Hot Rod Forum banner

For most of you guys seeking a little more power...

7K views 62 replies 10 participants last post by  BigEd36 
#1 ·
A customer of mine sent this to me:

Wasn't sure if I sent you this or not or if you had any info on a combo like this,thought I would share it with you. This is the one I did last fall, stock cast crank,Scat 5.7 rods ,SRP flat tops,Dart 165 iron head,their valve job,no port work,9.75 compression, Straub 510/510 221/235 108 LSA, Comp Cams roller tip rockers,Edelbrock Performer EPS, QF Slayer 600 vacuum,stock points distributor with a Crane electronic conversion.
 

Attachments

See less See more
1
#10 ·
Using the stated intake flow of any head you can calculate what the "potential" power is based on CFM. Since HP is a calculation we can do this. The formula used is CFM x .2575 x No. cylinders = HP Potential at 100% VE. Based on the published number on this head of 232 cfm at .500" lift the heads can support 477.92 HP at 100% VE. So a good street engine will be at least 90% and that puts potential at 430HP.
 
#14 ·
327Nut is in Southern UT. I have to assume he is up there, elevation wise so no air. The fuel used along with BSFC number I come up with 17.4% correction which in high elevation thin air is normal to what I see.

CT will be very close to sea level so the correction should be slight. Mine figures at 3.6% based on dividing the Observed by the Corrrected number which is in line with being a little above sea level.

One thing I don't own a dyno. So I am not running it. This customer doesn't own the dyno. He goes to a competing shop to get his stuff dyno'd.
 
#11 ·
If the induction inlet air temp isn't hooked up or is moved the HP will read 40 or 50 HP too high!! If there is no inlet temp cap and sending unit for air temp on the induction your HP and Torque readings are Bogus :eek::(

A clue to a bogus run is no oil pressure increase as RPM climbs, No water temp or climb in temperature ( or a cold run is water at room temp) fuel used Readings do not climb with rpm increase, No CFM info, Any of these Throws the new computer dyno way off ! And the new corrected readings are for a total of about 15% HP loss from all accessories, But the assumption of 85% mechanical efficiency by some Cheap Dynos on every engine is bogus and much higher on some engines!! The 85% should only be used in corrected readings when actual friction data is not available to that dynos computer!

I found this on the internet that shows in a video how a reading can be affected by just one sencer!!:eek:

https://www.youtube.com/watch?v=eRCZKn4eNBA

Jester (Chris)
 
#16 ·
Dyno's are intended to be a scientific measuring tool. Dyno cheating is a way to defraud the public into buying a product that has less performance than is claimed by the manufacturer – thus to sell more parts. builking the public for a profit gimmick -- I Dynoed many crate engines that sent a Generic dyno sheet with them that were exaggerated to the extreme and were over 100 HP shy of claims But when I manipulated the CF field (Correction factor) or shut it off and left the inlet air out of the equation HP climbed !

The CF is hidden and many operators never change it from HR to HR or day to day it stays the same on many dynos forever because operators do not know of it LOL or are too lazy to correct it (Re calibrate)

But it needs to be updated often, But never during the same runs ! If you just turn on a ceiling fan it will change the CF factor of the dyno !! Some operators try to get higher reading for their customers and manipulate the CF not knowing its giveing a higher false reading:drunk::nono:

Take a car with the Actual Conditions: of, RH=40% and AT of 70 degrees and BP 30
And The Dyno CF weather station factors reading is exactly this and the car makes 400 HP. If we change the BP to 33 ! But because this is a false reading the car is now going to make more power. Many Dyno shops never change or even look at the CFs ! If your wanting a good run just ask the operator (VERY NICELY) :mwink:)to see if the dynos weather station is set to the 'ON' position Many are OFF because the shop is lazy :( If its on make sure the readings are right if off leave the establishment :boxing:and find a reputable one:mwink:

Another thing to look for is a very stable tach needle if it is fluctuating any time during the run you have to find the cause (Engine or Dyno) because it will change your entire power curve and the CF will unknowingly smooth out on your graph LOL and your sheet will be way off:(

Jester (Chris)
 
#20 ·
Agree completely. This is my vote to put this back in the engine forum.

So many are tuned into dyno numbers that it is hard to imagine, at least to me. I recently discovered (this weekend) while at a car show how many kids are dyno racing. It's the rave of the Honda, Subaru, Volkswagen, Evo crowd. Their cars don't make it down the strip worth a crap, but dyno bragging is to the point that many of them are hanging dyno sheets on their cars while at shows. Considering the dyno sheets and the ability of the dyno operator to 'statistically deceive' the car owner I think this should be brought to attention of those going to dynos, whether engine or chassis dynos.

Thanks StraubTech for the nice post.
 
#22 · (Edited)
A while back extensive tests were done with the same vehicle on 7 different types of chassis dynos. And They varied By a 33% in HP from the lowest to the highest Readings.

Also Tests were done on an engine from fly wheel dyno to chassis dyno and the engine lost a supersizing 106 hp, which is a loss of 40 percent between the engine dyno and the chassis! but overall the engine suffered from an average loss of over 36 percent across the powerband from 4,000 to 5,500 rpm

Test:
Small-block Ford 357 ci in a ’63 Mercury Comet with an AOD automatic, a 9-inch rear, and a 3.50 gear.
Difference
Flywheel Power....rear Wheel...loss..%loss. HPloss w/o fan
RPM......... TQ HP TQ HP -HP -HP% -HP -HP%
2,500 384 183 - - - -
3,000 410 234 - - - -
3,500 420 280 270 180 -100 -26 - -
4,000 426 325 304 230 -95 -41 85 37
4,500 413 353 297 254 -99 -39 83 32
5,000 389 371 277 265 -106 -40 88 33
5,500 344 361 254 266 -95 -36 76 29
Avg. rear wheel loss 99 hp 36.4% and running without the fan 83 hp loss 32.7% A 19 HP gain from just removing the fan!!

This test was repeated with other engines and the average loss was 40 % through the accessory's and drive line I did these tests on my own but never got 40% the Highest on my equipment was closer to 30% always pretty close to 30 % about 1/3 and that's what I subtract from an engine dyno sheet I read any more 1/3 when converting to rear wheel HP!! Also a change to low OHM plug wires over from High OHM made gains of 10 to 20 HP The Packard gold strand and copper core wires gained over 25 HP, Copper core non resistor pluge more then 5 HP gain, Putting a shut off switch on the alternator for racing gained up to 10 HP, Thinner oil had significant gains, These guys with 100 pound oil pressure readings are losing gobs of HP and Torque, Change the pressure spring to 40 Lbs and gain back that HP and torque their throwing away, 50 WT. oil to 30WT. another big gain! 50 wt off road oil isn't needed in a drag car many only run 5 wt.!! ETC, ETC,

I'm not suggesting any one change what works for them , just pointing out a few things that bring back lost HP and Torque:thumbup: A clutch fan will only consume about 5 HP even a flex fan uses more then that! Most of these gains mean nothing on the street but at the drags 10 HP or 15 LBs torque could be your edge !

Jester (Chris)
That test I posted looks great on the edit page and my original post before being sent but looks like crap on the thread its all mashed together and will be hard to read:(:mad::drunk::eek: Sorry for that:(
 
#23 · (Edited)
:confused:I forgot this it should be on my other post :eek::(
A COLD RUN vs. HOT RUN- (The oldest and easiest variable to rip a buyer off.) Run the engine "hot" the first time, let the dyno fan cool it down and then when cold run it and get your graph and corrected readings. The cold run will make much more power from the computer CF. This is done for almost all crate engine dyno sheets! Not saying it was done on 327NUTs engine But its suspect to me when you see the water temp out on his dyno sheet its room temp! Unless its Celsius But he is in Utah not Canada !

Jester (Chris)
 
#25 ·
My engine was dyno'd at Snow Performance in Saint George, Utah. The closest other dyno is by Las Vegas Speedway bout 175 miles. Snow has a HUGE water tank outside that recirculates the coolant hence the cooler temp I guess. All of the engines are dyno'd this way, never really gave it much thought as this wasn't some all out race engine. Also the altitude in St. George is around 3500 ft. I live at 5600 ft so we tuned it for that level.
 

Attachments

#26 · (Edited)
Outside tank would be air temp water if its 60 out you would dyno at 60 water temp if its 100 out you would dyno at 100 water temp and get 2 different HP readings on the same engine! Are you sure he didn't have a recirculating heater available but didn't use it? If not then you had a cold run! Nothing wrong with that many dyno shops use full throttle cold runs Hell you get better looking readings (everyone likes that .:thumbup:) But they just show higher HP and torque readings then a hot run! Usually a shop will do a cold run and then 2 or 3 back up hot runs To make sure all Hot run reading stay the same for each hot run! Then you get a raw data sheet and a corrected sheet. Making 3 runs to establish accuracy and to verify that there is no "best" or 'worst" run variation. 1° of timing or 10° of temperature can make a big difference so a "cold" run can't be compared to a "'hot run",
. If the dyno runs are not consistent for 3 runs, then the test is flawed
because you'll never know which of the 3 was the right one !!
You should get graphs of the cold and double checked consistent hot runs and data sheets about 5 in total By most shops! All done with at least 91 to 93 octane for standard engines never regular on any dyno run! High octane has no HP increase over low octane but it does stop pinging and knock when running at street timeing.and lets you increase timing with less risk 1° of ignition timing = 4HP. 4° = 16HP etc.

If you tuned for your elevation what is your true HP for your elevation (" I live at 5600 ft so we tuned it for that level "). , Your sheet is a corrected HP and corrected TRQ run for sea level ! There is no barometer reading for elevation or a CF off raw data run on your sheet ? It shows corrected HP so the CF is turned on? If it was raw data the CF would be off? But at sea level your engine will have to be re-tuned ! The CF (Corrected reading) is specifically intended to help evaluate the data from a dyno run when you would like to know what the readings would have been if they were taken on an SAE (Sea level) standard dyno. But if the "Uncorrected" value is chosen it displays actual HP that the engine made in the actual altitude and conditions of that day of the dyno run. Did the operator tell you what your HP and Torque is for your elevation? Or just give you corrected data like on your sheet posted ? I'm just curious your engine is impressive and puts out good power I'm just NOSY about that shop LOL :thumbup: ! fact is if he used corrected reading (which he did) they figure in 85% efficiency if your engine is more efficient you will have more HP then your sheet says :thumbup:

Jester (Chris)
 
#30 ·
The other thing to mention is this was built by a professional with the machinery and tooling to do the work. Most don't have $65K seat and guide machine in in the garage or shop. Heads from the factory or heads from the Ebay guys have the factory valve job. A guy at home can lap the valves in but that is the extent of his ability. With a VGS machine, 1 can go in and "tune up" the heads with multi angle valve job. A good VJ can be worth another 18 to 20 cfm. What does that mean ....35 to 42HP is what that means.

Out of the box doesn't mean it is ready to RUN....its just ready to run. If you want it to RUN some tweaking can be done.
 
#33 ·
For what it's worth here is the chart on my power curve.....which I've shown before. I reckon the torque curve (red line) is like Texas. No matter what elevation I'm pleased with the results for an 8.7 comp. ratio home garage build..........and yes I wish the dyno run could have started at 2000 rpm where the engine will be normally operating in.
 

Attachments

#34 ·
"don't look at peak"
"width of the curve is what keeps us planted in the seat! IMO"

I think both are as important depending on the engines destiny of use :thumbup:

I also know that corrected readings do not show the true colors of the build in different conditions and guys at high elevation? or hot climate? or humid areas? Etc, think a corrected run is their engines real HP and Torque Through out the power curve! But its corrected to show power if tested in an ideal running Conditions , such as Sea level, Ideal humidity , perfect temperature , all ideal conditions! Its not REAL LOL !! There is no such thing!! If you engine dyno and say get 400 HP and set that engine in a closed hood car the turbulence and heat on the exposed air filter will rob maybe 30 HP under that hood! Add a sealed scoop and the rammed air will add maybe an extra 25 HP and more torque to the 400! You can't simulate a scoop on a Dyno!! Even the corrected power curve is smoothed out Its not real either!! If you lets say go to a track with your power curve and corrected HP and Torque sheets and brag it up you will be wildly disappointed when beaten by a guy with an uncorrected dyno sheet saying he has 400HP And your corrected sheet says you have 500 HP if your both running identical cars ! I want an uncorrected read out from the area I run my car in and a corrected read out too! Even your corrected 85% efficiency is bogus its pulled out of some ones A#& a theoretical number agreed on by engineers so that throws off a corrected Dyno reading even more so many shops change that corrected perimeter on their dynos to 100% and never change it! So you can't trust a corrected data sheet!! Most people do not care they just want to see big numbers and a lot of shops know that and manipulate a test, and word spreads and people hear how this Dyno shop is better because their Dyno readings 75 HP over another on a full throttle run LOL! and The laymen do not know a cold run from a hot run or what CF correction is ETC, ETC. And are ripped off with false info and bend over and say thanks for sticking it up my A#& LOL!! Thats the last I'll Post on here about Dyno Testing:thumbup:

Jester (Chris)
 
#35 ·
Thank you Jester for the explanations,especially hood scoops as a variable.Would it be ok to PM you about dyno questions in the future? I have a couple issues and Im wondering if I should dyno tune my combo before I freshen the engine? I have a leaky intake I was going to fix and realized my engine has been in service(low mileage) for 10 years
 
#39 ·
question to Straubtech to get engine combo back in "engines" part of the forum,,,

what if any mods were done to the intake manifold and or carb to get this combination to produce that high hp number? It seems optimistic? And are the rest of the dyno figures available to look at? The heads that you used you said were stock out of the box? Have you compared these heads to similar heads and had similar results?
 
#46 ·
I will have to ask the builder if he did anything to the intake or carb.

I don't feel it is optimistic. The observed number is on the sheet. It rarely is because guys what to show the corrected numbers only. The observed is what is measure in real life without correction factor. The number is 410HP.

Now the published flow numbers:
Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software
Dart 165 Heads flow 232 and 138 at .500" lift. with an I/E ratio of 59.5%. Now using SuperFlows formula on how to estimate potential power and using .500" lift numbers since the cam is .510 lift we can calculate the potential of the engine. 232 x .2575 x 8 cylinders = 477.92 at 100% VE. At 90% VE for most street pump gas builds the potential is 430HP.

So POTENTIAL out of this combo is well within reality of what the dyno shows. Now what no one has asked is why is the duration split so much on this cam. Note the IE ratio of the heads 59.5%. meaning the exhaust flows that % of what the intake flows. Knowing this number allows one to cam the engine based on how good or bad the port is. In this case it doesn't flow well so with the aid of the cam we are going to help it with more duration (time) to get the exhaust out the pipes. Paying attention to the flow numbers and I/E ratio ANYONE can get much closer on what they need for camshaft. Throwing a 490/510 226/232 cam in this engine would have yielded much lower power numbers even though the cam is simlar because without giving exhaust more time to get out the engine smothers because residual exhaust is left in the cylinder when the new intake charge comes in. A contaminated intake charge does not make power.

How do I cam. At 75% I/E ratio the cam at .050" should be the same duration. If the ratio goes up you need to add 1 degree of duration to the intake side for every 1%. If the ratio goes down from 75% you need to add 1 degree of duration to the exhaust for every % point.

Now rpm and CID will vary this some but if you use this method it will help greatly. Note this heads are basically 60% and cam has a 14 degree split. The cam being the brain of the operation makes this combination work together and make the power it makes. To many times we throw good money at engine builds to be disappointed. If people will take some time and do a little math it would save them a ton.
 
#40 ·
jus goes to show you. "you can't satisfy everybody".
whine and *****. ***** and whine.
everybody here with any kind of sense and experience with the gen 1 sbc, will plainly see this lil carbed, lil intake, lil headed motor, decent cr and very nice specs on the cam, will be a blast to drive.
if the dyno only showed 355 lbs tq/hp, it would still be a hellva of a combo for a street/ strip vehicle. I'd give it hell, and would not cry about it or give 2 chits about what a dyno sheet said.
not every engine needs a 950 dp carb, profiler 210 heads, 13.5:1 cr , 300* duration cam w/ .750 lift. to have strong lil low rpm, stump pullin motor.
get real fellas!!!!!! you don't have to spend every last dollar in your purse to impress people with your over priced bs parts, that you will probly never take advantage of/ or ever need anyway. save a dollar or two to get high heels to match you purse.
jus my .02cents.
now I gotta save 2 more cents for matchin lipstick.
some fellas jus whine more then women. its a fact, just go check out HOTRODDERS.COM. you'll see
 
#44 ·
I don't see any whining about any of this.I agree the combo is a good match & no doubt the engine should perform well.Personally,I think the dyno #'s are a bit optimistic for the combo of parts based on the description.I honestly don't think if you,or,me go out & buy these parts as described & build a 355 as described in this thread,that it will actually make the power stated on that dyno sheet.
 
#42 ·
"you can't satisfy everybody".
"whine and *****. ***** and whine."

I don't see any of that on this thread, I thought it was respectful and didn't read any whining :confused:

When I use the word YOU in any of these posts its "plural form" is meant ! If I ever single any one out or a post I use their on line name ! I don't think your aiming your post at me :confused: But you did say "everybody here with any kind of sense and experience with the gen 1 sbc" LOL:thumbup: Hell I run and build 302s LOL low on torque high on HP and very high on RPM LOL :mwink::thumbup:

Jester (Chris)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top