Canada Jeff

I agree.

Now, maybe Dustin at Whipple can chime in here, I wonder if Whipple dyno's without any acxessories? Power steering pump, water pump, ???

Quicksilver

There can be so many variances on dynos, calibrations slightly different, weather etc. The stock kit might have dynoed 700 that day.

mikes280

your heads are much better then stock so the cam is hurting you, with these heads you need more cam. A craine 741 would help and with it you should see in the low 800 range.

HALLETT FAN

It's the torque that will allow you turn a bigger propeller and faster ...prop it accordingly...

TeamSaris

You can mess with the correction factor on any dyno and get that sucka to read 850 if ya wanted. I give no credit to the people who do this but there are some.

Comanche3Six

Great advise!

Ratickle

Totally agree when you are still running the stock cam. It's your weak link to keeping stock number power ranges instead of being higher.

mcollinstn

IF (big if) the stock 500efi is able to consistently return 740hp (when corrected for altitude, etc) with the same kit you have installed, then YES you should be pissed off.

The key is the IF.

Bottom line is, your heads SHOULD be good for more hp than the stock heads when run in an apples to apples blower comparison. No bones about it.

We've established that you have BETTER THAN STOCK heads, and stock cam. Now we have questions..

Is the stock cam degreed properly? If not, you're losing power there.
Do the new heads have larger chambers (lower static CR)? If so, then you're losing power, but also have more potential to tolerate more boost without detonating.
Is the port matching and port cleanup an IMPROVEMENT or did he actually HURT your flow? I've seen some PRETTY ports that no longer flowed worth a diggity.
Is your motor set up to clearances that are actually robbing horsepower? If so, it may loosen up with break-in, but I would be a bit frightened if this is the case.

I read your build thread. I have some concerns.
What bearing clearance did he set your motor up to? What thrust clearance? What side clearance? etc. Sounds like he made a lot of wholesale clearance changes.

What rings did he swap you over to? The supplied rings with the JE marine piston are usually decent rings unless you want to go to 2 piece or something. If you use a gapless setup, you have to do a special hone finish. Also, a marine blower motor can stand to have a larger end gap than you would normally run, because if you lose a water pump under boost, you can scuff the cylinders very quickly with tight rings.

Valve guide clearance... What clearance did he set you up to? Exhaust stem clearance NEEDS to be looser than your grandma's Buick.

Best of luck.

Dyno to dyno, you can never expect to get the same reading. I wouldn't worry so much about the actual number. I would like to have seen what your stock motor pulled on THAT dyno for reference.

If if makes you feel any better though, the MATH says that 5 pounds of boost on an apples to apples comparison is only good for a theoretical 36% increase in hp. A 500 horse motor should only make 680 hp with 5 pounds of "perfect" boost (with no added heat).

So, using an adiabatically PERFECT blower (that doesn't add ANY heat to your intake air) pumping 5 psi into your 500 horse motor, assuming that the accessory drive isn't robbing ANY horsepower to spin the blower (which is just as impossible as the perfect boost), then you see 680.

That's what the MATH says.

Reality says that your boost is only at BEST 90% efficient, and your blower probably takes 30hp to spin it.
So you have a 33% (36 x .90) increase (to 665hp) and then take away the 30hp to spin it, and you're down to 635hp.

SO where does the advertised 740 come in?

Well, if you run 40 degree water thru the intercooler, you might be able to pulley up to an effective 7psi, and cool it back to a measured 5psi. This would be some REALLY cold dense intake charge. It would also give you a theoretical 50% boost in power. 500 plus 50% = 750. Take away the 30hp to spin the blower, and you're back to 720hp. Cut all the other belts on the motor and run the right set of dyno headers, and voila, you're back to 740hp.

On the other hand, the advertised test motor may have been exceptionally frisky. It may have been stock (ish) and may have actually belted out 740 that day with no tricks.

When you boil it all down, a measured 720 out of your combo with 5psi of manifold pressure is nothing to piss and moan about.

Like you, I'd wish and wish for those extra imaginary ponies back, but my guess is that the stock motor in the advertisements is just a touch more sprightly than your garden variety stocker.

mc

Michael Garibay

Don't feel bad. I have 575 sci motors with superchillers. First stage upgrade states 650hp with no other mods. With fuel upgrades (aeromotive pumps and return fuel system) and upgrade in pulley (4" to 3 1/4") they state 675-700hp. Well, I have all the upgrades and was dynoed at 652hp/701tq. Oh well, as long as it runs good and I don't eat drives ( I have XR's) I will be happy. Mike

Canada Jeff

Jesus MC, I had to read that twice. I can't answer all questions, hardly any actualy, But this builder is well established and is known for his head work.

I agree with you that the 740 hp number is going to be on the high side strickly for business reasons.

I'm trusting you on the mathmatical hp number, so that makes me feel good.