How do these specs look

I took a bunch of camshafts one day and put them in a block and mapped them out with a degree wheel.  I rember the WD-WD45 ones being around 176* @ .050 lift.  The late camshafts were about the same, the 175 gas camshaft if my memory is correct was 184* @.050.  Now condidering a guy with a couple dial indicators and a degree wheel, several years of wear on these used camshafts, etc these specs are pretty close, maybe not 100% accurate but they get us in the neighborhood.    I've got the specs for the intake and exhaust as well as lobe seperation angles wrote down in a book in the shop.

The .050" lifter rise is a pretty standard number, meaning most cams and grinders, master lobes will refrence this number.  The "advertised duration" numbers are alwayse higher.  Like saying 238 degrees of duration, there's a huge difference where that number is taken from as the initial ramp on the camshaft lobe is quite slow.  But the problem comes in when people (or in this case the cam grinder) decides to use that number in place of the standard .050" lifter rise. 

We only have so much material on these camshafts to work with, the engine is a siamesed port 4 cyl with a flat crankshaft.  It fires front, back-back, front-front, back-back.  We have 3 sets of "overlap" to deal with, one is overlap within the cylinder, meaning at a point both valves are open at the same time.  We also have intake to intake overlap on a given port.  Meaning as one intake is closing the other one is opening.  We also have overlap from front port to back port, but only half the time or half of the running cycles.

We simply do not have as many degrees of crankshaft rotation to fill and empty the cylinder on this type of an engine as we would on one with individual ports.  The engine also has relatively poor port shape, meaning the air stops and turns a few times to get from the atmosphere into the cylinder.  It's not a nice fluid motion, we can't allow the velocity to ram the air in the cylinder like a better breathing engine can.  Then we have the low RPM of the engine in the grans scheme of things, that piston is moving pretty slow.  It takes time to start the breath and not much time to finish it.

We just can't tollerate a lot of duration on these camshafts. 

A cam lobe will vary a lot, the speed in which we can lift the lifter is dependant on the geometry of the parts involved, in this case we have a decent sized lifter.  The lobe shape will actually be pretty fast in our case. Which means our .050" duration will be closer to our advertised duration than in some others.  In simple terms, the numbers don't look so impressive. 

Lift, everyone wants more lift, but in our case it doesn't do any good.  However a lobe with more lift also will increase the higher lift durations.  Think about it, that lobe that has .310" lift has how many degrees of duration at say .150" lift vs one with say .370" lift.  We don't need to open the valve higher, these heads are done flowing pretty early in the lift cycle, but it's nice for the valve to be open further for longer.  But we have to watch the seat to seat timing, it can't be to long because of the operating speed of the engine, the layout of the ports and breathing order. 

In order to reduce the overlap that is going to kill the engine, what happens if we shorten the duration on one lobe, we can lengthen it on the other to accomplish the same thing but give it more time to breathe.  But in this case we can also change the lobe duration and lobe seperation angles to change the overlap from front to back on the engine or the relationship from the first cylinder in the cycle to the second one in the cycle on the same port.  However it takes setup time, it takes multiple master lobes to be used.  It's not the quick and easy put a master lobe on the grinder and grind a camshaft.

If you want a  good camshaft guy, Quality Performance Camshaft in Spencer Wisconsin.  Randy is quiet, intelligent and very good with camshaft grinding and knowing what to use and where to use it. 

You need to check it with a degree wheel and put where your cam guy says to. But you would probably be better off with the stock cam in your nearly stock engine running nearly stock rpm. That cam in that engine will probably not be any improvement and you will probably lose low end power. The reason I’m saying this is I’ve been down this road before. Save this cam for when you build a 400 plus cubic inch screaming monster and put your stock cam back in don’t waste your time

Edited by nborga87 - 19 Jan 2018 at 9:55pm

Set valve lash to .030 and it's a lot better.