Hard starting when hot

My tudor (avatar) fires up "instantly" when cold but after driving awhile if I stop for a short period, like a fuel stop, it is very slow to turn over. I sometimes wonder if it's going to start. It's a sbc with "shorty" headers and a 2 1/4" head pipe that runs only a few inches under the starter. I'm running a stock starter/solenoid.

I ***ume the problem is "heat soak" that I've often heard people complain of. What are other possible causes for it and what are my options for a solution? I'd rather not wrap the starter because I don't like the looks of a wrap.

Thanks for any advice.

 

Get a mini starter. Most stock starter rebuilds are ****.

 

possibly your timing is too far advanced.

 

Make up a sheet metal shield for the solenoid, actually GM made them already, just look around the ground at any Pick-Ur-Part and you'll find 'em all over the place, as well as the nice aluminum or stainless carb to air cleaner spacer "pipes" which come in handy now and then.
A nice shield mounted to the exhaust header flange between the flage and starter would defect any exhaust leaks from the starter body too.

We use the GM shield on the solenoid in our 57 BelAir with 327 and shorty blockhuggers as well as the separate Ford-style solenoid mounted on the fender well below the battery...problem solved.

 

Check you timing, like rodknocker said it may be advanced.

 

sbc solenoids stick when they get hot. Either get a broomstick so you can tap the starter when you turn the key (only works for rhd), build a heatshield, or fit a hot start relay in the starter circuit.

 

When my car did that it was the starter getting hot (and then going bad). That doesn't mean it's your problem. There is a quick way to test it.

Next time it happens, poor some water over your starter. If it starts right up after a quick cool off, there you go.

 

Timing timing timing.
Played with a 350 like that for years until I decided to advance it alittle.

 

I have a small aluminum shield mounted to the head pipe under the starter with about 1/2" air space between the pipe and the shield.

Timing is set at 8 degrees advance.

The solenoid doesn't stick. It always engages, it's just really slow to turn over.

 

Check the starter nose cone bushing for wear, If it is worn it works on a cold starter but if it gets hot it will cause the starter to drag.

 

You need good battery cables also. Seen little one's smoke when they get hot and not deliver as much juice. Also check your grounds.

 

What kind of battery cables are your running? Most you buy from parts stores are 4 gauge (about the size of a pencil). Try switching to 2 gauge cables (about the size of your finger) This has cured hot start problems on a few of my projects.

 

I fought the same problem for almost a year. My problem turned out to be a bad ground connection. I ran the neg battery terminal to a welded stud on the frame to reduce the length of the cable. I thought that I had it all figured out. I replaced the starter, solenoid, built a heat shield.... same thing. The cables were over size also. I got the cables made at a welding supply house. Long runs of standard size cables will give the same symptoms.

I moved the ground connection from the stud on the frame over to a bolt in the tail housing on the trans and it never happened again. To be honest, I've heard about the heat soak problem but I've never had it happen to me. I think it can be a real problem but over diagnosed.

Mine started instantly when cool which hid the ground problem. The extra resistance from being warm was just too much. If your ground cable is not bolted to the block or trans case, move it. Others will disagree not having this problem but it got old real quick. I moved it reluctantly but I sure was happy when I could stop at the 7-11 and not have to wait to get it started again. There is nothing more embarr***ing than a cool hot rod that won't start.

 

so when its turning over does it sound like this, rump....rump.....rump, its rolling fast for a couple of seconds then slow then fast then slow, then i say its the timing.

 

Bad bushings will cause the starter to draw to many amps. In this day and age people replace rather than repair. I have repaired a lot starters years ago that have had that problem. most starters that go bad are bushings or brushes. (would check the ground first like Tommy said)

 

Had my 53 doing same thing when hot and it ended up breaking the head off the starter,all the ******** ,put new starter on thing still same problem after a few days,ended up being timing,already had heat shields on .but like said earlier good cables and wiring makes all the difference.

 

Do ya want the short list?

If the starter has a bad field (cracked etc) it will be more apt to suc*** to heat soak.

Also not only the started is prone to heat soak but so is the soloniod. you can run a remote soloniod and that helps.

You don't have to wrap the starter to keep the heat away. They make a chromed heat shield. Heat shields have been around since just after they started using an engine in the place of a donky. its as old school as it gets.

I don't wish this on you but sometimes they get hard to start when you have a main bearing go bad or spin. This is something that may not be evident unless you have a real good oil pressuer gauge and you have been keeping a good eye on it. Sometimes you don't even notice a major oil pressure drop at all.

Your engine may just be running a little hot. All engines don't want to start well when they are hot. That is part of the reason they have gone to gear reduction starters on late model cars and trucks. They run hotter than the thier earlier conterparts to helo control emisions or something like that.

The list goes on but those are the most common things I can think of right now.

 

I had a 348 do that to me. It was a cracked piston skirt.

 

dont build a space ship here buddy.

if your car runs and drives fine then i wouldnt worry about timing yet. i run about 15* in my cars but they have HEI so they eat it up.

i would just spruce up a heat shield and call it done. 90% sure thats your problem. i run em, i love em. couldnt imagine not having one ESPECIALLY with headers!

 

You can't have enough ground. A cable from engine to body, body to frame, battery to engine doesn't hurt a bit.

 

Thanks for the inputs.

To address some of the suggestions so far, the cables are about a year and a half old, #1 cables with factory installed connectors. Ground to the block via a bellhousing bolt with a second wire from there to the body.

Had the same problem with previous cables (smaller gage) and previous battery.

Starter was rebuilt about 1500 miles ago by a "reputable" local shop. I'll check bushings, etc. for wear anyway.

I don't think (hope not) it's internal engine damage. Only about 1500 miles on the rebuild and I have great oil pressure.

I've got several things to try now. I'd been thinking about the remote Ford style solenoid. I've got a copy of a tech post on that from a while back.

 

What's your compression ratio? When you get up to around 10 to 1 you'll start having hard starting issues when it gets hot. I was running a sbc 400 with double hump heads and had the same problem. Started fine when cold then it would hardly turn over when hot. It did the rup rup rup thing but would finally kick off.

 

Comp ratio is only about 9:1.

 

What about the rest of the ignition system? Has it been replaced. Nice looking rod, but if you reused the old ignition wiring harness, the degrading wires rear their ugly heads when hot. I fell into this with my 58 Belair. New harness fixed it instantly. My 2 cents, which, for us Canadians, is almost 2 cents American these days. For what its worth...

 

Every wire in the whole car (Ron Francis kit) and every component in the ignition system except the ignition switch and the distributor body was replaced during the build over the last couple of years.

 

the next time it does this try turning the timing back a little, see what happens, costs nothing to try

 

You need to mount a relay somewhere so that you get a full 12 volts to your starter when you turn the key. Normally it goes through the fuse box, then through your key and it's loses some power which makes it harder to start the car when it's hot.

This problem is common with Pontiac motors and this is a trick that they use on a lot of trucks and buses to avoid the problem that you are having.

 

Basically something like this (sorry for the bad photo, but it's all I could find).

 

If you're sure everything else is right these will do the trick. Especially with headers

http://www.jalopyjournal.com/forum/showthread.php?t=467734

 

Get a 1000 amp btry.....that should do it