tulip valves

[xltier]

could someone explain to me how a tulip valve occurs.it happened in my 5.7 mercruiser.also on a friends merc.we are both mechanics and have never seen this before.thanks

 

[cc lancer]

Re: tulip valves

I would like to see a picture of a "tulip" valve out of a 350 chevy engine.

 

[Bt Doctur]

Re: tulip valves

A very lean fuel mix in that particular cylinder(intake damaged also),water ingestion to soften a hot valve.(exaust).A very thin seat seal that allows the valve to heat up by passing the hot gasses.

 

[Bt Doctur]

Re: tulip valves

For CC: looks like the flower

 

[xltier]

Re: tulip valves

thank you.this boat was a 88 23ft.5.7 with about 200 hours.replaced the heads cause of crack with a set of truck heads from the local salvage yard.so do u think the valves were worn out,thats why they did that.run fine one day ,then the next it lost 3 cylinders.thanks again.

 

[Bt Doctur]

Re: tulip valves

I once had a volvo do 1 valve in a different cylinder for 3 seasons.had the head worked with all new valves and never had the problem again.unknown to me at the time was the fact that the owner had steamed it too.Was the head checked before you mounted it or was it just installed from the yard?

 

[Don S]

Re: tulip valves

Sounds like you might be getting water in the cylinders due to bad manifolds or risers. How old are they.

 

[Destin]

Re: tulip valves

Same as BT doctor said, also boat over propped and lugging engine, too little valve clearance.

 

[Don Brock]

Re: tulip valves

It happened to me last summer (5.7L, Alpha One, Wellcraft Nova XL 23). As I understand it, due to excessive heat the valve becomes cupped or tuliped. In my case the cause was retarded timing. Another common cause is too lean of a fuel mixture. Early symptoms were burnt tips on my spark plugs. During one outing it literally blew the ceramic insulator out of the spark plug casing of #8. In my ignorance I assumed it was a defective spark plug. Now I believe it was detonation. Later in the season it began running poorly with a loss of power, barely able to plane, and became harder to start. After troubleshooting awhile, I determined that I had lost compression in #2 & #8 cylinders from about 170 psi to 10 psi. It was the exhaust valves. I have them at work somewhere. If I can find them I'll take a pic and post it for you, cc lancer. The exhaust valves were cupped badly and also had cracks around the valve stem. I was "lucky" it didnt come apart on me from the looks of them. Taught me the hard way that its really important to set the total advance and not just the initial advance timing!

 

[rodbolt]

Re: tulip valves

hello<br /> its normally caused by over propping. the exhaust valves are prone to "swallowing" in the post 85 and later 5.7 chevy's. lug them and they die.<br /> in 1985 the center bolt valve cover engines had the heads redesigned and again about 1995. since then we have found that over propping will swallow a valve.<br /> good luck and double check your set up as well as the reccomended lean out problems. something is causing the valve to run to hot. retarded ign timing will do it as well and certain failures of the ign system will cause it.

 

[cc lancer]

Re: tulip valves

Are we talking about a semi-tulip, tulip, or a mushroom? <br />Bt Doctor, the first time I heard of a tulip valve was on the Chrysler Hemi back in the 70's.<br />Since then others have used them including the Chevy's.<br />Now if we are talking about a mushroom valve, with a 3 angle valve job, and as Rodbolt stated the stem over heats, the keepers come loose the valve drops into the chamber, and on the next cycle the piston drives the valve into the cylinder head "cupping" the edges of the valve.<br /><br />If the valve got so hot that it took the temperance out of the metal and made it soft, would not the electrode on the plug which is smaller also be red hot fireing the fuel as soon as it came into the cylinder?

 

[rodbolt]

Re: tulip valves

cc lancer<br /> not nessasarily. the pressure of the valve spring coupled with the sudden rise in combustion pressure from a lugging detonation coupled with the increase in combustion temps can actually allow the valve lip to distort and the stem will try to pull the valve through the seat making the valve head look like a tulip flower. some call this "mushrooming" or swallowing a valve also. not to be confused with mushrooming the valve stem tip. when the keeper pulls thruog we call this also a swallowed valve or a dropped valve. same results. you should see what happens when a 15*keeper fails with 350psi spring pressure at 8200 RPM. the results are rather sudden and nasty. but in the case of the new style center bolt chevy heads it does not tolerate over propping. EFI seems to compensate some due to the fact it has a knock sensor and can adjust timing and fuel delivery based on sensor inputs.<br /> good luck and keep posting

 

[cc lancer]

Re: tulip valves

You will get a kick out of this valve story, my second year of racing, I had found a set of 350/350 Chevy heads. Hones and Eanes in Richmond, Va., put in top quality valves with dual springs.<br />I was running 5th at South Boston, Va. and "Bam".<br />I flipped the engine switch, and coasted into the pits.<br />Next day we pulled the head, half of the valve head had broke off, cracking the head and destroying the piston. But where was the other half, I called a buddy that is a cup engine builder and asked him what he though, "he said pull the other head". We did, and what had happened, the broken piece had blew through the intake to the other side and damaged the head and piston.

 

[rodbolt]

Re: tulip valves

hahaha yep<br /> I blew a 455 olds in 1980 and found the oil control rings under the valve cover. still wonder how in the heck that ever happened.

 

[Capt Ken]

Re: tulip valves

Another cause not mentioned and being this started after you changed the heads, did you install the restrictor in the exhaust hole of the intake gasket? If you didn't this will also cause the valves to overheat on cylinders 4,6,3 and 5.