Big RPM drop going into drive

Fkidd

Hi all, I have a 1970 Javelin with a 360 and the Borg Warner M-12. When I rebuilt the engine I used a Comp Cams camshaft close to (or what I thought was close to) stock specs. I does have a little bit of a lope to it though. My problem is that I have to have it idling at about 1200 in nuetral so that when I shift to drive it will be at 600 RPMs. it chirps going into reverse when I'm backing out of my garage and it surges when I'm holding the brakes in gear. I've searched for a couple hours here on the internet and can't find much info. Do I need a higher stall converter? And if I do....where in the hell do I get one? Any info on this would be appreciated. And if you think I have something misadjusted, my ego can handle any and all tips or criticisms. Thank you

tufcj

I have a M12 in my 69 AMX, it doesn't drop like that. It idles at 850 - 900 in park, and about 650 in drive. I have a pretty aggressive street cam in my 390. If you idle it down to 800-900, check you timing, make sure its about 4-6 degrees advanced, vacuum advance unhooked and plugged. On the timing cover "A" is advanced (BTDC). Some people think it's "after" and go the wrong way. You might experiment with a little more advance too. Does it stall if you set the idle down that far and put it in gear? Is you trans over full? If not, you may have a problem with the trans or converter. Do you have the vacuum modulator connected and is the line undamaged? Stall speed on a converter is just the max speed that the engine will rev to with the tires not moving. A 2000 stall converter will theoretically let the engine rev to 2000 RPM while you stand on the brakes. It has nothing to do with idle. Just some thoughts. Bob tufcj

Fkidd

Thanks B for the ideas Bob. I'll recheck everything and repost with my results.

Fkidd

Well I finally got back to my car and I have to thank you Bob for refocusing my thoughts. I was overthinking the whole matter. What I think is my main problem is the timing marks on the balancer. I bought this car in pieces and tried to use as much that came with it in the tubs that I could. If I set it at TDC according to the marks it backfires through the carb. By the time I got the timing and the idle screws dialed in so that it runs pretty good, the timing mark was so far advanced using the timing light that the mark wasn't visible when the timing light fired. I've always timed by ear but since it has been about 15 years since I was into the hobby I was trying to tune it by the book. The way I have it now is just shy of spark knock with a load. Thanks again Bob.....you were a big help. Tom

tufcj

You can't rely on the marks on an old balancer to be true. I've seen the outer ring slip as the rubber decays. If the rubber is bulging out anywhere, it may be time to have it rebuilt. www.damperdoctor.com does a great job.

Glad you got it straightened out.

Bob
tufcj