Running rough under load

[The73vetteman]

Started up my L48 4spd this morning and it ran nice at idle (like it always does). But put it into gear and it doesn't want to rev over 1500. I can work thru the gears ok, providing I don't exceed 1500. Above that it feels like there's a rev limiter.

Timing? Advance? Help!!

 

[zachh]

Sorta sounds like theres something wrong with your distributor. I would check the distributor cap and your rotor.
Good Luck
zachh

 

[The73vetteman]

The cap and rotor are pretty new but I've looked them over and they seem OK.

I did find the dwell was out - about 20 degrees - but putting that right dropped the rpms from 900 to about 700. The timing is at 12 BTDC, the mechanical advance seems to be working, as does the vac. When I pull off the vac hose the timing changes to about 2 After TDC.

I'm starting to think it might be a coil problem. Can anyone give me a tutorial on how to check out a coil?

J

 

[Rowdy1]

Fuel?

How about the gas filter?

 

[BarryK]

if it worked fine the last time you drove it and this is a new problem that's started immediately I doubt it's a distributor problem.
Like Lou suggests check your fuel filter for possible debris obstruction and I'm thinking a possibility of the fuel pump going bad.
Also, are your throttle blades opening up?

this sounds more like a fuel or carb issue rather than ignition.

 

[craig32]

Ditto on the fuel filter, tht's just how they act! Not expensive or difficult to change, so even if it was good you're not out much.

Craig

 

[Vettehead Mikey]

The cap and rotor are pretty new but I've looked them over and they seem OK.

I did find the dwell was out - about 20 degrees - but putting that right dropped the rpms from 900 to about 700. The timing is at 12 BTDC, the mechanical advance seems to be working, as does the vac. When I pull off the vac hose the timing changes to about 2 After TDC.

I'm starting to think it might be a coil problem. Can anyone give me a tutorial on how to check out a coil?

J

Get your ignition timing sorted out too. Sounds like your points have gone south, irrespective of how old they are.

 

[The73vetteman]

OK, here's the update:

Removed and cleaned the in-line filters (I have a Holley and I use the powdered metal filters that fit in the carb.) There was quite a bit of crud in there. Then set the timing to 14 BTDC and away she went, running like a dream.

Thanks for the suggestions everyone. Wouldn't have fixed it so quickly without you!

 

[Scooter76]

Maybe too late to help, but it looks like you were setting your inital timeing with the vac advance hooked up, since you said that it dropped to 2* atdc when you disconected the vac advance hose. You need to make sure that your initial of 12 or 14* is without the vac advance.

Have a good one!

 

[The73vetteman]

Scooter,

You make a good point. I've never been clear about timing with vac advance disconnected. Should I just pull the tube off the advance at the distributor, and if so should i plug the hole at the dizzy and/or at the manifold?

J

 

[fine69]

Scooter,

You make a good point. I've never been clear about timing with vac advance disconnected. Should I just pull the tube off the advance at the distributor, and if so should i plug the hole at the dizzy and/or at the manifold?

J

Just disconnect small hose from the vacuum advance can... you can use a golf tee to plug up the hose.

 

[GerryLP]

Scooter,

You make a good point. I've never been clear about timing with vac advance disconnected. Should I just pull the tube off the advance at the distributor, and if so should i plug the hole at the dizzy and/or at the manifold?

J

Books usually tell you to plug the hose, for if your are attempting to adjust an adjustable cannister, it is implied that the hose still attached to the manifold. So plug either the hose (if it is still attached to the manifold) or the manifold port.

GerryLP:cool

 

[zachh]

When I had to play with mine, I just disconnected the hose from the distributer,. and plugged the hose. There isnt a need to disconnect it from the manifold, unless its in your way. Good Luk,
zachh