Dyno numbers. What would you do?

[Brass]

The car turned out a best of 230 rwhp and 290 rw torque on a mustang dyno.

Unless I'm mistaken, it seems to be under performing.  I am really interested in hearing reactions and getting some insight.  The tech said the car was well tuned but running out of cam or air at the top end.

Here is how the car was tested:

440 w/steel crank and windage tray.
906 heads which should have 9.2 or 9.5:1 compression.  79.5 cc. 2.08 in. 1.74 ex.
Crower HDP282.  In. dur: 282. Ex. dur: 292. In. lift: 0.478.  Ex. lift: 0.502.  LSA: 112 degrees.  108 intake centerline.
MP distributor and orange box electronic ignition. NGK plugs.
HP exhaust manifolds.  2.5" pipes with H pipe and ultra flo mufflers.
Edlebrock CH4B intake.
Holley 700 cfm double pumper with a 1/2 inch, 4-hole spacer.
Turbo Action 11" 2800-3000 stall converter.

I've been much happier with the recent cam, intake, and converter swaps but it seems like there is a lot of power left on the table.  Long term, I would like to make somewhere around 375 rwhp but 300 may be more realistic and reasonable(?)
 
Would these changes get me there?

Hone and port the intake and exhaust manifolds.  I'm willing to break down and switch to headers if necessary.
Indy EZ heads; ported and matched to manifold and exhaust.
Raise compression to 10:1.
Proform main body and metering block.
Electric fan.
MSD 6al.
Firecore wires.

Is there anything else I can do for now, short of an entire rebuild?

Thanks,
Michael

[oldschool]

the ez heads with a indy dualplane,would really wake that motor up.use headers also.i would guess 75-100 more horsepower,easy,with just those 3 things alone.

[greenpigs]

   1st thing is swap the wires for the Firecores then I would put the headers on. The proform main body and metering blocks is a good upgrade as well. Then if you can afford it I would test it again. The engine needs to breath and I suspect that is where a chunk of the HP you should be getting is hiding

[elacruze]

1. Carb's too small. Try an open plenum 1" carb spacer, an 850DP, or an open plenum manifold to prove this out.

2. Not enough compression for the camshaft duration. 906 heads should be 84-88cc's, I think. Who measured them?

3. Stock manifolds + low compression + cam overlap aren't helping.

Before you spend a bunch on heads, pistons, etc. find out if your carb setup is restrictive. The CH4B is a good manifold. A cheap set of headers will tell you how much the exhaust manifolds are hurting you. Being budget-minded, I'd find an open plenum spacer and $100 ebay headers before cracking the engine open.

[greenpigs]

I wouldn't sacrifice bottom end for HP. I don't think a open spacer would be good for you.   Did you install the blockoff valley pan? I assume the heads have been milled and CC'd. or at least checked for volume size. The cam doesn't sound that big for what you have now at least with iron heads. The carb might be small and if you could borrow an 850 hat would be good.

[elacruze]

The Crower HDP282 is only 228*/236* @.050 lift. It's not really big, just a notch up from the stock 375hp cam.

Without knowing actual compression, I would say you're lower than you think and it probably runs about right.

the 375hp engines were rated gross HP, so if you take away 20% for accessory and powertrain losses, that comes to 300hp. Chassis dynos lose efficiency at the tires as well, so I would expect 275-290 if everything is tuned right. Since you're still low, I'd guess that your compression is lower than the 375hp motors. What year is your block? Do you have stock 70's motorhome pistons or anything like that?
You can't really draw any hard conclusions without knowing compression with some degree of certainty. Can you get a cranking pressure reading at least?

[firefighter3931]

Mustang chassis dynos are notorious for reading low. I wouldn't place any weight on those rear wheel numbers. 

The good news is that it's tuned well and the AFR #'s look fine as well as the top end pull (5600) which is where it should be with stock heads. 

The CH4B is lots of manifold and capable of moving enough air for 600hp  A 700 holley is a bit small for all out power but it's a good choice for a street car with excellent throttle response. Your motor is not using all 700 cfm so the carb is not holding you back.

If you wanted to make a significant improvement a set of good flowing heads and headers are going to be your best option.

Do you know what pistons are in the engine ? Has the actual compression ratio been measured ?


Ron

[Brass]

Thanks for the responses!  This tribe is a first-class breed.  

To answer a few questions, the block is a 72 but I don't know what pistons are in it.  It was rebuilt to 68 HP specs and has about 10K miles on it.  The guy that did it was more interested in making the engine stock for longevity than building a performer.  The journal was a little rough when I had the rear main was replaced, so I don't know how good of a job was done putting it all together.  I definitely plan to do a compression test.  If it is low, will switching to a set of aluminum heads enable me to correct that - and would I be able to ring out a little more rpms?

For now, since I'm not utilizing all of the carb and intake's potential (I did get the valley pan to block off the heat crossovers), I'll plan to start with the headers and heads.  I've steered away from headers before because they can be problematic; not fit right, hang too low, trap the starter, leak, and run hot.  I'm also a little worried they'll lighten the exhaust note and make the car sound more "pingy" or "tin-can" like.  Still, power is what matters.  I know TTI seems to be everyone's favorite.  But is there a particular brand that would be a safe bet which I could look for on ebay?  The head$ will be another matter, to be sure.

Thanks again,
M

[BSB67]

If the hp numbers from the Mustang are correct, I think that you are down on power and I would try to find it before you pour money into hp parts.  I think you should RWHP at 275+ with what you describe.   I would take it to a track and see what it does and get a weight too.  From that info we can tell if you are in the ball park for power.   Get the cylinder pressures, make sure that the carb is opening all of the way, and is there any chance that there is a pluggage in the exhaust system, like something nesting/dead in there from the winter?  Did you get A/F numbers at the dyno, and how did they install the O2 sensor?

[Rolling_Thunder]

The Mustang Dynos do read very conservative...      When I dynoed engine in cars before I sent them out the door of the shop we would run them on a Mustang 7000 chassis dyno...      numbers at the wheels are not an exact science...

However all the things listed above will help you - RON as usual is spot on from what little i know (he knows a ton more than i do) - but i would get some heads and headers on it...     

I have Hooker Super Comp headers on my Road Runner with very little problems with them -  they do hang a little low but it has never been an issue...   they tuck up nicer on a 440 than they do on my 383.   they were around $350 if i remember correctly - about half price of TTIs. They were also ceramic coated -

[Cooter]

Even at 300 RWHP, I'd bet a bushel of apples that your pistons are "Off the shelf" Advertised "10.0:1", or "10.5:1" compression pistons that are closer to 8.0:1 actual compression pistons...Piston manufacturers advertise 10:1 comp., but do not tell you that they have had ALOT of people sending the ACTUAL 10:1 pistons back in the early years because of "Pinging" problems and now they simply sink 'em all in the hole about .040 just to be on the safe side..(Thinking for the dumbass so to speak, and covering their asses)...

I can't tell you how many people have come to me and asked why their 10:1 Whatever doesn't run like they think a 10:1 motor should all because when they ordered their pistons, they weren't aware of the fact the you have to Set the engine up in order to actually see that 10:1 they claim...You wouldn't believe how many sets of those Hypereutectic pistons when they first came online where sent back with the piston tops gone...Now, when you open the box, there's a HUGE, Bright Orange/red, label warning you to set your ring gap CORRECTLY for Gas, Nitrous, Supercharged, turbo, Alcohol, etc..

IF and only IF I were to pull those iron heads, the first thing I'd do was check My ACTUAL piston to deck height and configure my actual, real world, compression ratio..

[firefighter3931]

  I would take it to a track and see what it does and get a weight too.  From that info we can tell if you are in the ball park for power.   Get the cylinder pressures, make sure that the carb is opening all of the way, and is there any chance that there is a pluggage in the exhaust system, like something nesting/dead in there from the winter?  Did you get A/F numbers at the dyno, and how did they install the O2 sensor?

Good suggestions....a track mph will give us an idea how much power it's making. We would need to know the raceweight as well.

* BSB67 ; the afr & dyno data is posted in a link on Brass's first post at the bottom of the post text. I'd like to see what the afr #'s look like through the entire run though.

The best way to determine the proper course of action with the head selection would be to pull the current heads and have a look see in the bores. A piston to deck measurement is needs as well as determining whether or not the pistons have valve reliefs so we can do some math and pick out the correct chamber volume. Hopefully it has a set of 2355 forged Speedpro 6-pack replacement pistons.

You're gonna want a set of TTI headers with the angled plug heads in 17/8in primary tube sizing.



Ron

[frederick]

* BSB67 ; the afr & dyno data is posted in a link on Brass's first post at the bottom of the post text. I'd like to see what the afr #'s look like through the entire run though.

Isn't the lower, thin line for the AFR, bit hard to read though.

[SRT-440]

Sounds like a mid 70's low compression 440 to me..raise compression and it will prolly gain u 50-100hp. 

[HPP]

What altitude are you testing at and what is your cranking cylinder psi?

[Brass]

I'd love to get this Charger to a track and will look into that.  But it probably won't happen soon.   

Love the dead critter theory, BSB67.  Dude - were it only so!  Alas, I think the problem resides elsewhere.  Malign supernatural forces haven't been ruled out yet though.

By the way, the 02 was tapped into the passenger side exhaust pipe below the manifold.  Also, the AFR was indeed the lower thin line.  Initially, it blipped up a little rich and then leveled off.

So the general consensus is that while heads and headers would help, weak compression is probably hurting the motor.  I bet its true.  At least I now have a plan.  Even seemingly handicapped, the car still drives really well.   With summer coming, I want to change the stance and otherwise enjoy it as-is for now.  (Sorry - but the 14" rims gotta go.)  This will buy me more time to build up a little more capital.  Then I'll revisit these remedies after the weather turns to muck again.  Which in the NW will happen relatively soon anyway.  In the meantime, I'll do a compression test and at least confirm that part of the equation - so I know what I'm dealing with.

Again, thanks so much.  I'll let you know how things develop.

[BSB67]

Go to the track, If nothing else, you'll have a lot of fun.

FWIW, At one time I had a similar build to yours.  Second season, the car lost 4 mph (i.e. 45-50 hp).  It was one on my Dynomax Super Turbo mufflers failing internally causing a partial pluggage.  Other than laying down above 3500, everything else was perfect with how it ran.  Took me a month to figure it out.  Of course, with Ultra Flows, that's not likely.

[c00nhunterjoe]

in our big block world every 1 point of compression ratio is good for roughly 20-25 hp.

i am extremly surpised that everyone likes the intake on your engine. i had the "B" motor version of it and absolutly hated it. i could feel an extreme loss in mid-top end power in my car and gained zero low end. i rejetted the carb, adjusted timing, the whole works with no success. i swapped back to my old school torker and 1 inch phenolic spacer and was soooo much happier. the ports in that old dual plane were very small and narrow. i dont know if the "RB" version is that much different but the "B" version of the ch4b is horrible in my opinion.

assuming you find that your compression ratio is 9 or 9.5:1 then my suggestion is swap the stock ex manifolds for 1 7/8 headers, stick some roller rockers on it, tune that slightly small carb to its fullest potential, and get yourself a edlbrock performer rpm intake.  i think you will see a totally different car. it should pull good numbers and have a nice drivability attitude with plenty of power to play with.

[Brass]

Part of the mystery is solved.  I spoke with the prior-prior owner who told me he used the original pistons.  He didn't know how far down in the hole they were but said he would've set them at the standard, stock deck measurement.  Then I read this gem confirming what we already know:

"From 1972 on the horsepower ratings were lower ... muffled to a rated 335 bhp (250 kW) SAE gross at 4400 rpm through a drop in compression, cam timing and other tuning measures. Also in 1972, the U.S. industry switched to SAE net ratings, that is, with alternator, air cleaner, mufflers, and other real-world, power-consuming equipment attached, which resulted in a more realistically rated 225 bhp (168 kW) SAE net at 4400 rpm."

As Cooter mentioned, the compression is probably as low as 8.0:1 or worse.  They have to go.

[greenpigs]

You could swap to a Voodoo 301 cam and try and build cylinder pressure that way.