Dyno day this friday, place your guesses or bets

[Stegs]

thanks guys for the info again

I will have to think about the decision on what to do. Lots of good info here.....i do appreciate all your help!

Sorry that its repetitive...i dont understand engine building so im trying to learn over forums.


I will think about how i want to proceed from here

[PRH]

A few pulls on the chassis dyno would still be a worthwhile way of evaluating where you really are now.

Should help to figure out just how much rework will be necessary to get to where you want to be.

[PRH]

I just talked to a shop that is going to be re-doing a 446 that is a pretty fresh "high performance rebuild", and it wasnt cheap either.
The engine builder told the car owner he would be pleasantly surprised at how much more power the motor had than when it was stock.
The car owner had driven the car for thousands of miles with the motor in the OE configuration, so he was well versed in how it ran like that.
It was still running fine, but the car was going through a restoration of sorts, and he figured he might as well get the motor done at the same time...... And why not go for some more power while your at it?

Well, apparently it didn't even have the power, or at least the feel of power that the stock motor had.

So, after some tuning, etc, from the first shop.......it's up at this other shop for a once over.
Nothing is found "wrong" with the tune, etc, and the owner still wants more power...... So the engine is pulled and plan B is going to be executed.

The first step was to have the motor dyno tested as is.
Stock intake and exhaust manifolds, Edelbrock 750 carb.
Multiple runs were made, timing adjustments, etc.......
And what they ended up with was:

427ft/lbs, 304hp

(Yes......  It's actually a 440........ And yes those are crankshaft power numbers, not at the wheel )

I was thinking after the motor is apart, and the parts for this awesome build are known.......maybe it should be added to the "proven combos" list

[birdsandbees]

Maybe there should be a "failed combos list" ! 

[PRH]

Here's a similar story.....not a mopar though.

A friend if mine built a 396 Chevy years ago, following the build intructions of the local "396 expert".
When I got to be friends with this guy, the motor had been built and running in the car for a few years.
He had never really been happy with the power, although he was told the combo was an "easy 400hp".

When I got my first test ride I knew right away it was well under 400hp.
The motor basically just stopped pulling at around 4500rpm, but the owner was stretching out the shifts to 6000, cuz the expert told him how 396's really like to rev.

After a while I convince him to pull it out, put it on the dyno, and then swap out the cam/intake/carb, and add headers.

So, as it came out of the car, with exhaust manifolds...... It was 283hp.
As near as I can remember the headers picked up around 30hp(this was around 15 years ago).
This combo was pretty well tapped out by 5000rpm.

The original combo was a .030 396 with a rebuilder type cast piston, which was shorter than oem, and had a smaller dome than oem. 396's are another engine that are easy to build the wrong way, and this was one of them.
It had the correct oval port bathtub heads, an Edelbrock SP2P intake manifold(probably the lowest performing intake you can find for a BBC), a 600 emissions calibrated Edelbrock carb, a Comp 280h cam(hey, it sounded pretty mean)..... And of course some Cam Dynamics cast aluminum roller rockers.

I had a small solid cam ground for it, changed the intake to an RPM A/G, and used a recalibrated Speed Demon 650DP carb.
I left the short block as is.

The cam I had done was for manifold use, but after he saw what the headers did the manifolds never went back on the car.
With headers and the other changes the motor made 418hp, and would easily go right up to 6500rpm(as high as I took it with the stock type cast pistons).

Just another example of how a few details can make a pretty significant difference in power.

Had I known the motor would be run in the car with the headers I would have done the cam differently, and I'm sure that would have allowed the motor to make another 20-30hp.

[Kern Dog]

Thanks, These stories are cool to hear. I'll bet it is far more common for guys to OVER estimate their engines power than to under estimate it.

[heyoldguy]

Customer drove up with a 440 in his car and his car in a trailer, drove it off the trailer and into the shop. "Smokes a little and really doesn't run right," he says, "Put a stroker kit in it!"

He had taken it racing and forgotten to drain the water out. It froze and pushed the expansion plugs out. He replaced the plugs and took it to a chassis dyno where they "tuned" it.

Well, he did drive it into the shop. So when we pull the engine, we throw it on the dyno. Fire it up and the dyno headers almost immediately start glowing red and we cannot pull the slightest load. Spend a little time with the distributor, time the engine and make a pull. Darn near 500 HP, 490 something. I'm betting if it ran like that coming off the trailer we wouldn't be putting a stroker kit in it. But, still it smokes and has 35% leakdown in two cylinders.

So, in goes the stroker kit and some port work on the RPM heads. We have what I would consider low oil pressure and 580 HP.

What? Is that all! Did my dyno take a dump? I call a friend 150 miles away with a dyno and ask him can I run on his dyno. "Be here in the morning."

On his dyno with no changes from yesterday.......599.9 HP. "Are you satisfied?", he asked. No, we are not!

We go home, finally find the oil pressure problem, throw away that hydraulic roller the 440 came with that we reused in the stroker (it wasn't the oil pressure problem), change the ring pack.........657 HP @ 6,100 rpm.........now we are satisfied.

But......just maybe...........I should have gone back to my friends dyno? It did give me another 20 HP.