Engine noise

[USMC1812]

5th run of the year on the new setup, BBC 502, tunnel ram and 2 TPC 650 DPs. Get it out on the water, it's running for about 15 min and we hear a backfire followed by a banging/squeaking noise. Oil pressure is 50 psi and water temp is 180 with 20 psi water pressure at the intake manifold. The noise sounds like it's coming from the front of the motor but, with the headers it is hard to pinpoint. I changed the oil prior to the trip and it still looks good with no sign of water. When I got it home I cut the filter apart and did not see any metal. I did not disconnect the u-joints but they still look good. I checked the jet and the impellor looks good and the shaft is free of vertical play. After I heard the noise I shut it down for awhile a checked out what I could on the river. After about 45 min, I fired it up and noise was still there and sounded like it was getting worse. The motor still seems to run good, except for the noise. I does not sound like broken rod, especially with the motor still running well, but something with less mass. Does anyone have any suggestions where to look next? There is nothing that is making contact with the dampener or alternator. I changed to a Melling high volume oil pump but have not change the stock timing chain yet. The distributor is a new MSD pro-billet. Is a internal failure always indicated by metal in the filter?
Thanks for the help!
Doug
[ July 20, 2003, 11:49 PM: Message edited by: USMC1812 ]

[Rexone]

I'd pull the valve covers and check the rockers, pushrods etc first. This is a very easy and quick inspection relative to pulling the engine all apart.
Since you have oil pressure and no metal I'd suspect upper end. The fact that it backfired points to something in the valve train breaking possibly. Did it backfire out the headers or the carburetor?
I definately would not run it any more until you figure it out. frown
[ July 20, 2003, 11:52 PM: Message edited by: Rexone ]

[USMC1812]

Thanks Rexone,
It only backfired once, I did not see which way it went.
I pulled one side off and had a look. I did not see anything crazy, all rockers are tight and the pushrods as far a I can tell are indicated. The only thing that I saw was a little bit of stuff that looked like white grease. I'll pull the other side in the morning, what exactly should I be looking for other than the obvious broken parts?
Here is any old pic of the motor but the valve-train is the same. Nothing other than the hoses, exhaust and carbs have change in the top end since this pic.
http://www.***boat.com/image_center/data/520/218New_Motor_1-med.jpg
[ July 21, 2003, 12:07 AM: Message edited by: USMC1812 ]

[Rexone]

Anything out of the ordinary. Loose or tight rockers (you may have to tap the engine around to see this), bent pushrods. If it's a valve train problem that is severe enough to cause a backfire and a bunch of noise, it shouldn't be hard to spot.
So did the engine just backfire one time or did it continue to over and over, or did you just shut it off at that point? Did it continue to bang / knock if it kept running?
more info = better answers. :)

[USMC1812]

I only heard one backfire and then the noise. The second time I ran it the noise was still there but the motor seemed to run fine, no backfiring. When the valves are closed should the rockers be a little loose with the type of set up that I am using? I really appreciate the help!
Doug

[Rexone]

USMC1812:
I only heard one backfire and then the noise. The second time I ran it the noise was still there but the motor seemed to run fine, no backfiring. When the valves are closed should the rockers be a little loose with the type of set up that I am using? I really appreciate the help!
Doug If you have solid lifters you should have a little clearance with the valve closed and the cam on the heel (in the .015 to .030 range depending on the cam). If you have hydraulics you will have no clearance as they have a slight preload. Look for pushrods / rockers that are obviously loose or not moving much even though tight.
Did you run the engine hard at all after this happened or just cruise in? Sometimes engines seem like they're running pretty good a low speed on less than 8 cylinders and you may have been so fixated on the noise you didn't feel a miss. Just a thought.
[ July 21, 2003, 12:19 AM: Message edited by: Rexone ]

[USMC1812]

They are solid lifters. The cam I was told is a 670 lift. The second time I ran it I think that I was only up around 3500 RPM or so. I am running a set of Rewarders without baffles, would I hear it if it did drop a cylinder? It was also running rich on av gas.
[ July 21, 2003, 06:55 AM: Message edited by: USMC1812 ]

[Rexone]

I would think so, but you may have been focused on the noise and getting it in rather than how it was running.
btw, completey guessing here. This is just the area I'd check first based on what you've said and also because it's easy to check and eliminate possibilities. May turn out to be something completely different. Hopefully something minor. The fact you had good oil pres, not overheated, and no metal are good things.

[USMC1812]

I'm guessing too! Most of my engine knowledge comes for the farm and we did not have anything like this there. If we were talking about an M1A1 tank here it might be a different story. As far as the boat goes I have about exhausted any ideas that I have. I want to make sure that I have eliminate as many possibilities as I can with the motor still in the boat. Another thought is that the motor might not have ran long enough to get metal in the filter, although I would think that with the speeds that we are talking about here that it would not take very long. Thanks again Mike!
Doug

[Rexone]

No problem Doug, I'll be anxious to hear what you find. We all learn something from these situations. Good luck. :)

[Sand Dawg]

Just my .02 here but check all the plugs too, but a back fire and then noise sounds like bent push rod in the valve train.

[Moneypitt]

Yes, all of the above are possibilities. And look at the plugs for hints of damage. But what about the squeak? When things that are suppose to be lubed, aren't, they squeak. Are all the carburator parts still in the carbs? Could be a piece of "whatever" wedged against a cylinder wall. How about a broken cam button? I can't tell what type of fuel pump you use, but mech. pumps have been known to squeak. Nice looking engine, with that much camshaft, you might consider a stud girdle set up...Hope its minor...Moneypitt

[Hallett19]

I had an oil pump go 'out of round' that caused similar problems/sounds.

[058]

This may be a long shot, check for a broken valve spring.

[USMC1812]

Ok, I found the problem. I pulled the sparkplugs and found that one of the electrodes was bent over and pretty jacked up. So, as I was standing up I grabbed the intake and that's when I found that the upper portion was loose. So after that, the problem was crystal clear. I pulled the carbs and just as I thought one of the bolts holding the manifold together was missing. I pulled the intake and header off and was able to find only one small piece of the one inch + bolt. I can see what is left of the bolt or the piston, I'm not sure which, when I look through the sparkplug hole. I have never removed a head before, can anyone give me a step by step walk-through or point me in the right direction? I would much rather do it myself and learn than pay someone to do it for me. Thanks again for all of the help!
Doug

[DEL51]

I would pull the heads off and check the pistons and valves.I had a small piece of a valve break off break off and enter the cylinder next to it. This small piece pummelled the iron head and piston.I was able to reuse the piston and head after some clean up and new valves it worked fine. Good luck Marine,Chris P.S keep us updated.

[USMC1812]

I just got done pulling the head. The piston is trashed and the exhaust lifter is bent possibly along with the valve. But on the bright side the cylinder is fine, not one scratch. I am glad that I shut it down when I did or it might have been worse. I feel like a dumbass for not checking that these bolts had loctite on them before I put the intake on the motor! But, all in all it has been a relatively inexpensive learning experience. Again thanks for the help! I'll post some pics tomorrow for your viewing enjoyment.
Doug