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Working on my daughter's house for most of the day. I'll get back to you guys. I appreciate the response and interest.

Here's a couple of pictures of the pushrod pinch on the Speedmaster port that's currently on the bench. I've finally switched to a 2.08 valve after working forever with the 2.02 valve. Here are some opinions from my perspective, and I do not claim to be correct. Regarding the pushrod pinch, I...

If the Speedmaster version is a copy of the Edelbrock it should work well.

My truck had been sitting for 10 years, had way too big a cam in it, had 7.7:1 compression and the 1970 manifold. I had the heads milled 0.080", ported the heads, changed the cam to a much smaller cam and installed the Air Gap with a 650 AVS2 all at the same time. It does run much better but...

I have a 1979 Dodge truck with a 360. About a month ago I took off the 1970 340 4-barrel intake and intstalled and Air Gap. No problems whatsoever with the AC brackets except I had to grind about 1/8" off 1 corner of the bracket that mounts to the driver side intake manifold bolt. No problems...

I would have to go back and check, but I believe the pushrod pinch in the smallest in most small block mopars. The apex area at the top of the short turn is the biggest problem however. There is a little bit of time for the air to expand and slow down after the pushrod pinch. Not so after the...

I appreciate the post and the interest. I’m learning as well.

In a perfect port the throat would be the mcsa.

Let me make the disclaimer that this is not undisputed fact. I don't want to present it that way. This is the way I look at things and I could be wrong. It just explains a lot of what I see on the bench and fits with other things I've read. We can continue this discussion. I enjoy the...

A very poor head would also reach a choke point. Funny thing about MCSA is that it moves around and can even be variable. If flow is not very turbulent, hard surfaces are creating the MCSA. This could be the valve and seat at low lifts, it could be the pushrod pinch at high lift when the...

Darin Morgan has some posts on Speed Talk where he discusses the difference between sub-6500 rpm engines (most of our stuff) and high speed engines. Sub-6500 rpm motors will never get near the 124% VE maximum because there is not enough energy in the pressure waves in the intake tract to be...

Good stuff! Thanks for sharing. He does a good job of breaking down the MCSA equation.

Hello PolyJohn, I have actually been testing quite a lot lately. Usually 2-3 hours before work each morning. Most of my tests have been with the Speedmaster head and a 2.02 valve. For months I’ve been trying to make a 300 cfm port that does not nose over/back up at 0.500-0.600 lift. I...

Here are some results from recent testing I've been doing on a Speedmaster head with 2.02 intake valve. I've enjoyed digging into the data so I thought some of you guys may like it. The methodology is somewhat scattered because I'm looking for flow in certain areas of the curve. That approach...

Maybe just practicing for Nov 5th.

Here are a few pages from DV’s How to Build Horsepower book. Shows some of his thoughts on LCA vs displacement.

There’s a video on YouTube with Curtis Boggs of RFD. In that video he talks about really starting to understand what happens in the ports when he understood the relationship between pressure and velocity. He was referring to the Bernoulli principle applied to points in the intake tract, not just...

As with many calculations of this type, the most simple forms of the equations make a lot of assumptions and eliminate some of the more complex variables. The most simple forms of Bernoulli assume incompressible flow that is also non turbulent and frictionless. Non of those assumptions are true...

That is certainly one of the important ones to look at.

I think you are correct. In an adiabatic process where no heat is transferred to the surroundings, expansion would cause a drop in temperature and compression would cause a rise in temperature. There would be several things going on in the port (on the flow bench) that would cause temperature...

I agree. In theory the temperature rise through the port (on the flow bench) could be related directly to the inefficiency of the port. I don’t have the equipment or experience to do that however.

I’m sure we all keep expecting to see his posts. Quite the loss.

You are correct that the pitot measures local velocity. If we are trying to measure the average velocity in the curtain area, then taking multiple measurements around the entire perimeter of the valve and averaging them together will give the average velocity. That’s what the section...

Just stumbled across this guy on YouTube. He has quite a bit of drag racing and NASCAR experience. Some of the videos are old, but I found the tech talk to be quite good. He also has website dambest.com and a Facebook page. Some of you guys might enjoy.

I would be willing to get involved with this and commit some resources to it. We would have to come up with a set of heads, or at least one port in a head. Could even be one head to borrow for a little while. Anyone out there have one of his heads sitting around?

Totally shocking. What a wealth of knowledge and a willing mentor. You will be missed, John. May you Rest In Peace.

Near the end of the video he shows the narrow quench pad that he left on the shrouded side of the intake valve. He left it there to keep velocity up in that area instead of unshrouding the valve and increasing flow (which he said also decreased the velocity in that area of the valve). Fascinating.

That is part of it as well. Compare the 2 extremes here. Look at a wedge head chamber around the entire perimeter of the intake valve and compare it to the chamber around the perimeter of the hemi intake valve. In the chamber the hemi makes a nice 'cone' around the valve. This allows the air...

Darin explains all of this in other videos. A wedge head motor is generally capable of rpms in the 9000-9500 range because the cfm/sq in is limited by the in line valve arrangement. A canted/rotated valve head can support more rpm because it can flow more cfm/sq in of valve area and because...

I could be wrong, but here is my interpretation of the 118 cfm/sq in of valve area. That number is the current benchmark for a canted and rotated valve race head. It is not the theoretical maximum flow. The benchmark for a true hemi head would be slightly higher than 118 and the benchmark for...