Sorry for the X post but I was asked to post this

http://www.fbodycentral.com/forum/sh...?threadid=7206

Thanks
Dennis

 

bump for a good post........

btw, you spelled "fullish" wrong hehe.

 

Dennis,

I agree wholeheartedly with a large portion of that. People are caught up in something that most shops are willing to lie about, which doesn't do much other than waste $ & dissapoint.

As far as repeatability though, on the same model bench with the same test conditions, results should be within 1.5-2% every time IMO. I've checked many heads & consequently had many of mine checked. Every time mine are tested the results are within an acceptable deviation, sometimes theyre higher, sometimes theyre lower, but for all intents and purposes they're where they should be. When you get into variances of 5+ % with the same test setup, in my experience those are almost always 5%+ to the low side. IMO at that point it's pretty obvious the guy in question is simply fluffing his stuff to try to compete with others. Not that it matters too much however, as it all shows up over time on the dyno etc. .

Still, given the fact that the customer really doesn't know what they're getting in most cases, I agree... noone should have even started giving out flow #'s b/c that's all people want to buy now. They don't want to buy a dyno #, or a killer trap speed, they want you to tell them your stuff outflows everything else out there. Even worse, most only want topend #'s. What's so funny about that is that if you told someone they could make better/more power with lower peak #'s, they often times have a fit about needing XXXcfm & decide to go to the guy who's willing to claim the #'s they want instead of the HP they're looking for.

Yep.. if it's custom, it simply takes time to develop. I can calculate proposed specifications, and usually get fairly close to whatever goal I had, but to get a killer port, you have to spend the hours developing it. It's not unusual to go back & forth to the flowbench 50+ times even on more meager stuff like the 23deg sbc LTx heads most of these guys run - much less any decent race head.

I like Joe's flowing w/o a spark plug comment, I've received a pile of junk that makes you wonder if they did... . Though I disagree with the silly 'tq wins races' stuff.. that's for another thread though.



Nice post, there's so much to this that simply quoting flow #'s doesn't get you very far. It's akin to the whole "knowing just enough to be dangerous" deal IMO .

 

The biggest concern on deviation is how the test is performed...and no 2 people perform their flowtest the same. correlating the relationship of these mysterious flow #'s to HP #'s may work in the world of books, but has little to do in real life...I am sure that you fight with this day in and day out also....everyone thinks that they need x amount of flow capacity to create x amount of horsepower...given the airpump theory etc etc.... In real lift the same people would have a life altering experience if they new what the average stock eliminator cylinder head flowed!

Dennis

 

Thanks man, Very Informative. Great Help....


Thanks again,
-John

 

Thanks man, Very Informative. Great Help....


Thanks again,
-John

 

Informative post - guess the industry should work on developing a standardized testing procedure.

But what are we as consumers to do - I've been shopping for heads for a while now and realize that most flow numbers are bogus and that other important variables are never advertized or fully understood.

I do realize that we need to consider the heads, cam, exhaust, driving application and so on. But for many of us one of the single largest cost mods are heads.

Can we have any confidence in the work of some of the better know shops or people (GTP, Lloyd Elliot, ...) or should we look to aftermarket casting (lt4, AFR, canfield...)?

Or is it just luck that we may or may not get good heads from anyplace?

Or is it a complete waste of time to do heads?

I appreciate an expert telling us that flow numbers do not mean much and that no benches will flow the same numbers and that's it's not about flow at all.

But it would be nice if we could be pointed in a direction to go

 

flow numbers dont even matter that much, they need to come up with a good way of calculating port velocity. thats what really matters.

 

Port velocity sure does help. probably the biggest area that determines a cylinder heads potential is port shape. How you convey this to customers....I wish I knew!! It would sure help my business.

Thanks
Dennis

 

So basically - the advice is

1) Do not look at flow numbers - they are usually not measered in a consistent manner and don't mean much anyway.

2) Other important vairiables can not be measures or are not reported.

So we, as consumers, have nothing to judge things by and getting new heads that help increase HP is a matter of luck.

 

its not luck..................people who buy heads from the various companies usually come in here and post their dyno sheets. when you see a company that is consistenly putting out great numbers, thats the company you wanna go with.

a lot of local guys claim to do awesome portwork, but then their heads/cam cars dyno 350-360ish or barely break into the 12's.........thats not what id call awesome.

im sure there are a lot of great places out there that probably never get mentioned on the board.........but the ones that ive seen prove good numbers with LT1's:

advanced induction
combo motorsports
joe overton
lloyd elliott
TEA

personally i have a set of heads on the way from jordon musser, so we will see how they stack up. considering the other work ive seen him to, i think theyll put down some good numbers.

 

BPS, it isnt that flow #'s dont matter, it's that theyre relative and the biggest problem is that theyre so easily skewed. Go search for guys claiming whatever cfm out of an LT1 head, and you'll find that theyre all saying they get about the same amount of air through it. Now go look at dyno #'s... and some are consistently lower than what one would roughly expect, while others are consistently high. It shouldn't come as a surprise that many of those don't peak anywhere near the 280cfm+ people want to claim, and even on the rare occasion that they get close, the port is oftentimes very inefficient for what it does. It would seem that most don't have the time, or resources to develop valvejobs etc., or they just don't know better.

Like Dennis said, it isnt about peak #'s anyway.. it's about developing an efficient port that flows well across the board (and beyond regarding turbulence). So sure, look at the flow #'s, but take them for what they are.. a relative measurement on someone else's bench. Many don't seem to have a consistent method when it comes to testing. I'm not sure about Dennis, but I always use studs & then keep the cylinder head located on those studs in the same fasion every time, and I use machined 1/2" radius orifices blended in with a very small amount of clay, rather than making the entire thing out of clay. That along with not giving out exhaust flow #'s with pipes/extensions (though they can certainly be helpful for developing stuff at times) helps consistency a great deal in regards to quoting flow #'s to customers. IMO anyhow .

-Phil