Cam timing

[seniorchristo]

I am getting ready to install the cylinder head and degree my cams. I had the head reworked a couple of years ago but am now just getting around to the engine assembly. It has Ingram cams ING-425-V with .425 lift and 272 degrees duration. Also large valves, 1.62" inlet and 1.4" exhaust.

I don't have the original cam sprockets, only the adjustable ones as pictured. Without timing marks I'm not sure how to set the initial timing. From the Cam details it looks as though I need to rotate both inlet and exhaust valves to reach .121" of lift for correct position at TDC. I can do this with the head off the block to avoid interference. I don't know what the 106 deg c/l designates. Is this the MOP?

The recommended valve clearances from Tony Ingram are .006' inlet, .008" exhaust. My clearances are on average .004" more than this (.010" inlet - .012 exhaust). Could these have been increased to allow for break in?

Thanks
Chris

[Billmack]

Lobe center line and maximum opened position are same thing. I have only seen the m.o.p. term come out in last couple years

[Billmack]

With the head off turn the cams in direction of rotation so exhaust is closing by that amount and intake is just opening before putting head in place. Be aware that valves are sticking down from the deck so if you rest the head with deck down you will most likely bend a couple valves.

[2cams70]

The valve clearances need to be set to spec. if they are currently out of spec. You’ll need to check them again after the head has been torqued and the engine run for a bit. Sounds like the supplier has sent you the specification of the cam rather than how to set it up correctly. I’m not sure why there is a figure lift at TDC and then the meaning of “at 106 degrees c/l” that follows. Needs more clarification from the supplier and confirmation of how to set the cams up specifically. The Wilkins book by the way gives a good explanation of how to set up the cams. That’s one section in that book where the information is very good.

[rgh0]

The valve clearances need to be set to spec. if they are currently out of spec. You’ll need to check them again after the head has been torqued and the engine run for a bit. Sounds like the supplier has sent you the specification of the cam rather than how to set it up correctly. I’m not sure why there is a figure lift at TDC and then the meaning of “at 106 degrees c/l” that follows. Needs more clarification from the supplier and confirmation of how to set the cams up specifically. The Wilkins book by the way gives a good explanation of how to set up the cams. That’s one section in that book where the information is very good.

What Tony Ingram means is that the lift at TDC is what he specified if the cams are timed for a 106 degrees MOP with the clearances specified.

This gives you a good starting point based on this lift to do the initial setting at TDC when bolting on the head and then you can set the chain and rotate the engine cams to check maximum opening point versus crank degrees and do any fine adjustment with your sprockets

cheers
Rohan

cheers
Rohan

[2cams70]

Thanks for confirming Rohan. If he means MOP at 106 degrees that’s easy. You don’t need to worry about what the actual figure for valve lift is. You just need to observe when lift is at a maximum and see if correct. What the clearances are set to has no effect in that case - at least for the purposes of setting up the cam. You do need correct clearances for a correctly running engine however.

[seniorchristo]

I positioned the pistons at their midpoint in the bores to avoid interference with valves and set the cams for .121" lift. Next I will do a trial assembly to check the piston to valve clearance with clay in the valve cutouts. Then I will have to reassemble the head and set the MOP to 106 after the chain is installed. I plan to use the old head gasket and just snug the bolts.