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Fresh B20 engine tapping mystery

Hmm, is it possible the fuel pump lobe is machined wrong, so it's tapping on the pump lever?

Sucks you didn't find anything, that just makes it that much worse!

1mm seems a bit much on cam movement, shouldn't be THAT bad though...
 
gsellstr said:
Hmm, is it possible the fuel pump lobe is machined wrong, so it's tapping on the pump lever?

Sucks you didn't find anything, that just makes it that much worse!

1mm seems a bit much on cam movement, shouldn't be THAT bad though...
Click to expand...

No, I use an electric fuel pump. Just the cover there. The noise is all up top. Silent at the bottom near the cam.

Going to measure the cam lobes today. Only things left to make this kind of tapping are the cam, timing gears and the pistons. Starting to think there is a hole or large crack in the exhaust manifold. There was a crack when I got the car, and it did not make this noise. I drilled the ends of the crack, v-ed out the crack and brazed it. I guess it could have reopened or spread. Maybe it was the exhaust all along. It's wrapped with exhaust tape so I can't see if there is a leak.
 
A little late now of course. But here's the old school, shade tree, sludge hammer mechanic, method my dad showed me for finding an exhaust leak.
With the engine running dump diesel fuel, or something ,down the carb. Something that'll make it smoke like crazy. Then you'll see the leaks.
Of course we were working on an American car with a down draft carburetor, which facilities dumping things in much better than side drafts. :)
 
Well.. I finally found something. The crack I had brazed last year, then covered with exhaust wrap, has developed new cracks. Took it off, took off the wrap and sprayed water up the throat.. Massive leaks all around the old crack. The braze held, but it wasn't enough to stop more cracks. Effectively, the whole arm leading to #3 and #4 is compromised. Still can't imagine that leaking gasses could cause rough idle and tapping, but it's at least something.

Worth repairing or should I search around for a better one? Love to get a header and do away with this cast iron or cast steel monster.
 
I glad it's not the cam or a rod. If you want to stay with a cast iron exhaust, I'm sure Ken (Redwood Chair) or Jack (Jack) would have a good one.
 
There was that one time my 16VT motor developed a somewhat annoying rap/rap/rap noise. Just a bit more 'solid' sounding than a tapping valve. First I replaced all the hydraulic valve lifters (since I was pretty damn sure that was the problem), but no change at all. Tap tap tap tap.


So I pulled the motor and took it apart and found a broken wrist pin. I'd apparently been ----> <-----that close to blowing the thing up. I drove it about 10 miles home from where I first heard it tapping, including some 24 psi blasts along the way. How did that one-legged piston hold together? Dunno.
 
Update

Welp.. I THINK I got it. Exhaust leak. Can't be 100% sure yet. Ordered a ceramic coated patriot 4->1 from IPD. Reassembled head. New gaskets, etc. Fired up today. The patriot is still leaking from one of the 4 ports, can't nail it down just yet. BUT.. the stethoscope is showing no tapping from the head. Maybe I am just lucky and soon it will resume the tapping. But for the moment, it's looking good. The car is much zippier throttle response with the Patriot. That old cast iron thing was cracked almost in half.

One thing about the Patriot. The dual SU manifold did not fit up perfectly. Had to notch out the exhaust flange a bit. Not too bad. And the Patriot is making ever-so-slight contact with the oil filter. Not thrilled about it, but maybe I can clear it with a different filter make.

More later after first test drive.
 
blackbird939 said:
Welp.. I THINK I got it. Exhaust leak. Can't be 100% sure yet. Ordered a ceramic coated patriot 4->1 from IPD. Reassembled head. New gaskets, etc. Fired up today. The patriot is still leaking from one of the 4 ports, can't nail it down just yet. BUT.. the stethoscope is showing no tapping from the head. Maybe I am just lucky and soon it will resume the tapping. But for the moment, it's looking good. The car is much zippier throttle response with the Patriot. That old cast iron thing was cracked almost in half.

One thing about the Patriot. The dual SU manifold did not fit up perfectly. Had to notch out the exhaust flange a bit. Not too bad. And the Patriot is making ever-so-slight contact with the oil filter. Not thrilled about it, but maybe I can clear it with a different filter make.

More later after first test drive.
Click to expand...

I can send you the P/N's needed to do a remote filter set up, all my parts came from Summit and Jegs. The 4>1 thing is great but fitment is approximate, at best. I remember having to grind, bend and cuss a lot to make it fit on my old B18 and then this B20. But it does help with performance, no doubt.
 
Take a ball peen hammer to the header and clearance it as needed.

Don't worry about any performance loss, it's apparently an old wive's tail:
https://www.youtube.com/watch?v=azPKIjxmmdU

(Using a dyno and an SBC to see how much minor 'clearancing' on a header affects HP. They progressively bash the headers more and more with repeated dyno pulls)
 
JohnMc said:
Take a ball peen hammer to the header and clearance it as needed.

Don't worry about any performance loss, it's apparently an old wive's tail:
https://www.youtube.com/watch?v=azPKIjxmmdU

(Using a dyno and an SBC to see how much minor 'clearancing' on a header affects HP. They progressively bash the headers more and more with repeated dyno pulls)
Click to expand...

Haha.. :rofl: wow. Turns out they lost 0.25 HP? I might actually do that.. Just ding it a tiny bit right there. It's probably 1MM-2MM of interference.
 
Old thread, but I have been busy with other projects. I did some quick measuring with my dial caliper. Took the measurement from the caps of the springs to the milled surface of the head(where the gasket seats).
HTML: 
Cyl 	        Inch lift
8 		0.4252
7 		0.4059
6 		0.4043
5 		0.4394
4 		0.4173
3 		0.3933
2 		0.3705
1 		0.3756
I realize I should probably use the top of the pushrod, as the possibility of of the valve lash could swing the numbers a bit, but I adjusted them to within .01" several times trying to diagnose the issue. The ticking is so loud, you can feel it through the accel pedal. Do these numbers suggest that I have wiped the cam, likely due to an improper break in procedure?
 
it sure seems like it's worn cam lobes causing uneven lift. Make sure you don't have worn bushings in the rocker arms or a worn rocker shaft making lift uneven. If you measure at the pushrods then you are only measuring the lift as you mention.
 
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