Burned valve or worse 1997 5.7 LX

[AKJohne]

The 02 plate is NA, might have to make one. Picked up the heads yesterday, all new intakes as they were too thin to recut, guides and exhaust valves OK, new seals on the guides.
Lilley will never get a definitive answer on why that valve failed, I dont think it was the fact I was running at 3800 RPM, that could shorten the life of the motor but the valve shouldn't have failed, carb could have been slightly lean at that RPM, but why just that cylinder? Obviously got hot and was on the edge of detonation if it wasn't already detonating slightly, however no signs of that on the piston. Possible intake leak could have caused a lean condition.....? Although I never had any indication of that.

I bought the rebuilt motor with ~ 26 hours on it, the prior owner bought some used heads and just lapped the valves, possibly truck heads and my bet is that particular valve was a little thin on the edge.

Plausible?

Will be shopping for a long block as I am not expecting more that a couple hundred hours out of this engine with .040 pistons.

 

[dubs283]

I dont think it was the fact I was running at 3800 RPM, that could shorten the life of the motor but the valve shouldn't have failed, carb could have been slightly lean at that RPM, but why just that cylinder?

water intrusion

3800 rpm = piston goes up and down in the cylinder just over 60 times every second, firing half of that so ignition 30 times every second. water does not burn, no matter how hard you try it just wont ignite. it will however create pressure, and with increased pressure comes increased heat. do that 30 times a second for many seconds and its easy to see how a valve fails

 

[AKJohne]

water intrusion

3800 rpm = piston goes up and down in the cylinder just over 60 times every second, firing half of that so ignition 30 times every second. water does not burn, no matter how hard you try it just wont ignite. it will however create pressure, and with increased pressure comes increased heat. do that 30 times a second for many seconds and its easy to see how a valve fails

You have mentioned water several times, certainly its possible to cause this, however where was this coming from...? intake? typically cylinder pressure much higher than a 15 lb cap, so combustion gas usually goes to the cooling system and I saw no indication of that and in fact have a hydrocarbon sniffer and nothing showed up there. Certainly it could draw some in on the intake stroke, but I wasn't using any coolant, I dont mark the bottle, but I check it daily when on the water as I did have a leak at water pump that was irritating. Now fixed.

The exhaust manifolds...? This would mean one of the gaskets at the mannie/riser or riser/elbow was breached, no tell tale on the exterior, no coolant in the mannie when removed. I sucked it out first, but the mannie was dry inside. I just changed the elbows & gaskets 30/40 hours ago. I have been using the Quicksilver gaskets here as I think they are excellent and paint the surfaces before I assemble. The exhaust system was tight and leak free. I didn't see any questionable areas on the gaskets.... I am not convinced it was water/coolant.... just wondering why you are so convinced of this?

 

[Scott06]

The 02 plate is NA, might have to make one. Picked up the heads yesterday, all new intakes as they were too thin to recut, guides and exhaust valves OK, new seals on the guides.
Lilley will never get a definitive answer on why that valve failed, I dont think it was the fact I was running at 3800 RPM, that could shorten the life of the motor but the valve shouldn't have failed, carb could have been slightly lean at that RPM, but why just that cylinder? Obviously got hot and was on the edge of detonation if it wasn't already detonating slightly, however no signs of that on the piston. Possible intake leak could have caused a lean condition.....? Although I never had any indication of that.

I bought the rebuilt motor with ~ 26 hours on it, the prior owner bought some used heads and just lapped the valves, possibly truck heads and my bet is that particular valve was a little thin on the edge.

Plausible?

Will be shopping for a long block as I am not expecting more that a couple hundred hours out of this engine with .040 pistons.

Others make the o2 sensor plate as well. I dont think you will get an answer either, just thinking when you get it all back together bring able to see fuel ratio and go from their

 

[AKJohne]

Others make the o2 sensor plate as well. I dont think you will get an answer either, just thinking when you get it all back together bring able to see fuel ratio and go from their

I looked some and did not find one, will keep looking, paste link please if you know of another source. thanks

Having trouble getting the exhaust head to manifold gaskets. Shipping, covid, who knows. I checked a local shop that does a lot of engine replacements and he said use RTV, he said that Kodiak marine (KEM) and many others do not use gaskets on new engines... What say you guys?

 

[todhunter]

Looks like the Hardin Marine plate is just temporarily out of stock...it says you can order it but that it won't ship until the 6th...you'd just have to wait a few days...not that long.

Haven't done any AFR tuning on a boat, but on a car...it's definitely the way to get fuel dialed in.

 

[Scott Danforth]

I looked some and did not find one, will keep looking, paste link please if you know of another source. thanks

Having trouble getting the exhaust head to manifold gaskets. Shipping, covid, who knows. I checked a local shop that does a lot of engine replacements and he said use RTV, he said that Kodiak marine (KEM) and many others do not use gaskets on new engines... What say you guys?

felpro marine exhaust gaskets. can get from summit racing.

 

[Scott06]

I looked some and did not find one, will keep looking, paste link please if you know of another source. thanks

Having trouble getting the exhaust head to manifold gaskets. Shipping, covid, who knows. I checked a local shop that does a lot of engine replacements and he said use RTV, he said that Kodiak marine (KEM) and many others do not use gaskets on new engines... What say you guys?

google is your friend https://www.google.com/search?q=mer...57j0i22i30.6743j0j15&sourceid=chrome&ie=UTF-8

Any SBC exhaust gasket will work summit racing has a dozen different manufacturers gaskets in stock

 

[AKJohne]

The issue with ordering is the fact I am in Alaska and shipping times have become extended. I prefer to use OEM gaskets, I may see what NAPA has I.S. locally.

I have a trip planned with our daughter and hoping to pull that off by the end of the month.

Thanks for all the help/ideas.

 

[Scott06]

Napa will be fine any good quality gasket like fell pro will work. You always can stab the o2 sensor in later if you go that route.

 

[Rick Stephens]

I prefer to use OEM gaskets, I may see what NAPA has I.S. locally.

LOL. Isn't that contradicting yourself?

 

[AKJohne]

Napa will be fine any good quality gasket like fell pro will work. You always can stab the o2 sensor in later if you go that route.

Will see what they have,

LOL. Isn't that contradicting yourself?

Probably..... HAHA....... by OEM I meant mercruiser/quicksilver, NAPA will not have them, IMO they are best for mannie/riser/elbow, probably not as critical at the mannie/head. I dont know what they are made of, looks like graphite impregnated...? In any case they sure seem to do the job..

 

[AKJohne]

Motor is back together and running, valve's, timing & carb set, compressions all between 150 & 165. I think we are good for a another 100-500 hours, maybe more...!
Been pondering this valve issue and nothing is pointing to detonation, lean or water I simply believe the valve was thin and got hot. The shop that rebuilt the heads replaced all the intakes as there was not enough left. We bought this motor with 26 hours on it and the PO and bought a used set of heads and simply lapped the valve's, who knows what they were off of or how many hours/miles were on them. in that sense 550 hours isn't all that bad. Once a valve gets hot and doesn't seat, things go down hill quickly.
A couple of pics with it all back together, and yeah i do try to keep the bilge that clean, every time I get a CG inspection, I make em crawl over the side and look in the bilge....!

 

[Scott06]

Nice clean install good luck

 

[Lou C]

I thought the exact same thing, what a nice installation. One day my engine room will look like that lol.

 

[nola mike]

I thought the exact same thing, what a nice installation. One day my engine room will look like that lol.

Mine looked like that for about 5 minutes after my motor install till I lost all my oil into the bilge

 

[AKJohne]

I made a mistake on the intake manifold and had a leak on the backside. Mostly due to the fact I was stingy on the "right stuff". However it did provide the opportunity to change out the head to manifold intake gasket.
I was in a time crunch and waiting for gaskets to come in that had been ordered (Fel-Pro marine). I used a Fel-Pro from NAPA instead. What I noticed is the heat riser in the center of the manifold from the exhaust valves was getting hot and baked off the paint.

When I took it apart I noticed the opening was fully open compared to the marine style gasket. My old gasket had a small hole as well. I dont know if this a SBC GenI/GenII thing or a marine thing... I dont see any reason for the heat riser on a marine motor... IMHO...

Always learning, sometimes its painful and sometimes its just annoying...

 

[Lou C]

With the old school well type choke you need the exhaust crossover with an electric choke you don’t .

 

[Rick Stephens]

No need for any hole there at all.

With burned paint you probably should pull the motor and repaint

 

[AKJohne]

No need for any hole there at all.

With burned paint you probably should pull the motor and repaint

Thats what I was wondering, does someone make a "holeless" gasket...?

Paint of course... ha, did touch it up while the intake was off. Rust never sleeps...