I'm an Idiot

[chevycopcar]

Out of curiosity, I went out and checked a couple grounds. Drop between the negative post and the intake manifold at any given spot with the engine running: four thousandths of a volt. Same as the alternator bracket and case. The fender actually had more drop in some spots (not counting painted surfaces, of course). Perhaps I'm missing something, but I'd be alright using it as a ground if it were already set up like that. But hey, it's not hard to change if you have qualms about it.

 

[basketcase]

Out of curiosity, I went out and checked a couple grounds. Drop between the negative post and the intake manifold at any given spot with the engine running: four thousandths of a volt. Same as the alternator bracket and case. The fender actually had more drop in some spots (not counting painted surfaces, of course). Perhaps I'm missing something, but I'd be alright using it as a ground if it were already set up like that. But hey, it's not hard to change if you have qualms about it.

I was only curious about it inregards to the aluminum. There is not a strap from the motor to the firewall or frame. I've always grounded to the frame or the battery.

I need to get my multi-meter out and idiot light out and see where I'm at.

 

[El Coolmino]

If your intake isn't grounded well then you've got a real problem since it would mean the engine ground sucks, thus the coil/spark plug ground would also suck.

A point of reference, it is extremely common for SBCs to have a braided ground strap bolted to the firewall, and a mounting boss on the intake. Regarding aluminum's conductivity, will never be an issue with the Voltage/Amperage level that's used in an cars.

The only reason that you might want to avoid the engine for an MSD box ground is it's closer to the electrical "noise" created by the alternator, and the distributor. Moving the MSD ground out to the body or frame would minimize some of that.

 

[wiseman79]

I would think the intake would improve as a ground with the factory style alternator bracket that mounts to the intake and the water pump. That would be a good ground vs other alt brackets where the intake would only be grounded through the intake bolts that are covered in sealant. Still no excuse not to run a ground strap, I connected mine to one of the bellhousing bolts and then to the frame so it's not visible.