Re: How Check if Numbers Match

Kevin McLemore

Don’t know about the GT’s tags. Early cars didn’t have any engine reference on the tag but later cars might have??

As to the timing marks, if it’s a rubber-sleeved harmonic balancer (i.e. there is rubber between the outer rim and the inner hub, to reduce vibration), then definitely yes, as the rubber hardens and shrinks the outer rim can begin to slip around which of course makes the timing look like it’s off when it’s not (or worse yet, vice versa!)  One easy way to check to see if it’s slipped is to put a dial indicator on the front face of the rim and slowly turn the engine over... if there’s more then an insignificant amount of runout (wobble) then that’s a sure sign yours is shot. 

I replaced the one on my Sunbeam motor when I rebuilt it because when I went to have everything balanced they found excessive runout in the original.  I dodged a bullet on that - the timing marks had not yet slipped so it went unnoticed until then. 

Be careful when buying a new one... This is one case where “NOS” is NOT a plus. And a good, properly made balancer isn’t cheap. 


On May 4, 2020, at 4:41 PM, Roger Searle via <searlerb@...> wrote:

Hi All,

I hope everyone is well.

On my 1971 MGB GT, how can I check if the engine and transmission are the original equipment?  Should the tags on them match the
VIN no.?

Also, has anyone ever heard of slipping timing marks?  Ed Sweeney is working on my GT and discovered the timing was 20 or more degrees off.  But the timing marks said it was right on. 



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