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MG MGB Technical - tappet clearance

I posted before about my dilemma with tappet clearance.I have a 1975bgt with stage 3 head and unknown cam. Tappets were set to 22 thou but were quite noisy. With some reluctance I have set them to 15thou which has quietened them a lot but I was concerned about them being too tight and burning the inlet valves. I took the view that if I did a compression test and the readings were ok then the tappits are ok. Did a test and the readings were 170, 160,160,160. Do you guys agree that my tappets are set ok?


Rod
R E Merrall

I've had various cams in 1800 B's, the biggest exhaust clearance on a "fast road" was recommended at 0.019" , but clearance is particular to cam design as well as to allow for expansion. Without knowing the cam design and manufacturer your'e guessing and hoping.
Allan Reeling

Rod I think you will be pretty safe at .015". Most of the performance cams from the UK that I have seen are around the OE figure (.015") some US cams can be a little more although the most I have seen was .018" but unlikely in your area. Denis
Denis4

You will not burn the inlet valves you could burn the ex valves if too tight. Is your setting 15 thou cold or hot? Where did you get the 22 thou from? The compression readings do not tell you if you have the correct clearances, they just tell you the compression readings are fairly even. Did you do the test hot or cold and wide open throttle?
Peter
Peter Burgess Tuning

Rod, maybe not applicable in your case but my modified cam 45/75/75/45 has are recommended running clearance of 0.019" by cam manufacturer. This is futher increased to 0.021" because high ratio Titan roller rockers are used - proportional increase based on rocker ratios. Lobe lift is 0.328"
This setting appears okay but suppose I will only know when I strip the engine down next or have excessive tappet wear!
Mike
Mike Ellsmore

Rod
My two bob's worth
If it's a reasonably mild grind .015" HOT should be fine
Usually it's not until more radical camshafts are used that the clearance needs to be wider
Having said that, it all depends on the quietening ramps ground into the cam
Not knowing what the exact grind of your cam is leaves you in the dark a bit
I would run it at .015" hot but if it runs on after turning the key off noticeably more than with the wider clearances you might need to open the exhaust clearance up to say .017" or .018" for a try
The inlets should be fine at .015"
I ran a real crazy cam in my midget (320deg.) and it had .016" clearance but my supercharger cam which is a way milder design runs at.020" -- so, As you can understand , without knowing exactly what your cam is ,it's a case of trial and hopefully not error

willy
William Revit

Thanks for the comments. peter, I set the clearance cold and compression hoy with throttle open. The 22thou was the setting when I got the car but very noisy.Oscelli advised 22thou with modified cam. I appreciate that good compression does not indicate correct clearance but my reasoning was the it indicates valves are closing fully and therefore I would not burn the exhaust valves (I meant ex not inlet). I took the car for a long run today and it runs well with much quieter tappets. Can I assume all is well?


Rod
R E Merrall

Peter

I incidentally I am reading a book by Roger Parker on everyday mods and he speaks highly of you; wish I were closer to get an expert rolling road setup!

Rod
R E Merrall

Rog has been a good friend to me for many a year.
If Oselli said 22 thou they may well have fitted a Crane cam derivative such as Kent produce, the 717 being a mild road cam and the 718 a very fast road cam, settings are 22in/24ex for these. I would suggest setting them at say 20 thou hot and see if any are noisy. You can test this with an old feeler gauge of around 12 thou with the engine running. Sometimes cams are not ground perfectly and there can be a dip which makes the tappets rattly, if you have a noisy one turn the engine by hand to find the loose spot on that roacker and adjust accordingly. I have been advised not to go below 19thou for the Kent/Crane 717/8/9 to avoid damage to the ex valves, don't know if this is cold or hot setting.

Peter
Peter Burgess Tuning

Rod, don't let distance put you off visiting Peter. I have been to his workshop several times both with my old 1800 MGB (sold long ago) and with my BGT V8 conversion. Both cars wear Burgess Econotune heads.

I have usually arranged to go there while on a trip elsewhere, like to Silverstone, or to see family in the south. It's about the same distance from my place in Troon as it would be for you. It's well worth the trip. Great service from one of the good guys.

Mike
Mike Howlett

I have driven an "A" Series Midget since 1971 and am all too familiar with the oil that naturally leaks through the rear crank scroll past the non-existent rear oil seal.

I added a 1970 B to the stable last year. The car has always dripped oil but now the ponds under the front crank seal and rear main seal are huge. There is also evidence of oil spray on the rear number plate and rear of the vehicle after extended journeys. Oil consumption is minimal. I guess a little oil goes along way on the garage floor (the Midget drips a small amount but otherwise drinks oil at the rate of one quart for every three tanks of fuel).

Since the B evidently sat for an extended time before I put it on the road and into heavy service, I assume that both the crank and the rear main seals are shot. The question is whether I can keep driving it until something bigger, like a clutch replacement, mandates engine removal. I can keep mopping up the oil that inevitably spills beyond the tray on the floor indefinitely if I can be fairly comfortable taking the car on extended trips without worries that major oil loss may eventually occur while driving. The car has A/C which is holding its charge and works beautifully and engine removal would require removing the condenser, and dealing with the compressor connections. I just don't feel like removing the engine until I must.
Glenn Mallory

My 79 MGB has a Crane 270 cam and an alloy head. I set the tappets at .018 cold. After ten years, no problems

Cheers

Gary
79 MGB
gary hansen

Is 18 what the recommended settings from Crane were for the particular grind?

Peter
Peter Burgess Tuning

.017" is what is recommended for my Kent cam. RAY
rjm RAY

This thread was discussed between 07/02/2016 and 11/02/2016

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