refresh951

On my first "high flow" head (see here) I learned a great deal and I think the effort had reasonably good results. I really worked the head for my 2.85L Hybrid Stroker and then later used it on the 3.1L. With Winter coming I will be parking my car in a couple weeks and my goal is to work a new head over the Winter that flows significantly better. Originally I was planning to have someone do it for me (such as MM) but the more I think about it the more I want to do it myself. I realize it will probably suffer a bit but I really want to learn and share what I find.

Today I took an extra turbo head to my machinist for dis-assembly and cleaning. I also ordered 49mm (+4mm) intake valves from from SI. SI Valves has +1, +2, +3, +4, and +5mm. Amazingly I bought the valves for $22/each and they shipped today.

My plan is to sacrifice a head or two to experiment with port size and shape changes on a custom flow bench. I know to some this may seem crazy but I love doing this kind of stuff for fun.

eman930

This is gonna be a good thread... Not sure what's up with the intake valve... But wow that port is really changed they really opened up around the valve and above it.... Something you might wanna look into is valve stem sizes.... Thinner steams mean less restriction to air flow, also is it possible to have a custome valve guide made? Something shorter to keep it tucked into the head and out of the air stream. Also who parted that head, looks like a really good job

333pg333

Be interested in your findings Shawn. I know of this head and the associated claims. Be great to see some of the dyno sheets on that car too. Perhaps A will chime in.

blown 944

I would also look into thinner stem valves.

If you're going this far you may just look into it.

Be cautious not to get too caught up in peak lift flow numbers. Having solid flow from seat to sear is what you want. Think of it as a laggy huge turbo vs a perfectly sized one.

Your engine in particular would be a good example of maximizing the usable rpms.

I'm pretty sure you'll cover it well, I'm looking forward to it myself.

With that said, are you going to swap the cam prior and get a comparison? That is the change im really looking forward to right now. I also think it would benefit you to know what valve spring pressure you'll need.

refresh951

Thanks Sid. Yes, looking at everything. Looking to get a cam, I sent Dave McGrath an email and have not heard back from him.

refresh951

Very good article on port flow basics:

http://www.popularhotrodding.com/tec...g/viewall.html

Port molds:

http://www.diyporting.com/molds.html

refresh951

Working on a low cost flow bench to test ports in my test heads. Once I feel pretty good about a port shape approach I will have it tested on a SuperFlow. Here is the setup I am working on which uses my Arduino Logger

eman930

I've got two questions... Are you gonna use the shop vac and suck threw the head? Or are you using it as a blower?

Also I don't know the science behind it and maybe you can help me understand... You'll be measuring CFM but what about air speed, What I mean is couldn't you have the same CFM from a port but different air velocity? Say you were looking to
Improve CFM, So you Just make the port really Big to flow a lot of air volume but the air is really slow? You'd have the same CFM as a port that's half the size but moves the air fast? I'm I crazy and over thinkin this?

refresh951

I will be pulling air through the head rather than pushing it as this is the typical setup and closer approximates the actual conditions.

Yes, porting definitely effects velocity. The key is to try and control velocity within the port in such a way as to optimize CFM. An example would be slowing the velocity at a turn to let the air more effectively make the turn. This can allow the air to use the whole perimeter of the valve which can increase CFM. The dynamics within the port are very complex and affect the flow capacity significantly.

Tom M'Guinn

That's a great project! Will you test one port at a time, or the whole head. Do you know if the shop vac has enough CFM's? Have you seen this article?

http://www.jalopyjournal.com/forum/s...d.php?t=309410

refresh951

Yes read most of that. Thanks!

Yes, one port at a time. Lart is sending me some old heads for testing. Going to cross section 1 or 2 ports then try some different porting ideas on individual ports and look at the results. See here wrt shop vac cfm:

http://www.flowperformance.com/shopvac.html

V2Rocket

If you have a spare block, how about putting the vac hose at the bottom of a cylinder bore to recreate the chamber air will follow into through your head..?

Van

Spencer, that is actually what a flow bench does. It has a fixture that's the bore and stroke of the cylinder, and at the bottom of it is the connection for the blower/vacuum source. This way it mimics how the air has to travel in the cylinder filling portion of the 4-stroke cycle.

Ideally, you test the air flow with the valve at different lift points - e.g. 0.050", 0.1", 0.2", and so-forth up to the max lift, which is about .475" on these engines. This will help you put together a picture of what the theoretical flow numbers would be... with a little math, and the knowledge of your cam profile, you can figure out the volume of air that will fill the cylinder in one stroke.

Like Sid said, peak numbers can be a little deceptive... because the valve is fully opened for such a short duration. In fact, valves will spend a larger percentage of their duration close to the valve seat than wide open, so there are some good gains to get by getting a head to improve flow at 0.050" lift.

There are 2 things a flow bench is really good for: first, making sure the four cylinders are flowing evenly - this will maximize an engine's performance; second, by flowing all parts of the intake system, the most restrictive part can be identified (and corrected if necessary). If you've got great flow on the intake side of your head, but if your manifold, throttle body, AFM, turbo, intercooler, air filter, etc. can't support that much air flow, then it's all useless.

In short, a flow bench is a tool used to help make decisions about your whole system, in addition to providing a way to quantify the effect of geometry changes to an air passageway.

refresh951

This video shows basically what I will be doing:

refresh951

Another good read:

http://www.austincc.edu/wkibbe/headdesign.htm