Flow Question.. HELP

user-9274568 · Post by **user-9274568** » Tue Oct 11, 2005 5:19 pm

Hi Guys...

This is what I got. I have a SBC splayed valve head. It flows well up to .700, then drops at .800 and climps back up to 1.000. What's not happy? I'm sure it's in the ST, I think I've tried everything. HELP.. It only drops around 5-8 cfm. I've flowed at 28 and 36 inches and almost same results..

Chad

example only..
.500 360
.600 400
.700 420
.800 412
.900 424
1.00 426

Post by **ou812** » Wed Oct 12, 2005 1:00 am

What angle is the valve, 12-10...?
Is there a backcut?
How far is the valve away from the chamber wall, especially at that lift?

user-9274568 · Post by **user-9274568** » Wed Oct 12, 2005 10:01 am

12 degree valve, 50 degree seat. I've tried a 33. 35, 38, 40 backcut. I'll need to check out the distance.

shawn · Post by **shawn** » Wed Oct 12, 2005 11:41 am

Hi,
Can you "hear" the port go turbulent at this lift? If so, I would get in there with a pitot and try and find that spot. You might also try the antenna ball trick. If none of those things seem to work to find your spot, then I would look to the chamber.
Shawn

user-9274568 · Post by **user-9274568** » Wed Oct 12, 2005 5:56 pm

It sounds good, in fact it sounds better than it flows. I did probe the port. It's 388 over the turn. I just can't seem to slow it down. It's weird the port averages 285 in the ST area, top middle, and bottom. What do you suggest to slow it down and what would you look for in the chamber? THANKS..

Chad

SWB · Post by **SWB** » Wed Oct 12, 2005 7:25 pm

I'd look into widening the SST or raising the roof some more (work around the guide). If you've already done all that and made the average flow as slow as possible while the air is turning, you need to look into where the flow is the fastest.

If the flow is fastest over a given section of the short side turn, lowering the adjacent areas or raising the fastest section may help even out the velocity gradient slightly and "fix" your problem.

SWB

shawn · Post by **shawn** » Wed Oct 12, 2005 7:28 pm

Hi,
Without seeing it's really hard to say, but maybe you don't have enough "layback" on the short turn. By laying it back and putting the apex further back, you can get the speeds down going over it. Of course this doesn't always hold true, but if you have a way to weld it back up, I would try that. You might also try flowing it at higher depression and see what happens.
Shawn

Ron E · Post by **Ron E** » Wed Oct 12, 2005 8:19 pm

It's a problem with those heads. The short-side can get real thin in an attempt to form it like you'd really like to. I have no idea why GM hasn't bothered to fix the casting, especially if they had any idea of the hell the PST people went throgh to run at that level. Have fresh batteries for your thickness-checker. You may have to chill it a bit, and give up some .5 and .6 flow, to clean it up up high.

user-9274568 · Post by **user-9274568** » Wed Oct 12, 2005 9:08 pm

That's interesting Ron... I also made a mistake, it's a GM splayed valve head. I might have to stick to my original plan and use a SB2.2. I have a dumb question. On the HRD web site, all their flow numbers go to .800 or .850. Do you think the numbers back up that's why they don't advertise them? Or do you think most people arn't interested? Just curious. Anyone ever flowed a HRD SB2.2 or splayed, canted valve?

http://www.hrdracingheads.com/
check out the numbers

Chad

Ron E · Post by **Ron E** » Thu Oct 13, 2005 9:06 am

cspeier, I've never flowed any of their heads. They are showing impressive flow numbers. I notice several different max valve lift points on their flow charts. some at .700, .750, .800, etc. one could speculate they are "dodgeing the dip", but speculation isall it would be. On your splayed, 400 at .600" is real hot if the plan is to make it to 1 inch. But, you know that already. I'd think 370's at .600" might be in the range of a curve that makes it to 1 inch. but, that's only my opinion, not some well researched out fact.

Yea, it was the GM splayed head I was refering to about having the limiting thickness issues. A bunch of stop-leak has been sold in their honor. Curtis has done a bunch of SB2 heads and would be aware of any thickness problems, if any, when sized for bigger drag race motors.

user-9274568 · Post by **user-9274568** » Thu Oct 13, 2005 9:25 am

Thanks Ron. Everyone has been telling me that my SB2.2 won't work for my 4 cylinder project. The SB2.2 head flows a TON from .500-1.000. I had a friend who had a splayed valve and started to play with it. Looking over the design and comparing it to the SB2.2, I still think the SB2.2 is better. Design and flow wise. I guess you talk to 10 guys you get 15 answers! I decided long ago, to do what I want! I guess I should start listening to myself. Also anyone know what a hi/lo Sb2.2 head is? Thanks Ron, I appreciate it..

Chad

airflowdevelop · Post by **airflowdevelop** » Thu Oct 13, 2005 9:38 am

Chad,
Have you tried any positive bias in the port? What is the difference between bottom bowl and the venturi?

The GM splayed head should rock the sb2.2. their are ways to concur the sst problems. Foltz has probably the nicest program right now (that I know of) for ease and no frustration. I assume this is a comp motor?

Dennis

user-9274568 · Post by **user-9274568** » Thu Oct 13, 2005 6:25 pm

Yes, it's a comp motor. Have you or anyone else ever flowed a Foltz head? SB2.2 or SV?

cboggs · Post by **cboggs** » Thu Oct 13, 2005 11:48 pm

Chad,

I thought you had the SB2.2 working fairly well, .. didn't you?
Didn't you have some flow numbers on your heads better then Al
at HRD was getting.

I have a bias towards the SB2 myself, .. but I have limited
experience with the splayed valve head, .. I know it's a pain to do well, ..
at least the ones I did where.

As far as comparing flow numbers, .. don't you think it's a little
difficult to compare numbers from one person's bench and test
to another? 430 cfm on Al's bench could be 410 cfm on yours???

Seems like Dennis know something about these, .. perhaps he
could fill us in with more information.

Curtis

user-9274568 · Post by **user-9274568** » Fri Oct 14, 2005 12:00 am

I agree Curtis, you can't race a dyno or a flow bench. I just seems what's advertised and what's real life can be totally different. Yes, I have the SB2.2 working well. I just let someone put the thought in my head the the splayed is better. Just had to try it..

I was just curious why the flow numbers to 1.000 weren't posted. My thought was either most people don't care or they go backwards.

Anyway. Curtis how the heck are you? Get that bench going?

Chad