nm9stheham
Well-Known Member
This info post is for guys with older /6's that have been sitting a lot for years. There is probably not much here for folks with rebuilt engines or for the 'old hands' here.
My son and I have a been working on getting a /6 running better for a few months. This 52 year old engine was run a total of 3000 miles in the last 42 years and has never been rebuilt (60k miles total), and several steps have been taken to mildly desludge the engine. Initial valve adjustment (running/hot) smoothed it out a lot at idle. (I swear: the valves had NEVER been adjusted before on this engine!) But it never was properly smooth at over 45 mph and the car had a lot of vibration at speed. After the usual motor mount changes and such, I had concluded that the roughness was inside the engine (probably rings broken or sticking) and was thinking about an overhaul.
For grins, we readjusted the valves running/hot yesterday and it was smoother than ever. Ran it around for a while and finished with a 20 mile interstate run at 65 mph. Engine heated up pretty good and the roughness returned. We were not sure if the valve adjustment 'went out' but speculated that the hot running might have something to do with it. Also, we noted that it really sucked fuel when it got rough on the interstate. It had done this once before on an interstate run: got hot, rough, and sucked fuel.
So we redid the valves again today to see what was up. Checked them static (warmed up but not running) and found all intakes good at .010", and 3 of the 6 exhausts were a bit loose at about .025". We restarted the engine after closing up all the exhausts to .020" static, and were looking at the rockers when we thought we saw something odd.
The more we looked, we swore to each other that the action on the #6 exhaust valve looked 'lazy'. Looking at the rocker, it just did not have the 'snappy' looking action of the other valves. We wondered if the valve was not closing fast enough to follow the cam on valve closure, so pulled the rockers and spring on #6 exhaust with #6 at TDC and felt the valve action. It seemed OK, but we sprayed some gum cutter onto the exposed valve stem several times and worked it up and down. After some oiling, it now felt silky smooooth in the guide. After re-assembly and restart, the #6 exhaust valve action looked 'snappy' like most of the rest of the valves, not 'lazy' and there was a distinct improvement in engine smoothness.
After that we spotted some other lazy-looking valves, and decided to attempt a non-disassembly treatment. With engine at idle, we sprayed gum cutter between the spring coils into the guide area on the 'lazy' valves 2 or 3 times and then followed with oil squirted in. Then we slowly dribbled 1/3 of a pint of Sea Foam down the carb at very fast idle to clean the intake stems below the guides. This made a really noticeable improvement in smoothenss. More Sea Form was squirted into the valve guide area of all valves. By now, things were runing really smothly.
Test drives showed the engine far smoother over 45 mph and up to 65 mph than ever; it feels like the new smoothness of other /6's I have had. It really was shocking. A hard run on the interstate had the engine heat up (rad keeps getting crud in it from the block cleaning efforts) but today, the engine did not get rough when hot like before. And it did not suck up the gas!
Sooooo, this engine has clearly had 'sticky' valves; not 'sticking' valves, as it never missed on a cylinder or bent any pushrods. But it looks like the guides and valve stems have been gummed from all those years of no/low miles and the valves have been slowed in closing and were not following the cam. We suspect the slow closure got worse as the guides got hot on the interstate, and the extended exhaust overlapping the intake cycle was allowing a lot of the intake charge at high speed to be sucked out the exhaust, hence lost fuel/power/opening the throttle to compensate, and the fuel mileage went to heck.
I have never had an old engine worth bringing 'back from the dead' like this one. I just rebuild them. And I run synthetic in all gas engines they stay really clean. So I have never had the pleasure of experiencing lazy, sticky valves like this. So for you guys with old, high mileage /6 engines, check the valves while idling with the cover off and look for 'lazy' valve action on any of the valves. You really can see it with bright light and taking your time to look; it just looks 'slow' or 'lazy' in an odd way. If so, it's times to clean up the valve guides/stems and put in new stem seals to keep excess oil out of the guides to prevent more gumming.
My son and I have a been working on getting a /6 running better for a few months. This 52 year old engine was run a total of 3000 miles in the last 42 years and has never been rebuilt (60k miles total), and several steps have been taken to mildly desludge the engine. Initial valve adjustment (running/hot) smoothed it out a lot at idle. (I swear: the valves had NEVER been adjusted before on this engine!) But it never was properly smooth at over 45 mph and the car had a lot of vibration at speed. After the usual motor mount changes and such, I had concluded that the roughness was inside the engine (probably rings broken or sticking) and was thinking about an overhaul.
For grins, we readjusted the valves running/hot yesterday and it was smoother than ever. Ran it around for a while and finished with a 20 mile interstate run at 65 mph. Engine heated up pretty good and the roughness returned. We were not sure if the valve adjustment 'went out' but speculated that the hot running might have something to do with it. Also, we noted that it really sucked fuel when it got rough on the interstate. It had done this once before on an interstate run: got hot, rough, and sucked fuel.
So we redid the valves again today to see what was up. Checked them static (warmed up but not running) and found all intakes good at .010", and 3 of the 6 exhausts were a bit loose at about .025". We restarted the engine after closing up all the exhausts to .020" static, and were looking at the rockers when we thought we saw something odd.
The more we looked, we swore to each other that the action on the #6 exhaust valve looked 'lazy'. Looking at the rocker, it just did not have the 'snappy' looking action of the other valves. We wondered if the valve was not closing fast enough to follow the cam on valve closure, so pulled the rockers and spring on #6 exhaust with #6 at TDC and felt the valve action. It seemed OK, but we sprayed some gum cutter onto the exposed valve stem several times and worked it up and down. After some oiling, it now felt silky smooooth in the guide. After re-assembly and restart, the #6 exhaust valve action looked 'snappy' like most of the rest of the valves, not 'lazy' and there was a distinct improvement in engine smoothness.
After that we spotted some other lazy-looking valves, and decided to attempt a non-disassembly treatment. With engine at idle, we sprayed gum cutter between the spring coils into the guide area on the 'lazy' valves 2 or 3 times and then followed with oil squirted in. Then we slowly dribbled 1/3 of a pint of Sea Foam down the carb at very fast idle to clean the intake stems below the guides. This made a really noticeable improvement in smoothenss. More Sea Form was squirted into the valve guide area of all valves. By now, things were runing really smothly.
Test drives showed the engine far smoother over 45 mph and up to 65 mph than ever; it feels like the new smoothness of other /6's I have had. It really was shocking. A hard run on the interstate had the engine heat up (rad keeps getting crud in it from the block cleaning efforts) but today, the engine did not get rough when hot like before. And it did not suck up the gas!
Sooooo, this engine has clearly had 'sticky' valves; not 'sticking' valves, as it never missed on a cylinder or bent any pushrods. But it looks like the guides and valve stems have been gummed from all those years of no/low miles and the valves have been slowed in closing and were not following the cam. We suspect the slow closure got worse as the guides got hot on the interstate, and the extended exhaust overlapping the intake cycle was allowing a lot of the intake charge at high speed to be sucked out the exhaust, hence lost fuel/power/opening the throttle to compensate, and the fuel mileage went to heck.
I have never had an old engine worth bringing 'back from the dead' like this one. I just rebuild them. And I run synthetic in all gas engines they stay really clean. So I have never had the pleasure of experiencing lazy, sticky valves like this. So for you guys with old, high mileage /6 engines, check the valves while idling with the cover off and look for 'lazy' valve action on any of the valves. You really can see it with bright light and taking your time to look; it just looks 'slow' or 'lazy' in an odd way. If so, it's times to clean up the valve guides/stems and put in new stem seals to keep excess oil out of the guides to prevent more gumming.
