Valve help

[bosstime2]

Had a really bad backfire a couple years ago from a short in the distributor. That issue was fixed but the car hasn’t idled right since. Misses at idle and the exhaust will suck in a dollar bill. I pulled the head. Does exhaust valve #5 look bad? I’ve never done a valve job….just looking for some insight at was doesn’t look right . Thanks

 

[Sunny the Model A]

when I got my pickup originally, it had #8 exhaust valve stuck partially due to it being stuck in the guide. I released the springs and put some Marvel mystery oil on the valve stem and rotated the valve and tapped it up and down to free it. after that I did a valve lapping with fine lapping compound. lastly I adjusted the lifters because my engine has 'em. now all the exhaust valves in your engine are white, which means that your engine was running either way lean, or way retarded, either situation made 'em stupid hot. My opinion is replace all the valves and guides. I recommend the split guides, and original style valves to make the installation easy. Get the guide removal tool and the spring compressor before you try messing with the valves. It is possible to get by without the compressor, but don't try to pull the guides without the guide tool. here are some part numbers and current prices from Snyders to help you get an idea of what you need: A-6500-VGT valve guide tool $22.50, A-6505-SS-Q8 Valves $95.00, A-6510-Q8 Valve Guides, $56.00

 

[Bob Bidonde]

The white color of some valves indicates your engine is running lean. Also, the intake ports look nasty & wet. Did you do a compression & cylinder pressure leak-down tests before removing the head? Show us the spark plugs.

 

[nkaminar]

The intake valve on #4 cylinder appears to have been leaking. It should not look grey and should look like the other intake valves.

Do a valve job. Lap the valves or grind them and the seats if they are really bad. With the valves out of the engine, clean them up with a rotary wire brush. Hopefully you have adjustable lifters which make the job of setting the valve lash a lot easier. Set the lash to 0.010 for the intake valves and 0.012 for the exhaust valves.

If you have modern valves and guides, the stems should make a popping sound when pulled out of the guides while holding your finger on the bottom of the guides.

If the valves are the original type with the mushroom ends, replace them with modern valves, guides, keepers, and new springs.

If the lifters are the original type that are not adjustable, replace them with the adjustable type. But that will require pulling the engine to turn it upside down.

 

[BButturff]

It's really hard to tell from your picture if the exhaust valve from cylinder 3 is bad or any of them for that matter. I agree with the others that the engine has been running lean as 3 of the 4 exhaust valves are almost white. The spark plugs from those cylinders probably show a lean condition as well. As Bob mentioned a cylinder compression or leak down test would have been valuable. At this point, if you remove the valves as suggested you may be better able to evaluate the condition of the valves and seats. Another option would be to take the engine to a shop for evaluation.


This picture is not from a Model A but shows good exhaust valve color on 3 of the 4 cylinders. The cylinder 3rd from the left was lean because of an intake gasket leak.

 

[bosstime2]

Thank you to all who responded. For context…the motor was rebuilt in the 70’s with adjustable lifters and has a “B” high compression police head. Motor has about 12k miles on it since the rebuild. I acquired the car 6 years ago and it had an intake manifold leak which I fixed and the car ran fine until the huge back fire a couple years ago. I’ll post a couple more pics.

 

[BillCNC]

Set the lash to 0.010 for the intake valves and 0.012 for the exhaust valves.

Everything I've read say's Exh. at .015" and the Int. at .013". Is there a reason you set them at a .003" smaller gap?

Regards
Bill