Motor Backfires Thru Exhaust When Trying To Start - Page 5

Gaz64 · #81 (**permalink**) 11-24-2019, 02:14 AM

You need a timing light connected to any engine if the timing has been altered in any way prior to fire up.

I have seen a few cars started without a timing light, some with near drastic results.

So you need the light connected, and as soon as the engine is restarted, get the off cold timing down to 15 or so, then warm the engine up, and set idle timing at 12 or so.
I prefer a digital dialback light, so you can check timing at any rpm, including tracking the advance curve.

Gary

Jim Coleman · #82 (**permalink**) 11-24-2019, 02:31 PM

Gary,

Gonna have to get a better timing light, can't see this one well enough to set it correctly. Picking up another one tomorrow.

It started and runs, but won't idle at lower RPM's.

The other problem I have is the motor is getting hot, In about 5 minutes it was over 200 degrees and it has a 180 degree thermostat. The radiator is a new 4 row core with an electric fan that was for a Mustang. I don't understand what's happening. I installed new head gaskets on the block due to the age of the engine, and know for sure they were installed correctly. Very disappointing.

Thanks,

Jim

jhv48 · #83 (**permalink**) 11-24-2019, 04:22 PM

Is the fan coming on when the temp gets over 185 degrees? If not, then the thermostat isn’t opening. Might be in backwards.

Jim Coleman · #84 (**permalink**) 11-24-2019, 05:11 PM

Fan is hooked up to a manual switch. Thermostat is installed correctly.

Thanks,

Jim

Gaz64 · #85 (**permalink**) 11-25-2019, 01:52 AM

Jim,

Lets' go back to the valvetrain.

How did you set the valve lash, and what values?

And we need to have a good timing light before you next start the engine.

Is the fan blowing the correct way?

Gary

Jim Coleman · #86 (**permalink**) 11-25-2019, 05:10 AM

Gary,

I used a procedure found on the net for the 30-30 cam, this involved setting half of the intake valves and exhaust valves, then rotating the engine 180 and setting the other half.

Here's the you tube link: https://www.youtube.com/watch?v=DCxXd5ZpF94

I feel reasonably sure they are set right. The fan is on the backside of the radiator and is blowing through it. I will double check that. Will get the other timing light today and get the timing set correctly.

Thanks,

Jim

bobcowan · #87 (**permalink**) 11-25-2019, 06:20 AM

I use the instructions supplied by Comp Cams. It takes a little longer, but I get a perfect adjustment every time.

Intake: when the exhaust valve is just starting to open
Exhaust: When the intake vale is half way to closing

https://www.compcams.com/pub/media/p...1/5/151_4_.pdf

A lot of people say to tighten the nut until you can't turn the push rod any more, then add 1/2 turn. But with modern materials and lubes, you can sometimes turn the push rod after it is properly adjusted. Instead, spin the nut by hand as far as you can. That's zero lash.

For timing, a specific base number is impossible to tell ahead of time. You have a custom engine, and will need a custom setting.

With the engine warmed up, disconnect any vacuum advance and set base timing at 12-15* or so. Place a glass of water on the body of the car; at the base of the windshield in the middle works well.

Now adjust the timing until the engine is running the smoothest. Watch the ripples in the glass of water to see where it's the smoothest. Check with a timing light to see where you're at, and make sure it's not some ridiculous number.

You can use the same method to set your idle mixture.

Changing the idle mixture will change your base timing, and vice versa. Go back and forth between the two until it's really smooth.

During all of these adjustments, try not to burn your shin on the side pipes.

That was hot work. Drink the glass of water.

Jim Coleman · #88 (**permalink**) 11-25-2019, 03:13 PM

Thanks, everyone --

Got the timing set correctly today with the timing light, but still have the overheating problem to deal with. The fan on the radiator is a "puller" and seems to work OK.

Thanks,

Jim