Sunday, June 19, 2016

Porting Cylinder Heads, What's Stage 1 and 2?

Dart heads has put up some information about porting, that you'd enjoy. Especially David Vizard's work. He put out a seminar about how small shops can be profitable on porting cylinder heads. He really didn't help on the business side of it, like the title suggests, but he sure helps people know what they are doing!



I made 2 videos about porting heads (see my previous two articles, each has a related video). I'm concentrating on theory right now before I dive in to it. Sure, there's no substitute for practice, but I'm still missing some tools, so I'm learning for my mind first. The first video is about David Vizard's concept of swirl. Weather you have a 4 valve or a 2 or 3 valve head, my video has something for you there, that I haven't found anywhere else, besides buying his book. He has a patent on it, so we can't sell a cylinder head with his idea on it without giving him something like 7%, I don't remember.

I'm writing in response to this question by Dynamic's Productions on this video:
DIY Head Porting Small Block Chevy Vortec 062 Part 1 of 3 

"[I'm] thinking about doing this to the heads on my iroc i was a little unclear on this process and was wondering if you could clear it up, when u take this on are you just going for smoothing out the factory stamping and knocking out the carbon build up and taking the rough lines out of the factory casting or making all the ports bigger the whole way down through or is it a bit of both, id like to know as much information as [possible] i got 2 sets of heads but id rather not [#*&$] either one up"

To be more directly about what you asked, you're first suggestion, being minimal, is a porting that would be considered stage 1. Finish up by smoothing with 80 grit sand paper. Anymore and you're making things worse.

Stage 2 is where you open things up more rather than just some shaping and smoothing work.

I've only watched over half of TPV's video so far, but his information is dead on with what I've learned from other creditable sources.

Stage 2 requires that you know how much metal is everywhere or you could punch a hole in something else that the engine needs!

So, you'll either have to learn from someone else knowing your exact heads, or buy an ultrasound device meant to check how thick metal is, and you'd have to check everywhere, and stay away from thin spots.

More that I learned from David Vizard, that didn't get put on TPV Production's video:
Note: I originally wrote the below as notes, I may have quoted David, I may have only paraphrased, so I give credit to him and the video I embedded in the video above.
When you're porting your cylinder heads, don't let that customer walk away without getting a good exhaust.

It isn't the piston that draws in the charge, it's the exhaust.

When the piston is at bdc there is only a 1 pound drop of pressure, it's the exhaust that makes for 14 pounds of pressure. Don't worry about your intake only...this made me feel great about upgrading my exhaust before my intake by the way...so don't just worry about the intake on your porting work, the exhaust needs velocity, it needs high, more laminar flow too, or your intake work will look less stellar than it is.

Understand, these are lessons a flow bench can't teach you. The above paragraph are observations by David, and those he's learned with watching actual engine's function. Flow benches are a tool to test flow yes, but you couldn't learn that the exhaust is primarily what brings in the intake charge from a flow bench! This makes me want stage 2 cam's for my project. The increased lobe overlap would assist in bringing the exhaust's flow into the intakes flowing moments even more!

Would it increase emissions and lower idle quality? Probably. But I have an awesome catalytic converter that is already pushed leaner than most, it could use more fuel for cleaner air...may not be so good for my car's miles per gallon! LOL

By AutoBravado