[Scarebird]

Do you have a heavy cable from the frame to the block or better yet frame to the starter??

I ground the hell out of everything here.

I would also re-examine that heat blanket. Once heat soaked it is no good, worse holds heat! I would fab up a set of heat shields and use them. Air can still cool off the starter between the shield and starter.

[Jimbobeast]

Originally Posted by Scarebird

Do you have a heavy cable from the frame to the block or better yet frame to the starter??

I ground the hell out of everything here.

I would also re-examine that heat blanket. Once heat soaked it is no good, worse holds heat! I would fab up a set of heat shields and use them. Air can still cool off the starter between the shield and starter.

Yes, same 00 wire from starter to frame. I can fabricate a nice heat shield and try it in place of the blanket. I do NOT have a ground from engine to frame except for the starter. Can't hurt to try that also.

[Sirrotica]

I've been through this decades ago in a 73 T/A. Don't try to use the frame as a ground, there is too much resistance in the steel that sucks up amps needed to crank the engine when hot. A hot Pontiac engine will need 4-500 Amps to spin over.

Run a negative cable all the way up to the engine same size as the positive cable attach it to a bellhousing bolt near the starter. It will crank plenty fast no matter how hot the engine or starter gets. Every configuration I tried using the car as a ground, failed when everything got heat soaked. Even with a commercial battery and a freshly rebuilt high torque starter (gear reduction mini starters hadn't yet been invented in the mid 70s).

That's my experience, and how I solved the problem, never had another slow crank after running a ground cable all the way to the engine.

[Jimbobeast]

Originally Posted by Sirrotica

I've been through this decades ago in a 73 T/A. Don't try to use the frame as a ground, there is too much resistance in the steel that sucks up amps needed to crank the engine when hot. A hot Pontiac engine will need 4-500 Amps to spin over.

Run a negative cable all the way up to the engine same size as the positive cable attach it to a bellhousing bolt near the starter. It will crank plenty fast no matter how hot the engine or starter gets. Every configuration I tried using the car as a ground, failed when everything got heat soaked. Even with a commercial battery and a freshly rebuilt high torque starter (gear reduction mini starters hadn't yet been invented in the mid 70s).

That's my experience, and how I solved the problem, never had another slow crank after running a ground cable all the way to the engine.

Now this might just work. Are you saying that the frame ground passes marginally enough current when the starter is cold but is insufficient whenever the starter gets hot and requires more amps?

[johnta1]

Yes he is.

[Sirrotica]

Originally Posted by Jimbobeast

Now this might just work. Are you saying that the frame ground passes marginally enough current when the starter is cold but is insufficient whenever the starter gets hot and requires more amps?

Exactly, Steel is a poor conductor for high amp draw situations. Also as ambient air temp increases on any conductor the resistance increases.

On the top 11 metals used for conducting electric, iron/steel is #9. It is also continually rusting due to the moisture in the air, causing conduction problems.

Stop and think about how your OEM battery cable system is laid out. The main negative cable is 99% of the time connected directly to the engine where the highest amp draw in the whole car is. Moving the battery to the trunk doesn't change that need to have the main negative cable connected to the engine where the highest draw is.

All the secondary grounds are run through the body because the amp draw can be supported by the body and frame, also because the engineers/bookkeeper's save running a separate ground wire to all the accessories. The body ground isn't done because it's the best type of design, it's to save cost on each car.

Also think if the last time you had lighting problems and how many times the whole problem is bad grounds through the body, or frame.

Think also about a snowplow with a electric pump on it, They don't use a body/frame ground to run that pump motor. They run a dedicated ground cable to the pump from the battery, same principle. It's not cheap to run a welding cable ground wire from the battery, but it does work............

I can just about guarantee you'll sidestep you slow warm crank problems with a dedicated ground from battery to engine.

[Shiny]

Originally Posted by Sirrotica

Exactly, Steel is a poor conductor for high amp draw situations. Also as ambient air temp increases on any conductor the resistance increases.

On the top 11 metals used for conducting electric, iron/steel is #9. It is also continually rusting due to the moisture in the air, causing conduction problems.

Stop and think about how your OEM battery cable system is laid out. The main negative cable is 99% of the time connected directly to the engine where the highest amp draw in the whole car is. Moving the battery to the trunk doesn't change that need to have the main negative cable connected to the engine where the highest draw is.

All the secondary grounds are run through the body because the amp draw can be supported by the body and frame, also because the engineers/bookkeeper's save running a separate ground wire to all the accessories. The body ground isn't done because it's the best type of design, it's to save cost on each car.

Also think if the last time you had lighting problems and how many times the whole problem is bad grounds through the body, or frame.

Think also about a snowplow with a electric pump on it, They don't use a body/frame ground to run that pump motor. They run a dedicated ground cable to the pump from the battery, same principle. It's not cheap to run a welding cable ground wire from the battery, but it does work............

I can just about guarantee you'll sidestep you slow warm crank problems with a dedicated ground from battery to engine.

This!

[Geoff]

Sirrotica,
I am quoting from real world experience, started when I rebuilt my first engine in 1965.......& am still doing it today.
Anybody who doesn't read books to enhance their knowledge base is a fool.
I studied electirical engineering for a total of 6 yrears at a technical college.

Getting back to the frame issue.

Using the frame for grd return is a good idea, has lower resistance PROVIDED the cable connections at each end are clean & have good surface area contact.

Here is something else not mentioned. Starter cable is made of stranded copper wire. Many strands. There is an air gap between each strand. I couldn't find any battery cable for this comparison, so I used domestic power cable. It was stranded, 7 strands; I stripped the insulation off & measured the od with a micrometer: 0.102". Measured the OD of a strand, calculated the area & multiplied by 7. Combined area came to 0.073". A big drop from 102. The same principle applies to batt cable. you might strip the insulation & measure it at 5/16". But it would have the SAME resistrance as a piece of solid copper of a much smaller OD. Steel frame is solid, no air gaps, whsat you see is what you get....

[Sirrotica]

Originally Posted by Geoff

Sirrotica,
I am quoting from real world experience, started when I rebuilt my first engine in 1965.......& am still doing it today.
Anybody who doesn't read books to enhance their knowledge base is a fool.
I studied electirical engineering for a total of 6 yrears at a technical college.

Getting back to the frame issue.

Using the frame for grd return is a good idea, has lower resistance PROVIDED the cable connections at each end are clean & have good surface area contact.

Here is something else not mentioned. Starter cable is made of stranded copper wire. Many strands. There is an air gap between each strand. I couldn't find any battery cable for this comparison, so I used domestic power cable. It was stranded, 7 strands; I stripped the insulation off & measured the od with a micrometer: 0.102". Measured the OD of a strand, calculated the area & multiplied by 7. Combined area came to 0.073". A big drop from 102. The same principle applies to batt cable. you might strip the insulation & measure it at 5/16". But it would have the SAME resistrance as a piece of solid copper of a much smaller OD. Steel frame is solid, no air gaps, whsat you see is what you get....

Spoken like a true engineer, how did I predict that was your background? Simply by your attitude. I bet you love Lucas electrical systems too. The Brits do have a way to make wiring in an automobile as frustrating as it could possibly be.

There's a joke that goes along with Lucas electrical systems. Why do the British drink warm beer? Because they have Lucas refrigerators...............LOL

As I said previously you want to make something simple hard, and you ASSUME it's going to work out in real life just the way it's laid out in a classroom, or in a technical manual.

I went round and round with an engineer about an overheating 4-53 Detroit, did all his suggestions, and listened to his calculations. I told him my opinion was the transmission cooler in the radiator was overcoming the heat rejection ability of the radiator, causing the overheating of the engine coolant. I suggested an auxiliary transmission cooler. I got the same answer you gave me "NOPE". A year later after installing the largest custom made radiator that would physically fit in the machine, reversing the fan pitch, ruining the rings in the engine from continual overheating, and having to have the engine rebuilt under warranty, they tried an auxiliary transmission cooler, and it solved the overheating problem, the first thing I suggested to the engineer a year earlier. By this time the customer was disgusted, bought another machine that didn't overheat and the Gradall company lost their ass in wasted money because their engineer said on paper. "it can't overheat".

We have different weather in the US than you have, we have a lot of corrosion problems with wiring and electrical systems, the OP said that 20 some years ago the car worked with a frame ground, but now it doesn't. Your answer was maybe his engine is to tight, really that's your summation of his problem, and how he should solve it?

Believe me when I tell you that I tried your way in my own car, and until I ran a dedicated ground the engine would spin slowly when everything is heat soaked. It didn't work for me, and there have been numerous people on this board that have had the same problem when relocating a battery to the rear.

I did some due diligence about remote batteries, yes it required reading so you can retract your comment about reading.

Seems there are people split roughly 50/50 about using frames versus dedicated grounds. Some interesting facts that I found, that even though a frame/body ground will work without a dedicated ground, 2 drawbacks show up. The motor components have a reduced life with frame grounds, and there is electronic interference with onboard electronics. ECMs and stereo systems were among the most mentioned systems not getting along with frame grounds with remote batteries. While some people were able to get adequate function from a frame ground, the motors ran hotter, and gave up sooner than with a dedicated ground.

One thing you mentioned previously was tinning all the connection points. You intend to get under the car and tin each connection point where the cables attach to the frame, you must have way more time to screw with an electrical system than most people do. Would you be doing this to prove your frame grounds work. or just to save $50 on buying a ground cable?

Electric winch manufacturers used to ground their units through the winch cases, but due to the high amp draw stopped using a frame ground in favor of a dedicated ground cable. Warn was one of the manufactures that now supply's ground cables to reach the battery terminals, before they just supplied ground straps. An electric recovery winch also draws huge amounts of current, in case you're not familiar with them. The winches draw is likely equivalent to a heat soaked Pontiac starter. The winch draw is around 450 amps on average loaded heavily.

To sum it all up you can make all your tinned connections and screw with short ground straps connected to the frame, or spend $50 for some cable for a dedicated ground with 2 connections, and extend the starter motor life. You'll also be safeguarding any electronics that may not play well with frame ground connections. It's the OPs choice how he'd like to attack and solve his problem.

I suspect you'll have a laundry list tomorrow of why the frame ground is superior, engineers have a lot of pride and tenacity, but I've said my peace.

I'm going to get some sleep Geoff, it's 2:30 AM in Ohio.

[Scarebird]

Both recent builds I have done were trunk batteries.

First was a Trans Am with a LS3, had a separate ground cable and large battery - no issues,

Second was the Lemans, L84 (Gen V 5.3). Smaller primary cable and battery, with no ground cable running full length. No starting issues.

Both had heat shields fabricated as experience with Pontiac and Olds V8's showed this as a must when hot. Both have engine, frame and body grounded at every opportunity.

I think the asbestos is causing more issues than solving.

[Jimbobeast]

"or spend $50 for some cable for a dedicated ground"

00 cable is $6.50 per foot.

[johnta1]

Inflation!



So around $60/$75 now.
(in a couple weeks probably double that)

[Sirrotica]

As far as shielding, I've never used a insulated type shield. I've used a factory style tin, or just made one out of a piece of tin with a 90 degree bend and secured it to the outer starter bolt, either work in my experience.

I would guess the insulation would hold heat in as well as shield it. With a tin shield the air can still carry away some heat as well as shield the motor from the exhaust radiant heat.

[Sirrotica]

Originally Posted by Jimbobeast

"or spend $50 for some cable for a dedicated ground"

00 cable is $6.50 per foot.

I haven't priced it in awhile, but you're correct it has nearly doubled.

I believe I used #2 when I ran mine, but the car was sold about 6 years ago, so I can't verify what size I used. You might want to look at used welding cables through Marketplace on a ground the insulation having some nicks is irrelevant. Sometimes people sell welding cable on there pretty reasonably. Inoperative stick welder would be another possibility to find some bargain leads.

I've also heard of people buying 20 ft HD jumper cables, and cutting the clamps off, might save some money there.

Geoff is adamant that steel is best, I guess 1 inch rebar would be a whole lot cheaper................. Tough to bend though.

I'm thinking that next set of jumper cables I buy should be solid steel wire rope, like a cable excavator uses, instead of copper wire.

[HWYSTR455]

Not all battery cables are created the same, and some can perform less than another even among the same gauge.

Age also effects stranded cable, it just won't last forever, and the longer the run, the shorter the life span.

Use SGT or SGX cable for batteries and you will avoid a lot of that.

Welding cable is easier to run, easier to bend, but it won't last as long as SGT or SGX cable. SGX cable has near the same flexibility as welding cable but will last longer.

There's a resistance difference too. In general, you can use one or two sizes smaller SGT/SGX cable as compared to welding cable. (Depending on brand and quality).

SGT/SGX is a standard, 'welding' cable needs to be EPDM to equal SGT/SGX (nearly).

I've made my own battery wires for like 20+ years, remember to use quality connectors, it makes a big difference.

I don't use the typical clamp-style battery connectors anymore, only use ring/eyelet ends on cables. You can buy marine clamp-style if you want, makes it easier to swap out the ends and not have to muck with the cables. Otherwise, just use batteries that have marine type posts or side posts.

When doing grounds to a frame, use a thread-sert or riv-nuts. They crush to the frame and make a solid contact the entire circumference. It helps seal out moisture too. Star washers suffer from not making a full/good contact.

.

[Geoff]

I am blaming my comments in post #41 on a seniors moment.....
The info in post #41 works for the battery in the engine bay.

Of course, this thread is about a trunk mounted battery...

With a trunk mounted battery, bolt the grd cable to one of the bellhousing bolts, lower bolt to keep cable as short as possible. Leave a small loop in the cable to allow for movement/vibration.

[HWYSTR455]

I'm on board with using the bell housing ONLY if you make sure the contact(s) are not compromised by paint.

An engine mount bolt/bolt (block side) hole has less chance of being compromised in that way.



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