Logo
FULL SITE MENU

Another issue... Noise (clang) coming from motor under acceleration Mercruiser 3.0 with Alpha One

Hydraulic lifters will bleed down so yes they can be loose.

This is not of concern..........do not focus on this.


Why are you doing this anyway?

in order to find your timing mark for the timing cover you need to determine top dead center on the compression stroke on number one cyclinder with the use of a degree wheel...........it is really the only way to be sure.


when describing piston/valve position you have a couple of choices

intake valve opening, intake valve closing, then compression, then exhaust valve opening and then exhaust valve closing.

"firing position" is when the piston is on its way up during the compression stroke just after the intake closing
during the compression stroke both intake and exhaust vales are closed.
 
I know and the engine is currently (as we talk) in firing position in cyl.1 . Both intake and exhaust valve are closed and my timing mark is at 0 with the 1st piston all the way up (I can see it in the spark plug hole).

My other concern is that in all of the valve that weren't adjustable in this position (no.2 exhaust, no.3 intake and no.4 exhaust), they were all very tight except the no.4 exhaust. May-be that's the faulty one since all of the others were tight (probably on the way of getting opened)?

(Excuse me if I'm ignorant there, but that catched my attention when I was inspecting them.)
 
Last edited:
So you suspect a # 4 cyclinder valve train issue?



if this is so, carefully look at the vavle spring to see of it is broken........

if you think all the other cyclinders are ok then concentrate your efforts on # 4.....do th motor running adjustment on this one alone first.


if it does not adjust while running the way described then it may be your issue.
 
It might be just OK, but it was the only one that was loose and I think it's supposed to be tight since it's not an adjustable rocker in this firing position (no.1 cylinder).

That said, this valve should logically be on his way to open (and be tight) at this crank position?

EI IE EI IE

Adjustable rocker on no.1 cyl in firing position : no.1 exhaust and intake, no.2 intake, no.3 exhaust, no.4 intake

The other ones (no.2 exhaust, no.3 intake and no.4 exhaust) should all be tight (valve on their way to open) am I right?

Then, if I do a 360 with the crank: no.2 exhaust, no.3 intake and no.4 exhaust should all be loose (closed valve) and the other ones should be tight (valve on their way to open)

Correct me if I'm wrong.
 
Last edited:
plugs were OK, cylinder 4 spark plug was a little bit wet... Couldn't tell what it was (if head gasket was bad, it would be a lot worst no?). I did tighten the no.4 exhaust valve and it helped a bit after a test drive, but sound is still there, less noticeable though (I don't know if it's because there was not enough load (2 passenger instead of 6 + a wakeboarder last time)).

I will get back to it this weekend with a compression gauge and check it.
 
Last edited:
the push rods are contacting the hydraulic lifters. with motor NOT running,there is no hydraulic pressure. that is why the rocker arms are loose on the cylinders at tdc. not hard to adjust. i am more concerned about the ignition timing. if this noise is detonation , you will destroy the motor in no time running it. i recommend that you get the correct timing cover with the timing marks. there is no way that i know of to set timing accurately without . you mentioned changing fuel types. the lower octane fuel probably contains ethanol when your owner manual was printed, there was no ethanol enrichment of fuel. i know that some gas i buy for my truck seems to make it rattle a little more than other gas.something you could try, mark the base of the distributor to the motor.loosen the clamp bolt. turn distributor counterclockwise maybe 1/4 to 1/2 inch. retighten clamp. test run to see if noise goes away.
 
dtoole said:
the push rods are contacting the hydraulic lifters. with motor NOT running,there is no hydraulic pressure. that is why the rocker arms are loose on the cylinders at tdc. not hard to adjust. i am more concerned about the ignition timing. if this noise is detonation , you will destroy the motor in no time running it. i recommend that you get the correct timing cover with the timing marks. there is no way that i know of to set timing accurately without . you mentioned changing fuel types. the lower octane fuel probably contains ethanol when your owner manual was printed, there was no ethanol enrichment of fuel. i know that some gas i buy for my truck seems to make it rattle a little more than other gas.something you could try, mark the base of the distributor to the motor.loosen the clamp bolt. turn distributor counterclockwise maybe 1/4 to 1/2 inch. retighten clamp. test run to see if noise goes away.
Click to expand...

My friend will bring his snap-on timing light tonight and we'll time it at 2 BTDC on base mode. I put a timing tab on the cover and it seems accurate. We'll see!
 
thecca said:
My friend will bring his snap-on timing light tonight and we'll time it at 2 BTDC on base mode. I put a timing tab on the cover and it seems accurate. We'll see!
Click to expand...

I timed it yesterday in base mode... It was at 6 degrees BTDC (supposed to be at 2 ATDC). Put some 91 octane fuel and ran it a while.

My issue dissapeared, we went wakeboarding and we didn't heard a single noise, even under hard load/acceleration.

I guess gas and timing were my problem... Thanks again for the help and I'll let you know if the issue comes back.
 
i was thinking about your timing being advanced by 8 degrees . that seems like alot to me . there could be several causes for that. 1) someone set timing wrong previously . 2) cam / distributor gear wear ( this would cause a retarded timing issue ) 3) the mechanical advance has stuck in the advanced position. to check , reattach timing light and rev up motor. you should see the timing advance on the balancer/ timing mark . check your manual to see what total timing should be.
 
Back
Top