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Fri Aug 22, 2014 7:55 pm

1972 Westy just had tune-up and took her for a road trip. Ran without trouble on the way there but it was a 4-5 hour trip with 95+ weather. She ran kinda rough after camping for a few days and then on the return trip lost all power going up the hills. On our return I found that number 4 is not firing though there is spark to the plug and it was wet after running it for a bit. Dropped in a new plug and no change. What am I missing? I have fuel... I have spark and valves had been adjusted just before the trip. No oil on any of the plugs all at a nice brownish black. Anyone have any ideas?

Fri Aug 22, 2014 8:00 pm

dublubber wrote: What am I missing?
Compression?

Fri Aug 22, 2014 8:42 pm

One other thing is the internal resistor in some spark wires in the part that plugs on to the plug sometimes burns out! Or Gets a carbon Path going somewhere. Switch the wires and see if it moves the problem to a different cylinder. Also check the inside of the distributor cap etc...

Fri Aug 22, 2014 8:42 pm

You may have a bad valve seat. Do a compression check

Fri Aug 22, 2014 9:22 pm

check valve clearance on number 4 when it is cold tomorrow morning. See what it looks like. Then as Gary suggested run a compression check after checking the valve clearance.

Sat Aug 23, 2014 11:43 am

Did the compression check as suggested...Sadly there is no compression at all. So my next step it to have the head rebuilt? Or just a valve job? This (#4) was the weakest compression cylinder when I had it checked at the last tune up.
The others were all 115-120 but this one was under 100.

So the road trip and heat probably was what caused the valve seat to fail? or could it be something else? It does run on 3 cylinders without any smoke. I am hoping that means the rings / piston are still in good shape, right?

Thanks :)

Sat Aug 23, 2014 11:54 am

Get the heads rebuilt = $700 and change the rings too at a minimum. I was involved with one once like yours and the bad cylinder continued to have low compression because the owner continued driving while gas was washing away the oil on the cylinder walls.

Sat Aug 23, 2014 11:58 am

I have had a similar problem that was a plugged injector. Maybe alot cheaper than rebuilding the head, hope that's all it is.

Sat Aug 23, 2014 12:04 pm

I am glad you mentioned that, I did not consider that outcome of running with that cylinder not firing. You may have saved me additional damage to the motor as I was considering just driving it over to the shop...

Thanks for the help.

Sat Aug 23, 2014 12:08 pm

Did the tune up take 1.5 hours? If it did then the engine didn't cool
down enough to adjust the valves properly. You write that the #4
plug is wet, if you don't see metallic particles on it, the exhaust valve
just has a section burned off, so you get enough suction to see 65psi
or so with a tiny gap at the valve. The valve is $9-13, the labor is $$$.

Sat Aug 23, 2014 12:37 pm

Also....before you do anything to the head...make sure its the head. you have to remove it either way...but it could be a problem at the cylinder seat, a totally crapped out ring etc. Ray

Sat Aug 23, 2014 1:52 pm

probably a loose valve seat or broken spring because a scuffed piston or hole in one and you would be pumping oil making smoke. If a broken valve spring you don't even need to pull the heads. You can use either a piece of rope or compressed air to hold the valve while you pull and replace the spring.

Sat Aug 23, 2014 4:42 pm

SGKent wrote:check valve clearance on number 4 when it is cold tomorrow morning.