Scirocco Mk1 with RD head and 3A bottom swap - tapping noise

[hardrocco]

Completed my swap a week ago, got the engine start last weekend.
Unfortunately, I have got a rapping or tapping sound coming from the engine that we have to diagnose now.

The 3A bottom was completely refreshed. The RD head was also done, ported, 3 angle valve grind etc.

Here's a video of the sound:



We turned the motor off, cranked it by hand, didn't feel any binding or anything.
Thought it was the fuel pump, removed it and ran the motor, still had the sound.
Removed the plugs, ran the starter, no sound.
Today, I removed the cam cover and checked for clearances when the lobes are facing up, everything is tight.
No exhaust leak.

Any ideas? Next gonna drop the pan.

[ps2375]

You should be able to narrow the area down using some sort of stethoscope (screwdriver or other long item) to head or crank areas. Also had a noise from clutch when pressure was on pedal once. Simple adjustment to shield to cure.

[hardrocco]

We did do the stethoscope, narrowed down to the front of the motor area.
Took the pan off, didn't see anything hitting.

[ps2375]

When you had the pan off, did you check the mains and rod bearings?

[Glegor]

i vote for lifters that are not fully primed..

how much use has the engine had so far? if its not even been up to operating temp yet, i would not worry. VW lifters are almost always noisy (even brand new) when you fire them up fresh in an engine..

and VW lifters ALWAYS have the right clearance, there is a spring inside the lifter pushing up on it at all times. it keeps it in contact with the cam lobe, along with the pressure of the oil..

[Butcher]

i vote for lifters that are not fully primed..

and VW lifters ALWAYS have the right clearance,

I agree with lifter noise. You may have to drive it on the freeway at 4,000 RPM for a few miles before it goes away. A little un-nerving since you put so much time/effort in it.

I disagree that lifters ALWAYS have the right clearence. Incorrect/poorly machined valves, poorly cut/remanufactured cams, can eat up any clearence that a lifter can absorb.

Never ever believe the monkey in the back of the machine shop is the best there is. Everyone makes a mistake and can do something wrong. Double check their measurements and if you have no way of doing that, then you are SOL.

[WaterWheels]

The 3A bottom was completely refreshed. . . .Thought it was the fuel pump, removed it and ran the motor, still had the sound.

What do you have for a fuel pump that gave you the idea to "remove" it? A 3A block should not have the mechanical fuel pump hole in it like other engines (1.8L 8v often). Maybe it is a country thing but they, 3A, do not have that mechanical pump hole here.

As for what the noise is, I do not believe it is good. Who did the engine? I played the video a dozen times with different volumes and filters. For me it sounds like a rod bearing and racing the engine or driving it on the freeway is not a good idea until you know for sure. If that noise is lifters (followers) then send me the bill for the new ones you bought and a new clip of the same quite running engine and I'll pay the bill myself (up to $12 a follower though). You can save this and print it out for proof later cause that's how sure I am it is not followers.

[Glegor]

I agree with lifter noise. You may have to drive it on the freeway at 4,000 RPM for a few miles before it goes away. A little un-nerving since you put so much time/effort in it.

I disagree that lifters ALWAYS have the right clearence. Incorrect/poorly machined valves, poorly cut/remanufactured cams, can eat up any clearence that a lifter can absorb.

Never ever believe the monkey in the back of the machine shop is the best there is. Everyone makes a mistake and can do something wrong. Double check their measurements and if you have no way of doing that, then you are SOL.

ok, well, VW lifters,, if manufactured properly, and set in a properly spec'd head, should not ever need adjustment. they should adjust on their own.

[ny_fam]

Yes - but if not properly soaked in oil for 24 hours before installation you can get this noise(referring to new lifters or lifters that have been out of the engine for a prolong period of time). I also understand that the lighter mk4 lifters tend to make noise.
BTW - I'm not diagnosing the issue just commenting on the conditions lifters can be noisy.

Cheers
ny_fam

[fwdvw]

What do you have for a fuel pump that gave you the idea to "remove" it? A 3A block should not have the mechanical fuel pump hole in it like other engines (1.8L 8v often). Maybe it is a country thing but they, 3A, do not have that mechanical pump hole here...

I asked him the same thing, but he is using a Brazillian bubble block. Its an industrial 2.0 bubble block that has the Fuel pump opening like the older 8V's. In the US the normal 3A is like you are saying.

[hardrocco]

I asked him the same thing, but he is using a Brazillian bubble block. Its an industrial 2.0 bubble block that has the Fuel pump opening like the older 8V's. In the US the normal 3A is like you are saying.

Thanks guys, it turned out to be a stuck lifter, boy it was louder than I expected it to be. My problem, I got scared after the machine shop guy wasn't sure what it was. And because it was all new, I was babying the motor only to about 3k. I got to the point where I decided to drive it, after driving it around, one of my friends thought it sounded quieter. I didn't think so, he asked me to open the hood and he rev'd the motor from the throttle linkage up over 4k, did that a few times and the sound went away.

The 3A block I got is a Cofap crate motor. I wanted to use it because I knew it was really low miles and because the South American blocks were run with carbs and a mechanical fuel pump.