I just had my sbc 406 on the dyno and it only came up with 465hp and 461 lbs of torque.  The reason I am disappointed is everyone I talked to said I should easily get 500hp out of this combination.  My question is what you guys think and where you think I went wrong.  
 I really wanted to get my 1967 Impala into the high 12's and still take it to local roll-ins.

Here are all of my specs;
Dart pro 1 heads 215cc
Weiand team G intake
Holley 800 dp with a Proform main body
Lunati 1.5 roller rockers
Camshaft specs are,
600lift intake and exhaust
260 duration @ .050 on both
308 duration on both
105 seperation
Its a pretty nasty cam but I got it to idle very good and a I have no power brakes and a manual trans.  

Any help would be greatly appreciated..
Thanks Brent  

The guy thought the intake is choking it off at 5900 so I should get a Super Victor.  What do you think?  Brent  

I also forgot to add that the cam is a solid roller and it has 10 to 1 compression.  Brent  

Brent

That cam seems to be a little big at the seat and at .050 for a 10:01 compression engine. 105 lob sep seem a little tight.

Can you fax me a dyno sheet @ 207-892-7215

or call me at the same number

Carl Hinkson  

Here is a link to a 383 we built 2 years ago with 195 AFR's
http://www.chevelles.com/forums/showthread.php?t=106715&highlight=DYNO  

I'll try to find the card and get back to you asap.  This cam was custom ground by a local shop and I went by what they suggested.  Thanks Brent  

Are you talking rear wheel horsepower or crankshaft? If this is rear wheel, you're getting well over 500 on the bolty end of the crank.

This is a pretty serious engine what is it connected to for a transmission. Automatics have a way of dissolving torque and power thru slippage and thermal losses, stall speed get into this act as well where high power engines in heavy vehicles tend to push stall speeds up and some of these converters are better at turning oil to heated foam than they are at transmitting torque.

Most chassis dyno drivers like to run the car in a lower gear to keep the driveshaft speed down, then adjust for the torque multiplication factor of the gears. By the time the root numbers are adjusted for RPM thru gearing and for atmospherics, who knows what you've really got. If youre wonder why thay want to keep the drive shaft speed down, just imagine what it's like when one of those things folds up due to a slight imbalance and comes out usually bringing half the transmission with it. OK maybe a third!

In the end there's no substitute for tuning and if you're already playing on a dyno, you've taken the first step to using the dyno and some diognostic equipment to do some power tuning. Bolting an engine together with all the "right stuff" is just the first step to getting power, next you have to go to bed with it to get all it has.

Bogie  

Thanks Bogie but this is at the crankshaft.  I think my main problem is in the volume efficiency.  I only get over 100% from about 4400 to about 4600 and my torque curve is garbage.  I was just thinking that maybe the guy I had build my motor did not degree the cam?  Maybe its retarded to to far?  I'll have to ask him that.  Any more ideas would be appreciated.

 Thanks Brent  

Brent, let me explane myself about crankshaft horsepower. You say "at the crankshaft"; I mean was the engine tied to a dyno and measured directly or was the engine installed in the car which put the powered wheels on a dyno from which torque on the tires was used to calculate engine horsepower. Also, in both cases indicated torque and power is mathmatically adjusted to change test conditions to Standard (atmospheric) Pressure and Temperature (STP) or not. If a hot or humid condition exists in the dyno room or this is done at Denver's altitude instead of San Pedro's considerable difference in the power numbers will occur.

I don't know how to calculate volumetric efficency directly, lots more equations are used to infer this percentage, but one needs to realize that they are not infallible. Without a blower of some sort, it's usually agreed that the RPM of the torque peak represents the point of maximum cylinder filling, or perhaps a better way to think about it is that the torque peak represents the end point of maximum cylinder filling. Whether that maximum is 100% or not, or more, who knows?  

I agree with other contributors in that I think your carb is on the big side but that's mangeable. However,the 800 CFM Holley comes with a mechanical secondary, if you have this the secondary opening may not be coordinated with the engine's CFM needs, this is a real pain to get coordinated either taking a lot of passes or tuning on a dyno. Vacuum operated secondaries being somewhat easier to tune. and especially with a BIG carb it's easy to open too much throttle too soon which will kill the torque curve. The down side of big racing carbs is that the air bleeds are sized to a preference for competition, which means they're big. Big air bleeds play havoc with low and mid range mixtures making them too rich. The knee jerk reation is to lean out the mains and idle circuit which mostly serves to lean out the top end (leading to detonation) while not helping low thru mid emulsification of the mixture, so the engine appears to still be rich. And I'm not even getting into the power valve, which with a big cam can be a real headache to pick an opening vacuum since the difference between idle and WOT vacuum can by slim. I (of course) have my own way of looking at this problem. I like to look at fast cruise vacuum and WOT vacuum readings and pick a power valve that opens half way between those readings. So if fast cruise say a road speed of 70 to 80 mph has a vacuum of 9 inches and WOT has a vacuum of 3 inches, I'll pick a power valve in the range 6.5 to 5.5 inches. So it's adding fuel when the engine is working hard, but not at a fast cruise on the freeway.

Same can be said for ignition timing, there is a tendency to use too much advance too soon. The engine responds to this by loosing torque in the mid range and surging up on the top end. This is the never easy hunt between static advance, centrifugal both in amount and rate, and vacuum if used again in amount and rate as well as when.

As for cam postioning, most everbody including Comp puts 4 degrees of advance into the cam when it's ground. Then unchecking engine assemblers tend to add another 4 degrees because that's what everybody does. So you, well rather it, ends up with 8 degrees advance. But generally speaking like the carb and distribtor's advances; this is one of those tuning things you have to get into bed with the engine to do. If you're running a really aggressive engine, and your's is getting into that neighborhood, it's really a good idea to run a two piece front cover so you can get in there and make adjustments to the cam's position relative to the crank without having to tear the whole front off the motor and drop the pan to get into the timing case. It's enough you've got to pull the water pump everytime.

Detonation can be another problem that reduces torque. With the exception of too much static compression ratio, this is function of carburation (too lean a mixture), improper ignition advance (too much too soon), incorrect heat range for the sparkplugs leaving a glowing tip hanging in the combustion chamber. These days it's easy enough to put a detonation sensor on the engine and just use it to shut the spark off if you're not running a computer in the circuit. Which brings me back to advance systems, MSD and Accel offer electronic advance modules, these are a much better way to manage spark advance than centrifugal and or vacuum systems.

bogie  

Thanks again Bogie.  So you think its more of a tuning thing than just the cam duration is just too much for the 10.2 to compression I have?  Thanks

Brent  

Yeah, I think you have to go thru the tuning process to get it to settle down before you start tearing parts out.

A good place to start, especially since you think the cam might not be set up correctly is to check it out. It's a bit harder to do when the engine is in the vehicle, but usually doable without too much trama. With care, a degree tape can be "glued" to the damper's OD. You screw a TDC finder into the number 1 sparkplug hole and follow the directions for locating TDC firing. With the rocker cover off put a dial indicator on the intake valve's retainer. You should have a helper or 2 as this is a lot easier if one guy pulls the engine over, take the spark plugs out to make it easier to turn, another reads the movement of the dial indicator, and a third marks the data in a notebook. If you have the timing card for the cam, then it's pretty easy to see if there are any differences between when the manufacturer says things should happen and when they do happen. For super accuracy, pulling the hydraulic lifters, keep track of where they came from,and dropping in a solid insures that no motion is lost to hydraulic leak down.

Obviously it would have been better and easier to do this when the engine was on the assembly stand. I usually do this early on when only the crank and cam are in the block, since these things turn smoothly and easily without the pistons being in the engine. I also docment measurements and take general notes as I go so if there's later problems, I have an audit trail of what went on.

Bogie

Bogie  

Ok I'll check it, and the engine is on the stand and not in the car yet.  Also its a solid roller cam that was custom ground by a local shop so I'll call them as well.  Thanks for the info.

Brent  

you probably have so much overlap with that cam your bleeding off cylinder pressure.you'd have to spin that thing to the moon and have at least 11.5:1 and tuning ti get it to idle good i'm sure didn't help.you have a stick car and no vacuum brakes.let it idle where it wants.  

big lazy single pattern cam,low compression,heads that flow ok = low hp and torque numbers. id change the cam (comp cam makes a sweet roller,630 630 252 258 @.050" 106 lobe center)this one works with 10:1 compression,and with a super victor intake,should be a nite and day difference.good luck  

definately change the manifold, you can hit 500 with an EDELBROCK RPM AIR GAP manifold, and still have good torque BB