muscleman,
Did you do any deshrouding?

-Mindgame

 

man i swear you guys are awesome i mean a person cant ask for better help than what you get on this board. i think im gonna go with the 2.02 1.60 and americanmuscleman i do like the idea of lower lift flow. that will come in more usefull at times im sure. thanks again guys

 

Mindgame, after the seats were milled for the bigger valves there was a ridge left under the valve seat. I blended those ridges into the bowls and opened up the bowls a little bit. I also opened up and ported the combustion chambers. I opened those up quite a bit around the valves. You can't remove hardly any material between the chambers though. Its nearly 4.00 inches wide (the size of the bore) as it is. But I basically opened up the chamber and pocket to blend into the seat.

I would run the 2.00/1.56 valves if your not planning to machine the seats.

 

HHmmm... I pulled 349RWHP(425+)FWHP out of a set of heads with stock valves. This was nothing more then a Gasket match and cleaning up ports at the seat. Then topped off with a good Valve job.

Thi set of heads flowed 240 on the intake from in the range my cam lifts(waste of time to shoot for flow where your cam does not work). Why shoot for killer numbers in the .650 area and sacrifice the low lift when you cam only lifts to .550-.600?

You will give up port velocity and low end for a non used area. I would run the best valve to fit the seats. Many run the 2.02 and 1.6s because they are cheap. I would rather run a 1.57 and 2.00 that actually fitts the seat and pick up even more flow from not shrouding the valves then the largest valve in the cylinder just so you can say it is bigger.

So in reality I would run the smallest valve I could and still get the flow I want

Just me opinion and we all know how they work....
....Then again I have heard more then once my tail lights look nice

 

Whatchoo talkin bout Ellis, I thought bigger was always better

 

Oh yeah I also forgot to mention the fact that smaller is lighter and revs better hehehe

Now be nice Phil

 

Nice? I'm mr nice phil

Lighter, aye, thought the diff btwn another .010" radius is pretty minute.

I actually got some killer information from my valvetrain development buddy who runs a spintron all day on some tests he ran where the lighter component was much worse than the heavier counterpart with a given set of springs etc. Pretty nifty, but obviously.. matching the springs etc. to the lighter component should be better when all is said and done.

 

I totally agree, build the head to the operating range. However, the fact remains that a larger valve will always have a greater flow area than that of a smaller valve at the same lift. Whether or not it does flow more volume is a matter of how well the valve is deshrouded.
There lies the problem with production heads when you want to make serious power out of them. I'm talking 450+ rwhp here just to give some perspective. The problem is only compounded in a small combustion chamber, especially one where the valves aren't moved (intake towards the center & exhaust towards the cylinder wall).
That's why I won't be running production castings on my engine. They're limited... and I believe a guy trying to make 450+ n/a rwhp out a set is just chasing his tail around.
I ran a set of Dart 18º heads, 2.15 intake 1.625 exhaust on a 4.03 bore 367 small-block here a few years back. These are considered big valves by anyone's standards yet the engine made 768 hp at 7900 rpm and 468 lbs-ft at 5800 so it wasn't necessarily lacking in power. The point here is not the size of the valve... but how much room there is for air to flow around it. This is one case where bigger is always better providing the room is there.
Brodix and these other guys aren't just putting 2.08/1.6's in there for the looks. They're using them because they flow better throughout the curve.

-Mindgame

 

Mind games read what I wrote carefully. You need to match your valves to your seats Lloyd said it also.

If you have a 1.7 inch hole I do not care if you put 3 inch valve on it you still have a 1.7 inch hole

Every thing must be balanced and bigger is NOT always better you have to remember if you have a one inch pipe a 4 inch ball valve will not make it flow any better then a 1 inch ball valve and the bigger valve will disrupt the quality of the flow

Good luck

 

Well you should already know how much I hate disagreeing with people.
Truth is, no one ever learned anything from anyone who agreed with them all the time.

Without getting too teary eyed over it...... I disagree. The problem here is that we've failed to define a few things. Those 'things' being 'valve curtain' area or what Warren Johnson refers to as 'effective valve area'. If you put a 3 inch valve on a 1.5 inch hole and lift that valve you have an 'effective valve area' that is much greater than that of a 2 inch valve on the same hole at that same lift. Definition of 'effective valve area' is:
pi x Diameter x Height of valve x # of valves open (multi valve engine)
Some people even go through the trouble of subtracting the stem diameter area from the valve diameter area. But we're just out for the terminology here.
Now we have a definition and things get a little clearer... as they always do with description. So with that said, we should all come to an agreement... that agreement being that a larger valve has greater 'effective valve area' than a smaller one.
Now we have the throat diameter/area issue. From everything I've read... Smokey Yunick, Jenkins, Vizard, WJ, etc., the port area doesn't really come into play until the valve is lifted enough so that the 'effective valve area' (as we defined it) is equal to the actual valve area... which always occurs when 'the valve reaches a lift equal to ¼ of it's diameter'. From that point on 'the area of the port throat dicatates the breathing area available'. So... why do you think a larger valve is always less efficient that a smaller valve? Again... my point was that a larger valve loses it's edge over the smaller one only when that 'effective valve area' is reduced.... as in a shrouded situation. So this is one case where begger is better up til a point. Now we should all know what that point is.
I didn't just pull this stuff out my ****.. guys have been saying much of the same for quite a number of years now. Maybe someone with alot more knowledge than an old timer like me will chime in on this subject.
I stand on my points though.

-Mindgame

 

AND I will still disagree with the logic

It just does not hold with what i have seen

Puttin to big a valve on a small seat will not work well.

I guess we will just agree to dis agree. I will live with my REAL world testing

 

A LOT of power can be pulled out of heads with small(stockish) valve sizing. I run 1.94/1.60 with my heads and will be porting them even more this winter. The car might see 10's NA with those valve sizes.

If the seat is X size, then get a valve that is barely bigger than X. Anymore than that you hinder airflow. Your actually making it harder for the air to get in/out of your cylinders.

 

Real world testing...

In the last 24 years of drag racing....
3 times in Super Gas top 5 standings, 1 1st place points finish
6 1st place wins in Quick-16 event, 2 times as runner up
2 1st place standings in Street Eliminator Carquest Nationals
1 1st place finish in Top Dragster

That pretty much sums up my REAL world 'testing', care to compare.

Not trying to start a pissing match here, you may be Kurt Johnson for all I know.. I'm just stating what I know and have been told by many top engine builders over the years. If you're limited by the seat ring diameter, then it would be well worth the extra $ to replace the seat with a larger one. If you're gonna run a larger valve on a small inner seat diameter (less than 85% of the valve diameter), then you need more back angle on the valve. Do you honestly know that you are hindering flow Cantonracer? 2.0 to 2.05... that's only .025 more to one side of the valve... does this really hinder airflow... .025?? What if I put 2º more backcut on the valve... doesn't that make the transition a little easier? See, maybe you don't know???
It can and has been made to work. I attempted to quantify flow area as I understand it... I'm no engineer but I know what works too.. I've had some good results with my 'far out' theories over the years.
Then again, if we just adopt this attitude that it doesn't work because we simply don't understand it then we're not gonna get much out of any more discusion on the matter. If the cup is full, then it's pretty hard to get more in the cup. Happy to say I'm still learning. If you can school, then school me up... but I wanna see it quantified in factual data, not "well I don't think it works".
JMHO.

-Mindgame

 

did all this start with me getting a good deal on some valves? lol i guess i just figured for the money and time it couldnt really hurt by goin to a 2.02 instead of a 1.94 better flow is still better flow no matter how you look at it. i do know that both of you have lost me and i cant argue what yall are saying but i think im goin with the bigger valves. sounds like the best deal for me. if its not i'll be sure to poat and tell all. thanks again guys
Rob

 

Mindgame,
I think that EVERYONE in this post realizez that if done correctly that the larger valve would flow better. The ? was not about vebturi diameter and the valve size, it was about the seat diameter and valve size. This guy is on a budget and several people were trying to let him know how the stock seat will work with the 1.94/2.00/2.02 valves and if he HAD to change seats or not. If he is on a budget and changing seats was not an option then using a 2.02 valve has a few options on a stock seat...........1-scoot the 45 closer to the back of the valve and have the flow go around the extra .010 on each side of the valve since the seat is 2.00 in diameter. It hurts flow very little but we were just answering his ?. 2- ya could put the valve on a laithe and turn down the diameter or install larger seats. To get the valve sealing at the edge of the 2.02 valve with a stock seat the 45 in the head would be trying to seal in the aluminum and the bottom cut of the valve job would be in the hardened seat. It may work on a flow bench but not on a motor.
As was stated meny times..............
Will the oversize valves increase flow-yes.
Will the 2.02 valves work with stock seats-yes.....but a 2.00 works better with the stock seat. The 2.02 will work better than the stock valve but we were just letting him know the reasons why some people say thet the 2.02 will NOT work.
The best thing to do would be to scoot the valve guides over and use a 2.08 valve as you said. I am not sure how THAT fits in this guys budget (or is even related to his ?) or how much HP gain on his combination this would be. This may not be a big chore for you. All of this welding, measuring, machining, new guides, new seats, etc. , etc, may be nothing for you, just a lil extra time but for most people on this board these things things translate into a BIG machine shop bill if they can find someone that would wanna handle this task. Then again if they are spending this $ on some LT1 castings they would be better off with an aftermarket casting unless they are running a certain class that requires a LT1 casting.
When $ is a concern and changing seats in not an option would you agree that a 2.02 on a 2.00 seat would be better than a stock valve? If so than great, because that is what we told the guy. If not then maybe ya could explain why so maybe he could save some $.
If the seat dia is 2.00 would you agree that the 2.00 would be better than a 2.02. If so than great, because that is what we told him as well. I understand changing seats would be better but if on a budget and changing seats is not an option than it is not an option.

NightTrain66