Wot @ 3000 rpm?

[brewern]

Re: Wot @ 3000 rpm?

If you have a bad cam lobe, and Chev engines had their share back then, you have a constant partially opening valve meaning that the required air for that cylinder will be reduced. if the lifter is adjusted properly for that bad lobe, there still will be no valve noise. Since an engine is an air machine, and only 4 cylinders, it could seriously affect performance if really worn.

A collapsing hydraulic lifter on the other hand, if leaking, can collapse under pressure. This does 2 things: It won't open the valve fully so you have the same problem as a rounded cam lobe but also, when the rocker turns it (the valve) loose, it (the lifter) may remain in the collapsed state for a half second which is enough time for the rocker to leave the valve then re contact it when it recovers and WALA you have a tick.

I wouldn't expect all your lifters to collapse simultaneously. One or two maybe. So you should be able to go down the valve train with the cover removed and engine idling with something like the tube that paper towels are rolled on and find the ticker(s).

HTH,
Mark

The problem is the tick doesn't appear when idling. Watch the video and you'll see the tick only starts after the boat is under load. I can rev the engine all day and no tick.

 

[Texasmark]

Re: Wot @ 3000 rpm?

The problem is the tick doesn't appear when idling. Watch the video and you'll see the tick only starts after the boat is under load. I can rev the engine all day and no tick.

That supports my leaking lifter theory. At idle the lifter has time to pump back up and follow the rocker arm whereas at higher speed it doesn't.

Mark

 

[brewern]

Re: Wot @ 3000 rpm?

That supports my leaking lifter theory. At idle the lifter has time to pump back up and follow the rocker arm whereas at higher speed it doesn't.

Mark

Well, we have one more trip to the lake this year before school starts. I guess after that, I'll start pulling the motor out and getting my hands dirty. I need to find out where the minor oil leak is coming from, replace any sels that need it, change out the lifters, and look for anything else that needs maintenance. It should be a fun winter!

 

[brewern]

Re: Wot @ 3000 rpm?

3000 is low. However, what tach was used and is it set properly for your engine? If accurate is the carb opening fully, is the spark advancing as the engine revs up? Is it firing on all cylinders? How is the compression?

I should be able to get my hands on a compression gauge this weekend. Does anyone know the standard compression I should expect for this engine? Also, will a compression test expose if a lifter is failing?

 

[jimmbo]

Re: Wot @ 3000 rpm?

You are certain it is lifters? Not the fuel pump? Not a crank or rod bearing? Listening to the video it sounds like can full of marbles being shaken. Only once the camera operator is aways from the engine do I hear a distictive tick/knock

 

[brewern]

Re: Wot @ 3000 rpm?

You are certain it is lifters? Not the fuel pump? Not a crank or rod bearing? Listening to the video it sounds like can full of marbles being shaken. Only once the camera operator is aways from the engine do I hear a distictive tick/knock

No, at this point I have no idea whatsoever the problem is for certain.
If someone can give me a the steps, in order of what I should check, I'll be glad to post the results back here. As mentioned, I'll do a compression test on it, probably this Sunday.

As for the fuel pump, I did have a clogged fuel line at one point, so I removed the line and blew through it and it was very difficult to blow through. This was the rubber line, that leads up to the side of the carb, not the metal line. But, when I was debugging the problem, I detached the metal fuel line and turned the engine over. The fuel pump shot gas up 2-3 inches I guess. So, I don't have any pressure readings, but it's definitely pushing gas through. I did replace the rubber line.

I have no ideas about crank or rod bearings at this point in my trial by fire learning....

 

[jimmbo]

Re: Wot @ 3000 rpm?

What I was asking about the fuel pump... the pump has a rod or a lever that rides on the camshaft that moves the diaphram that pumps the fuel. A worn cam lobe, rod or lever could make a ticking or knocking aound.

 

[brewern]

Re: Wot @ 3000 rpm?

What I was asking about the fuel pump... the pump has a rod or a lever that rides on the camshaft that moves the diaphram that pumps the fuel. A worn cam lobe, rod or lever could make a ticking or knocking aound.

Well there's my ignorance rearing its ugly head again. I was under the impression (for no specific reason) the fuel pump would be an impeller driven pump.
Obviously the pump is pumping gas since the motor runs, but how would I check to see if it's the cam shaft that's causing the problem? I think next time I'm on the water I should take, as mentioned, a tube and try to isolate where the sound is coming from. Until then, would a fuel pressure measurement help maybe? I think I saw somewhere on these forums how to put a pressure gauge inline to check it.

The Kentucky river is right down the road. I think Sunday I will go put her on the water and try to isolate the sound, and also do the compression check.

Thanks,
brew