando Mendes]

Don, you are right on. I had a new cap and rotor in the garage and decided "Let's replace those and see what happens". The old cap the keyway was all kinds of worn away and the rotor it self was super loose on the shaft, I could rotate it 1/4 inch either way with out the shaft moving. Put the new rotor on and swapped the wires to the new cap. It fit in the keyway snug and tight. I took the truck down the street, I don't have time to go for a long ride, but it is much improved already. hopefully this takes care of my timing issue. Amazing what a little tune up will do....  I am still suspicious of a low fuel issue, so I will see if that problem rears its head again.

Mine cap was loosened because the rotor was too high shaving the inside contacts cap and one of the spring clip cap was too loosen.

[finmad]

You need to start by verifying that the timing is in the correct range. Until you know it is for sure you will just be chasing phantoms.

 

Jeff

 

 

With the replacement of the cap and rotor, you are probably getting more consistent timing but it still may not be correct timing.   Yes, it can rise rapidly if leaned out.  Merle believed his initial problem with valve clearance may have contributed to similar symptoms.  Do the timing and do the fuel pump flow tests first.  That eliminates 2 of the most likely possibilities and they are the easy ones to check.  Then you can move on to other possibilities that may require more in depth work.

So I was able to finally move the distributer and come to find out the backing bracket was not tight, The distributor was free to spin any which way. I was able to remove it which is a huge plus (It has been frozen in there since I got it.) After getting it off, I checked the vacuum advance and I think it is perished. I was told if you can blow through it is bad, and I can blow through and suck air trough with out effort.

 

Is this a part I can get easily of do I have to order it online?

[Jeff Balazs]

Well there you go. That sort of vacuum leak would cause it to run lean as well.

I would suggest you get a vacuum gauge and become familiar with how to use it. IMO It is one of the most valuable tools you can own.

Jeff

[55 Fargo]

So I was able to finally move the distributer and come to find out the backing bracket was not tight, The distributor was free to spin any which way. I was able to remove it which is a huge plus (It has been frozen in there since I got it.) After getting it off, I checked the vacuum advance and I think it is perished. I was told if you can blow through it is bad, and I can blow through and suck air trough with out effort.

 

Is this a part I can get easily of do I have to order it online?

Plug the vacuum advance line to the dizzy, until you can get another.

Someone on here should be able to help you out.

You can rely on the mechanical advance until you can get another, but plug the line to the dizzy until then.

Get a vacuum gauge, set your carb 1st, idle mixture in until engine stumbles, then back out until highest vacuum reading, then back off slightly. set idle on carb to desired speed.

The set timing for highest vacuuum reading, then retard timing slightly.....good luck

[Fernando Mendes]

"The cap should not move. There is a "key" as pictured that fits into a slot in the distributor preventing the cap from moving. If the cap moves this will alter the timing."

 

Bend two spring cap too,giving them more tension.

[finmad]

"The cap should not move. There is a "key" as pictured that fits into a slot in the distributor preventing the cap from moving. If the cap moves this will alter the timing."

 

Bend two spring cap too,giving them more tension.

I did that as well.

[finmad]

So, all of your advice has been extremely helpful. As seems to be the case, my issue was a combination of multiple problems. Like I said the disti was froze in place when I got the truck, luckily it was frozen in the right spot, but it looks like the driving over the past few months freed it up and since the backing plate was not tight it was able to rotate out of time. Also I rebuilt the carb and let the float stop ride too high, I bent the tab and brought it back down, finally I discovered a vacuum leak in the perished advance, I plugged the vacuum port in the carb, while I wait for a replacement. I can report a much happier and solid running truck. I was able to get it up to speeds today and very little knock/ping at max rpm. I did not loose power and it did not quit on me. Thank you all for your support, and patience with a newbie here. I am trying to keep these old cars and trucks on the road and your collective knowledge is invaluable.

[55 Fargo]

So, all of your advice has been extremely helpful. As seems to be the case, my issue was a combination of multiple problems. Like I said the disti was froze in place when I got the truck, luckily it was frozen in the right spot, but it looks like the driving over the past few months freed it up and since the backing plate was not tight it was able to rotate out of time. Also I rebuilt the carb and let the float stop ride too high, I bent the tab and brought it back down, finally I discovered a vacuum leak in the perished advance, I plugged the vacuum port in the carb, while I wait for a replacement. I can report a much happier and solid running truck. I was able to get it up to speeds today and very little knock/ping at max rpm. I did not loose power and it did not quit on me. Thank you all for your support, and patience with a newbie here. I am trying to keep these old cars and trucks on the road and your collective knowledge is invaluable.

As I posted earlier, run it as you are, until you have your new vacuum advance diaphragm.

That pinging on high RPM/load, if you have or get a vacuum gauge, time your engine as I also posted, if not.

Turn your dizzy with adjuster bolt loosend, just slightly clockwise, this will retard the ignition, and may stop pinging, hard detonation spark knock is not a good thing.

When I say slightly, just slightly clockwise............good luck

[finmad]

As I posted earlier, run it as you are, until you have your new vacuum advance diaphragm.

That pinging on high RPM/load, if you have or get a vacuum gauge, time your engine as I also posted, if not.

Turn your dizzy with adjuster bolt loosend, just slightly clockwise, this will retard the ignition, and may stop pinging, hard detonation spark knock is not a good thing.

When I say slightly, just slightly clockwise............good luck

I don't have one, but I will get one. as for now I will make small adjustments and see if I can dial in the timing.