Motors are wasted

Aggressor Tom · Sep 17, 2003

My season has officially come to an end. Both motors have crapped out and will not be rebuilt until winter.

502 efis all stock. Refreshed after last season and I got around 40-50 hours on the motors since refresh . Spent the day running fairly casual around 40-60 mph an occasional punch up to 70mph never hitting full wide open. Suddenly the starboard motor felt a little sluggish and when I slowed down to an idle I opened the hatch to find oil everywhere. Had to shut both motors down and was towed in.

Temperature was normal on both motors, had good oil pressure and didn't run the boat hard at all. One motor melted down the 4-6-8 pistons and the other motor had a hole the size of a dime in the top of the #8 piston. Any theories out there? I find it awfully odd that both motors crapped out at the same time, and in addition I ran the boat all summer without any problems.

Bayley · Sep 17, 2003

...this had nothing to do with you trying to keep up with some other guy in another Dominator, did it?

Sorry about the poke, I too am feeling your pain lately.

A quick question for all others out there: I was talking with Tom about this over my lunch break, and I was thinking that fuel delivery could have played a major role in why things went so bad. Basically I'm thinking that the pistons melted because they ran hot. Since the water temp gauges always looked good, I'm guessing that it wasn't due to inadequate water flow.

What do you guys think about faulty / underrated fuel pumps? This boat was originally equipped with carb motors and was recently rigged for EFI's. If fuel pressure was starting to drop off at upper RPM's, this could have been what burned up the pistons.

Now I'm not 100% sure on this, but I do believe the fuel rail on the EFI's feed the cylinders in this order:

7-5-3-1-2-4-6-8 (this is not the firing order, simply which injectors are in series with each other)

I'm thinking that if fuel pressure was a problem, number 8 would be the first to see a problem... followed by number 6... followed by number 4... etc. Since 8, 6, and 4 were all burnt up on the one motor, it sounds like there wasn't enough fuel running to these injectors. I would have to believe that number 8 looks the worse, followed by 6 then 4. I'm also more suspicious about this theory of mine after hearing that number 8 on the second motor was also burned up. I would take a good look at numbers 6 and 4 on the second motor and see how close they were to burning up the pistons.

Another key point in this theory of mine, is that low power output of the motors. Don't take offense Tom, but that boat should have been faster with 502 Mag's than the 73 - 75 mph your were running in it. If the engines were running lean (which would significantly reduce power from the start), you may have been kicking off the knock sensor which would have pulled about 10 degrees of timing out of the motor (yet again, reducing the power). I'm not 100% sure on this, but I'm rather confident that the MEFI-3 systems do not have the capability to adjust the amount of timing retard. It's either full timing, or 10 degrees retarded. Again, please correct me if I am wrong.

I'm starting to get suspicious that fuel delivery is what may have caused my own piston demise. Fuel pressure gauges have now officially been added to my Christmas "wish list". Tom, you may want to seriously consider getting a set yourself. If my theory is right, fuel pressure on even a stock engine needs to be monitored.

-Bayley

turbo2256 · Sep 17, 2003

Something like that is usally caused by wrong heat range spark plugs, improper timing, and/or fuel starvation.
Chevy motors also suffer from the cirulation pump pumping more water to one side of the motor over the other. Water distribution to the rear cylinders is also poor. Most BBC motors the two front and two rear cylinders show the valves running hotter than the middle 4. With out steam lines a mildly or better juiced BBC will not live on a dyno for long. On the older BBCs if you look at the water transfer holes between the head and gasket and the block one hole in the rear (near #8) and the front one on the opposite side has a missmatch. I corrected this on my motor in the Seabold and upon removing the heads later on saw valve coloration to be almost even. I have yet to get into the newer generation BBCs.

Mattjtowne · Sep 17, 2003

Good point Bayley...

Bayley,
Your idea makes alot of sense.. If you go to Jegs online and bring up their Marine Holley fuel pump its states that they do not recommend this pump for fuel injection systems..
I had a high end Mallory pump that was off a big block carburated engine and gave it to a buddy to use in his vette with a dfi system on a 383 and the engine builder said not to use it.....

There is definitely a difference in pumps for carbs and fuel injection.. Im assuming it has to do with psi and the ability to keep that psi under certain restraints..

Thats a very good theory and keep us informed with addition information.......I bet alot of guys do not change the pumps when switching to injection.........

Just my .02

turbo2256 · Sep 17, 2003

I have also noticed that in fuel injected motors if timing, fuel delivery, and or over heating occurs you end up with holes in the pistons much quicker than carb motors or wetted manifold designs. My thinking here is the cooler fuel in the manifold saves your butt. The FI motors are hurt before some signs are apparent and by the time you can read them its to late.

turbo2256 · Sep 17, 2003

Fuel injected engines require 39 to 40 psi under normal as designed conditions if Tom's pumps were from a carb motor he would be lucky it ran at all.

turbo2256 · Sep 17, 2003

I believe even the fuel filters are different the paper element type will come appart under the pressure of a FI system and are not recomended.

turbo2256 · Sep 17, 2003

Anothe possibility is just what was in those gas tanks to begin with. Guessing it was a repo boat.

Bayley · Sep 17, 2003

Good point about the carb vs. EFI fuel pumps. To play devil's advocate, however, I've been able to get some "carb" fuel pumps to run at 20 psi even though they were rated at a maximum of 12 psi. Also, I've seen fuel injected motors run with as little as 5 psi. I had to drive my LT1 Impala SS about three miles one day when my main fuel pump crapped out and my little "in line" pump for the Nitrous system was all I had. Granted, I babied the thing and never did any damage... but fuel injection motors can run on significantly less PSI than what is required. It won't run very well, but it will run. I'm still suspicious about those fuel pumps. Burning up two perfectly good motors sounds way to coincidental to be internal failures only (i.e. bad rings or pistons).

chjohn · Sep 17, 2003

Both engines at once? I fully agree with the fuel pump being wrong. But to be on the safe side I would also check out the gas very closely. Water, old, octane etc???

I will hold a small Irish Wake in my garage for your motors.

Bayley · Sep 17, 2003

Don't forget our recently departed Canadian friends while you are it!

Raypanic · Sep 17, 2003

The injectors batch fire 4 at a time, 1,4,6,7 and 2,3,5,8. I m not sure where you are going with the order but it sounds like fuel pressure is the problem. My EFI runs about 40 to 45 PSI.

Aggressor Tom · Sep 17, 2003

I ran better than 50 hours with no problems, why both motors at once? I ran the Sunsation rally and a few fun runs in those hours logged without incident.

The fuel pump theory is sounding the most logical, and yes one of the theories was I must have changed plugs to an automotive application, never touched the plugs. I purchased the boat a year ago and have run better than 600 gallons of gas thru the engines so "old gas" is not the problem.

Chasing Bayley, that could have been a problem!

Bayley · Sep 17, 2003

Ray,
What I'm suggesting is that the supply of fuel is possibly greater at some injectors, and less at others. If the fuel supply is inadequate for four injectors, then only the injectors closest to the supply of fuel (i.e. pump / regulator / filter / whatever) would be getting the fuel. The further away from the source you go, the less fuel would be available.

Yes?
No?
Should I smoke more crack?

Since I've got your attention Ray, which cam did you go with for your 502's with Whipples?

dominator scott · Sep 17, 2003

Tom,my suggestion would be to go to carbs and intakes
after you re-build the engines.
OH MY GOD!I just happen to have a set of carbs and intakes sitting on my work bench!!!!!

chjohn · Sep 17, 2003

Aggressor Tom said:
I ran better than 50 hours with no problems, why both motors at once? I ran the Sunsation rally and a few fun runs in those hours logged without incident.

The fuel pump theory is sounding the most logical, and yes one of the theories was I must have changed plugs to an automotive application, never touched the plugs. I purchased the boat a year ago and have run better than 600 gallons of gas thru the engines so "old gas" is not the problem.

Chasing Bayley, that could have been a problem!

Maybe I should have said bad or tainted gas rather than old. I really doubt that the gas is the problem but I have pumped bad gas from a station in the past and I tend to err on the side of caution. Check everything and anything.

Good Luck

runnin gun · Sep 18, 2003

sound to me like the fuel pumps or just one are getting weak or the regulater craped out. I had the same problem on aanother engine i had put it was due to the big 350 shot of nos. It ran like a bat out of hell to it melted two pistons and spit a rod but i won the race. Braging rights
terry

DonMan · Sep 18, 2003

Re: Good point Bayley...

Mattjtowne said:
There is definitely a difference in pumps for carbs and fuel injection.
I bet alot of guys do not change the pumps when switching to injection.........

An injected engine will not even start, let alone run on a carb fuel pump. We`re talking 6-8 psi VS. 50 psi.

Mattjtowne · Sep 18, 2003

ACTUALLY...

Actually a efi setup will run on a standard fuel pump until higher rpms...

Mattjtowne · Sep 18, 2003

Not the question

I dont think the question is whether a standard pump can run a efi.. The question is whether the pumps where changed with the addition of the efi and what psi are they holding now...

Every efi system i checked out recommended a new pump that supports the demand of the efi...

I think Bayley is definitely onto something since both motors let go at the same time...

We do have a guy in the neighborhood that has a 28 Pantera with big motors that went south this summer after getting water in the tank after filling up at a neighborhood restaurant.... I tried to get ahold of him but had no luck....to see what actually went wrong in the motors...

Motors are wasted

Aggressor Tom

Bayley

turbo2256

Mattjtowne

turbo2256

turbo2256

turbo2256

turbo2256

Bayley

chjohn

Bayley

Raypanic

Aggressor Tom

Bayley

dominator scott

chjohn

runnin gun

DonMan

Mattjtowne

Mattjtowne

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