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Manta valve stem oil seals.
Posted: Tue Sep 27, 2011 7:40 pm
by Bobbybedtime
Gents,
Purchased some of these to fit on my early heads ... wasn't sure if it would work but thought I would give it a go.
If you've not seen them they are metal on the outside with a rubber inner.
They fit on the guides okish but I had to 'pursuade' them damaging them slightly in the proces, I think they are on as far as they will go. Fixed with bearing lock and they won't becomming off in a hurry ... only did two for now.
Checked how much valve travel I would have before the spring retainer would bottom out on the seal, its about 8.5 mm.
I have a piper fast road cam which says valve lift is 10.67mm. Is this actual valve lift taking into account the rocker ratio of 1.6?
Thanks,
BBT.
Re: Manta valve stem oil seals.
Posted: Tue Sep 27, 2011 7:53 pm
by sidecar
Bobbybedtime wrote:Gents,
Purchased some of these to fit on my early heads ... wasn't sure if it would work but thought I would give it a go.
If you've not seen them they are metal on the outside with a rubber inner.
They fit on the guides okish but I had to 'pursuade' them damaging them slightly in the proces, I think they are on as far as they will go. Fixed with bearing lock and they won't becomming off in a hurry ... only did two for now.
Checked how much valve travel I would have before the spring retainer would bottom out on the seal, its about 8.5 mm.
I have a piper fast road cam which says valve lift is 10.67mm. Is this actual valve lift taking into account the rocker ratio of 1.6?
Thanks,
BBT.
I'm pretty sure the lift that the cam manufacturer states does take into account the rocker ratio. Therefore you do have a problem!
In fact if they had not taken the rocker ratio into account the valve lift would be 17.2mm which would be a BIG problem!
Posted: Tue Sep 27, 2011 10:37 pm
by katanaman
I agree with Sidecar, you have a problem. At best your going to smash the oil seals at worst your going to break something far more important.
Posted: Wed Sep 28, 2011 9:20 am
by kiwicar
The lift stated for a cam is the lift at the valve with standard ratio rockers but not allowing for any tappet clearance for the engine unless it is specifically stated as lobe lift, and this generally is only done for specialist cams where the tuner will fit anyone of a range of rocker ratios (SB 2 chevy is a good example). If you are ever unsure then the lift will be about a quarter of the diamiter of the inlet valve +10% -20% again unless it is a specialist cam.
Best regards
Mike
Posted: Wed Sep 28, 2011 5:30 pm
by Bobbybedtime
Thanks for the info,
Had another look today and there clearly isnt enough room. I know others swear by these. I'll have to check I've got the right parts.
With the valve lift I have there really isnt a lot of clearence between the spring cap(?) and the guide at full lift, may be 1.5 mm... so what ever I do it has to fit in the 1.5mm clearance.
It seems the only options I have are to machine the guides or replace them or leave the seals off.
Rgds,
BBT.