The Dodge Challenger Message Board

Hello all,

Have not been on here lately, move and job change, finally getting back into the car.

Started noticing a knocking in the exhaust under hard acceleration, knocks around 2,800 - 3,000 rpm. The engine is a mildly built 440, 9.7 to 1 compression, essentially a stock cam (comp cams), Harland sharp roller rockers - 1.6, 750 edelbrock, tti headers and 2.5 inch exhaust.

I thought timing, but checked, it idles smooth at 800 in park, about 10 degrees initial, and 33 degrees at 3,000 and about 47 all in.

Any thoughts on this? rebuild has about 1,500 miles on it. Just used for cruising, no strip.

Thanks,

- rich

Hey good to see you back on here

I'd suggest advancing the initial a bit, just so it can cope with modern fuel blends.
Have you got the vac can being fed from the constant or timed ports on the carb?
If it's constant switch it to timed. You may find that you've got vac advance when you don't want it.
Try disconnecting the vac line at the distributor and see if that stops it too.
At least then you can rule out ign timing.

What heads have you got?

Hi Adrian,

Thanks for the quick reply. They are 452's, new guts in the them, but nothing hi-performance.

I think you are right on with the timing suggestions. I have the vacuum on the timed port. It is just a basic chrysler (brown cap) electronic ignition conversion kit. I have not driven the car much, and had forgotten since I moved down here, I reconnected the vacuum line. I had, per Dave's suggestion in another post, unhooked it. The car did not knock when it was unhooked, and ran much better. At some point in the past year, I reconnected, and that is when the problem I think started again. I am my own worst enemy.

I have heard that the ignition I have can over-advance and folks put in stiffer springs to cut down on the mechanical advance. Maybe with all the advance, it is just too much.

Going to retime it tonight, with a little more advance, maybe 12 degrees, leave the vacuum off and road test. I would bet that is it.

Thanks again.

- rich