No Start After Cam Swap

[omillan99]

On my 1978 K20 with a 350 4BLT main, I swapped in a Comp Cam 280h 12-212-2, double timing gear on the key way for 4* of timing retard. I previously had an edelbrock intake, 1.5 roller rockers, MSD cap, rotor, and a Digital 6 plus box, a 750 manual choke carb.

I got everything in and situated, the motor turned over fine, I have fuel coming up and in the carb. I can imagine i have spark but have not fully checked. I can not get her to fire up, it'll turn over and at points the engine will sputter and turn faster than the starter as if it is going to run but as soon as I back the starter off it'll stop. I have confirmed I have the rotor at the proper position on the compression stroke. The truck started once and ran but I had to make some adjustments so I shut it off and it hasn't been able to start since then.

Do you folks have any recommendations before I send her off to a stranger to get checked? If any more info is needed, let me know.

Thanks in advance.

 

[1987 GMC Jimmy]

Double check firing order, and just so I’m on the same page the rotor was pointing to #1 and you felt the compression with your finger?

This is what I was gonna say when I hadn’t read that it ran once. Did it run correctly? Maybe the distributor wasn’t clamped down all the way and moved or something went haywire in the timing set?

 

[shiftpro]

And... why retard the timing at the crank...?

The way you describe it, might be a tooth out on your dizzy and be super retarded.

 

[omillan99]

Double check firing order, and just so I’m on the same page the rotor was pointing to #1 and you felt the compression with your finger?

This is what I was gonna say when I hadn’t read that it ran once. Did it run correctly? Maybe the distributor wasn’t clamped down all the way and moved or something went haywire in the timing set?

That is correct, the thing is that when it ran the idle was to low so it would only run with a little bit of throttle I also needed to charge my battery. I have reset the distributor 3 times after that though jumping one tooth forward and one back each time when the puff came out the spark plug hole.

 

[omillan99]

And... why retard the timing at the crank...?

The way you describe it, might be a tooth out on your dizzy and be super retarded.

I retarded the crank sprocket because I read that it can help give a little more power at the top end which my truck tend lack a little. The timing set I installed had multiple keyways to install, it had a stock keyway, an advance keyway, and a retard keyway.

 

[QBuff02]

Remember, Cam timing has nothing to do with ignition timing. When you advance or retard the cam, you're actually changing the timing of the valve train events and NOT the ignition timing. And i'm going to venture to guess that you have the distributor installed 180 degrees off and you're on the #6 firing position. If you went "dot to dot" when you installed the cam gear and timing chain, didn't rotate the engine over and installed the distributor, you're 180 degrees off. Cam gear at 6 and crank gear at 12 is #6 tdc, cam gear at 12 and crank gear at 12 is #1 tdc on firing order. Everyone usually installs the timing set this way for ease because the dots are right on top of one another and easier to "spot". My money is pull the distributor, rotate the rotor around to #6, re line up the oil pump drive shaft, drop her in and wire it up and fire it up.


EDIT: I'm just getting my morning coffee in me and am re-reading the posts.. So it actually runs? or just spits and sputters like it WANTS to run but doesn't actually run? because that's possibly something altogether different..

 

[omillan99]

Remember, Cam timing has nothing to do with ignition timing. When you advance or retard the cam, you're actually changing the timing of the valve train events and NOT the ignition timing. And i'm going to venture to guess that you have the distributor installed 180 degrees off and you're on the #6 firing position. If you went "dot to dot" when you installed the cam gear and timing chain, didn't rotate the engine over and installed the distributor, you're 180 degrees off. Cam gear at 6 and crank gear at 12 is #6 tdc, cam gear at 12 and crank gear at 12 is #1 tdc on firing order. Everyone usually installs the timing set this way for ease because the dots are right on top of one another and easier to "spot". My money is pull the distributor, rotate the rotor around to #6, re line up the oil pump drive shaft, drop her in and wire it up and fire it up.


EDIT: I'm just getting my morning coffee in me and am re-reading the posts.. So it actually runs? or just spits and sputters like it WANTS to run but doesn't actually run? because that's possibly something altogether different..

I got it to start once after a few minor fixes, I didn't leave it running since the idle was to low to stay on solo. Now I can only get it to sputter and have moved the distributor around and jumped teeth back and forth.

 

[71RAT]

I'll just throw a few things at you;
180 out, as suggested aleeady
Valves adjusted to tight
Large vacuum leak
Spark ignition issue, check it!

That being said, if your distributor timing is off you should be getting some backfiring out of one end or the other. If your getting fuel. Don't rule out more than one problem !
Good luck !

 

[omillan99]

Hello! So I did a few test and took some things apart. I double checked I am 100% certain I have fuel (jets spray in carb and I have 2 clear filters full of fuel), Checked each cylinder for spark and cleaned the plugs (slightly fouled from cranking so much), checked compression I'm at 120 (plus or minus 1 between cylinders), took off the timing cover and the timing marks are lined up on the sprockets and with the distributor at CYL 1 when the cam sprocket mark is at 12 o'clock and at CYL 6 when the mark is at 6 o'clock. Any other suggestions what may cause my no start?

I also noticed when turned the dizzy to advanced or retard it has no affect on the engine (usually the engine will struggle to turn over when turned one way and smooth out when turned the other), it does not back fire at all or make any other suspect noises. It only turns over at the same speed. Please toss me a few tid bits of knowledge.

 

[omillan99]

I'll just throw a few things at you;
180 out, as suggested aleeady
Valves adjusted to tight
Large vacuum leak
Spark ignition issue, check it!

That being said, if your distributor timing is off you should be getting some backfiring out of one end or the other. If your getting fuel. Don't rule out more than one problem !
Good luck !

I'm leaning to maybe the valves are to tight, when I assembled the engine I adjusted the valve lash with the lifters empty, could it be that possibly when the engine started the lifters filled with oil and changed the valve lash thus making them to tight? Just pondering here.