Back4More

Your within 3% of 740HP...Not bad. Thats like 1mph.
The stock cam is not giving you what you have in the heads.

BAJA WILL

Actually you are with in less than 3% what is advertised. Not being a Engine guru, I would say thats awsome with out spending allot of time making adjustments. My concern would be all the Tolerences that seem to be changed, we all know that adjusting this can rob some HP, if I had to guess that is what happened and once the motor is broke in you will see the 20hp, who knows maybe more??

Really hard to compare a stock 500efi/whipple set up to a 500efi/whipple set up not exactly stock. Cannot tell youhow many times changing something in a engine that should have made more power actually made no gain or less for no real reason???????

My 2 cents

WILL

CIG3

YOur right in the ball park. The cam is restricting you and I would suggest running your CMI headers to get a more true Dyno reading. Dean Gellner (MR. Horsepower) doen all my work and always runs the marine exhaust when tuning.

Canada Jeff

We wanted to run the CMI's but would have had to make an adapter for his exhaust colector. I decided to not to.

HaxbySpeed

I've got a similair engine in pieces in my shop right now. Stage two with merlin heads and stock cam. The dyno sheets from the "builder" show anywhere from 713hp to one mystery pull that made 789, and a bunch in the 730hp-740hp range. This was over a few days and really shows how much a bad dyno setup or operator can skew results. There were 30hp differences between back to back pulls without any tuning changes. Sometimes just changing the rpm/sec rate of the pull can show unrealistic results. Unfortunately they left the iron guides in without inconels and .0015 clearance. It lasted about 40 seconds at full throttle and grabbed a valve. Enjoy the blower whine..

Whipple Charged

We run with all the accessories, sea pump with water, power steering, etc. But the problem here is the exhaust system. You can't dyno a 500HP EFI motor with large tube dyno headers. You have to run the stock E-top CMI's. This richens the air fuel ratio well over 10%. You can see the AF is going rich on top when it should hold 12:1. You also have to verify, with a scan tool that the ECM does not retard timing, sometimes on a dyno, the engine vibration and absorber will cause the knock sensor to pickup noise, and therefore retard timing.

You could easily take fuel psi away for a dyno run, but it in fact needs to be setup the way it is in the boat.

Get the AF right and you'll see closer to 750+ HP, but again, it's calibrated for operation in a boat.

Thanks,
Dustin

Whipple Charged

I just noticed that you have Dart Pro 1 heads. If thats the case, and you DID NOT change the SC pulley, then you've lost almost all velocity through your heads. Those heads flow significantly better, but you need to keep the air speed up. By not changing the blower pulley, you kept airflow exactly the same, yet lowered the compression of the enigne and the temperature of combustion.

Aluminum heads need to be run leaner, they need some cylinder pressure to work properly. Changing to the different heads should allow you to install a 1/2" smaller pulley, which would put the boost up to 8psi, which will net another 50-75hp.

Remember the SC is the pump, if you don't change the speed of the pump, you WILL NOT get more air through the engine, therefore, changing heads to aluminum just lowers combustion temp, higher flowing head just causes loss of velocity, etc.

Put a pulley on it and watch it go.

Dustin

BAJA WILL

AAHH answer from a GURU, nice

WILL

Whipple Charged

The Merlin's won't make as much as the Dart's but because they're still cast iron. The boost doesn't drop as much. But, will make more power if Canada Jeff doesn't change the pulley because they keep combustion temps up.

Thanks,
Dustin

Panther

Dustin,

Quick question... Theoretically, if he has better flowing heads than stock wouldn't he make less boost and potentially more power with the same pulley since more air can get into the engine with less resistance? In the end he would make more power with less boost?

Then again...even if the heads flow better, now the cam would be limiting his power output?

Frank