1970 350/350 Hard Start
I have a 1970 350/350 HP Corvette with an 11:1 compression ratio. I have had the car for 50 years and it has always been hard to re-start after it has warmed up and stopped for gas, etc. When engaged, the starter motor pauses as if it is not going to turn the engine over and then suddenly starts (sometimes it doesn't). When the car is cold or cooled off, it starts easily. I have tried different batteries, starter motors and alternators to no avail. On the car, I now have the original, professionally rebuilt starter motor and alternator and a Restoration battery. The car has the original 350 CI engine with only 41,000 miles and the heads have never been off the engine. I use a battery disconnect switch when the car is not in use. Also, the car has a 180 degree thermostat and generally operates in that neighborhood. Any ideas or recommendations on how to solve my hot-start problem would be greatly appreciated.
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Re: 1970 350/350 Hard Start
Duane,
Do you have a heat shield installed at your starter? Where is your timing set? Congratulations on 50 years of ownership.Leif
'67 Coupe L79, M21, C60, N14, N40, J50, A31, U69, A01, QB1
Top Flight 2017 Lone Star Regional -
Re: 1970 350/350 Hard Start
Duane------
I had the same problem with my original owner 1969 with 300/350 almost from the beginning. Tried everything you did and much more to no avail. Finally, on the advice of an automotive electrical technician I have a lot of respect for, I installed a slave solenoid. Problem over. Forever.In Appreciation of John HinckleyComment
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Re: 1970 350/350 Hard Start
I Think that part of the problems with high comp engines is heat soak with high summer temps. and C3's have a 10 ft. long positive cable and the voltage drop across the cable. My advice is to start with wrapping the starter with a heat blanket ( Summit Racing sells) and retard timing a few degrees(2 to 4 degrees) from the normal. heat soak is common on a lot of cars with high outside temps and high compression.
Also I Remember that the big block engines use to have a high temp gasket that was used between the solenoid and starter housing , I wondering if something like this may be available still.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: 1970 350/350 Hard Start
Leif, Joe and Edward,
I very much appreciate your helpful comments. To answer Leif's question: I do have all of the original heat shielding installed and positioned properly. However, I have not recently checked the timing. I retarded the timing 5 0r 6 years ago to try and reduce detonation. As it turned out, I had a slowly failing water pump and the engine was running hotter. I replaced the pump and thermostat and now the engine runs a cool 180 degrees without any hint of pinging. However, I did not reset the timing, I guess I just forgot about it. A very good suggestion. Joe, I am not familiar with a slave solenoid. Can you provide more information? Edward, I'm going to check out the Summit Racing heat blanket. Thanks guys I really appreciate your help. I'll let you know what solved the problem, if I can solve the problem.Comment
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Re: 1970 350/350 Hard Start
Duane also check with Jegs for Taylor heat shields,wraps & sleeving .Thay make a lot for drag racing.
BobComment
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Re: 1970 350/350 Hard Start
Duane------
Here's one. It will include instructions for installation.
I have found that no amount of heat shields, blanketing, etc. will permanently solve the problem. The above-referenced kit will.In Appreciation of John HinckleyComment
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Re: 1970 350/350 Hard Start
Joe, if a $20 part will solve my 50-year-old problem, I will consider it a modern-day miracle. Many thanks , I'll give it a try. DuaneComment
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Leif
'67 Coupe L79, M21, C60, N14, N40, J50, A31, U69, A01, QB1
Top Flight 2017 Lone Star RegionalComment
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Re: 1970 350/350 Hard Start
Duane------
The problem is caused by heat-induced resistance in the purple "S" wire. This wire is from the ignition switch and activates the on-starter solenoid at the "S" terminal. By installing the remote ("slave") solenoid and associated heavy gauge wiring, full current to the "S" terminal is guaranteed. The ignition switch then activates the remote solenoid and the remote solenoid, in turn, activates the on-starter solenoid. I mounted my solenoid on the top of the splash shield below the right side louvers.
I can tell you that I tried EVERYTHING to solve this problem for a LONG time. Nothing worked until I installed the slave solenoid. That was the end of my problems. Period. After that, hot re-starts in Death Valley in the summer (yes, really!) were absolutely no problem, at all.
As I've mentioned many times before, if the root of the hot restart problem were not as I described above, then the remote solenoid would not do a thing to solve the hot restart problem. But, it does solve it, completely and permanently.In Appreciation of John HinckleyComment
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In Appreciation of John HinckleyComment
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Re: 1970 350/350 Hard Start
Retarding timing will make the problem worse! A 350/350 should idle with about 30 degrees total spark advance, but they were set up for emissions with ported vacuum advance. This significantly increases EGT, and the hot manifolds radiate heat to surrounding components and the whole engine compartment. With optimum total idle advance the exhaust manifolds should run at no more than about 500F at idle. The OE emission setup yields something near 900.
Converting to full time vacuum advance with a B28 VAC and 10-14 initial should help as will quickening the lazy centrifugal curve which maxes out at 26 @ 5000.
An optimized spark advance map will actually reduce the tendency to detonate because the combustion chamber boundaries will run cooler. It will also create more low end torque and better fuel economy.
More details are in my 2012 San Diego National Convention presentation, which is available on the Web with a simple search.
DukeComment
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Re: 1970 350/350 Hard Start
After the many good responses I have had to my restart problem, I have hope there maybe a cure. I plan to start with Leif's suggestion to accurately set the timing to factory specs. Next consider going to full-time vacuum advance as Duke suggested. And, I have ordered the remote solenoid that Joe suggested and plan to install as a third option. I hate to cut wires or add non-original parts, but I'm getting to old to PUSH. DuaneComment
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Re: 1970 350/350 Hard Start
Duane------
You can install the solenoid without cutting any original wires. So, the installation will be completely reversible (except for mounting holes you may drill in the splash shield for the solenoid if you do as I did). Do not cut the existing connector off of the existing purple wire. Simply fashion a connector to, effectively, extend the wire to the remote solenoid. You'll be able to remove the solenoid virtually without a trace. Of course, you'll never want to do that after you experience the complete freedom from hot re-start problems. Never again wonder if you're going to be able to re-start it after a hot shut-down.In Appreciation of John HinckleyComment
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