493 hard to start when warm

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1967 Cuda

1967 Cuda

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I have a 440 stroked to a 493 that is 10.5 to 1 compression and running a comp solid roller cam. It has an MSD distributor, ignition system and MSD high torque starter. I believe timing is set at 36 or 38 degrees and the distributor is locked out. The motor runs great and hasn't had any issues except for not wanting to start when it is warm. If the car has been sitting the motor will fire up as soon as you hit the key. If the car is warm, it will half way turn over and then nothing. If I keep hitting the key, it might take 3-4 times and then the motor will finally turnover and fire right up. I thought the it might be a ground issue at first as the battery is in the trunk, but I ran a new heavy duty cable from the battery to the starter and still am having the same issue. AS the motor is only 10.5 to 1 I didn't think this is a compression issue, but it seems like it. Thoughts?
 
Pull the coil high tension wire and ground it to kill the spark. See if it cranks. If so, it's not compression, battery, cables, or the starter. Its way too much timing advance

If it still does not crank it could be most any of the above. Start by looking for hot spots in the cables. Connections. You need to scare up a "carbon pile" battery load tester, which will allow you to measure both starter load draw, and to load test the battery

Are you sure the charging system is keeping it up?
 
Is this a race only deal?
 
Could be an internal problem where something binds up with hot. Check the rotating torque both cold and hot. If the rotating torque is the same then it is your starter.
 
Does it also run pretty hot on the hiway?

I had that one/two problem with my 367. (Hot-running plus hard hot-start).
In my case; It turned out to be too tight ring gaps, and/or tight skirts.
I tore the engine down, delivered the block back to the machineshop, where they honed the cylinders out another half a thou. Then I took it home, opened up the top gaps to .034, and the seconds a lil less . Then I put it all back together. That cured BOTH my issues. That was in winter of 2000; and she has run gangbusters ever since.
To be clear; my symptoms were like yours, PLUS running hot, that could not be cured in any of the conventional ways.
Sometimes when I shut it off, it would take 20 minutes for the engine to cool down enough that the Dakota starter could crank it over. Afterwards it was click/vroom-vroom, and off we go.
Oh and whereas before the change it was not happy idling less than 800/850 @14* Idle-Timing; whereas afterwards same combo would idle down to 500@5* Idle-Timing, and pull itself on hard flat even ground, with a manual trans.
and yes it had way more low-rpm power. I mean way more, lol.
It was a lotta work, but well worth it.
I was and still am running KB107s which are a hypereutectic piston.
The recommended skirt clearance from KB, for my 4.04bore was .0015 to .0020..
the machineshop originally set the clearance at .0030
I had it opened it up another .0005 or so
 
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If running a carb (i.e. not Fuel Injected), could be leaking float valve or float level set to high. This will allow fuel to fill cylinders and be over rich or slightly hydro locked. 4 cycle engines like to be lean on a hot start.
 
It’s very likely caused by the locked distributor. Get it hot and twist 20 degrees out of it then try to start it. Probably will spin nice and easy. You’ll need a curve in the distributor or a start retard to fix it.
 
Thanks for all the responses. I am going to try a few of the things mentioned to see if I can pinpoint the issue.
 
Put a kill switch on the ignition. Get it spinning turn ignition on.
 
My distributor is locked and it has no problems with starting even when it is at full temp.
 
Gr8polarbear said:
My distributor is locked and it has no problems with starting even when it is at full temp.
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There are way too many possible variables for you to say your distributor is locked and his distributor is locked, therefore they should act the same.
 
I am just saying a locked distributor would not always cause this problem. I bought the car a couple years ago and it was built for a toy at the strip and I am doing other things to it and have not got to that portion of the car yet but runs just fine on the street.
 
Newbomb Turk said:
Definitely needs a curve.
Click to expand...
Yep, 36- 38 degs is too much timing for 10.5 comp and a heat soaked engine.
I've had a problem at 24 degs on the 451 with 10.4 comp. I ended up backing the timing and getting the temp down to 160.
 
Gr8polarbear said:
I am just saying a locked distributor would not always cause this problem. I bought the car a couple years ago and it was built for a toy at the strip and I am doing other things to it and have not got to that portion of the car yet but runs just fine on the street.
Click to expand...
No one said “always”. “Likely” was the word used and it was a correct statement.
 
On a side note starting an HP high compression engine with lots of lead is a hell of a good way to break starters
 
Bewy said:
Is it the MSD DynaForce #5098 starter that you have?
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Not 100% sure and the car is at our garage so I can't under and look. I think that it is the 5098 starter

MSD Ignition Red DynaForce Starter Chrysler 318-440​

Part Number: 121-5098​

 
Make sure you are running like-size (match the positive cable size) grounding cables to your starter and alternator. If you can't do that, clean and properly ground those components.
 
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