Dyno results, dissapointing......

[Paul G]

Went to the Dyno day today. Lots of people there. I was impressed by some of the imports making 450+ HP. Over boosted little rockets! Spent about 3 hours waiting to get on the Dyno. Pretty cool watching the numbers come up on different cars. 

I expected better numbers from my little 360. I am very dissapointed to say the least. The first pull is with A/F ratio. The second is without A/f ratio working because the dumps were open and the sensor was still in the tailpipe.

First pull is 224 HP max around 4700 RPM, torque 269 max right at the start of the pull, then tapering off after around 4000 RPM. I had the dumps closed. Engine temp at 180°. A/F ratio started off around 12, then dropped to 11.5 around 4000rpm, then down to 11 around 4600 RPM for the rest of the pull. The dyno operator says I am too fat, I think he ment the A/F ratio...I think.  What can I do about being too fat? Short of diet and excersize. 



The second pull I opened the dumps. This was a crowd pleaser! Gained 4 HP for 228, gained 9# of torque for 278. The A/F ratio sensor was in the tailpipe still, so no reading.

[A383Wing]

"Too fat" in engine terms is you are running too rich....drop a couple of jet sizes in the carb

I did a dyno run with the Daytona years ago....came in right where I thought it would....but the operator also said I was running too rich at WOT.....I went down on the secondary jets 10 steps I think....car runs much better at WOT now

Bryan

[charger_fan_4ever]

Is it stock ?

[Paul G]

"Too fat" in engine terms is you are running too rich....drop a couple of jet sizes in the carb

I did a dyno run with the Daytona years ago....came in right where I thought it would....but the operator also said I was running too rich at WOT.....I went down on the secondary jets 10 steps I think....car runs much better at WOT now

Bryan

The secondary is a plate. Stock size for the carb. The primary side is jetted up one size, two numbers.

Is it stock ?

Not stock. Ported Iron heads, Eddy RPM air gap intake, Holley 750, Crane roller rockers, MSD ignition, 8 quart oil pan. It has the stock 360 crank. I dont have the specs on the cam or cylinder compression. I guess it was built for show, not go.

[HPP]

Actually not too suprising. I've been to enough dyno sessions to know that it is a very humbing experience for a lot of guys. What is your altitude there? That can have a big impact.

Looks like you don't have enough cam for the heads since your power is peaking at 4700. The wiggles in teh lines at higher RPM look like some spark scatter too.

[Rolling_Thunder]

agree with above. 

[Paul G]

Actually not too suprising. I've been to enough dyno sessions to know that it is a very humbing experience for a lot of guys. What is your altitude there? That can have a big impact.

Looks like you don't have enough cam for the heads since your power is peaking at 4700. The wiggles in teh lines at higher RPM look like some spark scatter too.

We are at 1200' here. Spark scatter? I replaced the wires with a set of Ron's Fire cores last year. Could the coil or cap be faulty? 10 year old MSD coil, cap and rotor.

I have suspected the cam is probably a stockish grind. No lope really. I figure this little "boat anchor" I am running puts out about 280 horse using 20% for drivetrain losses.

Why would the original engine builder go through the expense of using nice roller rockers, do some head porting, use a big Holley 750, deep sump oil pan, and then use a crappy cam?

[c00nhunterjoe]

Nearly 300 horse on a stock cam isn't really bad. The rest of your combo is ready for a bigger cam and your numbers should climb respectably.

[cdr]

headers ?

[Paul G]

headers ?

Yes. Hooker long tubes.

[A383Wing]

I guess I thought you were running a Carter 4bbl...

my bad

Bryan

[Challenger340]

"Fat" in tuning jargon means too "rich"....

From your Dyno Chart...I'll bet Dollars to Donuts that is an absolutely bone STOCK 2 BBL Cam !! , no matter how much Rocker train "bling"etc., is bolted on the Engine.

The good news, is you would see a DRAMATIC horsepower increase with a Camshaft change.

[firefighter3931]

  From the power curve it looks like the Cam is holding it back. Imagine how much better that power curve would look with an additional 1000-1300 rpm (5700-6000 redline) 



Ron

[bobs66440]

750cfm carb is definitely too big for that motor. Especially for a low rpm street application.  600-650 would be much better.

[HPP]

We are at 1200' here. Spark scatter? I replaced the wires with a set of Ron's Fire cores last year. Could the coil or cap be faulty? 10 year old MSD coil, cap and rotor.

I have suspected the cam is probably a stockish grind. No lope really. I figure this little "boat anchor" I am running puts out about 280 horse using 20% for drivetrain losses.

Why would the original engine builder go through the expense of using nice roller rockers, do some head porting, use a big Holley 750, deep sump oil pan, and then use a crappy cam?

1200 is dinging you a little but, but not a huge amount. If you were up the pass in Flagstaff, then these would be really good number for a built big block.

Spark scatter can be a weak ignition or a cap/rotor that has some errosion on it. It isn't a huge deal and you probably never noticed in during normal driving. If you were spending time at rpm, then it might be more noticeable. It might be worth replacing the cap and rotor, but I wouldn't worry about the coil.

It certianly is a mild grind on the cam. Hard to say why the builder put it in there. Keeping everything very street friendly? Something the previous owner requested? Hard to say. Trying to build cylinder pressure maybe. What's your cranking compression at in psi?

[Paul G]

What's your cranking compression at in psi?

I did a compression test a few months ago.
1 - 160    2 - 170
3 - 170    4 - 165
5 - 165    6 - 175
7 - 165    8 - 160

Any idea what what the CR might be based on the compression test? What was stock CR for a 72 360? I know it still has a 360 crank. 

[HPP]

I'm guessing somewhere between 8 and 9 to 1.  I believe stock was claimed to be 8, but actual measurements could have been as low as 7.

Here is a calculators you can use to try and sneak up on it, but you'll need cam specs to make it work. http://www.rbracing-rsr.com/comprAdvHD.htm

[BSB67]

First, it looks like the numbers are not "corrected" to standard conditions.  Your corrected numbers, which is what nearly everyone uses, would be higher than the actual that you posted.  99 degree temperature will suck considerable hp out of any internal combustion engine.  Corrected would probably be 5 to 7% higher.

Second, running rich also sucks considerable power from a motor.  Funny, as the first thing everyone does is to put bigger jets in.  Two jet numbers is two jet sizes.

Third, like pointed out by everyone, the power peak is at a relatively low rpm , likely due to the cam size.  However, it does seem a little odd that the motor continues to pull nearly 2000 rpm past peak.  Usually it will go for a bit past peak and then drop like a stone.

[Paul G]

I guess I have some options.

I can keep it the way it is. 

Try a smaller carb, 650/670, or smaller jets in the 750. Gain anything?

I could try a cam swap and see what improvements I well get. HP/TQ gain?

Go for a cam and some Eddy heads both at the same time. HP/TQ gain?

[Scaregrabber]

Jet it down a bit (I would go down 2 jet sizes at first), it's almost free and proper tuning is part of any engine build. the 750 will run fine on what you have if it is tuned correctly. The figures aren't really that bad for what you have but if you optimize it you may be surprised how much better it will run.

Sheldon

[Scaregrabber]

Oh: And after the rejetting if you want more I would carefully select a matching camshaft and torque convertor, that will bring it alive and fully utilize your headers and intake system. Hard to spec a cam without knowing the actual compression ratio though.

Sheldon

[Chryco Psycho]

I would just tune it , even go back to the dyno with a box full of jets , the 750 is fine on there , get the carb dialed in for best power both in full pull & cruise mode , set up the timing , make sure you power valve is right with the vacuum you are making .
What kind of dyno was it tested on , different makes will read differently ...... Nevermind , it is a dynojet which read higher than some other makes do . Unfortunatly you cannot do cruise runs on a dynojet dyno they only read acceration , Mustang dynos are better for tuning   . Dynos are generally heart breakers everyone makes around 500 hp until they get on a dyno . There is nothing wrong with what you have if you are happy with the power it has .

[charger_fan_4ever]

Maybe i missed it but what is the total ignition timing on the run ?

[cdr]

yes it was corrected hp, it says  CF-SAE, also look at bottom of run it says the amount of x 1.05,also dyno jets do run about 10-15% high

[Paul G]

Maybe i missed it but what is the total ignition timing on the run ?

Timing is 36 total, +or-.