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minorv8
Jukka Harkola

(269 posts)

Registered:
04/08/2009 06:50AM

Main British Car:
Morris Minor Rover V8

215 mech cam valve lash
Posted by: minorv8
Date: June 07, 2021 07:28AM

A question that I have been unable to find an answer for:

I have installed a mechanical cam that requires .020" valve lash hot. For initial setting IŽd like to set some sort of lash cold and warm the engine up and check the lash at operating temp.

Crane cams catalogue advices that for alloy block/heads you can subtract as much as 0.012" from hot lash and use that value for cold lash setting. This is a general value and should be approached with caution :-). Now, my cam is not a Crane cam and naturally extreme caution

Does anyone have real life experience about the matter ?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: 215 mech cam valve lash
Posted by: BlownMGB-V8
Date: June 07, 2021 10:32AM

Anywhere around .010" should be fine for a starting setting.

Basically what you are trying to do is set the max hot lash that won't make a bunch of clatter. Reason for the max is to stretch out the adjustment interval. If they close up too much due to wear you can either burn a valve or develop a miss. The spec gives you .020" to play with. You can close that down a good bit if they are too noisy. Frequent adjustment due to wear isn't as much of an issue as it once was, however you don't want to go much under .005" cold or hot. Usually hot will be bigger but it depends on the materials of the heads, valves and seats.

Jim


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: 215 mech cam valve lash
Posted by: roverman
Date: June 15, 2021 12:48PM

"If they close up too much, due to wear". Please explain ? When cam lobes, lifters and valve train wear, clearance increases ?
Cheers, Art.
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DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: 215 mech cam valve lash
Posted by: DiDueColpi
Date: June 15, 2021 04:07PM

Head gasket crush and valve seat recession tighten up the valve clearance over time. Lifter, rocker, camshaft and pushrod wear loosen the clearance but these seem to advance more slowly.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: 215 mech cam valve lash
Posted by: BlownMGB-V8
Date: June 15, 2021 07:15PM

Valve and seat wear may be less than it once was but it still occurs and it takes up the clearance in the valvetrain, to the point where the valves barely close. Then heat transfer from the valve to the seat decreases and valves get burnt. This is the main reason why you periodically adjust the valves when you have solid lifters. Thought you motorcycle guys would know that.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4512 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: 215 mech cam valve lash
Posted by: MGBV8
Date: June 16, 2021 09:40AM

The older motorcycles didn't seem to need it as often as these newer bikes.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: 215 mech cam valve lash
Posted by: BlownMGB-V8
Date: June 17, 2021 11:30AM

Maybe because they don't wind as high and therefore have lighter valve springs.

Jim



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