Stop Guessing , Try Hard To Use Logic And Base You Engine Build On Known Facts

[Grumpy]

Would gaining .040" lift be worth a $500-$600 investment? Got a 350 Chevy, with aprox 300HP. How much HP would I gain? I read in Chevy High Pref magazine years ago, that if you invest more than $10 to gain 1 HP, the costs will outgain the rewards.

without facts you can,t reasonably make anything like a valid prediction,
generally a .040 lift increase at the valve only ,
will not be overly significant in aiding power
to make an accurate guess the person ,
doing so needs a valid reference point to start from based on
what the average similar engine build has done using similar components in hundreds of similar engine builds
post a great deal more info about your current engine parts list, compression, displacement, cylinder head flow rates, cam duration and lift, cam type, ie roller or flat tappet,hydraulic or solid lifter,exhaust system info, fuel octane, , heads etc.
Id need to know more about any combo including both the engine and drive train trans and gearing and car weight and I can give you some decent advice based on both experience and a soft ware prediction
other wise its just random guess work
yeah I can make an educated prediction, but it needs to be firmly based on facts
yes theres soft ware thats been developed specifically to do this type of prediction,
but it needs a valid set of reference info

yes as usual read the links and think logically,
doing some detailed research, before you start writing checks,
is almost always going to save you from wasting cash and your time.
you might be amazed at how that helps your results later.
learn to ask detailed questions before the check book gets used.

http://garage.grumpysperformance.com/index.php?threads/virtual-dyno-software.2301/#post-9239

http://garage.grumpysperformance.com/index.php?threads/camquest.2926/#post-7652

http://garage.grumpysperformance.co...good-street-combo-your-after.5078/#post-14433

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/#post-37693

http://garage.grumpysperformance.com/index.php?threads/how-to-read-a-cam-spec-card.1477/#post-13044

http://garage.grumpysperformance.co...t-get-anticipated-hp-results.6853/#post-22236

 

[Mark Bradley]

Each cylinder head has a lift height where opening it any more does not add any flow.
Ideally it seems logical that you want to achieve that lift for the longest duration possible.
So it seems to me that if my cylinder head reaches max flow at .600” lift then going to .700 may be of no real value because of the actual cost ($) and valve train stress to manage the extra lift may not pay off although to hit .605-.610” may be a good investment because the motor reaches the max flow point when opening and closing plus a few degrees in between while reaching the .605 to .610” point. And you don’t beat up the valve train doing it.
My 2¢

 

[Grumpy]

theres a great deal that effects cylinder fill rate efficiency, far more than any minor change in cam lobe lift, alone and theres certainly, a good deal of rather well proven math to guide you in making valid choices, and limiting the potential for making poor choices if your willing to read the threads and sub linked info

related info
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations[/color]
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/#post-37693

http://garage.grumpysperformance.co...ing-parts-and-a-logical-plan.7722/#post-95663

http://garage.grumpysperformance.co...-potential-dream-bbc-combos.14607/#post-94395

http://garage.grumpysperformance.com/index.php?threads/thoughts-on-engine-airflow.15712/#post-94041

http://garage.grumpysperformance.co...ir-ratios-that-gets-ignored.15506/#post-92064

http://garage.grumpysperformance.co...ir-ratios-that-gets-ignored.15506/#post-92064

http://garage.grumpysperformance.co...llecting-cylinder-heads.796/page-2#post-90819

basic tips

run as much compression in your engine combo as the fuel octane available will allow,
but hedge your bet slightly, as your sure to occasionally find your choice of fuel or the engine temps are not ideal.

spend the extra coin on better, and in most cases aluminum, heads , in most cases you can,t modify stock heads to flow near the flow level of better aftermarket heads and the difference in potential power is significantly better.

a free-flowing exhaust system matched to the engines potential rpm and displacement and decent full length headers really helps un-restrict an engine potential

in most cases a better flowing set of heads on the largest displacement engine you can afford and a marginally less radical, in duration and lift cam,
will perform more consistently.

match all the parts used to the intended use,and stress levels ,
a common problem is assembling an engine with an assortment of parts, with several built for different power bands and rpm ranges, "think weak link in the chain", using a cam designed to produce power up to 7500 rpm, has little too no benefit if you auto transmission shifts at 5600 rpm, and your heads or the exhaust system max out at near 6000 rpm.

think about the whole car and drive train,
factors like good brakes, engine cooling, durability is important.
use of a very effective oil pan and oil cooler can mater a great deal,
you can,t expect stock 4-5 quart oil pans to keep up with the demands of a 7000 rpm engines requirements and gearing the car for its intended use,
makes sense, your not going to be using the car at 170 mph on the street
do some research, do the math, think it through.
if its daily transportation, you really don,t want to gear the car,
or use components,that force you to cruise at 70 mph in top gear at 3000-3400 plus rpm.
nor do you want to select a cam that won,t pull well below 2800 rpm, that on paper makes killer power at 7500 rpm, if your auto transmission shifts at 5500 rpm, and your heads and intake strangle air flow at 5600 rpm, but I see it happen all too often.