I was just wanting some input on valves i have ground
I have a cnc centerless grinder that is accurate up to .00005 , i have been playing around with my valve angles not the valve seat angles. i was just wanting to know if you think it helps. i did a stock b16 head like this and it really runs better. i have not put it on the dyno yet just street tuned with crome pro.i have a h22 that i am working on now. do you think i need a flow bench to do this. Also do you think i could hurt the flow of my head.just to give you a idea of what i am doing i did a little drawing in paint i have cad/cam at the shop but i am home now so i used paint

so the area in the red i just ground to the angle it was and then a created a new angle in the green section. The blue and yellow section i did not touch because i was scared it would make it week. i want to change the blue and yellow. i have some omni valves that the blue and yellow section is changed. but would oem valves break.with all this said i think it has helped what ideas do you have for doing this

 

do not touch the blue and yellow. thats asking for trouble. the only thing you cloud do is create more angles. wouldnt recommend unless your very good at it though.

main thing is to port the head to help flow with the valve, but having a good regrind on the valve seat to valve is very critical to

 

What would be the benefit in changing the angle in green?

 

i can put as many angles that i want. i think i am going to get a flow bench to see what the effects the angles have. i purchase a valve seat machine also so, i think it would be best for me to go with a flow bench. but for the valve grinder i have. i can program it to do what ever angles i want.i wander if putting a small radius between the gray to red
radius the red to green
radius green to blue.
also would thinning the red section do any thing

 

as for changing the green area i noticed that most aftermarket company's change that section
also this is what i am talking about grinding the yellow area to make it look like this valve



Modified by ashb82 at 6:44 PM 1/4/2008


Modified by ashb82 at 6:46 PM 1/4/2008


Modified by ashb82 at 6:46 PM 1/4/2008

 

Most , if not all, aftermarker performance valves come with a 30 degree back-cut in your "green" section. This is a generic angle that seems to work well with all ports, and usually pays off with increased low-lift flow. Interestingly enough, it can hinder high-lift flow. The perfect back angle for a valve depends on , just like everything else in IC engines, numerous things. But the 3 most important would be Height of short turn, camshaft lift, and actual seat angle. Im not spillin no mo beanz.

I have seen the under-cut stems, which you are referring to as the "blue and yellow" sections, gain 1-2 cfm, and i have seen them do nothing. But there is another benefit besides airflow that should be quite obvious.

 

As CC said many,many things affect the degree choice of a possibly needed back cut angle.W/O a flow bench or dyno it is impossible to tell if it will have any performance gain.

As for the necked down stem in yellow the main benefit is the weight reduction.As long as you are able to blend it into the valve head corectly you can do it.But if not,you will make the valve weaker thru a stress point from the tool marks.That is why aftermarket undercut valves have what's called swirll pollished heads into the stems.

No,do not radius the valve head into the seat.Imo and testing w/my port work the int side prefers to have very sharp defined angles,just like the valve job.But others may argue this point.

 

will a head that flow more cfm make more hp or can you flow to much cfm

 

yes heads need to be ported to the application.It makes no sense to put a race head on a street car and vice versa.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ashb82 &raquo;</TD></TR><TR><TD CLASS="quote">will a head that flow more cfm make more hp or can you flow to much cfm</TD></TR></TABLE>

You have alot of research to do. This question is ridiculous.

 

That is sort of a "philosophical" question.

The more appropriate question is if an engine can ingest more air [mass flow, i.e. number of 02 molecules] can it make more power. The answer is yes if there is an increased demand resulting from increased displacement, rpm, volumetric efficiency, exhaust flow or a combination of the aforementioned. This is assuming frictional losses are less than the increases in power.

 

Ok let me rephrase my earlier post,I gave a generic answer.
It's not that to much air is going thru the ports it's that the ports have to be the right size for the application.
Generally bigger motors or motors turning more rpm need the extra port volume to feed the cyl.