New valve seat setting - le Mans

I have had my Le Mans heads refurbished, aqua blasted , new valves, guides, and the engineering shop fitted new exh valve seats.
What I have noticed is that the exh valve seat is set differently to the previous old one. I know because if I measure the amount of valve stem sticking out of the valve guide is 1.5 mm less on the exh valve than the inlet valve.
Does anyone have experience of valve seat setting in Le Mans heads so I can give the engineering shop a measurement to go by ?

I am also fitting a Raceco SS2 cam, does anyone have experience of this cam and if I need to modify the heads to fit this cam ?

Appreciate any advice ??


Not sure on the Le Mans BUT in the Guzzi manual it does show and does have shims fitted on both the inlet and exhaust. If you look on Greg Benders “This old tractor” website the V1000 manual WITH Le Mans supplement IS downloadable.

I redid the heads on the V1000 recently as I am refurbishing the 1000 engine The shims under the valve springs position them correctly So I reckon either they have been put back incorrectly OR need new ones.

I DO know it needed very strong magnet to get the shims off prior to vapour blasting as the stiction on the oil was unbelievable.

I hope this helps even tho’ it probably needs aome PITA work

hi guzzi bearthanksyes the shimming of valve springs is the next job, but i need to get the valve seats and valves both set the same in the heads first. thats what i need advice for. does anyone have a std Le mans head that they could look at for me and measure the exact distance the valve sticks out past the valve guide ? i assume it should be the same for both exh and inlet valves ? thanks

My MG workshop manual implies both inlet and exhaust should be equal, HOWEVER is distance between tip of stem and the actual metal of the head, NOT from the end of the guide. Provided the stems each stick out the same distance from the base of the head I think guide variations won’t matter. Apparently guides should be 52mm long, and secured by like a wire circlip in a groove. This clip is sandwiched between the head alloy base and the bottom spring seat (and shim if any). FYI manual’s diagram says 36mm ±10% for the length of the outer springs, when fitted, mind you that’s using the base shims of the tune-up kit. HTH PS: (edit) ~ are exhaust guides fully pressed in (circlip flush with head) ?
Mike H2014-02-17 18:29:40

Ahh have they done the zorst valve to take unleaded, guessing BUT I suggest you ask the guys wot did the job OR someone like SMS (or is it SRM they do alot of this work OR someone like Paul at Corsa or Baldrick who will have dealt with these things far more than most of us have.

All I could go by is the Guzzi Manual

did they do the seats on both heads ?

hi guys
yes they replaced the exh valve seats and this is what has thrown up the problem, it looks obviously different to the inlet , which is the std valve seat, just re cut and fitted with a new valve.
what I am concerned about is that there is very little distance between the outer edge of each valve when shut, I am worried about valve clashing on overlap.
I am also fitting a Raceco SS2 cam which has different Lift/duration to std cam and if this will cause any more problems too ?
MIKE H; yes your right , I need to measure from the head surface to the top of the valve, not just what is sticking out, good point, didn’t think of that !
however the valve guides were left intact, they were K lined instead of replacing the valve guide itself.
thanks for the advice !

OK measure all the stems from the base, if exhausts are shorter then yes looks like the seats are ‘too thick’. I’m guessing.

Yes at TDC exhaust stroke both valves are open. Exhaust closing inlet opening, but at TDC they’re probably open by the same amount. Standard cams that is.