Fear the worse, loud banging sound comingfrom the engine

[RogersJetboat454]

Re: Fear the worse, loud banging sound comingfrom the engine

Yes do check the stud. Some are press fit, others threaded. I suggest adjusting them all when the engine is at idle. But first, use this to get you in the ball park:

To adjust the valves, it is vitally important that the cam lobe for the valve you are adjusting is on it's base circle... the round part of the egg shaped cam lobe, not the pointy end.

INTAKE VALVE ADJUSTMENT: Rotate the engine by hand until the exhaust valve rocker begins to push the spring down on the cylinder your are adjusting. That puts the intake valve cam lobe on it's base circle. Adjust the nut while trying to move the pushrod up and down or twisting it. As soon as you feel a slight drag, and I mean SLIGHT, tighten the intake 1/4-1/2 turn more.

EXHAUST VALVE ADJUSTMENT: Rotate the engine again by hand until the intake valve compresses fully and moves 1/2 way to 2/3 of the way back up. This puts the exhaust valve on it's base circle. Adjust the nut while trying to move the pushrod up and down or twisting it. As soon as you feel a slight drag, and I mean SLIGHT, tighten the intake 1/4-1/2 turn more.

Only do this for the cylinders that are having problems.

Then, start the engine. Loosen the adjusting nut on the valve you want to adjust slowly until you hear it make a TAP TAP TAP noise. Then slowly tighten the nut until the tap sound stops. Now add 1/4 turn tighter. You may notice that it takes a moment for the engine to stabilize when you add 1/4 turn. This is normal. Move to the next valve and repeat until they are all adjusted. Button up the VCs and go boating.

If this is a true Vortec engine, I believe he actually torques the rocker nuts, rather than setting lash like the old style heads.

This I believe is the correct Mercruiser manual for the engine; Boatinfo - Mercruiser Service Manual nr. 18 - 1993-1997 - Engines GM V6 Gen II Balance Shaft
Page 43 on discusses setting up the rockers. Torque figure for a Gen + engine is 20 ft.lbs.

He may want to check to be sure his lock nut is locking.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

If this is a true Vortec engine, I believe he actually torques the rocker nuts, rather than setting lash like the old style heads.

This I believe is the correct Mercruiser manual for the engine; Boatinfo - Mercruiser Service Manual nr. 18 - 1993-1997 - Engines GM V6 Gen II Balance Shaft
Page 43 on discusses setting up the rockers. Torque figure for a Gen + engine is 20 ft.lbs.

He may want to check to be sure his lock nut is locking.

I got new rocker arms, nuts, and pushrods.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

What do I use to seal the exhaust towers that sit on top of the exhaust manifold. I know a gasketgoes bet weenthe mmanifoldand the motor , but in between the tower and manifold, the boat place had some kind of sticky clear liquid that they used.

 

[spdracr39]

Re: Fear the worse, loud banging sound comingfrom the engine

Its called a riser and it has its own gasket. The gasket is metal.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Its called a riser and it has its own gasket. The gasket is metal.

Thanks

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

BOOOO, finally made it to the lake for the first time since I repaired the motor, and I had to get towed in. I cranked it before I left with the water hose connected. It was a little slow starting but ran good afterwards.
When we put it in the lake, It crank pretty good, but as soon as I took off, I noticed it popping again and half the power. My wot rpms was 3200. After about 10 minutes it shut off, and would not crank back up.
We took off the intake manifold and put on 2 new lifters and pushrods. The mechanic did have to turn the distributor a little to line it back up and adjusted the carb a little because it was running rich and smoking the plugs. ANY IDEAS?????

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Also, if I have to replace the chevy 4.3 v6, can I replace it with a v8 and use all my parts.

 

[Bt Doctur]

Re: Fear the worse, loud banging sound comingfrom the engine

If you put the pushrod thru the rocker arm you have some serious issues. the valve stuck open and the piston pushed the valve up forcing the rocker arm thru the rocker.
"Also, if I have to replace the chevy 4.3 v6, can I replace it with a v8 and use all my parts. "
you can use the engine wiring harness with a GEN IV system, not a GEN V system
transom housing stays
everything else is a NO.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

If you put the pushrod thru the rocker arm you have some serious issues. the valve stuck open and the piston pushed the valve up forcing the rocker arm thru the rocker.
"Also, if I have to replace the chevy 4.3 v6, can I replace it with a v8 and use all my parts. "
you can use the engine wiring harness with a GEN IV system, not a GEN V system
transom housing stays
everything else is a NO.

That stinks, ran good until I put a load on it today, after replacing the pushrods and lifters. I guess tomorrow it's time to break out the compression tester again. Also, I guess i'd stay with a v6 but hope it's just a cheap fix

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

bt, i'm not a mechanic, what would make a value stick open?

 

[Bt Doctur]

Re: Fear the worse, loud banging sound comingfrom the engine

water/rust,/over-reving it past red line, cam timing, piston hitting it, lifter pumping up,hi engine temp,

 

[spdracr39]

Re: Fear the worse, loud banging sound comingfrom the engine

Before I considered replacing the engine I would pull the heads and have them looked at. It sounds like all your issues are with the top end.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Before I considered replacing the engine I would pull the heads and have them looked at. It sounds like all your issues are with the top end.

ok, opened the value cover and the rocker arms and pushrods looked good. I did a compression test and the same cylinder was 0. The rest was around 115. I turned over the key to make sure cam rod was pushing valves up and down. They moved good. So I pulled the head expecting to see a hole in the top of the piston. It look good and so does the piston wall. I poured gas in the head to test for leaking valve in the head. It looked good. I thought I small a little metal in the water that poured out of the head but not sure.

Any ideas????

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Oh, it was the piston on the right

 

[Josh P]

Re: Fear the worse, loud banging sound comingfrom the engine

they look ok.. get a box and poke 6 holes in it in a line and put your push rods in the holes to keep them in order... Remove the plastic lifter retainer and remove the lifters for that cylinder one at a time. Look to see where the plunger is sitting in the body. whats the head look like? Shine a flash light at the valves and look in the ports on the head, intake and exhaust, you should see no light in either. Post your results

That piston did move up and down when you rotated the engine over right?

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

they look ok.. get a box and poke 6 holes in it in a line and put your push rods in the holes to keep them in order... Remove the plastic lifter retainer and remove the lifters for that cylinder one at a time. Look to see where the plunger is sitting in the body. whats the head look like? Shine a flash light at the valves and look in the ports on the head, intake and exhaust, you should see no light in either. Post your results

That piston did move up and down when you rotated the engine over right?

Thanks Josh, everything looks good. I turned the heads upside down and poured gas in them and they didnt leak out. I'll check it with a light today. Also, When you say the plunger, is that the inside of the lifter? I havnt turned over the motor to see if piston moves, just because it would mess up the timing. Thaks for the tips, I need it.

 

[smassey22180]

Re: Fear the worse, loud banging sound comingfrom the engine

Could broken rings give zero compression?

 

[Sergi]

Re: Fear the worse, loud banging sound comingfrom the engine

Just inspect the lifter whose rod dissapeared on the intake valley. It may be collapsed or inner parts broken if it suffered a hit when the rod bent so it could fall on the valley. They're easy to disassemble, only taking out a clip. Look manual.
Inspect only for finding out the cause of fail this 2nd time. Lifter may be replaced.

It's somewhat confusing, as I already saw, correct me if I'm wrong, that you replaced lifters:

1- found loose rocker bolt. Missing rod.
2- Replaced rod and torqued bolt with same rocker (no rocker damage)

3- Same problem when trial. Replaced lifters. Have you told what was wrong/damaged after that splash?
4- Pistons OK. Valves Ok. Springs OK? (I understand yes) But no compression.

Checked the cam for damage from the bent rod?
Checked the cylinder walls for serious damage causing no compression? Stuck rings?

Try to test compression on the cylinder now that it's opened. You may clamp a cap from steel or something with a tire valve on it so you can fill with compressed air. Seal with an old tire camera and just pour a slight amount of oil on it for rings to make seal if they're dry. Take care with the cap not coming of when at pressure.

If compression drops so fast on successive tests could be the oil on the rings dissappearing.
If tests are good, then your sure que problem it's on the head.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Just inspect the lifter whose rod dissapeared on the intake valley. It may be collapsed or inner parts broken if it suffered a hit when the rod bent so it could fall on the valley. They're easy to disassemble, only taking out a clip. Look manual.
Inspect only for finding out the cause of fail this 2nd time. Lifter may be replaced.

It's somewhat confusing, as I already saw, correct me if I'm wrong, that you replaced lifters:

1- found loose rocker bolt. Missing rod.
2- Replaced rod and torqued bolt with same rocker (no rocker damage)

3- Same problem when trial. Replaced lifters. Have you told what was wrong/damaged after that splash?
4- Pistons OK. Valves Ok. Springs OK? (I understand yes) But no compression.

Checked the cam for damage from the bent rod?
Checked the cylinder walls for serious damage causing no compression? Stuck rings?

Try to test compression on the cylinder now that it's opened. You may clamp a cap from steel or something with a tire valve on it so you can fill with compressed air. Seal with an old tire camera and just pour a slight amount of oil on it for rings to make seal if they're dry. Take care with the cap not coming of when at pressure.

If compression drops so fast on successive tests could be the oil on the rings dissappearing.
If tests are good, then your sure que problem it's on the head.

The first time, rocker arm was sideways and pushrod missing on exhaust. Pushrod was pushed thru on intake. The guts was gone on the lifter on the exhaust. So we replaced both lifters and both pushrods and rocker arms. Put it back togther and it idled great and run great outside the water. I should have redone the compression test then.
I'll try to add the video of my rocker arms moving with the ignition turning over. The boat place thinks it's the cam shaft. They think they see a little difference in movement.

 

[Alwhite00]

Re: Fear the worse, loud banging sound comingfrom the engine

Push on the problem piston and see if it moves - Broken rod maybe?

LK