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Old 08-31-2007, 02:25 AM   #1
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Recently I had the exhuast manifolds replaced in my 454 big block 86 Holiday Rambler class A. Before changing the manifold, the engine sounded almost like a dragster...the usual problem of warped manifolds.

Now the engine is very quite; however, when idling I hear a noise that is the sound of a knock to heavy tap. The sound goes away when I rev up the engine. The engine has 74,000 miles and has never given any problem.

What could this be:

1. Loose rod
2. Wrist pin
3. Tappet noise
4. Fuel pump rod tapping again the fuel pump arm
5. ??

What is the most like cause (1 - 5)?

Is there any way to isolate the cause without tearing down the engine?

I keep the oil changed regulary....is there anything I should be in my oil that might release the stuck tappet if that is the problem.

All opinions requested,

Thanks, HEMI
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Old 08-31-2007, 02:25 AM   #2
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Recently I had the exhuast manifolds replaced in my 454 big block 86 Holiday Rambler class A. Before changing the manifold, the engine sounded almost like a dragster...the usual problem of warped manifolds.

Now the engine is very quite; however, when idling I hear a noise that is the sound of a knock to heavy tap. The sound goes away when I rev up the engine. The engine has 74,000 miles and has never given any problem.

What could this be:

1. Loose rod
2. Wrist pin
3. Tappet noise
4. Fuel pump rod tapping again the fuel pump arm
5. ??

What is the most like cause (1 - 5)?

Is there any way to isolate the cause without tearing down the engine?

I keep the oil changed regulary....is there anything I should be in my oil that might release the stuck tappet if that is the problem.

All opinions requested,

Thanks, HEMI
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Old 08-31-2007, 07:19 AM   #3
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#3 & #4 in that order would be my guess........

How is your oil pressure? And what weight/type oil are you presently using....

Jim
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Old 08-31-2007, 09:11 AM   #4
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Jim, many thanks.

Oil pressure has never been a problem....it runs steady between the max mark and the middle mark on the guage....right around 70. And it stays this way even running for several hours traveling the hot Mahave Desert...where in Needles CA it was around 115 outside.

I am the third owner...I bought it in Spring 2005 in OR. I Immediataely changed all fluids and put Rotella T 15-40in the engine. The 2nd owner, a friend in OR, took great care of the unit-always garaged and the original owner was the owner of an OR RV dealership and I can only assume that his mechanic shop would have taken care of the unit.

I appreciate your "guess"; others who I have talked with also think it is 3 or 4....I might buy an electronic engine stethoscope to determine if I can detect any "knock" sound coming from the fuel pump rod.....

The unit is a wonderful rig now that the manifolds have been replaced...I've posted a picture of our rig + our Bigfoot/F350...on our return to FL from OR.
HEMI
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Old 08-31-2007, 05:18 PM   #5
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I'd say #3 or #4! If you can, Try a screwdriver and put the blade to the valve covers and also in the area of the fuel pump and see if you can figure out where it seems to be coming from. Put the handle end to your best ear! Good luck! Capt.
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Old 09-01-2007, 04:12 AM   #6
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Thanks Capt. Dan; I will give it a try and report back to the forum, HEMI
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Old 09-01-2007, 07:20 AM   #7
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I worked at the Chevy engine plant I in Tonn NY as a engine tester.There we took engines and put them in test stands to run test them on propane.We there used a long pc of bar stock with a handle on one end and sound check them.If it is the rod for the fuel pump,it is possible the ramp for the rod on the cam is worn out and then a cam change would be needed.A lifter noise could involve only a lifter,but if it was mine,I would want to do a cam change in any case to be sure because of a bad lifter I didn't have wear on that lope of the cam too.The best case of this is a rocker nut back off and a reajustment is all that is needed.If that is the case you need to be sure in that valve the valve spring doesn't have issues as well.You don't want to do patch repairs on this.Let'e face it,we all want to travel trouble free and to tow these things can cost lots once they have brokendown on the road.To remove the valve spring you put air pressure into that spark plug hole and remove that valve spring.Look to see if it is broken and check the spring pressure at the cams's rated lift to be sure it hasn't lost it's pressure.If it involves the cam,if it was mine,I would take the oppertunity to do a cam change ungrading to a RV style cam,lifters,springs to pick up aliilte more power at the same time.I don't think it involves a rod bearing given what you have said about still having good oil pressure.But of course that is with the limits of a web site and not being there to hear what you are calling about.A heavy knock with out any lost of oil pressure is normally a piston pin issue.I owned a recon SBC that someone had put it before I bought this 10' cube van.At idle for sure you could hear the pin knock,but off idle it would go away.BTW:I don't think much of the recon's.Going up a hill like in Pa you could hear the pin knock because I was putting it under stress and lowering the RPM.I suggest as I said,don't do patch work repairs because it will come back at you when you least want it to.Your pictures of your rig looks really nice.Worth spending money on it for sure.Wish I was there to help your out.Good luck on this problem.Let us know what you find.Gary
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Old 09-01-2007, 03:21 PM   #8
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Gary, thanks for your detailed analysis. As you know it is a major job to remove the engine; there is so little room to work on the engine while it is the rv chassis.

The knock sound does seem to go ahead when rps are increased...and you say this is a piston pin issue....

Yes, best not to do a patch job...as more serious problems occur later.

Thanks a lot, HEMI
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Old 09-01-2007, 08:55 PM   #9
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Hemi,
Here is the most important advise I could give you.If you don't feel you can do the repair yourself,don't do it.It sure is tight on these RV's.So then take to a repair shop you trust being a informed consumer.If the price of the repair seems high-remember you are paying for that tight engine compartment.You know full well the price of a new MH and that makes the cost of this repair easier to take.
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Old 09-02-2007, 07:00 PM   #10
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Hemi, I hope it isn't a motor! Good oil pressure is telling you that the motor is sound. I'd think a lifter knock is the problem. Like I said, Check with a pry bar or something like that and see if you can figure out what is making the noise. You didn't say if you had replaced the timing chain and they can get slop by 75,000 miles. Could be time for timing chain and adjustment of the lifters and maybe a rv cam. I would leave the cam alone if it looks or sounds ok. The main reason I took the motor out was the transmission needed to be rebuilt and the engine comes out easy thru the front of the older homes. I used a cherry picker to get mine out. You have a plate that mounts where the carb. mounts up and then the Cherry picker is hooked to the plate and you lift it and the picker rolls back and both the trans and engine come out pretty easy, Or mine did. I had a 120,000 Miles on the engine and trans. Both are now done. I added a lot of stuff to mine and went father than most people would have gone with in a older home but I ain't Normal!! Duh!!
I will die with my boots on and they can just make a hole big enough for me and Dusty! Have a [I hope] good one, Capt.Dan
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Old 09-03-2007, 03:04 PM   #11
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Hemi,Get any farther??????.let us know.
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Old 09-03-2007, 03:53 PM   #12
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Thanks Capt Dan and fleamarketer...

I am old 50s hot rodder; thus pulling an engine, rebuilding etc was great and easy during those days.

The RV is another thing; fleamarketer has some good advice...I just don't think I can muster the energy at 68 to pull the engine although I have a large rv garage and plenty of tools....I would need help in pulling the engine through the front....

About two months ago I labored on whether I should replace the exhaust manifolds myself--they were original and leaking....I was worried about studs breaking off and then attaching the manifold back to the exhaust.

Finally I took the RV to a garage that did manifolds etc....they worked 3 weeks on the rig...it was a terrible job to get the studs out...a few they had to weld a nut head to...then of course the new manifolds (which was very difficult to fine) outport did not match the exhaust pipe and thus some serious welding was done. I would have been in a terrible mess had I tackled this job...yes fleamarketer I took my own advice...which would have been yours too.

Something did happen however in that repair; when I got the rig home I noticed that the dip stick was out about 4-6 inches...I tried to push it in....after 20 minutes of wiggling I finely got it in. Apparently the mechanic must have put a little bend in the dipstick tube.

Any ideas on how to solve this problem?....I put a point on the dipstick but that did not help. I think a thinner dipstick would work...but where and what to get? Any ideas. One person on irv2 said that an Astro dipstick is relatively small...I need to find someone with an Astro. Also the RV dipstick is very long...more than 4 feet.

I do appreciate your ideas.

On progress: none yet, it is so hot and humid here in FL that I don't have the energy to tackle any kind of job on the RV outside or even inside (the RV garage has no AC)

....I usually start the rV every 2-3 weeks and run around the block to keep things from drying out.

Weather here will improve in late October and November...then I can do some work and will report to you, if not sooner.

Hemi
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Old 09-04-2007, 07:01 AM   #13
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Hemi,
Take out the dip stick and see if you have the same ticking problem.LOL-wouldn't that be a kick in the butt.
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Old 09-04-2007, 06:08 PM   #14
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Oi!! Wouldn't that kick you in the head!!??
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