Larry,

Your explanation is about 32.5 X better than mine would have been.

I'm familiar with the .25 rule of thumb, but was unaware of the upper end .37 rule. Like Bret said most of us aren't coming close to that.

Only thing that I could add is that cylinder filling is dynamic and that the pressure gradient the port sees isn't close to a constant 28". You already covered that in your 'flowing heads' responses though by discussing the higher depressions you and raceteams use when developing ports.

-brent

 

The way I saw it... for a street engine you need also reliability... and the lower the lift the longer spring life I will get... so I try to get to the "sweet spot" of the lift vs gain in performance... I dont think I will gain 40-50rwhp from going from 620lift to 700 lift...

 

LS1 guys also have some mysterous limit of max lift at the valve you can do on a stock block. They might want to think where that max lift limit actually is.
=======================================

Bret ...in the LS-1 or LS-6 ..there might be special circumstances

if you just FlowTest the Cylinder Heads only
you see pretty good flow numbers

but if you now repeat the same FlowTests
with the Intake Manifold bolted on the heads like real-live
engine....the intake hurts flow between 8 to 11 percent !!!

what can happen is => you loose more curtain area velocity at max piston velocity than you are gaining from opening the intake further

the .37 ratio that usually works 100.0 percent of time will
not quite workout on these engines

when someone does make a killer Intake Manifold that can come within at least 1.5 to 3 percent of cyl head numbers
thats when the .37 rule will work perfectly !!!

so with LS-1 or 6
a 2.055 intake valve will love and respond to .760" Lift when the Intake Manifold problem is solved !!!

until then....it will cause different observations/or results...like things me and Eric Koenig were talking about and seeing

http://www.maxracesoftware.com/Futra...ake_640_15.jpg

in that pic its hard to see...but all other intake manifold passages were taped up to cause the airflow path to be same as real path in flowbench tests....the other cyl head intake ports had red shop rags stuffed into them

 

I dont think I will gain 40-50rwhp from going from 620lift to 700 lift...


__________________
94z28



thats correct !!
but if you are looking for close max HP/TQ possible ??

all you have to do to see potential gain is to

multiple .257 times flow at .620 Lift

-VS-

flow at .700 lift to see if it might be worth the effort or the valvetrain wear and tear ??

.257= beginner engine builder
.285= pro engine builder

 

Im not liking you at all... I just spent $325 on my new cam and you are tempting me to sell it.. that is not fair...

 

its always safer to be conservative !!!

before you do anything have someone flow your heads with intake manifold and carb attached to Cylinder Heads

then repeat FlowTests and see differences
if its worth the effort to you ???


make dead certain all other intake ports have their valves/springs on them and seated ..don't do the quick deal like i did with red shop rags

and tape other side of the Intake Manifold off

and any other vacuum holes

******************************************
almost forgot =>
make dead certain there is absolutely NO GASOLINE in the carb anywhere...including taking off the Bowls and Squitter Pumps

**********************************************

don't blow yourself up and the FlowBench

 

Keep in mind that lift is nice but you have to control that valvetrain. For a street engine, I wouldn't sweat the losses from some .050 less lift for a bit more durability.

-Mindgame

 

that was my point which I chose the 620 cam and not more... my heads maxed there anyways...

but.. 20rwhp are always nice

anybody have the intake runner lengths and ccs (LT4 intake, not the head)

 

BTW, Larry.. I know of you (don't know you personally) but many people speak highly of your work.

Good to have you aboard! Always great seeing a little different perspective with hands-on knowledge.

-Mindgame

 

Well.. Larry

Can you help me.. I want my heads to flow more... 300s?

 

Mindgame ...many thanks for good words !!



Well.. Larry

Can you help me.. I want my heads to flow more... 300s?

Highlander .... probably would not gain enough from more work
with what you are trying to do...it wouldn't be cost effective
with small duration cam

280 cfm should be 575.7 hp potential .

but small duration and some restriction in Intake Manifold
will reduce the 575.7 hp potential

try heads like they are then see if you want more ??

theres a lot of work just in learning to get the best ET out of the combo you now have
make it run as fast as you can..then make a decision

its amazing to watch NHRA Stockers and SuperStockers go as fast as they are with the HP/TQ they make..they learn how to get the most out of their combo possible .

 

This will be for a boosted engine... the more flow the less boost i need to achieve my goals

 

Im going to stick with them... TEA didn't want to touch them... nor did cartek... and now you...

Oh welll got to follow the advice... I thought 300s where possible with these w/o that much effort.

 

Here's my flow numbers from my AFR 210's ported by GTP
.200--153.4/103.5
.300--209.1/157.9
.400--254.6/195.7
.450--269.6
.500--281.5/221.6
.550--291.8/227.6
.600--299.3/231.7
.650--306.0/233.6
.700--310.5/235.9




Neal

 

DAMN!!!!!!! how much power did that make??

have you flowed them locally?? What bore size did they use?

What do you guys think? GTP or AI?