16 replies to this topic

[RHDmini74]

This is the only picture of the camshaft I have. So I’m not sure what is a safe clearance to start the motor at. Can anyone possibly tell what can this is from the picture? It had a spider drive end for the oil pump.  71390CE3-EB74-4BC9-AF42-13976A52D36E.jpeg   34.49K   2 downloads

[Spider]

Mmmm,,,,, not really,,,,,

 

If you have a Dial Gauge and some patience, you can likely measure with some accuracy the lift of the Lash Ramps of the Cam as it rotates, as it's all in car, may as well measure at the valve and that'll give you a direct indication of how much lift is in the Ramps.

 

The Lash Ramps are the parts of the Cam Lobe just as it comes off the Base Circle when lift is about to commence and gain at the end of the lift cycle back on to the Base Circle. These are factored in to all Camshaft Designs so the Valve Train doesn't hammer itself to death. They are a very slow gentle lift and fall on the Lobes. Once you are off these Ramps, you'll notice a marked rapid increase in lift and like wise at the other end. These Ramps are typically over about 30 to 50 degrees of Crank Rotation, where you'll only have around 0.015 - 0.020" of lobe lift off the Base Circle.

 

So, if you find that your ramps are around 0.015" in lift, I'd suggest setting the tappets about 0.003" short of that at around 0.012", this way, all the slack should be taken out of the valve train well before the valve comes off it's seat.

 

I'd strong suggest to avoid guessing as too little clearance will likely result in burnt exhaust valves (and a possible cracked head), too much and it will hammer the valve train to death in short order.