This is getting good. Both you guys do really good work and I say this with experiance based on Brian doing head work for my friends cars and my own personal stuff and then with Jeff working his magic with Bob Mazzolinis and Ken Etters stuff for Super Stock. All the cars that I have seen with Brians head and Jeffs heads are FAST! To both guys keep up the good work! Look forward to reading both of your posts at any given time.

sure you could have 3psi of pressure on the back side of the intake valve,, depends on the combo, rpm range, really just about everything that has to do with the engine. really when you get to looking at a depression, and trying to effectively filling a cylinder,, it takes a free or good flowing head which is usually larger in cross section therefore you need to try to evenly pull on the port with how the piston comes off tdc. alot of guys think the rod connects the crank to the piston, but it will dictate the rate of accleration the piston will decend till the mid point of the cylinder, which is the same for any rod. usually this is a rod ratio of 1.65-1.7, dependning on the storke respective to the port cross section again, that can be changed to help an rpm range thats desired to run, or able to be run, we all want to run it as high as you can without the valve train blowing up.

another thought with sheet metal manifolds,,, its common knowledge that you should contain your swept volume at whatever efficiency your engine will run at,, i usually say 115%,,, in the runner so that your complete mixture that will end up in the cylinder has the initial inertia of being in the runner when the valve first opens to get maximum pressure effecting on the cylinder. by working on volumes in manifolds like that its crazy how much power you can gain,, for every degree of intake valve timing that i can hold it open longer ill get about 7hp. but for an engine like a pro stock, its closer to 12hp,, when you consider how much piston movement 1 degree is you understand how tempermental the pressures are and how a little bit,, can be a whole lot.

did i run on??,, i had a late night


jeff

I had lunch with David Vizard not long ago and we discussed this tuning a little bit, I asked him specifically about cylinder filling particularly as it related to long intake durations where the valve is closing well past BDC and the piston is rapidly moving back up the cylinder removing effective displacement with every degree.

He mentioned the one fact that manyt people don't completely comprehend...something a motor depends on but we're not really concieous of...the fact that air has mass and a column of air mass in motion has momentum. The very notion that VE's can exceed 100% in a race engine is testament to that fact. You also see and understand how variables in the air density effect power output if there is more or less pressure in the intake tract.

What dry flow benches do not take into account is the fuel atomization and if or how it stays in suspension at various RPM (proportional velocities) through the powerband, Also it's imprtant to realize that with an example 12.5:1 A/F ratio, ~7.5% of the potential flow is displaced by the fuel the air is carrying in suspension...especially in a carburetted motor. to muddy the waters further, on a bench we tend to only look at air moving one way (either into or out of the cylinder)...the effects of reversion when the rapidly moving column of air suddenly gets the door slammed shut as the valve closes and has to regain it's momentum. Then you think that all the airflow moving through an engine in a minute's time when we know that any intake or exhaust valve is closed roughly 2/3'd of the time....regardless of crankshaft RPM this is a mechanical constant.

I'm glad you touched on rod length....it's a great tuning tool. The best combo's I've build or seen had EVERY component working in the same rpm range. That is why alot of times I suggest to guys who get their heads ported, that they change the cam. Porting changes rpm range as much as it changes power.

A few times a year, I email back and forth with Larry Meaux in Louisiana and he has really helped me to understand some of the things I find. He's also helped me to realize what you just said Jeff about every little detail affecting power.
I see you have a nice write up in Engine Masters magazine about your BB edelbrock heads!!

Brian

If i would like to change the intake valves to 2.05" what length or maybe even a partnr.
Is it worth much?

I am not any kind of expert in this subject.
I have unshrouded(?)the valves as much as possible (head gasket) and I have opened the bowls to the point where I am sure I will not risk any performence loss and i guess the valve seat will be proffesionaly done. I will try to post some pics.
Where can i get the valves? are they chevy valves?

You can use any chevy type valve, it just needs to be .100 long chevy valve. .100 longer is almost exactly the stock sb mopar length.
I use Manley and Ferrea but there are others out there...

You dont happen to have a partnr of the one you preffer to use?

How much gain could i expect from upgrading to 2.055 valve?

some pics.
Tell me have I ruined these heads?

nr 2

3

4

5

Quote:

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Tell me have I ruined these heads?

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Can I think it, without saying it?

Seriously, I'm inclined to think you may have compromised the structure
of the head, despite any air flow improvements you have gained.

That's a lot of meat out of the straight wall.

What are your flow numbers?

I didnt take much off the straight wall just the headboltbulge and some polishing. guess there is some amount of core shift. As for flownrs I wouldnt ask if i ruined the heads if i had flownrs. 200 cfm bad 300 good.