poor dyno score on 540,s new facts !!
 

ok here is what I have . 2 each 540 cubic inch gen 6 motors, 632 lift 244-256 duration. Gil offshore exhaust . 1050 dominator carbs. Brodix 4500 style intakes. Problem was the dyno run . Hp was only 575 hp at 5200 then it fell. I anticipated abt 625. Timing is at 34 degrees. Any suggestions or opinions. Heads are big chevy rect ports with 230 intakes and 190 exhaust. They flow 322 cc(.Comp is 9;1). My bsfc was .46then .43 at mid range then .53 at top end . Could it be jetted to fat?

Re: poor dyno score on 540,s
 

With bsfc in the .4's, it might be a little lean. Also, what is your exhaust flow? The cam is pretty mild for a 540 with GM heads. I have a couple of Crane 651's you could try. 244/256 duration, .630 lift both.

Re: poor dyno score on 540,s
 

My 540 has the same heads but the cam is 680 lift solid rollerand I run a 950cfm.Made 630hp at 5700.torque 650 at 4750.made more hp with less timing,I run 32 total go figure.Im sorry I didnt get the afr heads.

Re: poor dyno score on 540,s
 

Can you post the actual and corrected horsepower and torque and BSFC numbers? That might help us to figure out what's going on. Please post the jet sizes if possible too.

Re: poor dyno score on 540,s
 

Ok I have my info in front of me.632 lift 244-256 duration @ .050 (320 intake runners}
rpm trq fuel lb. a/f ratio bsfc horse power
3200 611 168.5 12.6 .468 372
3400 611 170.9 12.4 .447 395
3800 616 194.6 12.5 .450 446
4000 625 207.1 12.5 .448 476
4100 635 210 12.6 .439 496
4500 629 238 13.2 .457 539
4800 614 244.9 13.3 .450 561
5100 589 263 13.3 .475 572
5300 550 278 13.2 .518 555

Re: poor dyno score on 540,s
 

Ok I have my info in front of me.632 lift 244-256 duration @ .050 (320 intake runners}
rpm trq fuel lb. a/f ratio bsfc horse power
3200 - 611 - 168.5 - 12.6 - .468 - 372
3400 - 611 - 170.9 -- 12.4 - .447 - 395
3800 - 616 - 194.6 - 12.5 - .450 - 446
4000 - 625 - 207.1 - 12.5 - .448 - 476
4100 - 635 - 210 - 12.6 -- .439 - 496
4500 - 629 - 238 - 13.2 - .457 - 539
4800 - 614 - 244.9 -- 13.3 - .450 - 561
5100 -- 589 - 263 13.3 - .475 - 572
5300 550 - 278 - 13.2 - .518 - 555

Re: poor dyno score on 540,s
 

didn't you run it any higher?? why do you say it fell off if you only ran it to 53?
torque will = horsepower at 5250 rpm I think you had more in it you just cut the test short

Re: poor dyno score on 540,s
 

I ran it to 5500 the numbers kept going south on us. 4800 rpm 614 lb of torque
561 hp
5300 rpm 550 torque
555 hp

Re: poor dyno score on 540,s
 

I see your point check the obvious coil bind or the retainers / keepers hitting the guides ( it happens I've seen it) I know it sounds wierd but try a different carb sometimes so;mething is wrong with one we switched a tricked out 1050 to a out of the box one and picked up 60 hp believe it or not ,with the big heads you should not be o;ut of air that early we have printed bigger numbers with a 502 with oval ports so somthing is wrong good luck

Re: poor dyno score on 540,s
 

I assume he is giving us corrected data anyway, HP = torque X rpm /5250

Re: poor dyno score on 540,s
 

What do you mean coil bind or the retainers ?

Re: poor dyno score on 540,s
 

if the valve springs and cam are not matched correctly the springs actually won't compress far enough for the valve to open the whole way . we had the retainer actually hit the top of the valve guide ever so slightly not to really notice but it scrubed power, also if you are running a hydraulic cam try backing the preload off and see what happens sometimes the lifters pu;mp up and hold the valves open

Re: poor dyno score on 540,s
 

I certainly could be wrong, but in my opinion the cam is too large---I believe it is making for a sluggish engine.

Re: poor dyno score on 540,s
 

IMO way too much cam for the heads and exhaust to start with. A little more timing would help some. Your bsfc numbers are out of line with the borderline lean condition the A/F ratio shows in the upper rpms. They seem to contradict each other. I think the HP numbers are in line for the setup. Put a set of headers on it and you should see 30+ hp immediately. 13+ A/F ratios are ok with good gas and no excess heat. Do you have exhaust temp info?

Re: poor dyno score on 540,s
 

These motors were bought from Derebery performance in Texas. He sells this setup alot. The problem has to be something superfiscial . Ignition or induction . My dyno guy was poor. But thats another issue . VA> SPEED stay away !!!!! .I am going to increase my fuel supply I was jetted at 97 squared . Others with the same setups run 87 squared and make more power ! Im stumped

Re: poor dyno score on 540,s
 

With an 850 holley the engines ran great. But little hp only a 3 mph insrease from last motors . 470 hp with 850,s 575 with1050.s

Re: poor dyno score on 540,s
 

97 square is way, way too much fuel. I would tend to trust the bsfc more than the A/F info given. Take some fuel away. You need to double check with egt's. No matter what, I think that the exhaust will limit you to very near that 575 HP range.

Re: poor dyno score on 540,s
 

Check exaust gas temps to find out where the carb jetting needs to be. It is an excellent
way to tune the motor without trial and ERROR.

Mike

Re: poor dyno score on 540,s
 

I apologize for the long post but this is very good information that will hopefully shed some light on the subject courtesy of Larry Meaux.
BSFC and Exhaust Gas Temperature (EGT) Information ;
In the old days of dyno testing , the dyno instrumentation
back then consisted of measuring Torque and engine RPM .
The dyno "luxury options" were also the ability to measure
fuel flow and exhaust gas temperatures , now these options
are standard equipment on modern dynos.

Fuel Flow readings are used to measure how efficiently
an engine was at turning each pound of gasoline or methanol
into HorsePower , in other words , how much fuel was being
consumed per HorsePower . The resulting terminology ,
is named "BSFC" or Brake Specific Fuel Consumption .

Brake = meaning as measured on a dyno water brake

Specific = results obtained relating HorsePower to Fuel Flow

Fuel Consumption = the amount of fuel consumed in Lbs. per Hour

the BSFC equation is ;

BSFC = Fuel_Consumed / UnCorrected_Brake_HP

.450 BSFC = 225 Lbs. Fuel per Hour / 500 UnCorrected HP per Hour

Note= UnCorrected HP means the raw , uncorrected HP as measured
in the current dyno room weather conditions , and as yet
this raw HP has not been corrected to Standard Weather
Conditions (ex=29.92" Baro, 60 deg F, 0 % Rh)
or has any other corrections such as Friction Torque
or to account for inertia losses due to acceleration,
have been made to the raw dyno room HorsePower numbers .

BSFC numbers are a means by which you can judge an engine's
efficiency. Also, BSFC numbers are often looked at
as representing "Rich" or "Lean" engine conditions .
That concept is somewhat true, but not totally true or
exactly how the BSFC information should be interpreted .

Examples of BSFC and EGT number misconceptions are ;

1- An engine is being dyno tested , and is tuned to its best
and proper Air/Fuel Ratio , and its BSFC is recorded .
If some person were to pull off a spark plug wire during
the dyno test, the BSFC would instantly skyrocket !!!
The resulting BSFC would then be higher , and could easily
be misinterpreted as going RICH , but in reality, the
Air/Fuel Ratio would have basically remained "unchanged" !
Both an EGT temperature probe and a Oxygen or Lambda sensor
on exhaust would indicate the engine went richer also ,
but in reality an Air/Fuel Ratio meter measuring the engine's
"Consumed" A/F Ratio would have remained unchanged .

2- An engine is being dyno tested , and is tuned to its best
and proper Air/Fuel Ratio , and its BSFC is recorded .
If for some reason , the distributor came loose, and
ignition timing went retarded, the BSFC would also "skyrocket"

All it did was start burning the same correct A/F Ratio later
and was continuing to burn as it went out exhaust ports
as you were pretty much wasting it and sort
of blow-torching the EGT probes

This last example would be "doubly perplexing" to the
novice observer because the BSFC will be higher
falsely indicating the engine went "Rich" , and the EGT temps
will be very much higher , falsely indicating the engine went
"Lean" ,....both occurring at the same time and instant !!!

In reality neither the engine went "Rich" or "Lean" ,
instead the "consumed" Air/Fuel Ratio remained unchanged !

There are many more examples of EGT , BSFC, and A/F Ratio
misconceptions, but the above 2 examples are primary reasons
and sources of racer confusion .

Sometimes i've seen a few racers come to my dyno and dyno test
their engines ...we make a few pulls, and i tell them from the
computer readouts what the A/F Ratio is or what the EGT temps are;

Some racers respond by ;
1-if i tell them its rich ...they want to increase ignition timing
to change the jetting

2-if i tell them its lean, ....they want to retard ignition timing
to change the jetting

Then i ask them ;
"How can increasing or decreasing ignition timing "
magically "UNSCREW" and "REPLACE" that jet in your carb ?????

The "Consumed" A/F Ratio remained basically the same,
no matter what you do with ignition timing .

What they "perceive" as Rich or Lean moving the ignition timing ,
are the EGT temps growing hotter or colder depending upon which
way you move timing ...and the BSFC numbers getting higher
or lower depending upon which way you move ignition timing .

Moving ignition timing will NEVER unscrew and magically replace
the jet in the carb with a new jet size !

You should tune by the "Consumed" Air/Fuel Ratio readings ,
then look at EGT temps , ...then and only then use these
EGT temps as a tuning "referrence" and not as the
"Last Word" in proper engine tuning !!!

If timing is too retarded , the EGTs will be very high
for a particular A/F Ratio and Compression Ratio/ Boost psi

I go after ignition timing 1st...we keep moving ignition timing
a step at a time one way or another, to find best combo
of torque/hp...then we go back and play with jet sizes
to fine tune ...if you go after jet size 1st with wrong timing,
sometimes exhaust conditions during overlap can affect
jetting slightly , if the racer happens to have mostly
header specs on edge of being wrong , or intake specs or
overlap period on edge of being wrong for rpm range.

Then after the engine is tuned for best average torque/hp
curve,....note the EGT temps as a reference !
but only as a reference , not the final word in jetting .

I use EGT probes to tell fuel distribution and other things ,
i never use or heavily rely on EGT as A/F Ratio determination
Using the EGT probes for fuel distribution studies is
their greatest value !!!!

You can't ask some other racer what EGT is best for you .
example= no matter how well you tune a 9:1 normally
aspirated engine, its EGT's will be higher than a similar
properly tuned engine with 15:1 Compression Ratio .
....no matter what you do , the 9:1 CR engine is going to have
higher EGTs because it will waste heat out exhaust more than
a 15:1 engine, or any CR higher than the 9:1 CR reference point .

If you asked a group of racers that all had their engines
perfectly tuned and maxed out with the best possible ignition
timing curve and A/F Ratio ....
one racer might say 1350 deg F ,
another might say 1250 deg F ,
another might say 1150 deg F,
another might say 1050 deg F
.....they could all be correct and have the very same A/F Ratios
.....the varying EGTs depending primarily upon Compression Ratio,
Volumetric Efficiciency percent % , and Combustion Chamber/Piston
top design .

You can dyno test the world's most perfectly tuned engine
with the most stable , most perfect A/F Ratio ,..it might have
1150 to 1250 EGT for an example .......
then dyno test this same engine at zero deg TDC ignition timing
advance under full load for a half an hour or so,
...you're going to completely melt the headers off the engine
in half an hour, thats is if it lasts that long
and doesn't 1st cycle/snowball into severe preignition
then detonation ! all the while its A/F Ratio would be perfect ,
but the EGTS will have gone thru the roof !!!
that is if you still have a roof in the dyno room
and it wasn't burnt in the fire caused by the melting headers .

Another thing you have to watch out for is
where are you placing the EGT probe??
1-at 12 o'clock or so ...
2-How far away from heads exh port flange ???
3-How deep is the EGT probe protruding into header pipe diameter ????
4-EGT probe type and response time

all these factors greatly infulence EGT temps making
it very much impossible to directly compare EGTs between racers
if no standards are set to probe placement

So basically , if you walk around the pits at a National Event
and ask the SS racers that have CR from 9 to 11:1 mostly ,
they'll tell you 1250 to 1350 EGT and maybe a few at 1450

you ask the ProStock and Comp guys with 16+:1 CR
they'll tell you 1000 to 1150 deg F
maybe some of the very large Mountain type engines
with HiCr tell you 850 to 1000 deg F EGTs

Hi Compression Ratio = Lower EGT temps
Low Compression Ratio = Higher EGT temps

Correct ignition advance(32+ to 40+ ign deg range)= Lower EGT temps

Wrong ignition advance ( below -25 or so deg range)= High EGT temps
..... burn slower and later in stroke , continuing to burn
while exhausting and if severe...cycling/snowballing into rising
coolant temperatures, preignition, then detonation.

Rich A/F Ratios = Lower EGTs (also extremly lean, misfire)

Lean A/F Ratios = Higher EGTs ..burn slower and later in stroke ,
continuing to burn while exhausting if severe...cycling/snowballing
into rising coolant temperatures, preignition, then detonation.


Some more aspects of EGT tuning ...
Example-> 4 cyl engine

Engine #1 cyl #2cyl #3 cyl #4 cyl
RPM EGT EGT EGT EGT
5000 1350 1250 1300 1325
....
....
8000 1390 1370 1390 1390

i would be worried about the
Number # 2 Cylinder out of the 4

Look at the "RATE of CHANGE" in EGT temps

Number #2 cyl starts off low , ends still lower than
others but its RATE is quicker

during a short 600 RPM/SEC dyno acceleration test
you might see engine's EGTs like above example

but if you were actually racing this same engine
in a road course or relatively long race
the number #2 cyl would grow way too hot ,
its EGT would out pace other cylinders and cause failure ???

Look at "RATE of CHANGE" !!!!
also at the lack of "RATE of CHANGE" in EGTs

Re: poor dyno score on 540,s
 

RMbuilder
Good information. On a/f ratio are you checking the quanity of air going into the motor & then looking at the fuel used to come up with your a/f ratio. That is the only way I can see where you get a real a/f ratio since it will not be dependant on timing, spark or lack of spark.

What do you feel is the correct a/f ratio in a marine engine? Part throttle or wot?

Re: poor dyno score on 540,s
 

If it's NA i'd bump the CR to 13:1 MY 02

Re: poor dyno score on 540,s
 

Drew,i Think You Should Pull The Motors Out And Put A 6 Banger In It And
Have Fun!!!!!!!!!!!just My 2 Cents
Stan

Re: poor dyno score on 540,s
 

Drew ,
The cam you are using , I assume is a crane piece . This cam has way too much overlap in it and requires a set of headers to make any power . This cam should also max out at 5800 RPM for HP, and 4600-4800 RPM for torque peak .
I ran the same cam in my 540 and ran it with GILs - The thing was a dog -
I put a set of CMI tubes on it and woke it right up .
Still , it is alot of cam and really is a poor choice unless you have 12:1 compression .

Re: poor dyno score on 540,s
 

Turbojack,
Air fuel ratio is computed as follows;
(Mass air flow)/(Mass fuel flow)=A/F Ratio (gasoline)
stoichiometric= 14.7:1
rule of thumb optimum= 12.8:1-13.2:1
I agree the cam is not optimum for this application, however the engine drops off drastically just in the band (4800 rpm+) where is should just be beginning to work. This cam should be making peak torque @ 5000 rpm+ and peak HP @ 6000 rpm+. Instead its making peak TQ @ 4100 rpm and peak power @ 5100 rpm so I believe there are other mechanical factors in play here other than mis-matched components. Your numbers indicated you drop off 64 lbs/ft TQ in 500 rpm from 4800-5300 with your BSFC #'s increasing .068 in the same span. I would go back to the basics (fuel/air/spark) with an emphasis on ignition. Failing that I would look closely at the cylinder head with emphasis on the exhaust side. In particular valve bounce, spring surge, installed height/coil stack, valves and seats, and seat/nose pressure. The cam has to much overlap and low cylinder pressure due to excessive duration and the resulting late IVC angle but that should be apparent earlier in the pull, not @ 5000 rpm.
Bob

Re: poor dyno score on 540,s
 

For those of you reading Bobs course here on Dyno intelligence, you are getting a great education. Listen to the "masters" who do this as a lifes work and passion. they will teach you the secrets of real engine power and save you a lot of Dyno time, broken motors and engine performance frustration. For those of you who really want to Graduate Head of the Class, hire someone like Bob to help you in your quest for Power! Its your best return on investment. Heck you don't pull your own teeth do ya!
Ray @ Raylar

Re: poor dyno score on 540,s
 

If it were me I'd put .010 lash on the valves and make a pull (after you fix the fuel problem.) With those jets you should be drowning the motor with fuel. To save a lot of time dump the heads. no offence

Re: poor dyno score on 540,s
 

Jim, are you suggesting loosening the valve lash? I had to tighten mine down to about 1 turn on most and 1.5 on several to quite them down. Could this be costing me power? Been that way for 100 plus hours now with no problems. Crane lifters and Crane gold rockers.

Re: poor dyno score on 540,s
 

Even with a blower?

Re: poor dyno score on 540,s
 

do you guys think a set of cmi headers will get me close to the 600 hp mark . My goal was to be in the 83 mph range at a minimum. Im close .

Re: poor dyno score on 540,s
 

whats funny is my air fuel ratio is correct. 12.8 - 13.2 . Im right there .Should I still rejett?

Re: poor dyno score on 540,s
 

Yes, just for one pull. It will tell you if the cam is to big or not matched to the heads. Make sure the fuel delievery is ok(pressure and volume) and ignition system is OK. By adding lash it will pull some lift and duration out. If the motor goes rich with the same jets I would suspect the heads are a problem. A 2.300 intake valve should flow about 400 CFM @ .700 lift. The 1.900 exhaust valve can be hurting as well. Knowing those exports, it's hard to get 250 CFM out of them and when you do their usually over ported.

Re: poor dyno score on 540,s
 

I would say it depends on how they checked the air/fuel ratio. If they used O2 sensors then you may need to rejet. If they used the mass air flow sennsor then I would say NO & start looking at some of the other items brougth up above.

Re: poor dyno score on 540,s
 

[QUOTE=rmbuilder]I apologize for the long post but this is very good information that will hopefully shed some light on the subject courtesy of Larry Meaux.
BSFC and Exhaust Gas Temperature (EGT) Information ;
In the old days of dyno testing , the dyno instrumentation
back then consisted of measuring Torque and engine RPM .
The dyno "luxury options" were also the ability to measure
fuel flow and exhaust gas temperatures , now these options
are standard equipment on modern dynos.

Bob how do you know Larry Meaux ?

If this is the same Larry from Meaux La. I would assume from the info and the last name . I used him on Dynoing My Chevelle motors . He is pretty sharp!!

Rob

Re: poor dyno score on 540,s
 

Iv found the Crane lifters to be noise and they quite down after oil gets hot

Re: poor dyno score on 540,s
 

Have you checked your cam timing by any chance? Maybe it is over advanced.

Michael

Re: poor dyno score on 540,s
 

Whatever happened? What is the final verdict?

Re: poor dyno score on 540,s
 

Rob,
Yes. One in the same. Larry is very sharp, your Chevelle was in good hands!
boatman 747,
While your A/F ratio may appear correct there are multiple factors at work that can easily lead to false conclusions. Because of the excessive duration, overlap and possible cylinder head problems you are experiencing low intake signal at the carb. The low signal will pull less fuel per given orifice hence you had to jet up to make the correct A/F. This results in poor fuel atomization and slowed rate of combustion. As Jim V correctly pointed out, if you add lash to the valvetrain for one pull you will effectively kill some of the duration, increasing the intake signal and making your jetting appear fat. If you jet down then pull the lash, the engine will appear lean on the next pull. Catch 22. I believe there are both mechanical and tuning problems at work here.
Bob

Re: poor dyno score on 540,s
 

I had Derebery rebuild an HP 500. When he got done with it, it made less HP on the dyno than a stock HP500. This is after his " improvements" and new headers. I don't trust Leon to work on my stuff anymore.

Re: poor dyno score on 540,s
 

Ouch!!!!!!!!!!!!!!!!!!!!!

Re: poor dyno score on 540,s
 

Are we talking about solid or hyd. lifters?

All hyd. lifters need to be adjusted to 0 lash plus 1/2 turn on BB chevy studs, that way at high RPM the lifter is less likely to hold the valve off the seat. Don't ever Gage your valve adjustments by the sound of the valve train,(unless the sound suddenly changes), just adjust it the valves in proper procedure with the correct lash you're putting in it.

On solid lifters you can't always be guaranteed adding or subtracting valve lash will tell you if the cam is too big or too small. By adding valve lash sometimes causes more valve bounce which starts early in the RPM band and will give you a false reading.

Not bashing just stating facts.