Running Rough

[Rajin]

I've got a 72 C20 4 spped, with what I believe is a 307. I've been having some problems with it for a while that I've been trying to diagnose.

It used to run fine around town(< 50km/h), and would start bucking once I got onto the highway and tried to give it gas. Eventually, it would stall out.

Then it started doing it in town, and melted part of the wiring harness.

So I replaced the wiring harness. Still ran rough. So far I've replaced the spark plugs (twice), plug wires, cap, rotor, points (gapped to .019"), fuel pump, new inline fuel filter, and changed the carb out for a 1405 edelbrock with an electric choke conversion. Now it seems to run ok at slow speeds again, but the second that I try to lay into the gas it has problems.

I've included a brief video of the truck to demonstrate what it's doing.I'm running low on things that I can try to check. Anyone have any ideas?

Video of the truck running: https://www.youtube.com/watch?v=PziB...ature=youtu.be

[stsalvage]

One thing. If you have melted wire what wires.Check your voltage and why has your truck have the looks to being peace meal together.One you should have full on gauge cluster 1969 was the last year of the no gauges.Please pick one up if you can and get the copper tube for your oil sending gauge.

Check and see what fuel pressure your getting you might need a electric fuel pump.After 750,000 miles on my 350 15 year ago I made the lob on my cam go round or Flat so it would not pump fuel and make my truck go lean and get hot Real Hot see if you have a crack in one of your fuel line rubber hoses you will be major pissed if that was the problem what color are your plugs are they gleaming white meaning going lean or are they Black or are they clean meaning your floats are set to high washing out the motor and the plugs

[Rajin]

Originally Posted by stsalvage

One thing. If you have melted wire what wires.

The negative that grounded from the alternator to the body was the one that melted. I've since replaced all of them. Battery cables, and harness.

Check your voltage

If I remember correctly, it sits in the 14V range. I changed the alternator out for an internally regulated one from a 78 Camaro.

and why has your truck have the looks to being peace meal together.One you should have full on gauge cluster 1969 was the last year of the no gauges.Please pick one up if you can and get the copper tube for your oil sending gauge.

That one I did not know. I'll keep my eye open for one. I might end up just picking up a small cluster to keep an eye on my oil pressure, water temperature, and voltage sometime. Would you recommend a copper tube, or would electrical be ok? I'm not a huge fan of having hot fluids inside the cab.

Check and see what fuel pressure your getting you might need a electric fuel pump.After 750,000 miles on my 350 15 year ago I made the lob on my cam go round or Flat so it would not pump fuel and make my truck go lean and get hot Real Hot see if you have a crack in one of your fuel line rubber hoses you will be major pissed if that was the problem what color are your plugs are they gleaming white meaning going lean or are they Black or are they clean meaning your floats are set to high washing out the motor and the plugs

I'll grab a fuel pressure gauge and check to be sure. The fuel pump is new though.

The spark plugs were black and sooty.

[Gromit]

Only thing I notice from your video is possible grounded plug wires.. I'll attach some photos of another member's truck (Bruce) who I think set the standard for good practice on this issue.

A quick check may be to start the truck at night and open the hood and look for arcs or flashes of light between your new plug wires and ground (if it is dark enough)..

Personally I like to keep about 1/8" between each plug wire and ground as well as 1/8" from any other plug wire (if that makes sense)..

Photos are better.. please see attached

Also you mention .019 on the points but maybe check the dwell too just in case.

[El Dorado Jim]

my advice would be to change distributor to a new HEI,Buy a new one, only around $90.00 from Summit, comes ready to drop in, but you need to change to 8mm wires and regap plugs to .045

[geezer#99]

Originally Posted by Rajin

I've got a 72 C20 4 spped, with what I believe is a 307. I've been having some problems with it for a while that I've been trying to diagnose.

It used to run fine around town(< 50km/h), and would start bucking once I got onto the highway and tried to give it gas. Eventually, it would stall out.

Then it started doing it in town, and melted part of the wiring harness.

So I replaced the wiring harness. Still ran rough. So far I've replaced the spark plugs (twice), plug wires, cap, rotor, points (gapped to .019"), fuel pump, new inline fuel filter, and changed the carb out for a 1405 edelbrock with an electric choke conversion. Now it seems to run ok at slow speeds again, but the second that I try to lay into the gas it has problems.

I've included a brief video of the truck to demonstrate what it's doing.I'm running low on things that I can try to check. Anyone have any ideas?

Video of the truck running: https://www.youtube.com/watch?v=PziB...ature=youtu.be

Mornin' from up Island!!
What's your initial timing?

[Rajin]

Originally Posted by Gromit

Only thing I notice from your video is possible grounded plug wires.. I'll attach some photos of another member's truck (Bruce) who I think set the standard for good practice on this issue.

A quick check may be to start the truck at night and open the hood and look for arcs or flashes of light between your new plug wires and ground (if it is dark enough)..

Personally I like to keep about 1/8" between each plug wire and ground as well as 1/8" from any other plug wire (if that makes sense)..

Photos are better.. please see attached

Also you mention .019 on the points but maybe check the dwell too just in case.

Those wire looms are gorgeous. for the time being, the zap strap seems like it would be a good way to check. I'll do that to them tonight after I'm done work. I'll see if I can track down a dwell meter to use.

Originally Posted by El Dorado Jim

my advice would be to change distributor to a new HEI,Buy a new one, only around $90.00 from Summit, comes ready to drop in, but you need to change to 8mm wires and regap plugs to .045

Wish that I could, but that's a pricey endeavor up here in canada. $90 (distributor) + $32 (plug wires) = $122 USD + $34 (shipping) = $156 USD. After Duty fees, and currency conversion, it's atleast $250 from summit.

It's on the list for one day.

Originally Posted by geezer#99

Mornin' from up Island!!
What's your initial timing?

Good morning!

I've currently got it sitting at ~10* BTDC

[toolboxchev]

Video cut short for me, when you started the truck. ????

[Rajin]

That's what I get for not actually checking the video

Here's the slightly longer version: https://youtu.be/JlqePF4deRk

[geezer#99]

Try more timing!
A bunch more!
Try 16 at the lowest idle you can.
What does it idle at now?
And what is the idle rpm when you check the timing?

[stsalvage]

By chance is your intake a 2bb intake and you have a 4bb adapter plate on there.One thing you might have a massive Vacuum leek.To me you don't need that alum spacer under the carb.

One other thing take the carb off and see if your runners are wet or if its wet in side the intake manifold.the brass Floats could be to high letting to much fuel into the bouls if you have some carb spray check for leaks

[Rajin]

Originally Posted by geezer#99

Try more timing!
A bunch more!
Try 16 at the lowest idle you can.
What does it idle at now?
And what is the idle rpm when you check the timing?

I'll try to increase the timing tonight. It currently idles at around 800 rpm, but seems slightly erratic going up to 950 at times.

Originally Posted by stsalvage

By chance is your intake a 2bb intake and you have a 4bb adapter plate on there.One thing you might have a massive Vacuum leek.To me you don't need that alum spacer under the carb.

One other thing take the carb off and see if your runners are wet or if its wet in side the intake manifold.the brass Floats could be to high letting to much fuel into the bouls if you have some carb spray check for leaks

Nope, it's a 4bbl quadrajet intake. I've got the edelbrock 2696 adaptor plate to go from the square bore edelbrock 1405 carb to the q-jet intake.

I've sprayed down the carb with some carb cleaner pretty thoroughly without any change in my rpm. When I check the runners, should I do that after the truck has been sitting for a while, or after running?

[cdowns]

check your camshaft for worn out lobes

[stsalvage]

No worries on the oil hitting your foot.if you know of a place guy you or some one selling old chevy part from 1964-72 Chevy and GM trucks with V8 engines and that oil line is interchangeable from all 283-427 engines here look

[stsalvage]

I was telling him of my 1965 3/4 ton that i had over 750,000 miles on cus i haul a trailer to you 2 times the mileage like how moterhomes do it cus of the weight you pulling all the time.I ran my cam lob flat on the fuel pump rod

[stsalvage]

I saw on your power steering you don't have the right brackets cus the pump should be straight up not slated to the side Here are the pics from my 1968 3 door suburban and my 1965 3/4 ton Chevy trucks

[stsalvage]

are you sure you don't have a plug wire in the wrong spot it could be exsalrator pump on the carb or you have a plug Jet in the carb

I know bad spelling i try on its the peace that squirts fuel to prime the carb

[geezer#99]

Originally Posted by Rajin

I'll try to increase the timing tonight. It currently idles at around 800 rpm, but seems slightly erratic going up to 950 at times.



Nope, it's a 4bbl quadrajet intake. I've got the edelbrock 2696 adaptor plate to go from the square bore edelbrock 1405 carb to the q-jet intake.

I've sprayed down the carb with some carb cleaner pretty thoroughly without any change in my rpm. When I check the runners, should I do that after the truck has been sitting for a while, or after running?

Get your idle down to 700.
Likely the mechanical advance is starting to kick in at 800. That's why it jumps up.
We'll sort your timing out first and then if all else fails, then you'll need to check for a flat cam.

[Rajin]

So I got a little bit done last night.

Adjusted the timing. It seems much happier sitting around 16*. Tried to adjust the idle. I think that I got it turned down some, but it's way more erratic than I initially though. It's anywhere from 700 - 1200. Seems to want to sit at a spot for a while before changing.

Separated the spark plug wires, and checked at night. No visible arcing is happening. Double checked the connections on them to make sure that they're in the right place.

For the power steering pump, I think that someone may have just put on a belt that's a bit too short. There looks like there's lots of adjustment left in the bracket.

Things that I apparently cannot find on short notice; a dwell meter, and a fuel pressure gauge.

Things that I did not get around to doing last night. Checking my fuel lines. Pulling the valve covers and checking for a worn camshaft lobe.

I did get a backfire out the carb once last night when I gave it some gas.

She's running happier. But still not awesome.

[Rajin]

I also did double check my voltage. It sits at 14.46V steady

[stsalvage]

Just to ask you might be one tooth to much on your distributor.Are you top dead center,Valve covers will not show you if you have a flat cam.If you take your hose off your carb and have a friend try to start the motor and see how much fuel come out.But really you need to find some one with a fuel pressure tester.By chance you you have a locale club around where you are that are in to old trucks like yours.

If not do you have a Teck school around you that has a auto shop that can help.They are always looking for trucks like yours to teach there kids on how to fix your kinda problems.Plus they have all the tools that will be for free to use

Any High schools that have a Auto shop them guys love your kinda trucks Plus some of the kids might know other people that have parts or have a truck like yours that can help if your stuck.

There are a lot of guys on this site that are from Canada trust me they are allways into helping fellow members

[stsalvage]

my father says your one volt hight meaning your going to boil your battery.

He tells me to ask you if you have a ground to your motor to your frame A ground from your motor to your Cab and your cab has to have a ground to your Farme He said you like my searching for a ground.

Like on New car's they have grounds every where and all it takes is a copper wire with a round end on ether end and your good Plus i like putting one from the bed to the Frame or 2 of them