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(This is my first time working with the 350 motors)
I got this 79 c3 Vette from my grandpa a couple months ago and I've been tackling issues after issue to get it running.
(Issue)
We have had this thing run for a couple seconds under some brake clean but can't get it to idle, it has times where it wants to but it seems to always find its way back to nothing. I've timed it at the distributor and timing chain a couple times. We can get it right there on the edge of taking over on its own but I can't get it to stay that way?
Just wondering if there's an issue I'm not seeing or if there's some special magic with these motors I don't understand.
Any thoughts?
At first I thought you were running it without connecting to the radiator.
Now I see you don't have a water pump, or timing chain cover.
The brake booster is not connected. You probably have a massive vacuum leak. At the very least, connect that distributor vacuum advance to manifold vacuum, and plug everything else. The problem is probably that carb. Before it catches fire and solves your problem, is fuel going into that plastic fuel filter? Is the accelerator pump squirting fuel?
How's the rest of the car? Maybe check the compression before you bother going any further with that L48. If you have to pull the engine, consider a junkyard LS swap.
OK
I see you went pretty deep:
The way I would tackle this, not knowing parts or run history:
Make sure you have the cam dots lined up with the crank dot. top to top, bottom to top, it does not matter. You'll correct that in a sec. Don't stress it.
Put it on top dead center according to the dots before you put that on. straight up & down, lined up. With a ruler.
Put the timing cover and crank balancer back on. Do not fire it with that open.
The line on the crank balancer should be really close to the line on the timing tab. We'll double-check the balancer soon. If it is way off, come back here.
Pull the drivers valve cover, and make sure you have the piston at top dead center for #1, on the firing stroke, where neither valve is down. SBC #1 is driver's front. You will either have it just right, or be a full crank turn off where neitheronly one valve is down. Rotate the engine a full turn if needed. Now your camshaft and piston #1 firing are lined up together. This will correct the dot to dot thing on the cam/crank.
Now rotate the engine small amount with a breaker bar, and use a piston stop, to find true TDC. It usually hits the timing stop about 3-4 inches on each side of TDC, and won't go any further. That is how you find piston TDC. Mark the two stops on the balancer with some tape. Measure 1/2 way in between. You need to find the real TDC, according to the piston, this way. This double-checks the balancer / timing tab, and makes sure it is lined up with #1 piston TDC. Do not rotate it it a full turn or you will lose #1 firing. Just go 1/2 turn back, and 1/2 turn forward.
If your timing mark on the balancer is way off from TDC according to the piston, come back here. They should basically match.
After all that, make sure you left it on #1 firing, no #1 valves down. Put the valve cover back on.
Bump the engine an inch front or back, with a wrench, until you get to your timing setting, around 8* BTDC (pass side of timing tab) of the big line on the balancer. Then do not turn the crank again until you are ready to fire.
Do you know how to install a distributor? Did you pull it? after you do the above, pull the distrib cap and make sure the rotor points at the #1 spark plug wire, not 180* off. If you timed the balancer at 8* it should be dead-on the #1 terminal. If it is an inch or two off you can just rotate it. Move the distrib as necessary and lock it down. If it is 180* off you will need to pull the distrib and rotate the center shaft, then put it back in. That may take a few tries. Watch a video. No timing light required this way. This makes sure the distrib is on #1 firing at the same time as the piston. You could have moved this around with your timing chain r&r.
When you are done the crank, the camshaft, and the distributor, all three, will be on the firing stroke for #1. It is so easy to have one of these 180* off. We have all been there.
Now pull the fuel line, stick it in a cup, and make sure your fuel pump has fuel flow. It does not look like you changed this part yet. Just spin the engine a little. With the distrib hot wire unplugged.
Did it sit along time? Did you drain the gas tank and put fresh gas in it? Did you use some air to blow out the lines? If not, do so now. You do not want 20 year old gas & varnish in your new carb.
Plug the hot wire back into the distrib. Pour a 1/4 paint can cap fuel of gas down the carb vent to put some in the bowls.
Pour a 1/4 paint cap of gas down the carb into the engine.
I do not know what the initial idle screw setting is for an Edelbrock, but try 1-1/2 turn out, unless someone else knows better.
Start it.
If it does not fire right up, check for spark, but I thought you said it ran some, so you should have spark.
If it doesn't want to idle you may have to set the mixture screws first, then the idle screws.
Then you can break out your timing light and make a small adjustment to the timing.
Do not run it for more than a minute or so with no water in it.
Last edited by leigh1322; Jul 5, 2024 at 06:08 PM.
OK
I see you went pretty deep:
The way I would tackle this, not knowing parts or run history:
Make sure you have the cam dots lined up with the crank dot. top to top, bottom to top, it does not matter. You'll correct that in a sec. Don't stress it.
Put it on top dead center according to the dots before you put that on. straight up & down, lined up. With a ruler.
Put the timing cover and crank balancer back on. Do not fire it with that open.
The line on the crank balancer should be really close to the line on the timing tab. We'll double-check the balancer soon. If it is way off, come back here.
Pull the drivers valve cover, and make sure you have the piston at top dead center for #1, on the firing stroke, where neither valve is down. SBC #1 is driver's front. You will either have it just right, or be a full crank turn off where neither valve is down. Rotate the engine a full turn if needed. Now your camshaft and piston #1 firing are lined up together. This will correct the dot to dot thing on the cam/crank.
Now rotate the engine small amount with a breaker bar, and use a piston stop, to find true TDC. It usually hits the timing stop about 3-4 inches on each side of TDC, and won't go any further. That is how you find piston TDC. Mark the two stops on the balancer with some tape. Measure 1/2 way in between. You need to find the real TDC, according to the piston, this way. This double-checks the balancer / timing tab, and makes sure it is lined up with #1 piston TDC. Do not rotate it it a full turn or you will lose #1 firing. Just go 1/2 turn back, and 1/2 turn forward.
If your timing mark on the balancer is way off from TDC according to the piston, come back here. They should basically match.
After all that, make sure you left it on #1 firing, no #1 valves down. Put the valve cover back on.
Bump the engine an inch front or back, with a wrench, until you get to your timing setting, around 8* BTDC (pass side of timing tab) of the big line on the balancer. Then do not turn the crank again until you are ready to fire.
Do you know how to install a distributor? Did you pull it? after you do the above, pull the distrib cap and make sure the rotor points at the #1 spark plug wire, not 180* off. If you timed the balancer at 8* it should be dead-on the #1 terminal. If it is an inch or two off you can just rotate it. Move the distrib as necessary and lock it down. If it is 180* off you will need to pull the distrib and rotate the center shaft, then put it back in. That may take a few tries. Watch a video. No timing light required this way. This makes sure the distrib is on #1 firing at the same time as the piston. You could have moved this around with your timing chain r&r.
When you are done the crank, the camshaft, and the distributor, all three, will be on the firing stroke for #1. It is so easy to have one of these 180* off. We have all been there.
Now pull the fuel line, stick it in a cup, and make sure your fuel pump has fuel flow. It does not look like you changed this part yet. Just spin the engine a little. With the distrib hot wire unplugged.
Did it sit along time? Did you drain the gas tank and put fresh gas in it? Did you use some air to blow out the lines? If not, do so now. You do not want 20 year old gas & varnish in your new carb.
Plug the hot wire back into the distrib. Pour a 1/4 paint can cap fuel of gas down the carb vent to put some in the bowls.
Pour a 1/4 paint cap of gas down the carb into the engine.
I do not know what the initial idle screw setting is for an Edelbrock, but try 1-1/2 turn out, unless someone else knows better.
Start it.
If it does not fire right up, check for spark, but I thought you said it ran some, so you should have spark.
If it doesn't want to idle you may have to set the mixture screws first, then the idle screws.
Then you can break out your timing light and make a small adjustment to the timing.
Do not run it for more than a minute or so with no water in it.
This is amazing, thank you so much. I'll get back to you when I've checked and redone everything.
It hasn't run in about 10-15 years and was parked for this reason I'm pretty sure.
Brand new fuel pump and lines, dropped the tank cleaned it and put it back in also with new lines.
That is a brand new distributor with new plugs and wires.
Ive been told before to bring #1 all the way up and line it up w #1 in the distributor on intake stroke but never all that. * Thanks again*
Pull the drivers valve cover, and make sure you have the piston at top dead center for #1, on the firing stroke, where neither valve is down. SBC #1 is driver's front. You will either have it just right, or be a full crank turn off where neither valve is down. Rotate the engine a full turn if needed. Now your camshaft and piston #1 firing are lined up together. This will correct the dot to dot thing on the cam/crank.
Leigh - good write-up but I think the bolded portions above are contradictory. At least how I'm reading it.
Josh: #1 and #6 will both be at TDC at the same time - one firing>power stroke, one just exhausted>intake stroke. TDC firing on #1 will have both valve rockers even and up from the head (both valves closed for the last 1/4 stroke). If the crank/cam is 180° out (actually firing #6), it will appear that the #1 exhaust valve has just closed with the rocker headed upward (during the exhaust stroke for #1) with the intake rocker headed downward (initiating intake stroke #1).
If you align your crank and cam gear dots such that the cam dot is at 6:00 while the crank dot is at 12:00 it's easy to visually align them. HOWEVER, this corresponds with firing #6. After aligning at 6:00/12:00, rotate the engine so both dots are now at 12:00 on their respective gears -- this will be firing #1 and where you want to drop in and set the distributor.
Just because @lars says 95% of carb problems are timing problems, there's no reason to ignore the multiple open vacuum ports on that Edelbrock carb, or the fact that it ran with starting fluid, but won't run on the carb.
Check for fuel in the carb. Prime it if you need to.
Leigh - good write-up but I think the bolded portions above are contradictory. At least how I'm reading it.
Josh: #1 and #6 will both be at TDC at the same time - one firing>power stroke, one just exhausted>intake stroke. TDC firing on #1 will have both valve rockers even and up from the head (both valves closed for the last 1/4 stroke). If the crank/cam is 180° out (actually firing #6), it will appear that the #1 exhaust valve has just closed with the rocker headed upward (during the exhaust stroke for #1) with the intake rocker headed downward (initiating intake stroke #1).
If you align your crank and cam gear dots such that the cam dot is at 6:00 while the crank dot is at 12:00 it's easy to visually align them. HOWEVER, this corresponds with firing #6. After aligning at 6:00/12:00, rotate the engine so both dots are now at 12:00 on their respective gears -- this will be firing #1 and where you want to drop in and set the distributor.
You're right. I think I need to change a word in there.
Anyway you explained #6 & #1 better.
I never worried about which dot was up or down, I just checked the valves on #1 and made sure they were both up.
Then I knew I was on #1 firing.
Not knowing the guys skill level, I gave him this sequence.
It should identify any possible issue with incorrectly paired timing marks/balancers, spun balancers, dots off, distributor on #6, etc. etc.
If it has fuel and spark, this should get the timing close enough it should fire right up.
Not knowing the history of the car, I did not have him check for flat cam lobes, but I figured if it ran rough, he could always check that later.
Think of anything I missed?
Last edited by leigh1322; Jul 5, 2024 at 06:15 PM.
I think it was really nice of you to take that much time to type all of that!
And I think it's a real good start for him.
Let him do all of that, including of course plugging off any and all unused vacuum lines and then take it from there.
His new distributor looks like a generic inexpensive one that's not likely to be curved very well for performance. But it should at least run. I'd be looking for the original distributor. Or a DUI unit.
The first few times I pulled a cam or distributor, getting it all back correctly always seemed such a daunting task.
I really empathize with someone learning how to do that.
Until I realized that all three parts just need to be synchronized.
Eazy-peazy LOL!
You know that satisfaction you get inside for fixing something, or figuring out how?
I get the same satisfaction when I help someone else "figure it out".
Last edited by leigh1322; Jul 6, 2024 at 07:48 AM.
Good Job with your write up leigh1322! That was a very nice write-up to provide the original poster as many folks are not as familiar with the procedure. I pull the distributor before starting the engine after a few months to allow the electric drill access to spin up the oil pump and get full oil pressure inside the engine before starting. I put the #1 at TDC and pull a valve cover to ensure the flow of the oil and then the distributor goes back in and all is in time so the engine starts right up. I do have to reset the initial timing with my timing light after re-installing the distributor.
To me I start at the most simple stuff and figure it out that way. I see so many people start at the the most complicated systems and work their way down. On the C4 Forum you see people always blaming the ECU for any issues they are having when in fact there are so many other things it could be before you touch the ECU.
Helping others is a great thing, it would be better for our country if everybody tried to help their neighbor when they needed a hand!
Timing issues?
