Tractorsport Flowbench Forum Archive

Posted: **Wed Oct 22, 2008 11:57 am**

I'm having custom exhaust and intake valves made for my flat head. The shop asked me what angle I wanted on the valve between the backcut and the radius to the stem. The stock valves are about 12deg which is very flat compaired to the top of the valve. The shop can make the valves 12deg like the stock valves or 25deg which is much more of a taper from the stem radius to the backcut. Any ideas from you guys that have worked with flat heads.

Ken

Posted: **Wed Oct 22, 2008 2:50 pm**

[color=#000000]each case is and individual basis. Hard to say what your engine will need. As and example I have always used Milodon Mega Flow valves in my small block chevy and had to do nothing to them. This last set of heads with those valves got super turbulent after .450" lift. I just back cut them 35

Posted: **Thu Oct 23, 2008 5:11 am**

Ken,
what make and model of flathead have you got , what application and what heads are you using ?. This might give some people an idea of what you require....Flowing a flat head is a bit different to the normal run of the mill OHV Chev, Ford , or the newer 4 valve OHC style heads ..

Cheers

Lynds

Posted: **Thu Oct 23, 2008 6:26 am**

At this point I don't want to give any more info about what I'm building incase some of my competitors are on the site. I understand that with the limited amount of info I gave its hard to give any absolutes what works. At this point I can't test both types of valves so that is why I made the post. I was looking for some nudges not pushes in the right direction. Since I made the post, I have made a decsion on which valve to use. Thanks guys for trying to help with the limited amount of info.

Posted: **Thu Oct 23, 2008 6:44 am**

Ken, make up some "dummy" valves. I do this by using an alum stem that has a threaded end. I then find some suitable material (I use PVC solid) I cut off a piece the thickness of my valve and thread the center to match the stem. I then assemble the parts and chuck them in my lathe and machine a valve head out of the round blank. If it doesn't flow the way it "should" I make up another head and do the same thing over and over again. Once I have what I want I can then make that valve design out of a Ti blank or other material.

Posted: **Thu Oct 23, 2008 10:27 am**

Posted: **Thu Oct 23, 2008 6:36 pm**

Thanks Bruce. I think I remember you showing me something like that when I was there. Now I'll be able test different shapes. Thanks again to the other guys that responded. Now I need to get the PTS flow bench dusted off and start testing.

Posted: **Thu Oct 23, 2008 6:39 pm**

I know that I will be interested to see what your results will be. Good luck!
John

Posted: **Thu Oct 23, 2008 6:47 pm**

Posted: **Thu Oct 23, 2008 8:40 pm**

Posted: **Thu Oct 23, 2008 11:28 pm**

Believe it or not but a nationally built single cylinder flathead cast iron engine for running in my class will cost anywhere from $5000-10000! Why someone spends that kinda money I'll never know to win a few bucks and a trophy. There are local people at my track that have spent that kind of money and place top 10 at national meets. Heck I don't have that much money into my whole shop!

There are only a few engine builders and they all work somewhat together on keeping the prices high. Only bits and pieces of info come out so there is not a lot of sharing of info. I for one do not let any other pullers in my shop when I am flowing any of my parts and my engine stays covered on the bench unless I'm testing. Not so much that I have any secrets I prefer to not share my fixturing setup, let'em figure that out themselves.

My carb design is probably the only thing that is a secret in that I run an annular discharge style carb.

Ken runs into the same thing in the lawn mower racing venue, it's an up and coming sport and it is going the same direction garden tractor pulling was headed a few years ago. Starts out as fun and becomes a money pit as everyone wants more power/performance.

Posted: **Fri Oct 24, 2008 12:25 am**

Great story John, and so true.

Posted: **Fri Oct 24, 2008 12:50 am**

Bruce,
You are telling the truth there for sure. I remember when NHRA started Jr. Dragster class so a father and son could dabble in racing together. Now they have more in them than we used to have in a real top fueler. Those little single cylinder "Briggs" style motors are pricey. They are fast - they had to limit them to slow them down a little. I have seen some of them crack the high 6.90's sec in 1/8th mile. That is equal to a 10 sec 1/4 mile run.

I do not mind helping if it is reciprocal, but it usually never is. That is why I like this forum. I have got a lot of help here. Although my wife wants to know why I keep having vacuum motors shipped here

Posted: **Fri Oct 24, 2008 12:59 am**

Posted: **Fri Oct 24, 2008 2:30 pm**

John;

It is kind of funny how when you have a shop and the skills you are never short on so called friends? And when you hand them the broom and dust pan it's allway's time to go home :-)

Tractorsport Flowbench Forum Archive

What style valves for a flat head - What style valves for a flat head