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Discussion Starter #1
Going to tune carb and put the beast on the dyno tomorrow. We'll finally be able to answer the question - "So, how much power are you making?"

Here are the cars particulars:


2012 Mustang:


- 427cid windsor
- Compression - 10.5:1
- Trickflow Stage 3 hydraulic roller cam with 1.7 rockers
- AFR 205 58cc heads
- QuickFuel Q-850 mech secondary carb
- Edelbrock RPM Air Gap intake
- MSD Ignition (Pro Billet distributor, 6AL2 control module)
- Headers with 1-3/4 primaries
- 3.73 gears
- Tremec Magnum 6-speed manual trans
- 93 octane gas
- Car has A/C and hydraulic power steering connected


The dyno is a Mustang in-ground unit, and we'll be taking it no higher than 6500 RPM.


I'm hoping for *at least* 450 RWHP.


Anyone care to make any predictions about how much the car will actually make?


There will be videos of at least the first and last runs.
 

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Sounds like a nice street/track combo. :tup: For HP, peak power means diddly. Your average HP after you've done logged comparative experiments with the fuel, ignition, valve timing and chassis will show what it's potential is, and where it's strong or weak. I'd say it makes 575hp if you give the dyno operator an extra $100. Or, 375hp if you piss him off. But, those are not the answers you want from him. ;) A chassis dyno is for information and tuning, so use it for that, else it's a waste of time and money. Good luck!
:tup:
David
 

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Discussion Starter #3
Sounds like a nice street/track combo. :tup: For HP, peak power means diddly. Your average HP after you've done logged comparative experiments with the fuel, ignition, valve timing and chassis will show what it's potential is, and where it's strong or weak. I'd say it makes 575hp if you give the dyno operator an extra $100. Or, 375hp if you piss him off. But, those are not the answers you want from him. ;) A chassis dyno is for information and tuning, so use it for that, else it's a waste of time and money. Good luck!
:tup:
David

:) Dyno operator is a friend of mine (and owns the shop where the engine swap happened, and while he has a vested interest in a positive outcome, he won't fudge numbers.

We're using the dyno for the very thing you mentioned - tuning the carb and timing.

Right now, the initial timing is set to 16, and advances to 30. We're going to set the initial to 18-20, and have a total advance of 36 or so. The distributor has the blue springs int it, and I'm thinking we'll have to change to the light silver (or at least one light silver and one blue). We'll probably change the advance bushing as well to get to the desired total advance.

As far as the carb is concerned, the motor is making about 7.5-7.8 inches of vacuum, so i changed the 4.5 power valve to a 3.5 (I have a 4.0 if we need it). The mixture screws are about a half-turn out (not enough IMHO). so we either have to jet it down or increase the air bleed size. Which is the best way to go on that?
 

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As far as the carb is concerned, the motor is making about 7.5-7.8 inches of vacuum, so i changed the 4.5 power valve to a 3.5 (I have a 4.0 if we need it). The mixture screws are about a half-turn out (not enough IMHO). so we either have to jet it down or increase the air bleed size. Which is the best way to go on that?
Assuming this is a street/track car, I'd wait to choose the power valve until you can get stable cruise vacuum readings, then install one that's 1" less. For idle mix, first be sure your primary adn secondary blades are set properly over their transfer slots to see where that gets you. Then go after the bleeds if it's still touchy. Remember, changing your idle timing will change your vacuum, idle blade position and idle mix settings.

David
 

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Discussion Starter #5
Assuming this is a street/track car, I'd wait to choose the power valve until you can get stable cruise vacuum readings, then install one that's 1" less. For idle mix, first be sure your primary adn secondary blades are set properly over their transfer slots to see where that gets you. Then go after the bleeds if it's still touchy. Remember, changing your idle timing will change your vacuum, idle blade position and idle mix settings.

David
So far, we're at 439.3 hp, and 456 lbft. It's falling over at about 5600rpm. First thing we're gonna check tomorrow is the fuel pressure (to make sure we're not sucking the bowls dry).

Current settings:

Primary jets = 70
Secondary jets = 79
Accel pump cam is pink 2-in-2
Power valve = 3.5 (7.5-8 inches of vacuum)
Hi-speed air bleeds = 33
Idle air bleeds are 74 (I think)
Squirters = 33
Timing = 8 initial, 36 total

Any recommendations regarding fall-over would be welcomed.

I'll post the videos tomorrow.
 

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So far, we're at 439.3 hp, and 456 lbft. It's falling over at about 5600rpm. First thing we're gonna check tomorrow is the fuel pressure (to make sure we're not sucking the bowls dry).
427ci breathing through a dual plane intake and 236/248 @ 0.050" cam isn't going to want to rev much higher than that.

What exhaust is on the car?
 

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427ci breathing through a dual plane intake and 236/248 @ 0.050" cam isn't going to want to rev much higher than that.

What exhaust is on the car?
I agree, might be able to nickle a dime a little, try less total timing (AFRs generally don't need much more than 34, sometimes 32), make sure throttle is open, consider a 1 inch carb spacer, but ultimately, the good heads are letting the cam hang in there, but it can only do so much.

One last thing, I highly doubt you need a 3.5 PV, you need the PV to open at roll on when there is a load on the motor, the idle estimate is such baloney I am not sure why Holley ever put it there. It may work for 16-18 in idle cars, but for yours it likely will cause a lean spot. It won't help power at WOT, but I would consider a 5.5 PV to make sure you don't go lean and rattle on the street.
 

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Wonder why the vacuum seems so low? My "race-ier" street/strip 427w runs 10-11lbs at 1000rpm idle (58cc AFR's, 10.7cr, 255/266SR cam, 1.6 rockers, Super Vic intake, 1 3/4" headers, 93 octane.) Would have thought yours would be higher--even at a guesstimated 700-800rpm idle. How much initial timing are you running? Mine's between 20 & 22*.

I agree that the cam (and intake) are pretty much done on your big windsor (a told you so moment.) With the larger cam my car is shifted at 6600, which is near the top of the motor's power band (also close to your dyno'd goal.) As recommended you should try less timing and perhaps experiment with carb spacers. IIRC my timing is at 30* now. The track times (what's important to me) are definitely better than when it was tried at 34*. Consistency improved too.

Don't be afraid to put a Victor Jr. intake on there if you opt for a better cam. Mine had absolutely perfect street manners with the Vic Jr and a 950hp carb and ran great at the track too. The Super Vic is a little overkill on my current motor, but my goals are loftier in the long run and it will be needed for future growth.

Finally, I suggest that you don't overly rely on wheel dyno results. Use it as a guideline and don't be afraid to vary away from it in actual usage. A timed track is a better environment to get real world results from your changes.
 

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Discussion Starter #9
Wonder why the vacuum seems so low? My "race-ier" street/strip 427w runs 10-11lbs at 1000rpm idle (58cc AFR's, 10.7cr, 255/266SR cam, 1.6 rockers, Super Vic intake, 1 3/4" headers, 93 octane.) Would have thought yours would be higher--even at a guesstimated 700-800rpm idle. How much initial timing are you running? Mine's between 20 & 22*.

I agree that the cam (and intake) are pretty much done on your big windsor (a told you so moment.) With the larger cam my car is shifted at 6600, which is near the top of the motor's power band (also close to your dyno'd goal.) As recommended you should try less timing and perhaps experiment with carb spacers. IIRC my timing is at 30* now. The track times (what's important to me) are definitely better than when it was tried at 34*. Consistency improved too.

Don't be afraid to put a Victor Jr. intake on there if you opt for a better cam. Mine had absolutely perfect street manners with the Vic Jr and a 950hp carb and ran great at the track too. The Super Vic is a little overkill on my current motor, but my goals are loftier in the long run and it will be needed for future growth.

Finally, I suggest that you don't overly rely on wheel dyno results. Use it as a guideline and don't be afraid to vary away from it in actual usage. A timed track is a better environment to get real world results from your changes.
Idle is about 850. Don't forget, the rockers are 1.7's so that added some lift (and duration?).

What are the plugs supposed to be gapped to for a motor like this? I'm currently at 45.

If I change intakes, I'm thinkin' I'm gonna go dual quads. It's kinda more about the eye candy and sound than anything else. The guy that helped me with the motor swap thinks I should put a 6/71 on it, but he's crazier than I am. :)
 

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Idle is about 850. Don't forget, the rockers are 1.7's so that added some lift (and duration?).

What are the plugs supposed to be gapped to for a motor like this? I'm currently at 45.

If I change intakes, I'm thinkin' I'm gonna go dual quads. It's kinda more about the eye candy and sound than anything else. The guy that helped me with the motor swap thinks I should put a 6/71 on it, but he's crazier than I am. :)
The 1.7's won't change the personality of the cam, and any gains in lift and effective duration are minimal in the grand scheme of things.

My advice, is to just get the carburetor right and DRIVE IT. It will be a TIRE SMOKING BEAST on the street as is... and if you don't plan on making it a track car... just go out and enjoy it!

Good Luck!
 

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Idle is about 850. Don't forget, the rockers are 1.7's so that added some lift (and duration?).

What are the plugs supposed to be gapped to for a motor like this? I'm currently at 45.
Eh, my lift is 690 int, 672 ex. As Mike said, the lift and duration change via rockers is negligible (and overhyped on the net.)

Although I think that your cranking compression is fine, have you measured it on all cyllinders?

My advice, is to just get the carburetor right and DRIVE IT. It will be a TIRE SMOKING BEAST on the street as is... and if you don't plan on making it a track car... just go out and enjoy it!

Good Luck!
100% agree with Mike. If its driving the way that you want, don't worry about the actual dyno #'s. Its a good street performer, irregardless.
 

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Well, there are your span of opinions. :tup: I think the point was missed that the chassis dyno is not for numbers. The point is to find the AFRs and timing that the engine likes best, and then go tune and tweak on the street or track for final dial-in. The greatest value of the dyno is to see real-life results when you make a change, and whether it's better or worse, then make a different change and zero-in on what your particular engine wants. This is all for fixed-throttle testing, whether WOT or 25% throttle.

An example is your ignition timing. If your ignition is wrong, the power can flatten or nose-over early. You should be running a series of sweeps (dyno pulls) in steps at different timing from too little to too much, to find what the engine likes, and at what rpm. Once best timing at WOT is found, then the sweeps are repeated at a lower throttle setting. Rinse and repeat. Once completed, the sweeps (dyno sheets) showing best timing at a particular throttle setting are all compared and the best timing curve will become very obvious. Set your distributor to follow that tested curve and move on to re-sweep fuel.

I would not worry nor touch anything that has to do with transitions (accel adjustments, pump shots, squirters, etc.) until you have the basic ignition timing curve and main jetting down solid. Everything else is based on those, so use the dyno to get those near perfect, and then go out and do your accel and transition tuning. From what you're saying, it seems you are playing with too many things on the dyno, and don't have a deliberate tuning plan or program to find your critical basic settings (base tune). Am I right?

David

PS: If your dyno is a steady-state load cell, where it will hold a specified vehicle 'speed', then instead of fixed throttle sweeps, you would use fixed speed and variable throttle sweeps. Which type of dyno are you on - inertial or steady-state?
 

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Guys, just remember a car on a dyno does not move.
In the real world you will have to jet at least 1 size richer on the primary & 1 size leaner on the secondary.
Liquid fuel will flow toward the rear of the intake thus keep in mind the above.
Thats the advantage of fuel injection where the intake is just moving air & not a wet flow condition on a carburated application.
Only full throttle runs will reveal the proper jetting.
 

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Guys, just remember a car on a dyno does not move. ...
+1. This is why final tuning is done on the track. However (and this plays directly into all the testing done on the dyno), the best values you find while testing are still the target when you hit the track. When you road the car, stuff will change as Billy says, and that's when you use the dyno results to know how and where to correct for the changes.

For example, the jetting does change and differently in every car, but you know where you need to correct it. You are still after the best AFR found, and now you have to make changes for fuel distribution, with stuff like staggered jetting, fuel tabs, throat mods, etc. Or, the jetting may go lean only at launch, and changes in your pump shot may be better than the overall jetting, that may quickly recover after launch. ;) Except for changes in weather or track/suspension condition, your tune should be stabilized at that point. Likewise, those new condition changes would mean only a slight adjustment of your now stable tuning, only compensating for the effects.

This is one reason racers keep all the dyno sheets, so they know from testing what change in tuning will cause what effect, such as how much the AFR will recover on a hot or cold day with one step jet change. Just one more reason EFI has become so popular, as it reads all that, and (if set up properly) will correct it for you automatically. Those pesky sensors are what give the system (and you) the information to know what to do to maintain and even improve peak performance.

David

[EDIT] - oops, I forgot this comment:
Only full throttle runs will reveal the proper jetting.
And to be clear - that's entirely true for a drag-only car. If it's an auto-x or other variable-throttle racer or street car, then for best performance in all throttle and load ranges (including WOT), then full throttle runs will reveal the best power AFR. Then the trick is to set best jetting for midrange, and combine it with tuning the power valve and PVCRs, to finally achieve best AFR and power at WOT. Tuning drag cars is easy. Tuning variable-throttle cars is a whole different planet. Note my comments above about part-throttle sweeps, and inertial or steady-state dyno types.
 

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Also, are your valves springs up to snuff?

Back over 10 years ago, I put together a 347, afr 205 heads, vic jr, mech roller ...revved to 7200 no problem. That combo ran 10.60s at 2900 lbs.
 
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