Oil flow

[Roscobbc]

It's the second valve from the front of the engine. Not knowing what else to try I think I'm going to have a go with some flushing oil or additive. Anyone got any experience with these?

So would that indicate that you are getting good pressure at that exact point in the oiling system - but perhaps not prior to that point (or after) a puzzle indeed.

 

[Forrest Gump]

Well presumably if there is no oil coming up the pushrod, then none is getting to the lifter, but in that case why can't I hear or feel any slack at the rocker? I agree with you the lack of noise through the screwdriver suggests to me that the lifters are all working. So what is the noise? By the way I checked the exhaust manifold bolts and they were all the correct torque.

When I primed my engine after rebuild (so all new valve train) I noticed there was variation in the amount of oil from the rockers. Some had a “flow” others it merely “appeared”. That didn’t seem to change with continued priming so took that as okay then proceeded to fire it up.
I would have thought that it would sound like a bucket of nails if several of your lifters weren’t pumping up.

 

[Forrest Gump]

Do you know which valve suffered the damaged rod and lifter? Is it the same one that is now squirting oil by any chance? Could the rocker stud be bent Or more sinister like valve stem bent?

 

[johng]

The valve that had the damaged rod was on the other side of the engine to the one that squirts now! Got to say I'm not overly keen to take the intake manifold off again although I'm getting quite practiced at it

 

[johng]

Could do with a bit more help please. We've tried putting flushing oil through the engine and that made no difference. We've also tried removing one spark plug lead at a time, which also made no difference to the noise. (I've read that if there is a small end problem, this should help identify it). However we aren't convinced that the noise is actually coming from one side of the engine, we think it's more likely to be from the rear of the engine and in the middle. We made this recording of the engine at idle and looking at the trace of this, the tapping noise is occurring at just over 5Hz. This would mean half engine speed at tickover. This suggests to me that it's either the camshaft, distributor or oil pump. Anyone got any thoughts?sound recording

Recorder

 

[Oneball]

The sound changes part way through, did you move the mic?

Have you had the dissy out and looked at the drive gear?

 

[johng]

Yes the sound change is when I moved the phone. Haven't taken the distributor out yet. I was thinking of removing it and turning the engine over on the starter, if the tapping noise is still there that would rule out the dissy and oil pump, but then again the noise might not be generated by just turning it over on the starter.

 

[Corvetteville]

My brother's 1970 400cu Trans Am sounded like that. The oil pump was partially seized & the drive rod from the dizzy, designed to break, had done so. The centrifugal force caused it to bang on the inside of the block. The dizzy is at the rear of the engine,? Could also explain poor oiling?

 

[HJG]

Have you checked the exhaust manifold isn't leaking? This can make a tapping noise.

 

[johng]

My brother's 1970 400cu Trans Am sounded like that. The oil pump was partially seized & the drive rod from the dizzy, designed to break, had done so. The centrifugal force caused it to bang on the inside of the block. The dizzy is at the rear of the engine,? Could also explain poor oiling?

I'm sure the oil pump is still being driven as I'm getting 40 to 50 psi oil pressure, but I'm struggling to understand what could cause this type of noise. It sounds like an impact once per camshaft revolution to me.

 

[johng]

Have you checked the exhaust manifold isn't leaking? This can make a tapping noise.

I've checked the manifold bolts they are all tight and I've put my ears pretty close to them and it doesn't sound like that's where it's coming from.

 

[Oneball]

Have you done a compression test?

Checked for broken valve spring?

Endoscope down the bores

is it a mechanical fuel pump?

Measured valve lift.

Checked push rods are straight.

 

[johng]

Haven't done a compression test - so could do this
I've looked for a broken spring and can't see one. Also have listened to the noise on each rocker stud and can't hear any difference
Don't have an endoscope
Electric fuel pump
Haven't measured valve lift - could do this
Have checked push rods because initially one was damaged.

 

[Oneball]

Could it be not engine related. How’s the drive transferred?

 

[johng]

Funnily enough we were wondering that yesterday, there's a flex plate and adapter bolted to the flywheel and a splined driveshaft fits into that. Thing is that would rotate at engine speed and the tapping is only half that speed.

 

[Chuffer]

If the tapping is half the engine speed that does rather suggest it being camshaft related as that rotates at half engine speed on a 4 stroke engine . Maybe a worn cam lobe . I had that problem on a 4 litre Rover V8 engine and it only takes a miniscule amount of wear on a lobe to cause knocking .

 

[Roscobbc]

When the oil pump drive shaft sheared on my engine the distributor (being driven by a bevel gear off the camshaft) was unaffected - so engine still ran. There is only two options - 1. oil pump works - 2. broken pump drive rod, oil pump dosen't work - full stop. The drive shaft is quite long but the weak spot is the slotted keyway where it's driven off distributor.
If you want to know what a badly failed no. 2 big end sounds like listen to this (on headphones perhaps?) Oddly (and as bad a state as the big end was - with at least 30 thou' play) it wasn't so easy as one might think to pin-point the location of the sound - using a large, long screwdriver as a 'sounding' tool and initially 'sounding' off top end of engine (rocker covers, inlet manifold etc etc) didn't really give a clue. 'Sounding' off the oil pan doesn't work for big ends (too far away). The fact that my engine has ally heads and rocker covers also confounded the issue of trying to locate where the sound was coming from with the ally carrying sound perhaps in a different way. Video's don't really help too much - the guy who built my engine was at a loss to the cause even with this video. I actually thought it was a small-end failure with so much noise seemingly up at the top-end.

 

[johng]

If the tapping is half the engine speed that does rather suggest it being camshaft related as that rotates at half engine speed on a 4 stroke engine . Maybe a worn cam lobe . I had that problem on a 4 litre Rover V8 engine and it only takes a miniscule amount of wear on a lobe to cause knocking .

If it is a worn cam lobe, why wouldn't the hydraulic lifter just adjust to remove the clearance? (on the Vortec engine there is no way to adjust valve clearance, it's just left to the lifter). Also I can't hear a difference on any of the rocker studs

 

[Chuffer]

If it is a worn cam lobe, why wouldn't the hydraulic lifter just adjust to remove the clearance? (on the Vortec engine there is no way to adjust valve clearance, it's just left to the lifter). Also I can't hear a difference on any of the rocker studs

The lobe may have worn into ridges across the face of the lobe . The Rover V8 has hydraulic lifters and the wear was not taken up by them on my Marcos . I had a knocking / tapping sound that was very noticeable at tick over and gradually decreased as the engine revs built up . Also , have you had the hydraulic lifters out ? If so it is important that they go back in where they came from as each lobe and lifter wear and bed in to each other .

 

[johng]

Yes I've had the lifters out, because originally the spring clip fell out of one of them! I've now put a complete new set in, but as they are roller lifters where they go is not so important as with flat tappets. It would be nice to think that the noise will just go away if I run the engine and let everything bed in, but I don't think that will happen.