MGB & GT Forum

I have a '76 RB, which had its engine rebuilt 20k miles (before my ownership) ago back to pre-smog spec with some goodies while it was all apart (hi-comp/OEM pistons, 268* cam, mild head porting, twin SU's). It runs well, revs clean and idles steadily most of the time and I try to keep on top of servicing and maintenance before things fail.

Every time I've checked the valve clearances for the last year that I've had the car, they are always at 0.013 cold. All the valves have the same clearance consistently, and there is still a tappet noise (noticeble when listening for it; not loud by any means) when hot so I know they're holding the valves open. I'm undecided whether to leave the valves at 0.013 since it runs well that way, or bring them back to the factory 0.015 clearance. I have no details on the aftermarket cam other than specs, so I don't know what clearances are recommended with it.

Anyone care to chime in with advice or experiences?

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Jeff; '76 B

I think this one for Hap to answer. Personally, I'd leave well enough alone. After all, you are running solid lifters and a little noise from them, for me anyway, is peace of mind. Set too tight and you know you're headed for burned valves.

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Si Vis pacem, para bellum

I have my '79B valves set at 0.013" cold. There is a little noise but the MG engines are not the quietest engines ever designed. I put an aluminum valve cover on which makes it very quiet.

"... and there is still a tappet noise (noticeable when listening for it; not loud by any means) when hot so I know they're holding the valves open."

I am probably misunderstanding. If the tappets are making noise (clicking) they have clearance, so the valves are not being held open.

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Be safe out there.
Kenny

Just how often do you think you need to be checking your clearances Jeff ?

Unfortunately there is rather too much unsubstasntiated rubbish written on the topic leading to equally unsubstantiated and overstated warnings of the consequences of deviating from the book.

Yes of course if you close the valve clearances up too far then you will run the risk of a burn out but to put that into perspective for the past 25 years and over 200,000 miles I've run hot clearances of 10 exhaust and 8 inlet with no sign whatsoever of a burnt out valve nor any other detrimental effect.

Hey Ernie. What benefit do you get from running your valves with a tighter lash than "normal." Just curious.

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

There's a fairly large margin of effort when dealing with the valve clearances in these engines. If running them a couple thousandths tighter makes it quiet...or run better...go for it. You're not burning anything up with such little deviation. I run my engine around .013(cold) because it's absolutely quiet. Some like the sound of their valve train "tapping"...I don't. No running or performance issues. I asked my A&P(and auto) engine rebuilder about adhering strictly to the "book" with those numbers. He laughed and said I'd be amazed at what type of numbers he'd seen in all of his years working on all sorts of vehicles. The "book" is not always gospel. Deviation doesn't necessarily result in draconian repercussions in many instances.

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"One test is worth a thousand expert opinions"--Alvin "Tex" Johnston...Boeing test pilot.

"Who do you think you are? I am."...Pete Weber

73 MGB. Tires: Round, black, hold air. Oil: Sometimes old, sometimes new...always slippery. Oil filter: Yellow, usually full of oil. Carbs: 2 SU HIF. Distributor: Yes. Headlights: Not that bright but bright enough. A bunch of other stuff most cars have but not really important enough to itemize. Oh, wait...it has a cool sounding exhaust with stickers on the chrome tips. Really slays the ladies...

If you adjust with feelergage its always a personal feeling and means some differents in gap.
Did mine with dail indicator on a magnet stand an the enging was running much better than before

These engines are solid lifter engines, meaning some ticking is normal, that's why later US cars went to hydraulic lifters because they are quieter.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

How often is it recommended to adjust the valves anyway??

I like a quiet engine and let my ears tell me when to adjust my clearances, in that sense you could say that I never actually check them.

Remember we're talking agricultural engineering here not space age and if a couple of thou either way made any meaningful difference or stood to cause damage there would scarcely be a B series engine left on the road.

In your case .015-.017 cold: performance cams with greater lift call for more not less lash.
.013 cold on a 268 is limiting the capabilities.
Tight valve lash lower torque and slower acceleration at street driven power range,higher rpm and mor power at high rpms range
Loose or proper .015-.017 or to cam card spec more torque down low and quicker acceleration.
You are changing the duration of the cam so ere on the side of caution.
Some of us that Drag race still use valve lash to gain off the line or upper end of the track when every 1/10 of a second counts in the outcome.
Running a radical cam on an MGB that won't show any street manners and poor idle gap it a few tho loose and it will lose some of the lumpiness and tame the cam. Less duration in effect.

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Edited 1 time(s). Last edit at 2014-12-18 12:50 PM by ohlord.

"Tight valve lash lower torque and slower acceleration at street driven power range, higher rpm and more power at high rpms range
Loose or proper .015-.017 or to cam card spec more torque down low and quicker acceleration."

I thought that tight intake lash (less valve clearance) opened the valves sooner (advancing the cam timing) and moved the power band lower in the street driven power range.

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Be safe out there.
Kenny

Jeff,
I had a B that had a louder than normal ticking, it was due to worn rocker shaft components. The sound was most noticeable at initial start up and as I was turning the engine off.
It's not very hard to disassemble the rocker assembly and look for wear on the rocker arm bushings and the shaft itself. It doesn't take a great deal of wear to make noise.
David

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Visit my artists website at www.WicklowWanderer.com

Decrease lash open valve sooner,increased duration and more lift,in effect a larger cam increase top end.

Increased valve lash opens valve later,closes sooner less perceived duration ,less lift smaller cam more torque off the line.

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LNDRVR4X4.COM
Home of Project "INCARN8'


1957 Series 1 Land Rover electric VEHICLE CONVERSION

FIXITUPCHAP.COM
FIXITUPCHAP INCORPORATED

RD3 Radar/ Electronic Warfare Technician
VIETNAM 1969-1972