Advice needed please! GTS 1 cam with odd valve train problem/question

[hawk1903]

Dear Friends,
I have test fit the GTS1 to the head.
I can say that the Rocker geometry/attitude is perfect when checked against the manifold faces. The swept area is also confirming this, at least according to my knowledge.
However, the full lift is 0.60 mm is higher than the book value, valve clearance set. ( 12.80 mm VS 13.40 mm ) ( normally, this would mean that the valves are way too short BUT the geometry is not saying so ) ???
Shall I modify the valve lenght to get to the advertised max lift or be happy with the 13.40 mm ?
Then, naturally the valve tip to follower edge contact is producing the result which can be seen at the below photo. Although I have run camshafts before with a similar result by milling the edge of the follower, but I don't like this situation.
I would like to have your opinion for this odd situation please !!!
Would you just mill the edge of the CF36 followers or use longer valves ( disturbed geometry ) to kill the lift and totally avoid this situation.
I know that, changing the valve lenghts will also effect the cam's character etc but then what is the correct geometry to produce the cam's intended duration figures etc ?
Quite typical Pinto situation and it may also be the case that cam grinded wrong from the beginning.
Regards

[Graham]

i would be happy to have the extra lift, what i would be tempted to do is recut the valve seats on both head and valve, that will drop the valve back into the chamber a bit and reduce lift, but it wont have a significant effect on lift or geometry

[hawk1903]

i would be happy to have the extra lift, what i would be tempted to do is recut the valve seats on both head and valve, that will drop the valve back into the chamber a bit and reduce lift, but it wont have a significant effect on lift or geometry

Hi Graham,
Many thanks for your help.
As a matter of fact, while I was seeking a help on TS, I thought about recutting the inlet seats carefully to sunk the valves. I have a VGS machine and a valve grinder now in house but we don't have much experience on it yet )
Your advice will certainly work and reduce the lift slightly which will give a relief.
However, I can also mill the edges of the followers for even a more relief which I did before.
What do you think of seeing a 0.60 mm more inlet lift than the Kent's advertlsed value ? Because, as I mentioned with the correct cam follower attitude ( in other words correct geometry ) seeing this 0.60 mm higher lift is strange, is not it ?
Theoretically, the valve had to be at least 1.50 mm longer than what it is to see the advertlsed value. But then, with a 1,50 mm longer valve in this head, I am quite sure that the cam follower attitude/geometry will be quite off the desired attitude, would not it ?
Again, strange Pinto issues !!

[Graham]

sorry perhaps its early and im being thick, but whats the issue with the follower is it hitting the retainer or collets? if so just grind it away where it hits, dont that a million times never had an issue.

as long as the cam isnt wiping off the edge of the follower i usually get excited when i have more than the quoted lift

[hawk1903]

sorry perhaps its early and im being thick, but whats the issue with the follower is it hitting the retainer or collets? if so just grind it away where it hits, dont that a million times never had an issue.

as long as the cam isnt wiping off the edge of the follower i usually get excited when i have more than the quoted lift

no problem !
No, the follower is neither hitting the retainer nor the collet but follower's little radius is not running right at the center of the valve tip. Also, the front edge of the follower is just about the scrape the valve tip. If I give a little radius to the front edge of the follower by milling or grinding it, it will be relief, I think.
However, I think anything over 13.20 mm max lift ( with the correct geometry ) in the Non-roller Pinto head is about the limit. Further than that is kind of pushing it with valve train in my opinion.
Apparently, the lobe swipe area on the cam follower seems good. I am on the move today and tomorrow but I will get photos from my colleague and post the photos within today or latest tomorrow.

[Dyno]

100% sure your follower is exact at 90° with the outer surface? It's seldom cam's give the correct valve lift, let along more. Both extra lift and follower running on the tip give indications the valve is shorter as needed or ground circle smaller as needed (for the valve length). OK, can be wrong, never tested all followers. Valve lift does go up quick with this high lift cams if you "move" the follower. Maybe the follower they sell today is more flat as the one used in the original design ?

I would not worry about the extra lift if all rest is OK. Who says you got a GTS1 anyway? They have send an invoice with GTS1 quote but in my live it does not automatic mean the cam is GTS1

[hawk1903]

sorry perhaps its early and im being thick, but whats the issue with the follower is it hitting the retainer or collets? if so just grind it away where it hits, dont that a million times never had an issue.

as long as the cam isnt wiping off the edge of the follower i usually get excited when i have more than the quoted lift

I tried to upload the cam follower swipe area photo but I am not sure if it uploaded.

[hawk1903]

By the way, there is certainly something very odd with this GTS 1 and as Dirk comments, it may not be a GTS 1 although it has stamped GTS 1.
The timing does not match up with the advertised 2.80 mm @ TDC figure. When I time the cam with 2.80 mm, exhaust valve is 3.60 mm. Equal lift reads 3.25 mm. According to these readings, it can not be a GTS 1. I have sent an enquiry to Kentcams but they have asked the cam lifts but as we were on holiday, I couldn't yet measure this data from the camshaft. I will do that within next week.
However, at the end of the day, even if it turns out to be a miss-stamped camshaft ( I mean not a GTS 1 ), it certainly is one of the Kent' s high lift cams and coming back to my orginal problem with high lift cams in a Pinto head, it seems that having the follower tip to valve tip situation/issue represents a problem in my opinion. Although the swipe area looks acceptable ( well, the geometry was almost perfect in my example ), I am not comfortable with the actual point that follower riding on the valve tip. It certainly is not riding on the center of the tip.
From my findings, I feel that on the correct geometry Pinto head, max lift should not be more than 13.00 mm for a reliable valve train UNLESS a different cam follower developed to give better results without lowering the lift.
Anyway, there are just my findings and friend here may well be successfully and reliably using much higher solid cam followers in a Pinto head. I would love to hear your comments please.