Thread: Marine BBC has squeek in valve terain and has minor backfire

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I have a 454 Chevy in a jet boat. I have been chasing all kinds of problems since a local auto store did a crappy job on a rebuild many years ago. Being that it is in a boat has taken longer than usual to comb through everything. However, I have a high pitch squeak and backfire coming from the valve terain on the right side of the motor.

I do not know how to begin to tackle diagnosing the problem so I can fix it. It is running hudraulic lifters and roller rockers on aluminum heads. I don't know weather it is a valve or a lifter or what cylinder it is coming from. Could the valves need readjustment? I imagine for some reason something is causing a exhaust valve to be out of adjustment and causing a backfire... If anybody has any experience or ideas dealing with this I could use some help.



Thanks.

to me it sounds like a lifter and the cam... Since its is one or the other or both I would pull it down and look then you know for sure what it is. boat season is coming

with no load on the eng. and the air cleaner removed hold the rpm sready at about 2000 if you have a steady pop pop pop from the carb. you have a flat cam (vary common problem with the politicaly correct oil we have today ).....ted

There is no pop pop from the carb. It is only backfiring/poping from the exhaust out of the right side that I am hearing the squeaking come from. Maybe I need to try and replace the lifters on that side...

Originally Posted by vetteguy

There is no pop pop from the carb. It is only backfiring/poping from the exhaust out of the right side that I am hearing the squeaking come from. Maybe I need to try and replace the lifters on that side...

take off all belts run engine for a very short time just long enough to see if the nose go,s away could be water pump .alt . starter could be hanging in so cold be a bendix . poping threw ex check pulgs . then check rockers if loose if the ex rocker is loose cam could be gone or bent push rods or collapsed lifter .if lifters bottom is gone or beat up then a new lifter is not going to fix it and engine needs to come apart to get all the iron that went thru it if the cam break in failed

The only accessory the motor runs is the altinator. The cooling water comes in from the jet pump. I'm pretty positive it is not the starter hanging up. The plugs all look good on the motor. I just replaced the ignition and had pulled the plugs and looked at all of them prior to replacing it. I had the motor rebuilt about 5 years ago and at the end of that summer I did have a piston hit the valve. I took it in and they cleaned the motor out and put a sleeve in the cylinder. They had replaced some parts. I don't know what they did but they didn't do a very good job the 2nd time around. They were good at taking my money though. The past 3/4 years I have been chasing down problems when I get a chance. Last year I pulled the heads and installed new head gaskets and intake manifold seals because it had problems with oil leaks from the manifold and cooling water leaks into the oil. This year I replaced the ignition and sealed up an vacuum leak in the timing cover. I just need to find the source of this squeak so I can put an end to this nightmare.

I made the leap and spent $42 on a compression tester. I went and tested the compression and all cylinders read too little to register the gauge. I assume they were nowhere they should have been. I literally just noted it as a few psi. The number one cylinder has no compression at all. Cylinder 7 reads about 107 psi.

I imagine I need to re-adjust all the valves because it appears they are not adjusted correctly. We had pulled the heads and had to set the valve lash and we followed a set of instructions I found online. Guess it isn't quite right. Odd how I can still get it to run though.

I wondered why I couldn't get it to start and I thought it was a ignigion problem because I could get it to run on occasion it was just really hard to start. Just thought the ignition was weak. Well I got the new ignition and it must really work well because it is lots easier to start this low compression beast than what it was before I replaced it.

I guess I need to set the valves correctly so I can tell what if any cylinder it is or if the valves being set incorrectly is causing my problem. What is the best and proven method to set my valves properly? What compression range am I looking to achieve for a mildly modified BBC?

so it not hard try unhooking the alt ? you have to make a list and start crossing things off you say you know .but do you if you have not check it?? i work at a boat yard this is how we did it . has for plugs looking good many times i had boats with new plugs that were junk did you try a new plug in that hole .did you check fire order you cross 5and7 it will pop but that not the right side less it driving off the crank nose ? did you check that hole for compression did you take the valve cover off and check for the things i listed ? if all this look s good then it wipe a cam and thats nothing new for a bbc sounds like the engine as on it way out any ways and it sounds like you must of over RPM it to a point to bust a wall out of the block so 5 years of EZ use or hard ? alum rocker start to fall apart if cheap one in less time then that whos alum heads name brand ? whos rocker arms ? was the block cut for added oil to the lifters . did they use CROWER hi lubes / johnson lifter with the flat ground in them ?

I have the plugs pulled out of the engine from the compression test today. I'm going to pull the valve covers and give it a look over. I'm going to go in and re-adjust the valves as well while I'm in there, providing I do not see anything out of the ordinary. I'll take it from there and see what I can eliminate as a potential problem. Will keep posted. Thanks again.

I went down to the shop and adjusted the valves according to a a tech article online through Centry Performance:

Century Performance Center, Inc. :: Adjusting Valve Lash

I went behind and checked the compression again and see noticeable results already. There are a few cylinders I want to tweak to try and get a higher compression out of though.

Comparision results are as follows:

Cylinder Before After
1 0 124
2 a few psi 130
3 a few psi 117
4 a few psi 100
5 a few psi 125
6 107 120
7 a few psi 110
8 a few psi 135
* I noted most cylinders as a few psi because it wasn't even enough to really register on the gauge.

Now that the valves are set correctly it is running a lot better than before. It's actually running smoothly and firing on all eight cylinders. The squeak from the valve terain is gone on the right side. The backfire is not there anymore, that I can tell of.

I remember that I had paid a pretty penny for those heads. They are rectangular port aluminum heads. I don't know for sure but I'm thinking the valves are stainless? I rather do it right and have it run correctly. I wish I didn't have to pull the heads again and have to reseal and reset all the valves again but the second time around shouldn't be such a pain in the @$$.

What needs to be done to the heads to fix/improve the compression?

Now that you have the valves set and the engine is running better, you might want to drive it some, then recheck the compression and see if it has equalized some from cylinder to cylinder.... with the valves set wrong and misfiring, could have had some excess fuel washing down the cylinders and effecting the sealing of the rings......

Yeah, I'll try and run it on the trailer and bring it up to temperature then re-run the compression test tomorrow. I had a member on another fourm mention trying to adjust my hydraulic lifters like solid lifters to make sure there was nothing holding the valves open. If my results are still off I'll try that adjustment and re-checkkng to see if that may be the problem.

I'll run my checks "today", since it is already Sunday, and post the results.

Thanks again!

Originally Posted by vetteguy

Yeah, I'll try and run it on the trailer and bring it up to temperature then re-run the compression test tomorrow. I had a member on another fourm mention trying to adjust my hydraulic lifters like solid lifters to make sure there was nothing holding the valves open. If my results are still off I'll try that adjustment and re-checkkng to see if that may be the problem.

I'll run my checks "today", since it is already Sunday, and post the results.

Thanks again!

bent valves will hold them off the seat .hyd lifters will not hold the valves off the seat for very long till you wipe out the cam . you would have to run the push rod down in the lifter past the valving .so you could very well end up with burnt up valves or cup vavles and a trashed cam