Problems with 1972 Chevy 307. Help!!

kevinllee · 06-26-2009, 11:15 AM

The motor ran before I took it apart, no problems noticed except really couldn't get the timing correct and noticed I had a bad cam.

My original cam wore a lobe off and I replaced with a new cam/lifters, timing gear and chain.
1. The motor won't stay running. When it starts it might fire off and that's it, or it might run for a few seconds to a few minutes.
2. To get it to where it will fire off, I have to turn the distributor way out of whack to get it to start. If I turn the distributor to where it will turn over easy, it won't start. I have to turn it to where the engine has a hard time turning over and eventually it starts, but only with the stipulations of #1 above.

I "swore" I aligned the new timing gears to where it was "dot to dot". I adjusted the lifters with about 1/4 turn at zero lash. I've put new points and condensers in.
I don't know if It's a carburetor problem/fuel problem, or more of a timing problem. I figure if I could keep the truck running I could easily tackle the timing problem. If it's a huge timing problem, I wouldn't think the truck would run at all since it runs a little, whether seconds or minutes.

I wish I could physically talk to someone with a lot of experience on the phone. I know this motor is a easy one, but it's kicking me in the butt.

Please help???!!!!!!

kevin

**Raylo** · 06-26-2009, 12:27 PM

Try readjusting the lifters. If they were pumped down when you did the first adjustment some or all clearances can change once they get pumped up by oil pressure from running a bit. I had one that ran real bad until I readjusted the lifters.. but it ran and didn't die so maybe you have other issues, too? It does sound like you have timing issues. If you are sure you have the cam and crank dots lined up perhaps the distributor is inserted a couple splines off.... or something simple like crossed spark plug leads?

kevinllee · 06-26-2009, 12:52 PM

I'll try the lifters again. I changed the carb-intake gasket thinking maybe a vacuum leak also. Like I said earlier, I "think" I got the dots lined up, almost certain, but.......
BUT, while changing the gasket, I "thought" I saw on the bottom of the carb what looked like water and fuel mixed. It looked like little bubbles/sweating underneath, which to me could mean water in fuel? how much of that would have a play in everything?
I also checked the spark plugs too. If the lifters were out of adjustment, would that through the timing off so much as well?

**Raylo** · 06-26-2009, 01:27 PM

No, lifters would not affect timing. But you could have some valves maybe not opening much or perhaps even some excessive overlap between intake and exhaust. Could make it run bad.

06-26-2009, 11:15 AM	#1 (permalink)
kevinllee Registered User Join Date: Jun 2009 Posts: 7 OS: OSX	Problems with 1972 Chevy 307. Help!! The motor ran before I took it apart, no problems noticed except really couldn't get the timing correct and noticed I had a bad cam. My original cam wore a lobe off and I replaced with a new cam/lifters, timing gear and chain. 1. The motor won't stay running. When it starts it might fire off and that's it, or it might run for a few seconds to a few minutes. 2. To get it to where it will fire off, I have to turn the distributor way out of whack to get it to start. If I turn the distributor to where it will turn over easy, it won't start. I have to turn it to where the engine has a hard time turning over and eventually it starts, but only with the stipulations of #1 above. I "swore" I aligned the new timing gears to where it was "dot to dot". I adjusted the lifters with about 1/4 turn at zero lash. I've put new points and condensers in. I don't know if It's a carburetor problem/fuel problem, or more of a timing problem. I figure if I could keep the truck running I could easily tackle the timing problem. If it's a huge timing problem, I wouldn't think the truck would run at all since it runs a little, whether seconds or minutes. I wish I could physically talk to someone with a lot of experience on the phone. I know this motor is a easy one, but it's kicking me in the butt. Please help???!!!!!! kevin

06-26-2009, 12:27 PM	#2 (permalink)
Raylo TSF Enthusiast Join Date: Feb 2006 Location: Maryland, USA Posts: 525 OS: XP Desktop, Vista HP Notebook, XP Notebook	Re: Problems with 1972 Chevy 307. Help!! Try readjusting the lifters. If they were pumped down when you did the first adjustment some or all clearances can change once they get pumped up by oil pressure from running a bit. I had one that ran real bad until I readjusted the lifters.. but it ran and didn't die so maybe you have other issues, too? It does sound like you have timing issues. If you are sure you have the cam and crank dots lined up perhaps the distributor is inserted a couple splines off.... or something simple like crossed spark plug leads?

06-26-2009, 12:52 PM	#3 (permalink)
kevinllee Registered User Join Date: Jun 2009 Posts: 7 OS: OSX	Re: Problems with 1972 Chevy 307. Help!! I'll try the lifters again. I changed the carb-intake gasket thinking maybe a vacuum leak also. Like I said earlier, I "think" I got the dots lined up, almost certain, but....... BUT, while changing the gasket, I "thought" I saw on the bottom of the carb what looked like water and fuel mixed. It looked like little bubbles/sweating underneath, which to me could mean water in fuel? how much of that would have a play in everything? I also checked the spark plugs too. If the lifters were out of adjustment, would that through the timing off so much as well?

06-26-2009, 01:27 PM	#4 (permalink)
Raylo TSF Enthusiast Join Date: Feb 2006 Location: Maryland, USA Posts: 525 OS: XP Desktop, Vista HP Notebook, XP Notebook	Re: Problems with 1972 Chevy 307. Help!! No, lifters would not affect timing. But you could have some valves maybe not opening much or perhaps even some excessive overlap between intake and exhaust. Could make it run bad.