431A Volvo Noise

[vstol]

I have a 1992 19.5" runabout with a 431A 4.3 volvo penta and 290DP lowerunit.

There seems to be what sounds like a piston not firing, can hear it out the exhuast.

Changed plugs, check cap and button on distributor, and pull valved covers to check for oil and rockers, all looked good, what else can I do without tearing apart the motor?

 

[Don S]

Re: 431A Volvo Noise

Do a compression test.

 

[vstol]

Re: 431A Volvo Noise

Ok I finally got around to doing the compression checked and it checked bad.

On 1 and 3 I had 40 and 38 PSI respectively, the rest were between 170 to 185 PSI.

What does this mean, head gasket (if I'm m lucky)?

 

[Don S]

Re: 431A Volvo Noise

Time to pull the head and look. Could be just a gasket, could also be the gasket surface on either the head or the block is also damaged.
Might even be bad valves, or rings, or.
Might try a leakdown test to determine the exact location if you really want to know before you pull the head, but it will still have to come off.

 

[vstol]

Re: 431A Volvo Noise

Does the intake have to come off for the head to come off?

Gut tells me it does, also, I suppose there is no way this could have anything to do with the exhaust manifolds?

 

[Don S]

Re: 431A Volvo Noise

Does the intake have to come off for the head to come off?

Let me guess, you know nothing about engines, and don't own an OEM service manual ........... right?

I suppose there is no way this could have anything to do with the exhaust manifolds?

Of course it could, if water was getting into the cylinders when the engine was shut down, and was then trying to hydrolock when trying to start it next time.

 

[vstol]

Re: 431A Volvo Noise

one other thing, when i had checked the rockers earlier with the valve covers off it did thake the second pushrod from the front on this same side as this a little longer to start pumping oil than the other, by about 8 seconds or so, could that be ssosicated with the lack of compression pressure on 1 and 3?

 

[vstol]

Re: 431A Volvo Noise

Your right, i do not know alot about engines, i am assume with that said i will have to take the intake off to get the head off.

I got a couple of manuals but I have not looked into how to pull the head section, some of the folks in this forum had mentioned how the manual i had was not very good anyways, not always the most accurate one to use for replacing and troubleshooting but had good pictures?

Nonetheless I will get that head off in my next free moment and start looking for the problem.

Thanks for the help.

 

[vstol]

Re: 431A Volvo Noise

It was the head gasket; I finally got around to pulling it all apart and plain as day big missing part of gasket between #1 & #3 cylinders, all back together now, almost.

I tried adjusting the rockers the way my manual said but still had some tapping when I started the motor, so I resorted to what I used to do for my old 79 K-10 (truck not boat).

Tightened down rockers enough for all the tapping to go away (but not to tight) then from the front, backed nut off until tapping would start just a little then tightened 1/4 turn past when noise would stop?

Is this sufficient or just really jacked up, I suppose I will find out when I take the boat out and check WOT and Speed compared to what I use to have but I would like the opinion of the forum, maybe full 1/2 turn or 1/4 turn is too much?

What do you guys think?

 

[KJSmitty]

Re: 431A Volvo Noise

Vstol,
I'm not claiming to know the exact answer for valve lash on your 4.3 yet most of the hydraulic lifter applications I have worked with took between 1/2 and 3/4 turns past zero load. This is actually done with the engine not running.

Basically you rotate the engine so that lifter is at the bottom of the cam lobe (valve closed position). Loosen the rocker nut until you feel the pushrod is loose (slight up and down movement etc.), then gently tighten the nut until no play - as in the pushrod is just touching both rocker arm and lifter. This is what is called zero "pre-load" on the lifter. Then you tighten 1/2 to 3/4 turn. That adjustment is now the "pre-load" on the hydraulic lifter.


Now knowing that, you adjusting 1/4 turn past ticking (while engine is running) is probably real close to the 1/2 to 3/4 turn above with engine not running etc.

You could always check one lifter with the engine off to see how close you were etc. Just get the lifter at the bottom of the lobe then count rotation of the rocker nut (loosening) until you have "zero pre-load". See how close you are etc..

Good luck - nice job doing the work yourself!!

 

[vstol]

Re: 431A Volvo Noise

thanks for the reply, did not get to play with boat today due to real job but will try what you said when i get a chance, i am looking forward to getting back out on the water.