1962 340 valve seal replacement recommendation

[Gordon M.]

Not sure of the best type of valve seals to use. I am getting some fouling of some plugs but not all. I see the "O" ring and umbrella seal but also a one piece seal that seats on the head.

[Edward J.]

Re: 1962 340 valve seal replacement recommendation

Gordon, I would use the o-ring seal, sometimes with the 097 cam at high RPMS the umbrella seals can break because the valve keepers can contact the top of them. Most machinist can machine the guide to accept the umbrella seals with the spring clips but this requires removing the head to send out.

[Joe L.]

Re: 1962 340 valve seal replacement recommendation

Not sure of the best type of valve seals to use. I am getting some fouling of some plugs but not all. I see the "O" ring and umbrella seal but also a one piece seal that seats on the head.

Gordon------

The stock type valve seals will work well if the following is observed:

1) Valve guides have to be in good condition. If the valve guides are worn, no seal will work effectively;

2) The stock valve oil shields (cup shaped) MUST be used;

3) The seals MUST be installed correctly. Although often referred to as "o-rings", these seals are not actually o-rings, per se. O-rings have a round cross section. These seals have a "square" cross section. They must be installed on the valves so they are not twisted. In addition, and most important, they must be installed AFTER the valve spring, valve cap, and shield assembly is compressed, NOT BEFORE.

You can also install positive type seals. Positive seals are generally better but there is one risk. That risk is that the valve stems will be caused to be "too dry" and faster wear of valve guides will occur. As Edward mentions, many of the positive type seals require machining of the valve guides and that, in turn, usually necessitates head removal. However, there are some positive seals on the market now which do not require valve guide machining. EngineTech is one manufacturer that makes these.

Regardless of the seal type, stock or positive, I GREATLY prefer VITON material.

Some, if not all, Gen II small blocks actually used positive valve seals.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Thanks guys. Very helpful. Now I can work on putting the water pump back on after replacing the generator bracket mounting bolt/stud.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

New issue: my 1962 340 hp spark plug in #4 cylinder builds up a carbon residue that eventually shorts out the plug after a couple hundred miles. Got 160 lbs of compression.

[Terry D.]

Re: 1962 340 valve seal replacement recommendation

Check plug wire and cap for hairline crack.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Thanks Terry. I will check that and hope that is what it is as and EASY fix! I'll let you know.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Replaced distributor cap, rotor button and spark plug wires. Did a 200 mile, mostly 60-70 mph, test and the plug still fouled! Did a compression test with the throttle wide open and got 175 lbs. Squirted some oil in the cylinder and got 184 lbs. Using synthetic oil and was told NOT to use it in these older engines.

[Joe R.]

Re: 1962 340 valve seal replacement recommendation

Probably that advise not to use synthetic oil was meant not to use for break in!

JR

[Joe L.]

Re: 1962 340 valve seal replacement recommendation

Replaced distributor cap, rotor button and spark plug wires. Did a 200 mile, mostly 60-70 mph, test and the plug still fouled! Did a compression test with the throttle wide open and got 175 lbs. Squirted some oil in the cylinder and got 184 lbs. Using synthetic oil and was told NOT to use it in these older engines.

Gordon-------


Advice to not use synthetic oil in older engines is TOTAL nonsense. Synthetic oil is the best for ANY engine. Period. I can absolutely guarantee you that your oil fouling problem has nothing to do with synthetic oil. Something you might try, though, is high mileage formulation synthetic oil. I don't think it will solve the problem by itself but it's worth a try. It's a good thing to use, anyway, if the engine has 50,000+ miles on it.

[Terry D.]

Re: 1962 340 valve seal replacement recommendation

Did you replace points and condensor? Do you have access to a plug wire tester? You need to be able to check spark at that plug with engine running. Tester I have looks like a pencil and you hold om the wire cap at the plug. lights up at each spark, very old school but you compare brightness against non fouling one. Has engine been rebuilt? Did this problem just start? If so what was done right before it started.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Did not replace the points and condenser. Only got 10K on them and they seem to be working well when the plugs are clean. Only got 48K on the engine and I have a plug firing light and tested all of them and they are firing fine. Wasn't sure about the synthetic oil issue BUT changed it anyway. Cleaned all the plugs and it runs great initially, any way. It did look like I am running rich on the other plugs so I also may have a carb tuning issue. Need to road test for a couple mikes and see how it looks. To be honest not expecting much. This problem was happening before I replaced the heads so I am leaning towards the piston/cylinder but really wanted to eliminate all the "Easy" fixes" first.

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Actually I meant a couple of miles not mikes. Also thinking about replacing the valve seals in #4 just for drill...

[Gordon M.]

Re: 1962 340 valve seal replacement recommendation

Interesting find when I removed the valve springs! There wasn't any "O" ring gaskets! I replaced the umbrella seal and placed the "O" ring gasket on the valve stem. Went for a short drive but had to return shortly due to a heater leak pouring water down the passenger side. It appears that the 90 deg rubber L bow didn't like the hot temp water and failed. Ordered new one...
But the plug after 50 miles was running rich, not sure if it was really better yet. need more test miles. Getting cold in Maine!!

Just asked about plug heat and the forum response defiantly recommends the R45S over the R43S for this engine!! Heading down to O Reilly's to get some tomorrow! Hopefully this will be a very thanks giving day!

[Joe L.]

Re: 1962 340 valve seal replacement recommendation

Interesting find when I removed the valve springs! There wasn't any "O" ring gaskets! I replaced the umbrella seal and placed the "O" ring gasket on the valve stem. Went for a short drive but had to return shortly due to a heater leak pouring water down the passenger side. It appears that the 90 deg rubber L bow didn't like the hot temp water and failed. Ordered new one...
But the plug after 50 miles was running rich, not sure if it was really better yet. need more test miles. Getting cold in Maine!!

Just asked about plug heat and the forum response defiantly recommends the R45S over the R43S for this engine!! Heading down to O Reilly's to get some tomorrow! Hopefully this will be a very thanks giving day!

Gordon-------


If your engine had no "o-ring" seals and did have umbrella seals, then someone eliminated the "o-rings" and installed the umbrella seals. I can absolutely guarantee you that the engine was not originally built this way.