Missed on this combo?
Hey the cam guy that said your head was up your *** wasn't named Jim was it? I think ya know who I mean.....I hope it wasn't him cause that's one of the guys I planned to call.
I know I need more duration on the intake side. Not sure I completely get reversion, but have an idea. What do you think about a split duration with LESS on the exhaust side? Or how bout LESS lift on the exhaust side?
Seems like I want to make the exhaust less efficient now...........far as I can understand it.
Now as for asking Dave Hughes to spec me a cam, I won't do that. I've spoken to him....he's a good guy to talk to and I really believe he means well, but I don't know if he's the guy for that.
Tell ya what . He really wants his stuff to be good and he really appreciates your business. That's a fact.
Monday will be phone day. Shane at Crower, RacerBrown, maybe call Bullet and see what they think about the dyno numbers. I think they missed on this combo as well as me.
No, it wasn't Jim. Ill PM you so you know who I called.
It's not just reversion that's a *****. It's does the head flow as well backwards as it does in forward direction. If the head flows just as good backwards, any reversion you have at overlap is magnified. Thats why I don't like back cuts, except with SOME 50* seats and all the 55* seats I have used can use a back cut. But a 45* seat almost never a back cut. Why? Because it increases low lift flow and makes the low lift flow better backwards. Now, as the exhaust valve is closing and there is a low pressure in the exhaust port and the header and you open the intake, all that initial flow (which at low lift is MUCH higher than what the flow bench says at 28 inches) doesn't go into the chamber, but right across the seat and out the exhaust port.
If you are closing the intake too late, the piston goes around BDC and pushes the intake charge back out the intake port. This is what causes standoff and you can see it with stack injectors as fuel will come back out the stacks at idle. If you have a carb, every time air goes through the booster it picks up fuel. So, the air stream picks up fuel on the way in, the piston pushes the column of air goes back out the carb and picks up fuel again (now twice what you need) and then the air turns around to go back into the engine and it gets air a third time (now that is 3 times the fuel you need. You can see exhaust on the bottom of the carb and sometime in the carb when this happens. Usually with a long, slow lobe do you see this. Not so much any more.
There is a good article and graph by Jim McFarland on the HotRod site but damn if I can post the link to it. The graph shows how reversion is much more significant at overlap the intake valve closing.
I think there is more going on with your stuff that just the porting. I've seen many many valve jobs that were power killers. I already talked about back cuts, but the numbers guys love the fact that a back cut almost always looks good on the flow bench. Seat width is a big deal, but th angle and width of the top cut is HUGHE, specifically when it comes to pressure recovery. Your heads could be a valve job away from being what they are advertised.
