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Kent AH4 Camshaft

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Walter74

Walter74

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Good afternoon,

I am able to source a Kent AH4 cam shaft to upgrade my BJ7 engine, but I am not able to determine whether or not valve pockets in the pistons are necessary for this cam shaft.

Does anybody know this?

Thanks in advance for your advice!
 
Do you know the lift for that cam? That will determine if you need pockets. Are you using the stock rocker arms? If you change the arms to a different ratio, you may need pockets.
 
Walter74,

Welcome to the forum.

Sorry, but I don't know if the block needs to be pocketed.
I found the specs on the web site for Kent Cams.
11.57 mm valve lift.

This cam is for an MGC motor.
Good Luck.

Doug Glesmann
 
I have just put a Kent AH4 profiled cam into my rebuilt engine and I did include valve pockets for clearance.
 
Yes, 11.57 mm definitely requires pockets. I have a Denis Welch DWR 8 cam with 10.18 mm lift and pockets are required. The Denis Welch DWR 1 cam at 9.09 mm lift does not.
 
Too early to tell as it is still in restoration. I have run the engine, but only to bed things in.
 
Engine builders use a type of clay--PlayDoh works, I hear--positioned on top of a piston. They rotate the engine through a compression stroke and measure the depth of the pocket left; if a valve hits the top of the piston I'm not sure what they do (maybe mill pockets until the valve clears?).

Betcha Dougie knows.
 
Walter74 said:
Is it difficult to determine the positioning and depth of the pockets?
Click to expand...

In the case of the Healey motor it's pretty straightforward because the valves are vertical and the only interference is with the exhaust valve over the deck (it would take a very radical situation to have piston to valve clearance issues - perhaps Dougie's motors are that radical?).

Locating the pocket is simply a matter of blueing the deck, setting the head on with a loose exhaust valve (no spring/retainer) and manually spinning the valve against the deck to make a mark in the blueing on the deck. Typically adding an 1/8" or so to the diameter of the mark for 'safety'.

Depth of pocket is determined by knowing the lift at the valve of the cam you want to use. Then measure the distance from the surface of the closed valve head to the head gasket surface + gasket thickness (stock type is typically .040) + whatever clearance your machinist suggests (typically around .040 for this situation). So, if the valve lift is .450 and your measurements add up to .400, then you need .050 deep pockets. You don't want the pockets any deeper than necessary because they enlarge the combustion chamber size therefore lowering the compression ratio.

And playdoh is a nice confirmation before running the motor.

Dave
 
There’s no pocket in the pistons, there are pockets in the block. The intake valves go wider than the bore. The head gasket has pockets in it to avoid the valves. That will tell you the position of the pockets. You’ll need to assemble the head off the engine and apply 11.57 mm lift to the rocker arm and measure how much the valve extends past the face of the head. That will tell you how deep to go.
 
Here is a visual for you on the pockets.
engine pocket ported.jpg
 
Radical yes, but no pockets needed in the piston, just a beautifully milled dome. With the combination of cam lift and roller rocker ratio, I'm at the max pocket depth.

'57 Domed Race Pistons.jpg

Roller Rockers - Beehive Springs.jpg
 
What are the black flare fittings for Dougie , an external oil cooler ? Also what are all the threaded plugs for by the freeze plugs .
 
Healey Nut said:
What are the black flare fittings for Dougie , an external oil cooler ? Also what are all the threaded plugs for by the freeze plugs .
Click to expand...

Race motors never see freezing temperatures, but simple plugs can fail under extereme (6-24 hour) race conditions. The threaded plugs stay in place and the large freeze plugs are epoxied sealed. The black flare fittings are part a special designed and engineered side oiler system which inputs the oil from the oil cooler directly to the crank & main bearings first before circulating throughout the entire motor. This is the key to extending the life of the custom billet crank....

Billet Crank 1.jpg

Billet Crank 2.jpg
 
That crank is a piece of art . Tks Dougie .
 
Wow, that is next level engine building. A bridge too far for my road car:smile:
I will stick with some simple pockets in my block. Thanks for all the useful information. I already found a good machineshop to help me out
 
Walter-

Given that you come from the Netherlands I had to laugh when you said "A Bridge Too Far".;)
 
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