Clacking/tapping noise due to blown head gasket

[roosm]

Hi,

I have a Supra Launch 22 SSV with a 2002 Indmar Marine small block, 350 / 5.7 litre engine. Block-wise the same as a mercruiser.
The engine is a TBI (throttle body injection), is salt water cooled and has about 800 hours on it (first 400 in sea water though).

This saturday I was out wakeboarding and while I was behind the boat after I will down the first/second time and we were getting on plane again my girlfriend pulled off the gas. I heard a strange noise and she obviously did as well.
I got in the boat and there were no strange noise at idle. Put it in gear and everything was fine until we tried getting on plane. Then the clacking / tapping noise began. It seem to follow engine RPM, though we quickly got off the gas. In neutral we can rev her up to 4000 rpm without any strange noise.

I checked my oils on both the v-drive and ZF hurth tranny, and they seemed fine. Might have been on the low side, but still, in the range.
I checked the engine oil which was also a bit on the low side but still on the good side of "minimum". I added some oils to top them off closer to the "max" mark. I tried again, no change. (Thought this might be relevant further on).

I went online and found thread about a guy having a TBI 350 and what sounded like the same issue. An other one chimed in on his thread that had the same issue. Turned out both of them had a blown head gasket between two cylinders and the clacking was believed to be pressure releasing from one cylinder into the other causing the valve to smack open. Both of them changed the head gasket and the result was that the engine was fine afterwards.

I, of course, went down to the boat yesterday with my compression gauge and meassured compression on all cylinders. I removed all spark plugs at once, disconnected the ignition coil and wired an accessory switch to be able to run the starter engine without the ignition on.
I am a little unsure about the cylinder numbers, but since I have a v-drive and the engine is put in backwards I guess the starboard-stern one should be number 1?

In that case I had between 195 and 210 in compression on all cylinders, except 4 and 6 that read 0!!
Yes, zero.

In the other guys threads they seemed to read about 100, but it was unclear if they had in fact removed the number 4 spark plug when measuring compression on number 6.


My conclusion is a blown head gasket between cylinders number 4 and 6.
Repair seems straight forward = replace head gasket, resurface cylinder head if needed etc. (Though I haven't done this before and would greatly appreciate any advice, usually I am able to find the instructions online).

Now to the questions:

A fel pro 17030, would that be a good head gasket for this?
The engine is a vortec engine if that matters.

Should I exchange gaskets on both sides? I sure don't want to fix what isn't broken.

I think I saw a small droplet of water on the number 4 spark plug. Might be condensation, might also have ingested water and that caused the blown head gasket I guess?

Anything else I should look at when I pull the heads?

Do I have to pull the intake manifold to be able to pull the heads? In that case, do I need a new gasket for that as well?

Best regards,
Mike

[michael hunter]

Felpro makes great gaskets that should be fine. I would do both heads . Yes you have to pull the intake. Before you pull the heads pull the valve cover and check the rockers ,valve springs and cam lift.

[pridekit]

#1 is closest to the stern on the starboard side. #2 is closest to the stern on the port side.

I encourage you to read my thread (https://forum.supraboats.com/showthr...ion-in-5-and-7), the job is a lot of work, but definitely do able. I believe we have nearly identical engines except the intake manifold and MEFI (Mine is MEFI 5). I bought FEL-PRO 17232 which includes the vortec head gaskets, intake manifold gaskets, and distributor gasket (along with some other stuff for the intake manifold, but were not applicable to mine). Summit carries this for $125.

There can (and will) be a lot of speculation. You can perform a leak down test if you have the equipment, but you will get a lot of information from pulling the bad head and having it analyzed. Does it have a heat exchanger or was it running saltwater through the motor?

As for the ticking, it seems to me that if the ticking was only occurring while in gear the ticking would not be coming from the engine but from the trans or v drive. Your valves are moving whether you are in gear or not, so if the cause was a blown gasket and pressure moving from what cylinder to the other it would occur in neutral as well. You can buy a mechanics stethoscope for under $10 and listen to the trans and v drive as someone drives.

[leetudor]

The clacking noise could be the drive plate going bad.

[CJD]

Yep...unfortunately that head will have to come off to see what's going on.

The clacking does have me stumped. Could be sticking valves or cracked flex plate. I would lean towards sticking valves, as it would be a huge coincidence to have the flex plate fail simultaneously with the head.

[pridekit]

CJD, wouldn't clacking valves occur when revving in neutral?

I suppose either way the head has to come off to resolve the no compression issue :/

Sent from my iPhone using Tapatalk

[roosm]

I hope I am allowed to link to another forum, otherwise I appologize in advance.

This is what is happening to me, exactly: http://www.shamrockboatownersclub.co...p/t-30519.html

The noise might be backfiring or valves smacking shut.

Since I dont have a V8 anymore, but rather a V7 with a dual cylinder firing out of sync I guess what is happening is when the piston tries to compress the gas it pushes it over to the cylinder next door, then fires and the explosion occurs partly in the wrong cylinder. This could cause backfiring or the valve at this point being open smacking closed, though I am unsure of how it works exactly. That is, what keeps the valves closed, what opens them etc. But the fact that the no 6 piston is in the wrong position and the cylinder is still full of gasoline gases and gets a spark when the no 4 spark plug fires could possibly cause all kinds of trouble.

I will tear down the engine this saturday and post pictures. Then we can diagnose this further.

My spark plugs showed evidence of carbon buildup.
This could be what caused detonation and a blown head gasket. Just a theory.

Thanks!

Mike

[CJD]

Pride, you're right...that's why I'm stumped. I follow the backfiring theory, but I wouldn't describe that sound as a "clacking tapping" sound. But it could just be semantics on what it sounds like.

Even with a blown gasket, I would think the compression check would show at least some reading. That is what has me thinking that the valves may not be closing all the way. The clacking would be when the cam lobe takes up the slack and the lifter smacks the pushrod. I don't have a theory as to why it wouldn't make the same noise in gear, though.

But, the main thing is, with 0 compression in 2 holes, the head will have to come off to fix any of the possible causes.

[roosm]

Pride, you're right...that's why I'm stumped. I follow the backfiring theory, but I wouldn't describe that sound as a "clacking tapping" sound. But it could just be semantics on what it sounds like.

Even with a blown gasket, I would think the compression check would show at least some reading. That is what has me thinking that the valves may not be closing all the way. The clacking would be when the cam lobe takes up the slack and the lifter smacks the pushrod. I don't have a theory as to why it wouldn't make the same noise in gear, though.

But, the main thing is, with 0 compression in 2 holes, the head will have to come off to fix any of the possible causes.

Well, I havent really listened alot to the sound, the sound of my engine possibly tearing to pieces aren't really my soundtrack. It is quite a bit of other noises going on at the same time.
On an other note, english is my second language and this is the first time I even use the word Clacking... =)
I guess someone else described an issue which I might have prediagnosed as my own problem as having a clacking sound when in gear and so I did too.

Just to try and go with the theory of backfiring being the noise (which was actually what my mother who was in the boat and who has actually heard backfiring before described it as).
Why wouldn't it be heard when out of gear?


I don't really understand how the whole valve-thing works and what would cause it not to clack. Especially only when in gear.
It is strange is what it is...

Couldn't the 0 compression be caused by the leak in the head gasket between the cylinders and the spark-plug being removed from that cylinder. I guess if I put a spark plug in that cylinder and try again I could get a different reading?

Mike

[CJD]

Sorry to say, I'm pretty familiar with the sounds of my engines self destructing!?!

You can re-do the compression check, but the bottom line is the head has to come off, whether it's a head gasket, valve, or anything else that would cause a loss of compression.