'Heat soak' in Chevy starters.

Dr Crankenstein said:

Like Bama said, the Ford solenoid/relay setup eliminates the small wire at the Chevy ''S" terminal.

Heat increases resistance and resistance decreases current and/or voltage... so, the skinny wire (already impeded by switches, connections and running length) gets hot and resistance increases, current and voltage drop... "start fail".

A strap or bus bar from the "S" terminal to BAT terminal puts the demand on the BAT cable, no skinny wire...

... like sneaky said, the Chevy solenoid still has to function as before, only now, thru the fat cable and the cable "switched" by the Ford solenoid. (We used this system with "our" Chevy race cars as heat from the headers increased the failure rate considerably.)

Naturally, connections must be clean and tight, don't forget the GROUNDS... as my shop instructor once said, "90% of electrical problems are ground"... an exaggeration, yes, but the point was taken all the same. .

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Just a thought, but if you are using the Ford solenoid to switch the main power, as in the left pic below, then you don't actually need to put the power through the Chevy solenoid, that thick power wire could go direct to the starter motor itself. The solenoid would simply move the starter gear, not transmit current. Heat soak would not be an issue. Turning the motor is the problem people have, not engaging the gear. Poor electrical connection through that solenoid causes that.

Obviously you'd need to wire it so the solenoid gets the correct feed, but it is only shoving a gear home.


This all gets confusing though, as some people only run the solenoid trigger through the Ford solenoid. A normal heavy duty relay would suffice if that were the case, surely? Most electric fans draw more than 30 amps continuous, so why the need for a starter relay?

And here's a pic where they use the correct item, a normal heavy duty relay, in the solenoid power line, rather than gaffing in a starter relay.

So far, in all the pages I've looked at, nobody has shown a true reason for putting the Ford relay in the main power line. Using The Ford one, then the Chevy one, in series, is not improving anything. Increasing the power supply strength for the solenoid sounds reasonable though, but then you don't need a Ford starter relay for that.

Excuse the crappy 'Paint' wiring job, done at work. Gives an idea what I'm getting at though. Takes the Chevy solenoid out of the power line altogether.

Wired like your "Paint" photo, you'll spin the starter without engaging the drive.

Energizing the solenoid engages the pinion/drive and provides power to the starter motor. Take a good look at sneaky's post...



The standard Chevy wiring has the BAT cable live and when the solenoid energizes through the small IGN wire, the solenoid plunger connects BAT power to the starter motor's field terminal.

The theory and proven idea here is, a hot solenoid can demand more than the skinny wire can provide. The Ford solenoid simply isolates the BAT cable and delivers maximum power to the Chevy solenoid's BAT terminal and bridged "S" terminal, eliminating the "S" wire and any possible shortcomings.

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Dr Crankenstein said:

Wired like your "Paint" photo, you'll spin the starter without engaging the drive. Energizing the solenoid engages the pinion/drive and provides power to the starter motor. Take a good look at sneaky's post...
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Take a good look at my post, and you'll read this bit:

Obviously you'd need to wire it so the solenoid gets the correct feed, but it is only shoving a gear home.

Please grant me just a little bit of intelligence.

I still fail to see WHY anybody would choose to put the power through TWO relays, when they can easily connect directly to the motor, so, like I said earlier, the only work the Chevy solenoid has to do is move the gear.

Yesterday I got a snotty reply from a self professed electrical guru on some forum, when I asked how it works:

"I don't know why, I just know it works"


[S

Having read about fifty different discussions across a wide spectrum of car forums and web pages, I come to the conclusion that most guys who do it don't know why they do it, or exactly what it is they are doing.

IF the issue is merely that skinny wire is not supplying enough current to the solenoid, why, oh why don't people simply use correct electrical practice and fit a suitable sized wire and relay?

And if the solenoid is not working, why does my motor still turn, but just slowly?

The solenoid is nearly working? The terminals are nearly connecting?

I think cleaning the terminals in the solenoid is the first thing I will do when I get home, and forget about all this Ford nonsense.

No insult intended, King. I misunderstood your previous post and stated the obvious. (Apparently, my brain turns into a pumpkin at midnight. )

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Think of the Ford solenoid as just a big relay (which it is) . One of the things I like about using the Ford relay is to get the electrical stuff where it's easily accessible. Chevy starters can be a pain in the tukus to get the wires on sometimes and were always a source of trouble if a connection got loose, which they often did because they were hard to get to and tighten properly. With the buss bar and Ford solenoid, that problem is eliminated. Install the bus bar and the battery cable before you put the starter in.

I'd like a heavy spring loaded steam punk 'Frankenstein' style switch in the dashboard, that needs to be pulled across to light the fire. [cl

King Herald said:

Excuse the crappy 'Paint' wiring job, done at work. Gives an idea what I'm getting at though. Takes the Chevy solenoid out of the power line altogether.

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Your on the right track,that was my point if you dont "bypass" the old Sol what is the point, and if it does fix it then run a better chevy sol.lol I fixed your pic so as to energize the drive gear.

The chevy solenoid still has to pull the starter in, will it do so wired like that? Looks like it would spin the starter without engaging it.

OOps, after looking closer I see the smaller red wire, my bad.

sneakysnake said:

Never quite understood this one myself.Always sounds like you either need a new Sol or starter. I understand the principal ideal of adding the ford Sol but the chevy one still has to work to engage the bendix drive.So unless the heat is breaking down the chevy Sol what is being accomplished by remoteing the Sol.
Some where there has to be a breakdown in one of the components for this to be helpful?

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The very first time I read about this Ford 'trick' little alarm bells started going off, and now, after some clever detective work, using the miracles of the interweb, I have reached my own conclusions.

In a nutshell, after all the different ideas and solutions, we come down to the wire to the solenoid being the much related 'heat soak' problem.

If your motor won't turn over properly when hot, you can short that solenoid to the main heavy terminal on the starter, using a screwdriver. If it then spins happily you know exactly what the problem is: run a heavy wire and a relay to the solenoid.

Hard to believe 150,000 car guys are running round with Ford relays bolted to their firewall, and most of them have no real idea why. [cl

Yeah, pretty much true with anything electrical, more good rodders struggle with wiring and electrical than any other issues. So "because it fixed it" is all the reason they need. You don't have to know what electrons look like to know they can't get through a bad connection,lol.

Pretty much all I know about electrics is that it works and runs like water. All the stuff about amps x ohm = watts, or whatever, means very little to me. If I have any doubt about the size of wire needed, I run a big one. If a switch gets hot in use, I fit a bigger or better one.

One thing I found wiring my RPU was that I made mistakes, and that the wiring loom developed slowly but surely, that I had to go back and change things. It is not so formidable a task when you work it out circuit by circuit. Draw it out circuit by circuit before you start, if you need to, find out where you can share wires etc. Take your time, think about it a lot. It can be fun.

I nearly bought a ready made loom, but it seemed kinda pricey, so I bought a roll of black wire and a small fuse box instead, and went from there. [S

I nearly farmed out my paint, but my wife pushed me to do it myself, and I'm so glad I did. it ain't perfect, but it is all mine.

Looks pretty darned perfect to me...

King Herald said:

Pretty much all I know about electrics is that it works and runs like water. All the stuff about amps x ohm = watts, or whatever, means very little to me. If I have any doubt about the size of wire needed, I run a big one. If a switch gets hot in use, I fit a bigger or better one.

One thing I found wiring my RPU was that I made mistakes, and that the wiring loom developed slowly but surely, that I had to go back and change things. It is not so formidable a task when you work it out circuit by circuit. Draw it out circuit by circuit before you start, if you need to, find out where you can share wires etc. Take your time, think about it a lot. It can be fun.

I nearly bought a ready made loom, but it seemed kinda pricey, so I bought a roll of black wire and a small fuse box instead, and went from there. [S

I nearly farmed out my paint, but my wife pushed me to do it myself, and I'm so glad I did. it ain't perfect, but it is all mine.

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Nice Work...[cl

Ford has even went to using this system on their starters. Both of my 4.6's have a firewall mounted solenoid, and a starter mounted solenoid like the Chevy/ GM style starter does. The firewall solenoid ensures that the starter mounted solenoid has full current to start. Imagine, a manufacturer copying a hot rodder trick! Who'd thunk that? Must be something to it, huh?

An old timer told me 18 years ago that when he had chevy starter heat soak problems, he'd take the armature out and put it on a lathe, and turn a few thousandths off of it. He said some of them were just too tight for the amount of heat. I guess he did a bunch of them like that.

In addition, as Dr Crankenstein said, heat increases electrical resistance, a lot.

I went from 1 gauge cables to 00 gauge on my '59, just because I came across the bigger stuff for free. I noticed better cranking, but I never really had a problem with it before.

Now, to confuse you people with heat soak problems. [ddd
I have a 454, bored and stroked to 489. My initial timing is 10°-12°, I can't remember right now. It's got 10.1 to 1 compression, and long tube headers running right past the starter, with no heat shield. The exhaust temperature on the dyno was up to 1,900°. I was eating a taco from the drive through one time, and some cheese fell on the bare metal floorboard, and melted into a puddle. It's hot. My starter switch wire going to the solenoid is just 16 gauge stuff that was laying around, spliced to some other junk wire. (I really need to rewire the whole thing.) It's so hot here that your engine temp gauge is almost in the normal range when you start it.

I use a standard over-the-counter starter from whoever I got it from 15 years ago. I think it was AutoZone. No heat soak problems. [S

8literbeater, like I said earlier, thousands of guys are running Ford relays, and most of them have no idea why.

I'd wager the only reason this modification fixes most 'heat soak' problems is because all the wiring was undone, and put together fresh and clean, with fresh clean connections and probably fresh wire, which would probably have sorted the problem if it was done to the stock system.....

Most of the guys I knew who ran the Ford relay did it for various reasons, one of which is to get the wiring so you can get at it. Like trying to crawl under a race car, get the alligator clip of your remote starter clipped on (and stay on) so you could bump the engine to find tdc, adjust valves ect. And to have a hot lead under the hood. Everyone I ever asked seemed to have a logical reason to use one. But then electrical is voodoo to a lot of rodders, they will put a pos chevy alternator on just to get rid of a wire or two. Or a hugemongous HEI so they only have to run one hot wire.

Well, I got home from work last week and pulled my started off. Everything looked good, cleaned the contacts, checked the bits that need checking etc. Reconnected all my wires, checked for clean solid grounds etc.

I spent awhile inching the motor over repeatedly while setting valve clearances and it started to get slower and slower.

Turned out the battery was on its way out after all that. Just three years old, not really used a great deal, but it died.