Dartht33bagger

Back in May I completed an engine swap and got rid of my tired 305. I replaced the 305 with a L31-R crate engine. Ever since then, there is a lot of static noise on my AM radio when the engine is on. The pitch of static increases as I give it more throttle. I've also had issues with warm starts with the car that BobR has suggested that a bad ground could be causing that issue.

Thinking about what could be happening driving home this week, I remembered that I think the heads on the L31-R are painted black from the factory. If the weather plays nicely this weekend, I am going to go out and check if I remember correctly. If the heads are painted, could that be causing the static in my electrical system?

John in RI

iTrader: (167)

Yup,... Paint can/will prevent a good ground. Radio / electrical static / interference can be caused by MANY things, but it's a good idea to be sure that you're engine ground strap is real good.

Once I rebuilt a engine and the starter wouldn't work because I painted the engine and painted the starter and forgot to clean the paint off before installing the starter.

I built another engine once that wouldn't start after a complete rebuild and it turned out that I painted the engine @ the ignition module mounting surface,.... again - no ground.

Clean both ends of your ground strap REAL GOOD and then re-post !

sofakingdom

iTrader: (1)

It's also possible that the distributor body isn't well grounded to the intake, or the intake to the heads, even if the heads are well-grounded to the block and the chassis to the heads which is what the factory braid thing does... a piece of wire screwed to the bottom of it (there should be LOTS of holes, or you could just D&T one) and running to a known good eeeeeezy-to-access ground such as the firewall end of the braid, might be of help.

Tibo

iTrader: (15)

Pretty much what's been said. Totally clean the ground(s) at the head, no paint or oil or grease. If you can use a star washer that may also help. I also prefer to use studs for grounding (especially on the heads) since you don't have to hold the ring terminal on the bolt as you try to thread it.

It could also be that you have too many devices grounded to one single point and you now have a ground loop. Now would also be a good time to make sure your ground to the block from the battery and frame rail from the battery are good. From what I've understood they should also (collectively) be the same size as the power wire.

Dartht33bagger

I went out for a bit today and tried to track this down. The body ground by the battery looked okay me to. I tested it with my multimeter and had no voltage drop between that ground and another ground. The car was not on though so maybe it was not a true test.

The head ground is buried on the passanger side rear head. I wasn't able to get my hand down there or my light down there from the engine bay. Next time I'm going to try going under the car to see if I have more luck that way (its too cold for that outside today). I do remember that when I was putting the head grounds back on during the engine swap one of the end rings on one of the ground was cracked. I thought it would work fine but maybe that is my culprit.

Finally, I found a lose power and ground wire floating around on the driver side by the brake booster. I think they came from the alarm system that my dad ripped out during the engine swap. Apparently he just cut the wires and left them dangling....I put some electrical tap over them now but I'm thinking this may also be adding to the electrical noise issues. Maybe I'll try running these wires to ground somewhere so they aren't just floating.

Dartht33bagger

I poked around on this today now that is it warmer. Initially I probed around with the key completely off and was getting reasonable values. 0.2 ohms of resistance between the head ground and the head. Same with the head to the body ground by the battery. And also the same from the head to the negative terminal of the battery.

As a last ditch effort, I pulled the coil wire and turned the key to the on position to get the ECM on at least. This is what I should have done from the start. Again, I saw 0.1 ohms of resistance between the head and both body grounds. However, I saw about 1.8 ohms of resistance between the head and the negative terminal of the battery. I also saw the same 1.8 ohms of resistance between the negative terminal of the battery and both body grounds.

A voltage check netted me a 1.8V drop from the negative terminal of the battery to both body grounds and to the heads. The battery cables in my car are gnarly and chewed up from the PO, so my guess is I need to replace the terminals and the wires. 1.8V from the negative terminal to the body ground that it is directory connected to it sounds like it is causing my issue. Unless there is actually supposed to be this much of a voltage drop - which sounds wrong to me.

hockeyman48

Try connecting a battery jumper cable to battery negative and with static noise on radio, connect other cable end to various ground points on engine and ground connections to see if it affects radio noise.Usually rfi to am radio is from ignition system (high voltage) to plugs.