So I just picked up a 71 Roadrunner 383/auto stock except for MSD Pro Billet (no vacuum advance)/ 6AL/ edelbrock 650/ headers. When I picked it up, it was a dog. Wouldn't even spin the tires. The timing was at 10 deg. I set it to 12 deg with no appreciable difference. Then this morning, I started it up and it was backfiring through the carb. Before checking for vaccum leaks, I turned advanced the timing until I could go WOT without a backfire. The timing is somewhere near 25 or so on the dampener! Well I drove it, the backfire is gone, the car burns out and doesn't ping.

What the heck? Has the dampener slipped? One thing is that the distributor has light green advance springs. I only see silver and blue in the MSD catalog/manuals. The distributor does advance the timing, though i'm not exactly sure how much and at what curve.

Any ideas?

Well it may have been recurved, but your typical MSD kit only ocmes with bushings to limit dizzy travel to 18 degrees, which would mean you'd want 20 degrees initial at the most. FBO sells bushings for 10 and 14, so if its been played around with it may want 25 degrees, but I doubt that since most people don't know and anyone who would have known how to recurve the distributor properly likely would have had it running strong.

However, that is all in regards to making good power. The engine should still respond okay with less timing, but even 5 to 10 and it shouldn't backfire/ it should rev clean.

It could have very light springs and be advancing at idle, whats the idle speed? Turn it down and see if the timing retards.

Also many timing lights don't like MSD, particularly dial backs. But I'm guessing you're not using a dial back since you don't know the total timing. Slipped balancer is always a possibility too, as you mentioned.

Thanks for the reply. I'll check what you told me to. At 10 or 5 deg, it runs worse. Idle quality is worse. I am going to pull the carb and change the gaskets too.

Whoa - I just looked at the reluctor gap and it looks huge. and the reluctor looks a rusty. I'll deal with that too then see what happens.

It starts good runs good no kickback no ping. All good except for the timing reading on the dampener looks excessive. What Matt said make sure you ain't into the springs at idle which would give you a false initial timing reading (you actually have less than what it's showing). A slipped dampener would sound like a sure fire cause but k.i.s.s. I'd be inclined to think that that's not it. I would make a mark on your dampener 2&1/4" to the right (clockwise) of the TDC slit which is 35.5 degrees & see how close either way you are to that at total advance & post what you get. Holler how it goes. EDIT A mark 1&1/2" to the right (clockwise) of the TDC slit is 24 degrees. does that sound right for what your showing at idle? The rusty reluctor ain't hurting you but yes I'd reset the gap.

What is the TOTAL timing and when is it all in by ? Initial is only at idle and for start up , total is what you are more concerned with then you tailor the amount of mechanical advance to get the initial that is best.

well the two issues are idle and total timing with lighter springs set at 25 idle may only be 32 total cammed motors like more idle advance (thus the lighter springs) and still like the 36 to 38 total. so if the total is less than 36 turn it up some more but if it is kicking a bit on the starter put a stop that allows 25 or 28 advance withing the distributor but still gives 38 total.
http://www.summitracing.com/parts/msd-8464

The real issue is you don't know where TDC is. Find that and your problem will be at least halfway solved.

R.

Thanks for all the replies. I'll mark the balancer and see what the total is. I don't think that the advance is kicking in at idle but, I'll drop the idle/rev the motor and see what's going on. It s definitely advancing the timing quite a bit as I rev the engine. There's no tach and my friend took my tach/swell meter. Does a standard tach work with an msd 6AL? I am using an equus inductive timing light with no dial back.

I just pulled the carb - there was a 1/2 inch phenolic spacer with no gaskets. Pulling that and putting in a gasket. Set the reluctor gap. Going to mark the balancer like Robert said and see where it all leads and let you know.

Thanks for the help, guys.

Yeah - I've seen that - my springs are light green?!

Um, I wouldn't start messing with the carb. till you have the timing done.
One thing at a time keeps things a little easier.

Arg, I had the wrong info on the reluctor gap and apparently set it too close at .020" and broke the reluctor. I think I might just get a ready to run distributor with vacuum advance instead of messing with this one already. The motor is so close to stock that I would think it would be better to run vacuum advance anyway.

check firecore dizzy.

TDC is when the piston is at the top of its stroke, NOT when the pointer is pointing at the mark. The two may coincide, but sounds to me that's the first thing.

Second, after reading your last post it occurred to me that your distributor may have a problem with the top bearing being loose. My '71 donor pickup 318 had a distributor with so much slop that the points didn;'t open all the time, you could move the cam sideways and open and close the points. Could something like this have happened to your distributor?
I mean, how can you have a collision with 0.020" clearance? Stock is, I believe, 0.008".

R.

Thanks for all the help. I decided to fix the distributor and replace the pickup/reluctor(talk about annoying - bad machining/fit). I figured out that the springs were the heavy ones and the advance came on way way too late. I put on the lightest springs - all the advance in by 2700 rpm. Set the advance bushing to 21 deg, and the initial timing to 14 deg. The car runs much better. It has good off throttle response and power now. This car still bores me compared to my Chally with a built 440, but it goes.

This all made me ask questions, research, and learn a lot more about setting the timing and curve. I want to thank all you who helped me out.