396 L34 hard to start when hot

[RAS68]

HELP!!! I have a long standing problem - my 68 L34 has a starting issue when engine is hot. I have tried so many things: New battery cable, new battery with high CCA, double checked and rebuilt alternator + replaced voltage regulator to make sure battery is being charged, Checked voltage at coil (12 v at start ~ 9 -10 v at run), adjusted timing and finally a reduction gear starter. So now it will turn over when it is hot ( not real fast but fast enough) but it does not want to start when hot. I can get a jump box or a jump off another car and it will start right away within one or two cranks. By itself it will not start until I wait about 30 minutes. What is going on here? I don't know what else to try. By the way this 396 has been rebuilt and compression is 10:1. I love CRG and the discussion forum and the experts here have helped me out many times. I am hoping CRG can help me get this bug out so I can fully enjoy my car. Any ideas are welcome.
Thanks,
Allen

[169INDY]

Any ideas are welcome.

Triple Check the Grounding at the Engine. (ie Neg side of your circuit)

You Say it Starts when Jumped,,,, "Wondering out loud",,,, When another 12VDC Source is added via a jumper cable or box lead they create another Path & source of Amps around your existing Neg Circuit.

Just a Random Thought,,,,,,

I am understanding your frustration.

Jim

[RAS68]

Thanks Jim for the prompt reply. I will try that and triple check the ground side tonight.
Allen

[WorkinProgress]

I have around here a Chevrolet Service Letter for a solenoid problem. Engines after they sat that were brought up to full temp, were hard to start shortly after. Not sure if that is your problem, but GM solved it with a different solenoid.

                                     - Warren

[WorkinProgress]

I found a couple of sheets on hot start cranking. Doesn't say anything about the solenoid but that could be something I read on a different sheet, whereabouts unknown at this time. Discusses starter replacement.

I cannot post the sheets as file too large.

Anyone that wants copies, put in subject "Service Bulletins" and email me at keepitallgm@yahoo.com 

                                              - Warren

[william]

Are you using the solenoid heat shield [#5]?

[Kelley W King]

I had a 396 that did pretty much the same thing. I backed off the timing a little and turned over better and started. I cannot remember the timing numbers but big blocks like a lot of timing to run the best but it is not the best for starting. The main ground issue stated above should also be checked.

[RAS68]

Thanks for all the replies and suggestions. I will try the heat shield as well. But the motor does over. I used to have the issue where when it was hot the Starter would barely turn over. Now that I have the reduction gear starter from 1980's GM truck it turns over pretty well even when hot. But the engine does not seem to want to start. Just turns over. After it cools down again it will start. But like I said - if I add a jumper cable from another car it turns over quicker and starts right up. Its a mystery but I am determined to solve this once and for all.

Allen

[RAS68]

One more thing - I have the Pertronics ignition conversion but I use the stock distributor and high performance coil. Could this set up be part of the problem?
Allen

[usa1ti]

Just a couple of observations on this. Your voltage really should be checking 12.8v to 13.8v most all of the time. As far as the timing the higher the compression the more total timing you need to get the flame travel over the dome so you fire the cylinder early with bigger piston domes. On my 14 to 1 598 alcohol motor I run 42 degrees total. My 12 to 1 427 engines I run about 38 degrees total. On a 10 to 1 396 motor 34-36 degrees is prob good. It will take a fresh starter to do this but I run good GM starters up to 38 degrees with no problem. Another IF... If the float levels are too high a hot fuel line / under hood temp will push a little fuel over the needle and seats causing some minor flooding after shutoff. hard to start until it clears the fuel out. Have had this happen before.

[RAS68]

Todd - Thanks for the idea about the flooding. I have original Quadrajet carb on it. How can I tell if it is flooding? Will I be able to see a trickle of fuel if I take the air cleaner off? If that is happening, what do you adjust to correct it? Can you adjust float level while the carb is still on the car?

[TODD]

Allen so the resistance wire to the Petronix is in place? The hot 12V wire from the starter to coil is intact? If I remember correctly Petronix units caused stock tach issues but starting issues would only be if its not wired correctly for cranking voltage to coil. I would recheck the Petronix set-up requirements for your unit.
Todd

[Henry Cloutier]

Hello, I had the same experience with my 327 in a 1968 Camaro. For sure it was not stock; had angle plug heads, Offenhauser 360 manifold, Holley 950 three barrel, 11-1 pistons and dual point ignition. The engine liked a lot of initial timing. I don't remember the settings from back then. But one way I knew to much timing was set was hard starting when hot. My friend at the time was driving a 1967 tri-power 400ci GTO. His did the same thing when to much initial was set. GM products at least the old ones anyway like lots of timing to run, just not in the start sequence. At the time it was explained to me that to much initial is firing the fuel mixture to soon impeding the start process. Once the engine is running no issues. Good luck in your troubleshooting!

Henry   

[Kelley W King]

I agree with Henry. Turning the dizzy vac can a little towards the firewall is free and takes only a couple minuits to try.

[RAS68]

Ill try the adjusting the timing and let you know. Im also going to try an Odyessey battery with 880 CCA.
Thanks to every one for ideas and advice.
Allen