89 d-50 2.6 doesn't like hills

Changing carburetors will not reset the timing. That's why it knocks under load.

Budd

thanks for your reply. timing was set by a trusted proffesional.what else?

Vacuum leaks (manifold to head, carb to manifold) or incorrect carb jetting ( the same carb may fit different engines and use different jets. If bought as a rebuilt carb, it might not be jetted right).

If those are ok, then double check the timing. Sorry, but your mechnaic is a human and can make musteaks . . .messtake....errors.

;)

Budd

thanks again.this motor has approx. 44-46 vaccum hoses.is it probable that the mechanic could have gotten something wrong? vaccum advance appears to work fine. if jetted wrong,what next? thanks.

Look under the hood for a vacuum hose routing diagram. If it's gone, you'll need to get a manual with one in it. Then just trace each line down according to the diagram.

Of course, just looking around under the hood may locate a leak or two from old lines that have gone bad or simply fallen off. A stuck EGR can cause ping also.

The vacuum advance only works when under part-throttle and cruise conditions. It can be tested in the drive way with timing light by pulling the distributor vacuum line off at 1/3 throttle, ( about 1800 RPM, if you have a tach), plugging it with a finger and seeing if the timing setting returns to about 10 degrees BTDC.

Well, the hard part would be to try and find the right jets since the carb is pretty old now, the easy way would be to find a carb on a junkyard engine and rebuild it yourself.

Happy New Year!

Budd

you've been a great help.thanks! have a great year!

It's what most of us are here for, to get help or to give it.

You're welcome, and a great New Year to you also.

Budd