Rebel_Heart

My engines are scheduled to be put on the dyno this week. What should I expect to be done? I know they will make several pulls, but what if anything can be changed in the engine at this point? The cam will have already been set, the rocker arms are installed, what is left? I guess, I am looking for any fine tuning that takes place since I have paid for a full day. Thanks.

stevesxm

seems to me that the "what you wanted to do " was sort of the REASON you are going on the dyno in the first place...

if they are fresh from rebuild then they will run a break in sequence which will take an hour or so... then , if an unmodified efi motor , they will check and confirm the timing and do some power pulls with the correction factors jacked out of sight so youll be thrilled and then theyll send you home...

if a carb motor and they are good at what they do, they will read the egts and do some carb and jetting work to get the fuel curve correct vs the timing... and its always a good idea to bring 20 gals of the fuel you are actually going to run in the boat...

if these motors were a known entity and just freshend the they won't screw w/ the cam... if they were all new, purpose built and they were on their game, they might make some runs and move the cam around to get what they want from the shape of the curve.... the permutations are endless and depend on the skill and honesty of the operators vs your wallet and the VERY specific list of requirements you have defined for them...

its really up to you and is based entirely on what you have for an engine...

Cattitude

timing optimization but most importantly verify air fuel ratios throughout the range. If I had not done this I never would have discovered I was way lean on my 540. You can also verify where power is falling off, maybe ID some tired valve springs etc.

Rebel_Heart

These are new 540's built from 502s. Running 1050 Holleys, heads have been professionally flowed, 1.8 rockers on the intake and 1.7 on exhaust. The cam is a Crane cam spec'd at 109, set in at 106. I am just wondering what I should be asking them to accomplish other than just producing a dyno sheet. I know this helps with break-in time, but wondering if there is something specific they should be trying to get the most out of the motors. What needs to be done with lashing the exhaust to determine how far the cam carries?

vandeano

What does it cost for a day on the dyno?

Wobble

About $450-$500here in Houston

Wobble

Jetting
Timing
Timing curve
carb spacers
air cleaner design
jetting again

have them hold a pull at max torque for at least a minute to verify that EGT's stabilize. Also have them hold a pull at the point before the secondaries open to verify the same thing.

if they dont have them,
bring spring kit for distributor
a couple of different height and design carb spacers
a coupe of different bases for air cleaners
they should have a selection of jets
idle speed and idle mixture adjustment.

you may want to play with the cam timing if you have time.

this should give you a good basic setup for the boat

Rebel_Heart

I am paying $700 for the dyno time and this will be the second time since I had the heads flowed and am using the 1.8 rockers on intake this time. I think they are adding a little to my bill as it seems this might be a little high. Thanks for the input.

The person that flowed my heads said he is willing to go to the dyno with the engine builder but it would be quite a drive so I wanted to be sure it was worth his time and effort.

Wobble

I forgot, you might need a selection of power valves also.

Good Luck

articfriends

iTrader: (1)

On top of what everyone else mentioned you could try carb spacers,different intake manifolds,some kind of plenum wedges or "turtles" (they are pieces that go on floor of manifold in the plenum area to help with fuel and air distribution).What kind of exhaust is dyno guy using,in a ideal world you should have the same exhaust on your motor that you use in the boat and ALL your accesories so you don't end up with BS dyno numbers and have to tune motor as much after comes off dyno and goes in your boat. Your numbers wouldn't be as artificially inflated but motor won't go from 12.5 air fuel ratio to 10-1 when you drop it in the boat either.Ask dyno operator what your correction factor is and what variables he is using to achieve it. Recently a new to the scene "engine builder" posted a TOTAL BS 540 buildup on another website,solid roller cam 540 with hand ported canfields,made 667 hp on dyno with dry dyno headers,no accessories,14.5 to 14.7 air fuel ratios then to top it off corrected the numbers 11% to 740 hp. We asked him to justify his 11% correction factor being motor was dynoed in low 60 degree weather,45 degree dewpoint,28.8 baro/29.4 calculated atmospheric pressure,900 feet elevation (correction factor should have been 2%) and all he could come up with was his fresh air supply came from his hot attic at 90 degrees (which still would have been only 4.5%) and was BS anyways. Be sure your dyno sheet shows pounds fuel per hour used and bsfc,Smitty