MGB & GT Forum

Finally got around to adding setscrews to each of my rocker shaft pillars. This was mainly to eliminate fretting which annoys me but I also had a hunch it would quiet down the tappet noise by keeping the clearances constant. I have a fist full of old rocker shafts from a number of different MGBs and they all exhibit fretting where they pass through the rocker pillar bores.

To do the mod I disassembled the rocker assembly... and drilled a hole through each pillar. The end one with the oil feed obviously doesn't need modifying. I tapped the holes to 3/8 x 24 and re-assembled everything. Once everything was torqued back down I tightened the setscrews. You could see the rocker shaft lower down a few thou as I tightened.

I set all the valves to 15 thou, popped the valve cover back on and fired it up. The result is I now have no tappet noise at all... even with the oil filler cap off. I've never heard an MGB with no tappet noise. It's a bit weird.

I realize this is a sample size of one but the result is very much worthwhile on the face of it... to me at least. I will monitor the thing and see if anything goes awry over time.

Attached is a picture of a fretted rocker shaft where it wore inside the pedestal bore and a picture of the setscrew added to one of the pillars. The mod cost me $1.06

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

15 thou clearence is tappet noise.
They still tap
Just a constant non varying tap
Right?

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I can't hear any tapping... 15 thou or otherwise. I'll take it over to a friends and see if he can hear any. Like I said... sample of one, early days. Would be interesting to hear if another individual had the same result after this mod.

Maybe I've simply gone madd... from all the tapping...

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.





Edited 1 time(s). Last edit at 2017-08-16 03:30 PM by pinkyponk.

Was the hole shown in the first picture already there prior to disassembly? Or was that added as well?

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1973 MGB: Blow through supercharged, intercooled, 10psi boost. VP12 cam, aluminum flywheel, 8.9:1 compression. Black label OD, Saab 15” minilites. Goes a lot better than it looks.

Adrian,
You are saying that a significant amount of tappet noise is a created by the rocker arm shaft rattling inside the rocker arm pillars? Maybe the factory knew this and inserted the shims under the center two pillars on the later engines. Your work is very innovative, and I am going to try it.
Kenny

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Be safe out there.
Kenny

Adrian,
Too funny.
I did this many, many years ago. The early B series engines came fitted with alloy cast pedestals.
These alloy pedestal wore quickly or so I thought at the time so I did this screw mod as you did. My goal was not sound attenuation rather to keep the shaft from 'rattling' about. Can't recall if the sound reduced.
I should rummage about to find this rocker assembly. I think I kept it for a 'show n tell' one day but forgot until now that I may still have it.
We do 'interesting' things to these engines some of them are cool some are miserable failures.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

Did you install a new shaft. ???? If I saw one like that pictured, I would replace it, or was that for demo purposed.. I Have never seen that kind of wear on the shaft, "Inside" the pedestals. Under the rockers yes, but not the pedestal ?????

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IN ALL SUBJECTS.: For those who believe, no proof is needed. For those who don’t believe, no proof is possible.

"Strive for perfection in everything. Take the best that exists and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough"
Sir Henry Royce
co-founder of Rolls-Royce .

"I take no credit for my own, of another man's fame".
Joe Baba 2021

I installed a new shaft last year. The fretted one was from my scrap heap. Demo only. I have a number of fretted ones and if you google MGB rocker shaft wear and look for the fretting it is easy to find. Fretting is real... and real common.

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.





Edited 1 time(s). Last edit at 2017-08-16 04:37 PM by pinkyponk.

That's the hole for the "grub screw" that keeps the rocker shaft from turning. Stock part. Curiously, it is the site of the most extreme fretting... the only place the stock shaft is clamped. Although "clamped" is a bit of a stretch. You usually can't go past finger tight if you want to line up the slotted "keeper".

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

I'm saying my early findings seem to indicate that it is. I think it's from not being able to adjust the valves properly on a "moving" shaft.

By all means, try it Kenny but usual disclaimer applies. I've done this one only and driven it around the block. No idea what strange wear might occur over the long term. Please post your results. Hopefully they will be same as mine.

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.





Edited 2 time(s). Last edit at 2017-08-16 04:35 PM by pinkyponk.

Sounds like a good idea. Is is hard to believe that a shaft that size would break at high RPM and a missed shift. My Spitty Race Car originally was a 1147cc engine. The #1 and #8 rockers rode the shaft on the outside of the front and rear pedestals kind of like the MGB, but the shaft was smaller. Snapped two of they bubbies.until I changed the pedestals to the 1500cc style. I worked on a 1275 that had a terrible TAP< TAP, . I suspected one of the rocker arms had a dimple in its face. Found it by slipping a feeler gauge between the rocker arm and valve stem "With the motor running"
When I got to # 5, the sound went away. "Bingo" that was it. Pictures below are a 1275cc, actually the shaft looks pretty good. I always install a new one. Just Saying.

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IN ALL SUBJECTS.: For those who believe, no proof is needed. For those who don’t believe, no proof is possible.

"Strive for perfection in everything. Take the best that exists and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough"
Sir Henry Royce
co-founder of Rolls-Royce .

"I take no credit for my own, of another man's fame".
Joe Baba 2021

Joseph,
To echo Adrian, this "wear on the shaft, "Inside" the pedestals." is more common than most think.

Many owners rarely correct the worn rocker shaft/bushes let alone dig deeper. I wonder the %ge of cars out there with this wear present, I suspect it would be quite high.

some samples from the past (below.)

B

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Life's most persistent and urgent question is, "What are you doing for others?"

Adrian,

As usual, an interesting post! Can you post a video of the engine running with sound?

Adrian I think thats a great idea, cant hurt anything, not a big job and a worthwhile project. Denis

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68 B roadster, Daffodil yellow, supercharger, Burgess SC head, SC cam, Mikuni HSR 48 carburetor and engine built for supercharging.

73 BGT V8 conversion starting with a bare shell. Built the engine "3.9L Rover" early in 2016 with high comp pistons and a few other nice bits, plus a T5 ford trans. Started on the body late 2016 and complete late 2017, Did all the work myself, mechanical, body. paint etc.
Finished and going well, great to drive and quick. Now has a nice 3.23 LSD.

I'll see what I can do. I hate to post a sound clip of my engines nasty, lumpy idle.

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.