How much metal is available?

[emarsh]

Hi Folks,

I'm starting on a B/ND project and think that I'll probably go with a small Ford engine combo. These cars burn methanol and from the research that I've done it seems that because of the extra fuel volume the consensus is that ports should be about 8%-10% larger than for gasoline fueled engines.

I'm looking at starting with a set of Dart heads and then doing what I can to kick up the airflow. This brings me to the question of how one knows if there's enough metal to remove without breaking through a port wall. Just experience? Ultrasound? Something else?

Also, what's the feeling about hand porting vs. CNC? To talk to people you would think that hand porting is almost old school, and that argument does seem to make some sense when comparing it to the mechanized perfection of a computer controlled mill.

Any thoughts?

Thanks,

Eric

[jfholm]

Eric,
I would probably look for a sonic tester on ebay - there have been some good ones for about $170

Next buy Larry Meaux's PipeMax software and that will help you calculate the port sizes. Larry has worked on a lot of the A/ND and B/ND heads.

As far as CNC goes it does not necessarily mean you get a better port than a hand ported head. What they do is hand port a head then run a tracer through it to map the port into the CNC program. After that every port you do using that program will be exactly like the original hand ported port. Be it a good port or a bad port, they will all be exactly the same. Also the CNC can turn out a lot of heads but they may not be even close to what you need. Every engine needs it's own size port that is determined by CID, camshaft, peak HP RPM, rod length, piston speed, piston swept area on and on and on. So you have do design the head for your engine so how can a CNC'd head be perfect for your engine if it was a head designed for a broad range of engines.

I still like to do my heads by hand as I can fit to each engine exactly. Takes a lot longer. Most serious racers that I know may buy CNC heads that are slightly smaller than they need and then take them to where they need them. Saves time having the majority of the hogging done already. Me I usually have the time.

Welcome aboard!

John

[emarsh]

John,

Thanks for the note.

Looks like Larry's software is a bargain at $40.

I've always enjoyed trying different combinations in the pursuit of performance and I'm looking forward to what I can learn from a flow bench and hopefully a dyno a little further down the road. I've also a turbocharged bike and I think that doing porting work aimed at what the turbo would like is another interesting topic.

Eric

[jfholm]

[color=#000000]Also keep in mind that NHRA seems to be really watching the heads in this class

i.e. on the SBC they have to be the 23

[emarsh]

I don't get too excited about what NHRA does. To be honest, I'm not particularly excited about (or impressed with) the NHRA in general.

We have a local circuit in Texas and that's where I plan to go racing. I don't have the money or interest in trying for a national championship, I just want to go fast, have fun and hopefully win a race or two.

As for welding heads, the whole idea of using cast iron in the class is to keep the cost down and as such in my opinion any welding should be illegal because of what it does to the cost of engine development. IMHO if they were to allow welding then lets just go for alloy heads since they are easier to weld and not really that much more expensive than iron.