Bad Start to Summer

[Rich]

Started this issue on another site, however quick to remember that many in the know have migrated this way.
Ran boat out for the first time this year on Sunday, all seemed ok.. But on way back, seemed to lose power... Next day, had a hard time starting and maintaining idle. Long story short, lost compression in two cylinders. Took heads off and found the intake valves were tuliped on cyl's 3 and 4.
A third was just beginning to show failure as well. What gives??
Is this hydraulic lock? I saw no real evidence of water, but I could be wrong.
Motor is Gen IV 454, bored .030, decked .010, with TRW forged pistons, L2465"s, with .226 dome. The cam is a Comp. cam, #11-306-4 with duration at .050, 222 intake, and 226 ehaust, with .309 lift for both, and lobe separation of 110. Heads were a set of peanuts, rebuilt stock,using better Isky springs. Exhaust is EMI thunders. Intake is Edelbrock Rpm, with Edelbrock 750 carb. Ignition is stock. Motor was no show stopper, but still had plenty of torque and boat moved along just fine. Pistons and bores appear fine.
Any input guys? Thanks..

 

[Geronimo36]

who did the head work and set-up??? What was seat pressure set at; 130 lbs?? What kind of exhaust do you have. Got any dyno A/F numbers. I believe that's a flat tappet hydraulic cam? Have you verified all the lobes are in tact?

My guess is setup but with limited info it's hard to know.

 

[Rich]

Just to clarify,
motor is not new build. It has approx 100-150 hours since rebuild. As for spring pressure, I cannot answer at the moment. Motor was built approx. 3 seasons ago. I know it has better Isky springs over stock installed, that's all. Heads are basically stock otherwise. Exhaust is Eddie Marine Thunders. Lobes on cam appear fine. Would detonation, or lean out condition cause this, and only on intake valves??

 

[Geronimo36]

From what I've seen lean can burn an exhaust valve and rich can two-lip a valve. The richness causes excessive exhaust temps and pounds the seats out. Detonation/lean can tulip intake valves.

Water, valve float or detonation are my guess.

 

[ROGUE]

You could be close to 10-1 compression ratio with those pistons and decking. You need 92 octane or better. My guess is bad fuel that lost octane, ( the stuff we have now doesnt hold octane very long) and detonation tuliped the intakes. Been there, done that.

Was this fuel in the tank all winter?

 

[Rich]

yes,
fuel was remaining in tank from previous winter, approx 25 gal worth. attempted to top off with fresh 92 octane, ending up with a 50/50 mix or so.
Had hoped this would be enough to dilute, if in fact this was problem.
You are right with compression ratio, at about 9.7:1 or so with current setup.
I am no cylinder head guru for sure, so here is a question. Would detonation only tulip the intakes? I guess it might hit them first, seeing that the diameter of intakes being much larger. An old timer gear head who teaches at the local trade school and has built a few engines in his time looked at my heads this evening said it looked like they were seeing alot of heat. He was wondering how my cooling flow was.
I guess my concern is not letting this happen again. Water temps never seemed to be a problem according to the guages. In fact, I always thought she was a little cold blooded. My next concern was inadequate fuel delivery at high rpm's causing this. He questioned this being the cause of tuliping of intake valves because normally they are cooler due to fuel charge coming in, and I might have seen more damage to exhaust valves as well.
Last question is whether this may be result of water in cylinder, but I cant really see anything to lead me to this, but I may be wrong.
I appreciate the feedback.

 

[2112]

One thing that may bake you feel a little better is that you caught it before the valve head broke off and had sex with the cylinder, piston, other valves, and so on. Small consolation? Probably not, Sounds like you will be back on the water soon.
.

 

[Ratickle]

Tuliped Intake Valves

The AERA Technical Committee offers the following information concerning tuliped intake valves shortly after rebuild. This condition has been noticed after rebuild of engine or reconditioning of the cylinder head. A tuliped valve has an increased total valve length and the top of the valve has the appearance of a cup.

Combustion chamber temperatures that have exceeded the engine's original design parameters usually may cause a tuliped intake valve. Each valve used in an engine has a specific requirement, which results in different materials for intake and exhaust valve locations. Design engineers will specify which materials will economically work best for the intake and for the exhaust locations.

Intake valves run at a much cooler temperature than exhaust valves. The air and gasoline mixture temperature is generally in the range of 150- 250° F. This cool air passes over the intake valve while it's open in route to the engine's combustion chamber area. That process also has a cooling effect on the valve.

Some exhaust valves are made from 21-2N or 21-4N stainless steel, which
offers greater temperature strength to lead oxide corrosion. The 21-2N and 21-4N material is used at the exhaust locations because it withstands higher heat temperatures. Exhaust valves usually have to endure temperatures that are generally in the range of 1000-1500° F. The result
of an abnormally high combustion chamber operating temperature. This temperature is in the cylinder of the engine, NOT THE ENGINE COOLANT TEMPERATURE. The temperature surrounding the valve got much higher than the valve was ever designed to withstand. That excessive temperature resulted in the valve material softening, allowing the valve head to stretch to create what is called a tulip shape.

A normal combustion process operating temperature in the combustion chamber could be considered 2500° F with cylinder pressures between 900-1200 psi. Engine valves will only survive the normal temperatures because they are seated during the combustion process and transfer heat as designed to the head casting.

An abnormal combustion process may increase the operating temperature in the combustion chamber as high as 5000° F with pressures between 3,500 - 5,000 psi. If this tulip condition re-occurs after rebuilding of the engine or reconditioning of the cylinder head, the original problem has not been fixed. This condition may affect one or more valves at a time.

Items to check; properly working EGR system, correct ignition timing, ECU operation, vacuum leaks (intake manifold, hoses, etc.), correct air to fuel mixture, correct angles between the valve and the valve seat, excessive valve spring pressure and any other source that affects the combustion process.

The AERA Technical Committee

 

[Ratickle]

The only other thing I know of that will cause tuliped valves is weak springs allowing the valve to "float" and then slam into the seat.

Guys, are there more than two causes????

 

[Ted]

I tuliped several last year and it was due to lean out. I have 502 MPI's and 3 injectors failed, causing low flow only when pulse tested. This in turn leaned the cylinders and I tuliped a couple of intakes and came within about 1000 revolutions of dropping an exhaust valve too. I would think the combo of old gas and maybe a little gunk in the carb did you in. Make sure you at least do a couple of pulls and then read your plugs but I think you will need to either fatten up the carb a smidge or at least give it a good cleaning. Water in a cylinder will almost never effect a valve.

 

[Chris]

Bad gas kills alot of engines, yet people continue to use last-year's gas. It's just not worth it.

Even really good valves are stupidly inexpensive compared with the kind of damage they can do. Valve springs too. If they have more than a couple hundred hours on them, or any much sitting, I'd definitely replace them. Also, double-check your valve stem clearance. Overly cold can cause a hot stem to expand inside a cold guide and stick a bit. That can cause big problems. There's nothing wrong with running a few tenths over on guide clearance.

While you're in there, you need to do a couple things. First, CC your heads and KNOW exactly what they are. Then measure your piston deck height. Now you can get the proper thickness head gasket to maximize combustion chamber quench and hold back detonation. And you'll know your static compression ratio and know how close you're cutting it with fuel choices.

 

[Geronimo36]

* yes, fuel was remaining in tank from previous winter, approx 25 gal worth. attempted to top off with fresh 92 octane, ending up with a 50/50 mix or so. Gotta get rid of that fuel, not worth it. I pump mine out every winter, it's free gas for the vehicles.

* You are right with compression ratio, at about 9.7:1 or so with current setup. Gotta have better than 91 Octane

* Would detonation only tulip the intakes? Yes and could burn exhaust valves.

* An old timer gear head who teaches at the local trade school and has built a few engines in his time looked at my heads this evening said it looked like they were seeing alot of heat. Do you have and dark heat marks between the cyliners on the block or the heads?

* He was wondering how my cooling flow was. When you put it back together be sure to use the correct head gaskets. Gen IV vs. Gen V/VI have different coolant flow pattern and use a different gasket. If you use the wrong one the heads wont cool properly.

* I guess my concern is not letting this happen again. I'd pump all that gas out and start fresh

*My next concern was inadequate fuel delivery at high rpm's causing this. Do you have a dyno sheet that shows your Air Flow ratio numbers? How is your fuel system set up? (size lines, fuel filter, fuel pump size etc.)
\
* Last question is whether this may be result of water in cylinder, but I cant really see anything to lead me to this, but I may be wrong. If there's no water present in the cylinder when you pulled the head or rust marks anywhere I doubt that's the issue

Hope this helps!

 

[Rich]

I really appreciate all the replies guys.
I never had motor dynoed by the way, so that info is lost. There are many suggestions here that I will follow up with, such as fuel delivery (stock lines by the way), getting all gas out and starting completely fresh,, etc..

Dropping the heads off today at machine shop who did original machining to see what he has to say. (Horsepower Engineering out of Ellington Ct.)

Chris, you may have touched on something regarding stem clearance. I did not mention previously, but in one of the cylinders which lost compression, I noticed the intake valve kissed the top of the piston, leaving small crescent mark on top. I blamed it on the valve tulip,(extending overall length) but perhaps this was sign of valve sticking instead?

 

[Chris]

Could be.

The tulip makes the valve longer and if you're running solid lifters, there's nowhere for that length to go, so thet can stay open.

I'm guessing with the dome pistons you'll find your compression is higher than what you're estimating.

On water in the cylinder, there's several versions of how that can happen and wht it's a problem- and how it can be different problems.

Reversion is a big one. That occurs when valve overlap allows the intake valve to be open at the same time the exhaust is. At moderate to high RPM, it's a necessity if you want to make power. But if your exhaust riser/mixers are close, it can pull water back onto hot exhaust valves. The other one is leaking riser gaskets or cracked exhausts. Sometimes you see this causing the same issues as reversion, but more often they leak when the engine is off. When you try to crank the cylinders lock- water doesn't compress very well. Often you'll find mechanical damage. The third is a leaking head gasket. Sometimes tough to find, especially with raw-water cooling. You're not losing antifreeze. More often than not, you'll find water in the oil as well and that's how you'll find that one.

If I had to guess, I'd say your fuel system architecture is nominal at best. It probably met the minimum requirements of your demand when everything was working 100%, but it was right on the line. Once you're right on that line, that additional 1% over is still over and sometimes that's all it takes.

 

[ROGUE]

I will say I do run winter fuel every spring but I never, ever, take it over 4000 rpm until that is gone and I get new fuel. I also run rich so I keep things cool. Good luck, while I have basically rat motors I dont scrimp on head and valve train parts. Thats usually where a marine BBC will have trouble.

 

[Blue Thunder]

You don't say what valves you were running, but if replacing them go with manley severe duty on the intakes and ferria on the exhaust valves. This will give you a little more insurance if you are indeed on the edge with your fuel delivery.

BT

 

[ROGUE]

You don't say what valves you were running, but if replacing them go with manley severe duty on the intakes and ferria on the exhaust valves. This will give you a little more insurance if you are indeed on the edge with your fuel delivery.

BT

Yes, even with my little toy engines, I use severe duty intakes and extreme (inconel) exhausts.

 

[Rich]

Update:
Consensus from shop is definitely got lean and hot. No big upgrades to speak of due to current budget constraints. (unfortunately this boat is not my only headache right now)

Replacied all intake guides (too loose)
Opening up existing exhaust guides a touch,(too snug).
Exhaust valves were fine, (stellite).
Intake valves all replaced (stainless).
Cut all new seats.
Existing springs were tossed as they were only getting 100 lbs force.

Now back to identifying root cause in the first place.
Bad gas? Carb too lean? Mechanical pump failing? Vacuum leak somewhere?
Restriction at tank? Timing?

Not really sure, so will start at tank and end at carb.
Here is what I have so far.

Will drain and refill gas

Check out anti-siphon valve operation

Check out tank vent for obstruction

Replace fuel pump (wish to stay mechanical)
I am told Edelbrock carbs do not appreciate too high a pump pressure, so will stay realistic with this ( ideas appreciated )I do not have a return

Jetting carb up two stages for both pri and secondary (as a starting point )

Replacing base gasket at carb

Looking for input here from you guys,to add to this list, as I do not wish to have same happen again.
Thanks guys...

 

[Geronimo36]

It's hard to speculate. Lean could have been the problem but with only 100 lbs seat pressure you could have been floating the valves, hammering seats and tuliping the valves. You also mentioned there was a mark on top of the piston from the valve so it may have floated and kissed. Intake valves are larger so they tend to hammer the seats first.

Before you took the heads apart did you happen to look at the valve stem tips? There should be a cross mark that runs across the top of the valve where the roller rocker hits. If you have multiple cross-markings the valve was floating. When the valves float they turn.

I think you're on the right path though and I'm curious what others have to say.

 

[Rich]

Going back up today

Finally got the time and necessary machining, parts etc to complete rebuild. I think I may have found root cause to leaning out. Realized as I was matching things up, that my intake manifold alignment wasn't right. Ended up needing to remove .060 from all 4 sides before it would sit correct with gasket. Even without gaskets, manifold was sitting way too high. This time through the machine shop, heads needed about .010 removed to square up, but not nearly enough to cause mismatch I was looking at... So, hoping this may have been problem all along. I also said screw it, and spent about 15 hours on the business end of a dremmel, and port matched and cleaned up the runners and pockets.. What a mess they were.I could have cut my fingers with all the slag in there. Hard to believe motor could even run like that. I must have had 1/4 inch of meat all the way around intake gasket as well that needed removing and blending. They are peanut heads, and I already know what I was getting for performance with them stock, so it will be interesting to see what if any difference it will make..
River this weekend is junk with all the rain we just got,and marinas are not allowing launching, so not feeling too left out yet.
I do have a question about the intake manifold exhaust restrictors. Did not have them in before.. Came with gaskets this time... Use them or not???