Stuck valve

comnoz · Jul 5, 2014

I recently had a case of a new valve sticking in a new guide after only a few minutes of operation. I was confident of the guide clearance and the assembly was
well done. The only difference seemed to be the prelube used for assembly.

It had been assembled with STP and oil as a prelube. That is something I have never tried although I googled it and found it is pretty common.

STP is a long chain polymer added to oil to make it thicker. Long chain polymers work because as the temperature increases the molecules clump together creating long chains which increase the viscosity. Long chain polymers [also known as spin additive] were commonly used in oil from the 60's to the 90's to make multiviscosity oil from thin base stock. They are not thermally stable and were blamed for ring sticking , valve deposits and cam failures through the 80's.

Better base oils became available through the process of hydrocracking and synthesizing and long chain polymers were pretty much done away with. Even STP has been discontinued although there is a lot of stock left . There are still a few other additives available which use long chain polymers.

Here is my test.

lcrken · Jul 5, 2014

I remember adding STP to tired car engines, and it did help control the smoking, at least for a while. I remember a '55 Ford that we kept adding STP to until the rod knock could barely be heard! Presumably using heavier grade oil would have had the same effect. Do they still make "Motor Honey"? It was a similar product, just didn't have enough marketing hype to keep up with STP.

Ken

comnoz · Jul 5, 2014

lcrken said:
I remember adding STP to tired car engines, and it did help control the smoking, at least for a while. I remember a '55 Ford that we kept adding STP to until the rod knock could barely be heard! Presumably using heavier grade oil would have had the same effect. Do they still make "Motor Honey"? It was a similar product, just didn't have enough marketing hype to keep up with STP.

Ken

When I stopped by Advance auto this morning the Motor Honey was right next to the STP. STP was 2 for the price of 1. Maybe I will put the second can in my worn out lawn mower. Jim

worntorn · Jul 5, 2014

In the case of the sticking valve, perhaps it is just that an oil film takes up space and an oil film with very high viscosity STP in it takes up even more space?
Anyone remember the ad/publicity stunt for STP where a fellow in somewhere in the Midwest rebuilt his 440 Chrysler Imperial ? He coated all the moving parts with STP before assembly, then proceeded to drive the car something like 400 miles from one major city to another, without any oil in the engine. The engine was then disassembled and showed no damage to any part.
I actually believed the ad and believed in STP. My go kart had a big STP sticker and lots of STP added to the engine sump. The engine was a 10 horse Wisconsin with the governor removed so that it revved out to 5500 rpm instead of 3600. 5500 gave just over 70 mph, no brakes.
The engine endured years of this abuse from the neighbourhood kids, my brother and me before the babbit conrod bearing finally let go, so maybe the STP helped?
We rebabbitted the bearing and continued on, the whole neighbourhood ( kids anyway) was in mourning while the engine was down :mrgreen:

Glen

Fast Eddie · Jul 5, 2014

Wow Jim, that's a brilliant video, I am staggered at how tight that valve became. Great learning there Jim, I guess the moral is to buy the correct thing for the job, ie good oil and proper assembly paste.

jaydee75 · Jul 5, 2014

It takes a good man to admit a mistake and allow others to learn from it.
Thanks,
Jaydee

Rohan · Jul 5, 2014

Sticky valves from burnt oil/carbon deposits building in the valve guide used to be a common problem, back in the 'good old days'.
Ashless and near ashless oils have all but eliminated this problem - mostly from piston-engined aircraft oil experiences ?
Doing away with metallic residue additives - to suit catalytic convertors - hasn't hurt either.

Perhaps STP haven't read the additive formulation guides recently....

comnoz · Jul 5, 2014

I think STP was a very good advertising company that also made an oil additive.

STP may have it's place but not in a tight clearance that gets hot like a valve. The residue on the stem was like an abrasive gum after it got too hot. Solvent and a scotchbrite pad does not remove it. Jim

nickguzzi · Jul 5, 2014

Back In the 70's, STP was the official Lotus assembly lube for the twin cam, at least the cam/followers. I don't recall many other assembly lubes back then apart from the paste type.
The most common was another RR spin off, in the same vein as Hylomar. All I remember is it came in a blue tube. Perhaps a member with an RAF background will have better recall.

I only have very vague recollections of a rather poorly presented college lecture which discussed the merits or otherwise of graphite and molybdenum disulphide. The guy obviously had a vested interest in the latter. His assertion was XXXmoly actually modified the surface condition of bearings and wear surfaces.
As was the norm back then, a few very poor overhead projector slides, backing up a somnambulant delivery were supposed to convince us.

Time Warp · Jul 5, 2014

Thats a nice head is it a RH1.

Quite frightening to see, especially if you multiplied it by all four valves.
I just bought a new tube of CRC moly lube, hope that is OK. :shock:

dynodave · Jul 5, 2014

Thanks for the heads up. My engine assembly procedure is fairly consistent. Only STP I use is on rod shells to help until pump oil gets there, so there may be the size of 2 peas. I'm still using from my first can bought in the mid 70's. I believe it helps with all the turning over during assembly against the drag of piston rings. Molybdenum disulphide grease on cams and lifters. Oil on valves/guides, cam bushes. So far, So good....

Hobot · Jul 5, 2014

Very informative Jim though I've shied away from engine honeys inside engines since it came out expect for really worn out stuff kids would try to keep going. Its good on stuff needing grease that zerk is scloged so can weep some in and get going or mowing again. Makes good hand drill cutting oil as sticks around with its own cutting compound as slowly drools down drill shank. Helps my pliers stored in open shed stay pliable, files and saw blades time to time too. Beware of the Moly in guides and stick with proven - made for the job > quality synthetic diesel multi grade hi detergent engine oil with a dash of break in additive. Note just the guides and other tight spots for initial start up not for mass volume of break in oil.

I'm sticking valve in Kohler 18 hp twin today so was checking up on this to find this.

https://www.google.com/#q=valve%20guide ... bly%20lube

https://www.google.com/#q=breakin%20additive

ashman · Jul 5, 2014

I have been using STP in my Norton for over 30 years and have found it does a good job and when I rebuilt my engine 5 years ago now that all the bearings and conrod bearing to still be good with not much wear, but I only use it after the engine had been fully run in, i mix it in with new oil when doing oil changes, my motor has done a lot of miles as well indured lots of high speed running, inside my motor was very clean and had well over 60,000 miles on it before the rebuild (had to replace the crank cases), I have well over 140,000 miles on this bike since new and I am still running the orginal valves, when it got rebored many years ago the final hone to bore tolorance was very tight and had to take it very easy for the first 100 miles but after more than 6 years of running my motor is still tight and has a lot of compression, doen't use oil between oil changes, don't blow any smoke at all and still performs the way it has always performed.

My mate also uses STP in his old Triumph for 16 years without any problems with the motor and he flogged the shit out of it, he has sold it now but it is still going strong after all them years of hard riding.

Ashley

Nater_Potater · Jul 5, 2014

It's great when you can do a with/without experiment with proven results. I hope you were able to recover the head with the stuck valve. I used STP in a '77 Dodge 318 to quiet a noisy lifter. It was added every other oil change, and it was still running quietly after 138,000 miles when it was sold.
btw, the Lynyrd Skynyrd was a nice touch.
Nathan

aceaceca · Jul 6, 2014

My brother put some STP in his primary and had to take the clutch pack out and clean it all out. It just slipped wildly. I got an 11 hp Briggs I/C engine for free that I have on my pressure washer. It had a stuck exhaust valve. I had to use a pickle fork and a leather belt over the valve to pry it out. It was really stuck. I do not know whether STP was involved but after the valve came out it slipped fine in the guide. My 350 Chevy motor in a 71 Suburban had the heads assembled with STP on the guides. The next day I was cruising on the freeway when about 4 valves got stuck and all the power went away. I never realized it was the STP. At a tech school we pulled a Ford Granada in that would barely run. Pulled the valve cover and a bunch of valves were stuck in their guides. I told a student to pull the head off. He said, "I can get this thing going". Off he went and came back with Marvell Mystery oil. He fired up the engine and poured the mystery oil over the valves. I was stunned when all the stuck valves freed up and the motor purred like a good old Ford six should. Live and learn. Great demo on STP. Thanks for the input.

laurentdom · Jul 6, 2014

I got the same problem as yours Jim some months ago with my fully rebuilt cylinder head (bronze guides - standard valves). The left intake valve stayed stuck open. I brought the cylinder head back to the guy who rebuilt it (who has a very good reputation with machining of classic british bikes and cars). He found no problem with the claerance and simply honed the guide a little bit to clean it.

To me, the Number 1 suspect is the Lucas Engine Break-in additive (TB Zinc Plus) that I used for the beak-in.

Laurent

laurentdom · Jul 6, 2014

Forgot to mention that the additive was mixed with Motul 7100 20-50 fully synthetic oil.

Laurent

zotz · Jul 6, 2014

I've never put STP in an engine but it works great for thickening up swing arm oil.

trident sam · Jul 6, 2014

Really interesting Jim, thanks for posting.

What do you use as an assembly lube ?
sam

comnoz · Jul 6, 2014

trident sam said:
Really interesting Jim, thanks for posting.

What do you use as an assembly lube ?
sam

I normally use CMA assembly lube for rod bearings and other bottom end stuff. For valve guides and wrist pins I use synthetic motor oil. Jim

Stuck valve

comnoz

lcrken

comnoz

worntorn

Fast Eddie

jaydee75

Rohan

comnoz

nickguzzi

Time Warp

.......back to the 70's.

dynodave

Hobot

ashman

Nater_Potater

aceaceca

laurentdom

laurentdom

zotz

trident sam

comnoz

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