Guess my horsepower

[Barry_R]

If that is a traditional non-annular Holley 850 double pumper they are rather finicky on calibration in any case.  No waist in the venturi - plenty of airflow but not much for circuit sensitivity or refinement.  The 830 (or the HP900 which is pretty similar) are better carbs from a tunability standpoint even if they give up a bit of peak airflow/power capability.

Torque per cube at 1.32 is a nice solid number - should be a good strong engine and probably rip through the gears nicely.

[cobracammer]

If I would guess 0 HP at 0 RPM's....seems logical ?

I want to say 575 at 6000 RPM's

[blykins]

If I would guess 0 HP at 0 RPM's....seems logical ?

I want to say 575 at 6000 RPM's

You're late to the game, homey.  Results are on last page. 

[Joe-JDC]

I would be curious as to the vacuum through out the pulls?  If the vacuum was more than .4-.5, then the carb was definitely too small.  Did you happen to take vacuum readings?  Joe-JDC

[jayb]

Joe, vacuum peaked at 1.5 inches.  We talked about that during the dyno session, there was probably power to be had with a bigger carb.  That carb is definitely suspect.

[HarleyJack17]

Where is Drew when you need him! JK.
Nice motor, nice power, cool thread.  I got close on 597 but off on RPM's and surprised by the TQ.
Definitely some work went into the design/planning and seems it turned out pretty darn well. Rip some Chebbys a new a@@hole!
 
"Baby roller" is that like a cuddly alligator? 

[jayb]

I'm enjoying all the comments about the rocky curve, and I think a lot of them are right on the mark.  Now, take a look at the graph below, and tell me what you think of this:




Believe it or not, this is the same engine.  In fact, the curve is from exactly the same data as I posted a little earlier.  The difference is, the curve smoothing algorithm in the dyno software has been turned on.  This lowers the whole curve a little bit but smooths out the numbers, so that the discontinuities in the curve completely disappear. 

I have a lot of things to say about this, but primarily I think that the curve smoothing algorithm hides potential problems with the engine.  And almost every dyno operator uses it, because it makes the curve look better to the customer.  For this reason I NEVER run the curve smoothing option on my dyno.  Sometimes the curves look choppy, but I think this is telling you something.  Yesterday, while dynoing Jim's engine we noticed that jet changes were not really having the expected effect on the A/F numbers and the horsepower/torque curve.  Experience points to the carb, as quite a few folks here have pointed out.  But it would have been a challenge to see that, or really understand what was happening, with the curve smoothing turned on, because the torque and horsepower curves would have looked fine.

Now, one other thing to consider is that the dyno is an electrically noisy place, and electrical noise can mess up the signals from the dyno's tachometer output, and the torque sensor output.  This can also lead to discontinuities in the horsepower and torque curves.  However, I have dynoed enough really strong engines to know that when everything is right, those curves look very smooth, with only an occasional glitch, even when the curve smoothing algorithm is turned off. 

There are options for the curve smoothing, called first order, second order, and third order, referring to the mathematical formula used to modify the data.  Below are four dyno charts from one pull, the first with no smoothing, next with first order smoothing, next with second order, and finally third order:










The moral of the story is that it is important to understand the data that you are looking at, if you want to really see what's going on with your engine - Jay

[Jim Comet]

Is there any chance that the blocked off power valves caused any of the fluctuations. Or do they just enrich the same main circuit that the main jets do?

[Barry_R]

Is there any chance that the blocked off power valves caused any of the fluctuations. Or do they just enrich the same main circuit that the main jets do?

That's not the problem.

We are all fixating on fuel bleeds/emulsions because the indicators are all pointing to a fuel mixture/delivery issue.  The bumpy power is matched by similar discontinuities in air/fuel ratio, BSFC, and fuel usage/consumption.  I guess its possible that we are seeing a reversion issue that is manifesting itself by farting around with the fuel demand.  Take a flashlight & look down into the intake runners.  If they look blackened - like an exhaust runner would be - we might have another clue.  In any case its a strong running piece.

[Joey120373]

Jim, looks like you have a great runner there, congrats.
Too bad that the fuel issues kinda corked it up, and pulling 1.5 inches of vacuum was not helping.
Just to bad there wasn’t a bigger/better carb available to try, I’m guessing there is a decent amount of power still in that thing.

[plovett]

If the carb was a restriction, might that have been found using tall open spacers?  It sounds like they tried a lot of different spacer combinations.  Just reread it and see there was only a 1" open spacer. 

paulie

[Joey120373]

If the carb was a restriction, might that have been found using tall open spacers?  It sounds like they tried a lot of different spacer combinations.  Just reread it and see there was only a 1" open spacer.

Probably showing my ignorance here, but how would a larger carb spacer influence weather the carb was a restriction or not?
Taken to the extreme, slap a 600 cfm carb on that motor, I'm not seeing how it's ever not going to choke the airflow through the engine regardless of how big a spacer you put under it.
Or is it more subtle, where a carb that is close to big enough can benefit from a larger plenum area due to the larger area acting to slow or buffer down the pulses  seen by the carb?

[Barry_R]

As a crude generality a dual plane intake will "want" a larger carb than a single plane intake.  Viewed as a single event (no such thing in reality), an intake runner demand will only "see" two barrels of the carb on a dual plane while it "sees" all four barrels on the connected plenum of a single plane.  An open spacer connects the two sides and gives the active runner a view of both sides of the carb at the same time it adds plenum volume.  It also helps even the air/fuel ratio from side to side.  This is assuming that the engine wants an even air/fuel ratio and that it wants the added volume and that it wants the added carb area....you get the idea.

You can spend lots of time expounding theories on carb spacers, but it usually far better to just clip them on a try them.  Things like an air/fuel ratio variance, vacuum in the intake at WOT (1.5 ain't really all that bad...put a 600 on it and it would probably be over 2.5), and a different than expected peak power or TQ RPM can clue you in that an opportunity for improvement exists.  But it does not mean that anything is really there - or that chasing it is worth the cost in power at other points in the power band for a given application.

[plovett]

If the carb was a restriction, might that have been found using tall open spacers?  It sounds like they tried a lot of different spacer combinations.  Just reread it and see there was only a 1" open spacer.

Probably showing my ignorance here, but how would a larger carb spacer influence weather the carb was a restriction or not?
Taken to the extreme, slap a 600 cfm carb on that motor, I'm not seeing how it's ever not going to choke the airflow through the engine regardless of how big a spacer you put under it.
Or is it more subtle, where a carb that is close to big enough can benefit from a larger plenum area due to the larger area acting to slow or buffer down the pulses  seen by the carb?

My thinking, could be wrong, was that a if a taller open carb spacer reduced the vacuum and increased power, then that could indicate that the carburetor itself was a restriction.  Because the greater open plenum area makes the carb seem bigger to the engine.  In a sense, more open area under a carb allows it to come closer to its true maximum flow potential (and enlightenment). Yes, I know, you have to try it and see.  I am on board there.  Just trying to throw myself on to the fire for the good of the group.

[Jim Comet]

We tried a lot of different spacer combos. The only combos we didn't try were no spacer, and a 2" open spacer which I believe the 1" open spacer with the HVH on top of it that we did try would be very close to.Jim