Hi - I cannot figure out why my 440 cranks over very slow only when it's warmed-up. I heard about starter heat soak so I wrapped the headers, but it made no difference. Here's some more of the particulars: 1970 Barracuda, 440-6V, AT, MSD billet dist. w/mech adv., MSD 6A box, MSD coil, new mini style starter from DB Electrical on ebay, Hooker headers wrapped and sealed, battery in trunk with 00 gauge + cable, standard + battery cable used for solenoid to starter, timing set at about 15 degrees of initial advance, 100 amp alternator.

I saw on another web forum that wiring in a Ford starter relay solves the problem - anybody ever try this? I'm going to make sure that my battery is good and double check my initial advance. I'm also going to swap out the coil after warming up the motor to rule out a bad coil. Could I have wired something wrong (like the ballast resistor) that could be causing this?

It's really driving me crazy - any suggestions would be greatly appreciated!

Thanks,
Greg

It's not the ballast. Could be resistance in the cables due to heat or maybe the ignition timing. How about a heat shield for the starter?

Add another braided ground strap from the motor or head accessory bolt to the frame. Also you didn't mention the size of your negative battery cable or its mounting location/condition. Slow crank when hot as stated is usually a resistance issue. You may hear some mention vapor lock but that will not slow down the starter. That will only break your chops for the motor to actually start.

And the battery should always be grounded to the frame and to the motor.

As mentioned, it could be several things, the next time it is hot, pull the coil to distributor wire and see if it cranks normally. If so, it may be advanced too much. But it could also be starter drag, bad cables, I had this problem on an old Camaro, (400 cube) it ended up needing a high torque starter and better cables. But try pulling the coil wire and see what that does first.

well it turned out to be a bad battery. I did the coil wire off check for too much initial advance and it still cranked slow. I put my battery charger on it and it cranked fast and starter right up.

Thanks for all the input!!