Magnum 300 crate engine - how should it go when tuned up right?

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MRGTX

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I'm a novice when it comes to tuning so I could use some perspective and advice here.

So far, I have ~750 miles on the Magnum 300 that I bought used from a good guy here on the forums. The motor is tight, doesn't burn oil, good oil pressure, no leaks...idles great too.

Performance isn't impressive at all.

So far, I haven't messed with it too much but subjectively, it doesn't feel that much better than the stock 318 2bbl when it was running at its best, especially in the low rev range. The Demon 650 carb is probably due for a rebuild (this winter), there's probably some timing advance left on the table, carb could probably be leaned out a bit...so I know it's not optimized. Yes, I realize that this is a mild motor with relatively low compression and a very tame cam but on paper, I thought my setup would be a bit more lively.

Stock cam/heads
Demon 650cfm
Mopar Performance M2/dual plane
Doug's long tube headers through 2.5" (no crossover)
4.10 axle ratio/27" tall tires
2600 rpm stall
Mildly built A904
5900 RPM governor weight, TF2 shift kit

What would you change first?

I'm still running a steel fan (electrics are sitting in a box), mufflers are probably restrictive (cheap-o Summit type)...could those be pulling off that much power?

In CT, we have access to 93 octane...how much timing can folks get away with? ?

Any thoughts are welcome.
 
What is a "Magnum 300?" N' yeh.....it is a serious question.
 
What is a "Magnum 300?" N' yeh.....it is a serious question.

Back in the 90s or so, Mopar Performance offered two versions of the Magnum 5.9L as crate engines. The Magnum 300 is the 300hp/400lbft version which is basically the ram engine with a carb/dual plane intake and some LA style components. The Magnum 380 had a hotter cam, single plane manifold and possibly different valve springs.
 
Well I suspected. And it's slower than a 318 2bbl? That has to take some WORK

Mufflers.......not a chance, unless they were for a Pinto. You obviously have duals, and there might be "a little more" there but nothing like you are looking for

Distributor........You know the ignition curve? That is where you START. I've seen "everything" in my 70 years including RUSTED ADVANCE mechanisms which were just plain LOCKED

WHERE is the timing initially and HOW FAR does it advance? I DO NOT EVER play with an unknown engine WITHOUT using a positive piston stop to verify TDC and then grabbing the timing light.

Carb........You say you "need a rebuild." Does it leak? Won't idle? Why? "Needs to be leaner?" Why? At what RPM? Idle/ mid/ power? You have to figure out how to nail this down.

FRANKLY IN THIS DAY AND AGE I don't know how anyone can justify buying an expensive engine and NOT springing for a wideband O2 setup. They just make things SO much easier

..........And then there's the "stupid simple" stuff.........have you checked that the carb is actually fully opening with the throttle?
 
Well I suspected. And it's slower than a 318 2bbl? That has to take some WORK

Mufflers.......not a chance, unless they were for a Pinto. You obviously have duals, and there might be "a little more" there but nothing like you are looking for

Distributor........You know the ignition curve? That is where you START. I've seen "everything" in my 70 years including RUSTED ADVANCE mechanisms which were just plain LOCKED

WHERE is the timing initially and HOW FAR does it advance? I DO NOT EVER play with an unknown engine WITHOUT using a positive piston stop to verify TDC and then grabbing the timing light.

Carb........You say you "need a rebuild." Does it leak? Won't idle? Why? "Needs to be leaner?" Why? At what RPM? Idle/ mid/ power? You have to figure out how to nail this down.

FRANKLY IN THIS DAY AND AGE I don't know how anyone can justify buying an expensive engine and NOT springing for a wideband O2 setup. They just make things SO much easier

..........And then there's the "stupid simple" stuff.........have you checked that the carb is actually fully opening with the throttle?

Good points all around.

Carb doesn't leak but the advice that I keep hearing is that ethanol content in our gasoline eats gaskets, etc. Just a hunch that a flake of gasket could wander its way into a jet or something.

Good call about making sure the throttle fully opened...and it does.

I suspect that it could be leaner just based on the smell of the exhaust which seems to be laden with some unburnt gasoline. It also bogs a bit when I tip into the throttle which could be explained by it running too rich. Is that scientific? Not at all. That's why I'm here asking :D The plugs aren't obviously blackened but then again, I probably don't have enough miles to rely on that age-old method for fuel mixture clues.

The mufflers were low on my list until I saw the Engine Masters episode on YouTube (which seems to have been pulled). IIRC, there was a pretty sizable difference from stock type mufflers to some of the better performance pieces.

Yeah, my tuning experience has been with wideband O2/OBD2 access. It's a whole different thing to tweak fuel maps on your lap top. What setup do you recommend for these cars?

Thanks for all of the advice!!
 
So, those magnum engines are no longer available?

They have not been available from FCA for a few years now. They are trying to switch over to Gen3 Hemi only. Plenty of Magum engines available in wrecking yards though, and lots of good ways to build off of one.
MRGTX has a decent head start with his 300 horsepower version. Make sure it's mechanically sound, then do some bolt-ons.
 
- Fill up with 93 for tuning

- Verify TDC matches balancer markings

- Inspect distributor mechanical flyweight and vacuum advance operation

- Obtain 34-36 degrees of total advance with the vacuum advance disconnected and plugged. Reconnect to the correct manifold vacuum port after setting total time.

- Set idle speed and mixture simultaneously to obtain maximum idle manifold vacuum

- Ensure carb power valve is the proper size for your engines vacuum numbers

- Adjust the carb accelerator pump circuit to remove any lean stumble or bog down. I like make it the leanest setting possible and then enrichen it til the lean stumble is gone.

- Set main and secondary jetting by inspecting plugs, by MPH and ET, or by wideband o2.

Wideband o2 helps out with a lot of these adjustments and is relatively cheap these days. Will save you time and money in the long run.
 
My small block likes 32-34 total. Now my heads are open chambers and my guess is yours are closed, but 32-34 is a good starting point. Not sure of the history of the motor, but my brand new BG might demon 825 needed to taken apart and clean all the aluminum shavings out of it before it ran well. It was very good after, just QC from BG was horrible. I would search for the manual for the carb and follow the tuning instructions. Atleast to get it to baseline.
 
What elevation are you at?
From the catalog:
The cam P5249663, is a 250/264/110/ .385/.401 lift roller cam,very similar intake duration to the stock 360 cam.
The heads are supposed to be P5007086 swirlport Magnums at 60cc/190cfm, 1.92-1.62valves
The block is P5007549 and with those heads is spec'd to come in at 9.1 Scr
The power curve is almost dead flat from 4000 to 5000, and beyond. The torque curve is a big fat bump from 3500 to 4000; 5900 is as good a shift-point as any.
It is spec'd at 300/375;
In an A-body with a 2600TC and 4.10s, it should run like the proverbial scalded cat

At a 2600 stall, that engine is probably putting out around 285 ftlbs. With your 4.10s and 27s that would be;
285# x 2.45x4.10x12/13.5=2550 road footpounds corrected to a 12" radius. 2000# is more than enough to spin 295s,both of them. You will need a double pumper tho to control it cuz with a VS the secondaries will not stay open if you back off the throttle; and that just kills drifting.That engine wants a 750,(Will run very well still,with a 650 mechanical secondary)and a spreadbore would be ideal. With only 37* of cam overlap,that spreadbore could make pretty good fuel mileage, despite the 4.10s.
BTW that is not a low compression engine. I mean the 9.1Scr number might be, but the Dcr is right up there with cylinder pressure almost maxed out, for the best gas. Do a compression test; I bet it will be close to/over 160psi, at sealevel. If it isn't, that might be part of your problem. What elevation are you at?
With closed chamber heads and tightQ, you should be able to run close to 36* with 93. However, on the street your butt-dyno will not be able to tell 2 or 3 degrees from optimum, but your engine will complain about just one degree too much. Point is, sneak up on it. Fatten up the timing from stall to 3000 instead.
Edit, Ok so no tight-Q on this one, My math puts the pistons about .060 down. So 32 to 34 will be pushing it, as mentioned by others.

_________________________________________
My engine was once dressed similar to yours but with just 3.55s and a 4-speed. It was hands down my favorite combo.
Whenever I suspect low-power, the first thing I do is check the pressure. You can spend all week tuning, but if the pressure is down, you get to fix that and start all over.
_________________________________________
if you want more power; spec wise,that engine is ready for a little more cam. But then it might want more TC too,lol.
And a higher shift rpm, and so a teardown to perform the oiling mods necessary to survive multiple blasts past 6000.
Of course since it's all tore down, now would be the time to zero-deck it.
Of course since now she has potential, the next logical thing to do would be to put aluminum heads on it and drive the cylinder pressure up past 185psi, and;
finally you have the engine of your dreams, able to spin street tires to 80/90mph, whoopee! Welcome to HotRodding.
What elevation are you at? Did I ask that already,lol? I think you might be at 500ft or less, so I guess global warming doesn't excite you much,lol.
At 9.1Scr, the Wallace calculator puts you at 160psi/150VP@500ft, This should be very strong below 3000
 
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The 300hp Magnum crate has the factory 5.9L production camshaft in it. So there's just not much power on the table. But - it should be a lot peppier than what you're saying. At least spin the tires hard in first. IMO the 5900rpm shift is way too high for it. It would be quicker shifting at 4500. The engine's out of air by then with that cam. In terms of tuning - the Demon carbs are not my favorite. They are very finicky when set up properly. Especially in a state like ours with nights where its 75 with 90% humidity and then mid 50s with no humidity the next... Plus the 650 wet flowed Demon is probably too much for that package. That's close to a 750cfm dry flowed carb, and again, that's too much for a mild 360 with no cam.
Magnums don't like timing. So you need to set the timing curve, then set the carb. If it was me I'd look at initial around 15*, with the centrifugal of 17*, all in by 2500. I'd run a vacuum advance too, off ported vacuum. Rebuild the carb and pay attention to the power valve ratings and cleaning the parts. Demons are famous for having poor cleaning and I've found "hanging chads" of aluminum left in the metering blocks in different sized carbs years apart.
If you are used to an 02 then either install one or find someone that doesn't need it.
 
Thanks to all for the input.

Before I start messing with stuff, I wanted to collect a baseline for performance. I hooked up the G-Tech meter and did half a dozen 0-60 runs. This model uses accelerometer and GPS so it’s pretty decent, I guess.

Weather is low 80s today, low humidity. Elevation is 1000 feet above sea level or so.

I’m about 200lbs, my (very supportive) wife is 130ish lbs who was in the in the passenger seat plus a full tank of fuel.

Holding it to the floor, it shifted at 5,000 on its own. I know that governor weights are an estimate but that’s pretty far off too...maybe that’s ok in this case.

So 0-60 was pretty consistently mid 6 second range. Not pathetic but far from good.

Based on my estimated 3600lbs, the G-tech calculated that as 225ish hp for whatever that’s worth.

So it’s a full two seconds slower than my basically stock 6spd Coyote Mustang as measured with the same gizmo on the same roads.
 
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The 300hp Magnum crate has the factory 5.9L production camshaft in it. So there's just not much power on the table. But - it should be a lot peppier than what you're saying. At least spin the tires hard in first. IMO the 5900rpm shift is way too high for it. It would be quicker shifting at 4500. The engine's out of air by then with that cam. In terms of tuning - the Demon carbs are not my favorite. They are very finicky when set up properly. Especially in a state like ours with nights where its 75 with 90% humidity and then mid 50s with no humidity the next... Plus the 650 wet flowed Demon is probably too much for that package. That's close to a 750cfm dry flowed carb, and again, that's too much for a mild 360 with no cam.
Magnums don't like timing. So you need to set the timing curve, then set the carb. If it was me I'd look at initial around 15*, with the centrifugal of 17*, all in by 2500. I'd run a vacuum advance too, off ported vacuum. Rebuild the carb and pay attention to the power valve ratings and cleaning the parts. Demons are famous for having poor cleaning and I've found "hanging chads" of aluminum left in the metering blocks in different sized carbs years apart.
If you are used to an 02 then either install one or find someone that doesn't need it.

Good info all around and in particular, about the Demon. I’m already looking around the house at what I can sell to fund a FiTech. :)

You’re right on about the way our weather fluctuates...all the more reason to get the wideband O2 tuning up and running.

In the meantime, off to pick up the timing light and get started.
 
4.10s are not the best gear to test zero to 60, with a 904.
5000 is 38 mph/298hp in first. The Rs then drop to 2960/180hp;which you then have to power thru to 60@4650/300hp. There is your crappy performance.
The published power curve for that engine shows about 180 hp at 3000, and 285@4000, and hitting 300 @4625.
So from 3000 to 4000 the average is; 180 plus 285 divide by 2= 232hp.
4625 is 35 in first, and 5000 is 38..... So you are on the pipe for exactly 3 mph in first gear. Hang on that's an exaggeration. Remember I said the power is shown to be nearly flat from 4000 to 5000.
In second you hit 4650@ 60, so you were on the pipe for a micro second,lol.
So your Gtech at 225 is pretty dang close. Or maybe I should say my interpretation of your situation is pretty close.

I see three problems;
1) is the short shift
2) is the shift splits
3) is the 4.10s
The published power curve is only down a couple of hp at 5000. There is no way for me to accurately extrapolate that curve, but I can guess. I know that the 1-2 split in the 904 is .59, so I, ME, would be carrying first to some higher rpm where the power has fallen to about the same level as what I'll be entering second at. This will give me about the highest average power possible for the run. So, in your case, I'm gonna call that outshifting at 5400@210hp and entering second at .59x5400~3200@210hp. So that fixes #1
And since we are stuck with the 904,there's nothing we can do about #2.
And that leaves rear gearing. According to the graph your engine wants to trap 60mph at about 5200. That will take a 7.32 road ratio, which would be
2.99s in first, or 5.05s in second. (or 3.81s with a 4speed in second,lol)
And that takes us back to "4.10s are not the best gear to test zero to 60 with a 904".
Ok but
What ratio were you using in the Ford,ptoui,lol.
Your power to weight ratio is 3600/300=12 pounds per hp. What is the Mustangs?
And how much time did you give up on the start line due to tirespin, compared to the other. With 4.10s and 245/60-15s,and street suspension, you shouldda still been spinning at 60,with the Mopar,lol. 275/50-15s should spin all thru first at least
And like you said 6.5 is not terrible, especially if you are spinning most of the way,lol. And if you're not, it's time for a compression test.

So in review; what gear should you be using? Answer; the 4.10s are already in there, and neither the 5.05s nor the 2.99s are ever gonna be on the table, are they? So 4.10s it is, just work on the tirespin. You can easily lose .5 to say .8 second on the line, and another .3 to .5 during the run. That cost is .8 to 1.3 from zero to 60. If you can optimize that, you stand a chance of pulling a mid 5 second run, or less.
If you want to change something, my vote would be the TC. The chart does not go to 2600 but extrapolating it, I get about 100hp; which translates to 200ftlbs and that is about 2160 to the road with your TM, more than enough to break your street tires loose. After that you need to sustain to 4000 where the power is, slogging your way up thru 3000,3200,3400,3600 and finally 4000@285hp. Now yur getting on the pipe. But if she's spinning all the way, well a bigger TC will just spin worster.
Anyway I hear Rumble snoozing, so I better quit rambling
 
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Oh my Lord! A mile long of dribble. AJ get to the freaking point already!
What elevation are you at?
From the catalog:
The cam P5249663, is a 250/264/110/ .385/.401 lift roller cam,very similar intake duration to the stock 360 cam.
The heads are supposed to be P5007086 swirlport Magnums at 60cc/190cfm, 1.92-1.62valves
The block is P5007549 and with those heads is spec'd to come in at 9.1 Scr
The power curve is almost dead flat from 4000 to 5000, and beyond. The torque curve is a big fat bump from 3500 to 4000; 5900 is as good a shift-point as any.
It is spec'd at 300/375;
In an A-body with a 2600TC and 4.10s, it should run like the proverbial scalded cat

At a 2600 stall, that engine is probably putting out around 285 ftlbs. With your 4.10s and 27s that would be;
285# x 2.45x4.10x12/13.5=2550 road footpounds corrected to a 12" radius. 2000# is more than enough to spin 295s,both of them. You will need a double pumper tho to control it cuz with a VS the secondaries will not stay open if you back off the throttle; and that just kills drifting.That engine wants a 750,(Will run very well still,with a 650 mechanical secondary)and a spreadbore would be ideal. With only 37* of cam overlap,that spreadbore could make pretty good fuel mileage, despite the 4.10s.
BTW that is not a low compression engine. I mean the 9.1Scr number might be, but the Dcr is right up there with cylinder pressure almost maxed out, for the best gas. Do a compression test; I bet it will be close to/over 160psi, at sealevel. If it isn't, that might be part of your problem. What elevation are you at?
With closed chamber heads and tightQ, you should be able to run close to 36* with 93. However, on the street your butt-dyno will not be able to tell 2 or 3 degrees from optimum, but your engine will complain about just one degree too much. Point is, sneak up on it. Fatten up the timing from stall to 3000 instead.
Edit, Ok so no tight-Q on this one, My math puts the pistons about .060 down. So 32 to 34 will be pushing it, as mentioned by others.

_________________________________________
My engine was once dressed similar to yours but with just 3.55s and a 4-speed. It was hands down my favorite combo.
Whenever I suspect low-power, the first thing I do is check the pressure. You can spend all week tuning, but if the pressure is down, you get to fix that and start all over.
_________________________________________
if you want more power; spec wise,that engine is ready for a little more cam. But then it might want more TC too,lol.
And a higher shift rpm, and so a teardown to perform the oiling mods necessary to survive multiple blasts past 6000.
Of course since it's all tore down, now would be the time to zero-deck it.
Of course since now she has potential, the next logical thing to do would be to put aluminum heads on it and drive the cylinder pressure up past 185psi, and;
finally you have the engine of your dreams, able to spin street tires to 80/90mph, whoopee! Welcome to HotRodding.
What elevation are you at? Did I ask that already,lol? I think you might be at 500ft or less, so I guess global warming doesn't excite you much,lol.
At 9.1Scr, the Wallace calculator puts you at 160psi/150VP@500ft, This should be very strong below 3000
 
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4.10s are not the best gear to test zero to 60, with a 904.
5000 is 38 mph/298hp in first. The Rs then drop to 2960/180hp;which you then have to power thru to 60@4650/300hp. There is your crappy performance.
The published power curve for that engine shows about 180 hp at 3000, and 285@4000, and hitting 300 @4625.
So from 3000 to 4000 the average is; 180 plus 285 divide by 2= 232hp.
4625 is 35 in first, and 5000 is 38..... So you are on the pipe for exactly 3 mph in first gear. Hang on that's an exaggeration. Remember I said the power is shown to be nearly flat from 4000 to 5000.
In second you hit 4650@ 60, so you were on the pipe for a micro second,lol.
So your Gtech at 225 is pretty dang close. Or maybe I should say my interpretation of your situation is pretty close.

I see three problems;
1) is the short shift
2) is the shift splits
3) is the 4.10s
The published power curve is only down a couple of hp at 5000. There is no way for me to accurately extrapolate that curve, but I can guess. I know that the 1-2 split in the 904 is .59, so I, ME, would be carrying first to some higher rpm where the power has fallen to about the same level as what I'll be entering second at. This will give me about the highest average power possible for the run. So, in your case, I'm gonna call that outshifting at 5400@210hp and entering second at .59x5400~3200@210hp. So that fixes #1
And since we are stuck with the 904,there's nothing we can do about #2.
And that leaves rear gearing. According to the graph your engine wants to trap 60mph at about 5200. That will take a 7.32 road ratio, which would be
2.99s in first, or 5.05s in second. (or 3.81s with a 4speed in second,lol)
And that takes us back to "4.10s are not the best gear to test zero to 60 with a 904".
Ok but
What ratio were you using in the Ford,ptoui,lol.
Your power to weight ratio is 3600/300=12 pounds per hp. What is the Mustangs?
And how much time did you give up on the start line due to tirespin, compared to the other. With 4.10s and 245/60-15s,and street suspension, you shouldda still been spinning at 60,with the Mopar,lol. 275/50-15s should spin all thru first at least
And like you said 6.5 is not terrible, especially if you are spinning most of the way,lol. And if you're not, it's time for a compression test.

So in review; what gear should you be using? Answer; the 4.10s are already in there, and neither the 5.05s nor the 2.99s are ever gonna be on the table, are they? So 4.10s it is, just work on the tirespin. You can easily lose .5 to say .8 second on the line, and another .3 to .5 during the run. That cost is .8 to 1.3 from zero to 60. If you can optimize that, you stand a chance of pulling a mid 5 second run, or less.
If you want to change something, my vote would be the TC. The chart does not go to 2600 but extrapolating it, I get about 100hp; which translates to 200ftlbs and that is about 2160 to the road with your TM, more than enough to break your street tires loose. After that you need to sustain to 4000 where the power is, slogging your way up thru 3000,3200,3400,3600 and finally 4000@285hp. Now yur getting on the pipe. But if she's spinning all the way, well a bigger TC will just spin worster.
Anyway I hear Rumble snoozing, so I better quit rambling

Well done, man.
I need to chew on the info a bit but your points about the ratios are spot on. That definitely makes sense and it’s making me wish I had the budget/time for the T56 swap already.

So this may be obvious to everyone but me but aside from the governor weight, what Needs to be done to hold off that shift for 400 more rpm? Aside from the Dart, I drive nothing but manuals...I always thought the biggest benefit for the slush pump was that you set it and forget it. :D

Well, traction isn’t that big of an impediment so far. Launching around 2500, it burns the tires for ~15 feet and hooks...I tried rolling into the throttle less abruptly to spin less and the times were significantly slower. So...compression test may be necessary? The motor doesn’t smoke so I’m hoping that the tuning may be more relevant.

Yeah the Mustang is a 3600lb landwhale but it has a motor that pulls from 2k straight through 7300, 285 wide W-rated tires and six gears. It’s not a fair fight. I opted for the 3.55s over the 3.73s because it would trap in 3rd rather than 4th. Someday, it’ll make it to the drag strip. Lol Trust me, if Dodge offered a sub 4000lb muscle car that was smaller than a Country Squire I would have bought it.
 
Well done, man.
I need to chew on the info a bit but your points about the ratios are spot on. That definitely makes sense and it’s making me wish I had the budget/time for the T56 swap already.

So this may be obvious to everyone but me but aside from the governor weight, what Needs to be done to hold off that shift for 400 more rpm? Aside from the Dart, I drive nothing but manuals...I always thought the biggest benefit for the slush pump was that you set it and forget it. :D

Well, traction isn’t that big of an impediment so far. Launching around 2500, it burns the tires for ~15 feet and hooks...I tried rolling into the throttle less abruptly to spin less and the times were significantly slower. So...compression test may be necessary? The motor doesn’t smoke so I’m hoping that the tuning may be more relevant.

Yeah the Mustang is a 3600lb landwhale but it has a motor that pulls from 2k straight through 7300, 285 wide W-rated tires and six gears. It’s not a fair fight. I opted for the 3.55s over the 3.73s because it would trap in 3rd rather than 4th. Someday, it’ll make it to the drag strip. Lol Trust me, if Dodge offered a sub 4000lb muscle car that was smaller than a Country Squire I would have bought it.
There's a reason ,why you paid that price tag ,on that Mustang..GTX..
Just keep that in mind, and old school works .....and be patient....
 
Comments in the Quote, in blue, click to expand
Well done, man.
I need to chew on the info a bit but your points about the ratios are spot on. That definitely makes sense and it’s making me wish I had the budget/time for the T56 swap already.

So this may be obvious to everyone but me but aside from the governor weight, what Needs to be done to hold off that shift for 400 more rpm? have you tried manually shifting it..... Aside from the Dart, I drive nothing but manuals...I always thought the biggest benefit for the slush pump was that you set it and forget it. :D When the 4.10s went in, the old governor shoulda been swapped out.
You can try adjusting the KD mech. But if it is already maxed out, you will need a different lighter flyweight. You can lathe some off the one you have or just order up one from a supplier, A&A I think has them.
Alternatively, you might get away with cranking up the line pressure a tad.
But 4.10s do normally require a different governor package. Arbitrarily messing with the line-pressure, with a maxed out KD mech, can introduce other driveability issues.

Well, traction isn’t that big of an impediment so far. Launching around 2500, it burns the tires for ~15 feet and hooks...I tried rolling into the throttle less abruptly to spin less and the times were significantly slower. So...compression test may be necessary? The motor doesn’t smoke so I’m hoping that the tuning may be more relevant.
If you can't sustain the spin, I would suspect the secondaries are not opening, or that 2600 is about to receive the heave-ho. But I would still do a compression test.
The loss of secondaries might be good for 10 hp at 2600
The TC could be 130 or more for a 3500 versus your 2600
The powerloss from poor compression is tricky to estimate, but could be more than 10, and waaaay less than 130,lol.
It should be obvious that the TC would be the biggest performance contributor........ on the start line.


Yeah the Mustang is a 3600lb landwhale but it has a motor that pulls from 2k straight through 7300, 285 wide W-rated tires and six gears. It’s not a fair fight. I opted for the 3.55s over the 3.73s because it would trap in 3rd rather than 4th. Just curious, do you know the ratios in that box?
Someday, it’ll make it to the drag strip. Lol Trust me, if Dodge offered a sub 4000lb muscle car that was smaller than a Country Squire I would have bought it.
 
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If the carb has vacuum secondaries, make sure they are opening.

Many moons ago, a friend of mine complained about his 66 389 Goat not accelerating hard enough. The choke was designed to not allow the secondaries to open if the choke was not fully opened. (Cold engine.) The adjustment was off. End result: 2 BBL carb.
I had a 72 340 Demon. The Thermoquad had the same fail-safe system: the choke linkage would would prevent the secondaries from opening if not set correctly.
Another friend had a 69 Road Runner with a 440 6 Pack. It ran very poorly at the track. He inadvertently had the end carbs (vacuum operated of course), connected wrong. End result was it was a 2 BBL.

By the way, you can't tell if they are working by winging the throttle while looking at the carb. There's not enough load on the engine.

Edit: Don't know what specs the "stock" cam has, but if similar to a stock 340, it'll stop pulling about 5k or so if the secondaries aren't opening. About 6k if they are.
 
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Screenshot_20171212-101519.png

Thats a dyno comparison 300 hp create vs comp cam eddy airgap and heads. If i remember right a comp 275 hydraulic roller cam.

There no way that engine can be as dead as you say especially with 4.10, something got to be wrong. I got a 380hp create engine and its pretty soft under 2000 rpm and i only have 2.94 gears for now. And it still goes pretty good.
 
Thanks to all for the input.

Before I start messing with stuff, I wanted to collect a baseline for performance. I hooked up the G-Tech meter and did half a dozen 0-60 runs. This model uses accelerometer and GPS so it’s pretty decent, I guess.

Weather is low 80s today, low humidity. Elevation is 1000 feet above sea level or so.

I’m about 200lbs, my (very supportive) wife is 130ish lbs who was in the in the passenger seat plus a full tank of fuel.

Holding it to the floor, it shifted at 5,000 on its own. I know that governor weights are an estimate but that’s pretty far off too...maybe that’s ok in this case.

So 0-60 was pretty consistently mid 6 second range. Not pathetic but far from good.

Based on my estimated 3600lbs, the G-tech calculated that as 225ish hp for whatever that’s worth.

So it’s a full two seconds slower than my basically stock 6spd Coyote Mustang as measured with the same gizmo on the same roads.

Read through the entire thread. Good move with the G-tech-I had one of those and wish I never sold it. Ran it at the strip many times and it was within a tenth of the clocks every time.

Your engine's performance is just about spot on I'd say. The only thing that messes me up is you say it's no stronger than the 318 it replaced?! Your 360 should fry the tires effortlessly and as Moper has said that engine would be out of breath by 4500-5000 rpm. IIRC the G-tech calculates HP based on weight and G's so that 225ish HP would be rear tire shove and that is just about 300-320 @ the flywheel. Your engine is fine and making the power its supposed to. I'd want to know why it isn't snappier off the line though.

Whenever I take on a tuning/setup case like yours I follow a procedure:

1. Remove all plugs note heat range I'd want a Champion RC9YC and perform compression test-write it down. If you find a cylinder way off stop here. Any tuning will be a waste of time and effort.

2. Jack up car and weld in O2 bung. Install O2 meter. I have an innovate LM1 that taught me I didn't know anything about a carb first time I used it.

3. Get a good dial back timing light. 95% of all "carb" problems are timing and timing curve problems. Verify firing order. Disconnect vac advance and observe initial timing. Rev engine and observe total timing and at what RPM its all in at. I would want to see 14-18 at idle and 32-33 all in by 3500 on something like that.

4. If step 3 doesn't reveal an issue then start carb tuning. I'd start by complete disassembly and pin all holes and write it down. Demons are notoriously lean and have a very unconventional emulsification package. I'm not getting into that novel here.

I don't think your engine is far off--I think you and all of us are spoiled by just how good modern vehicles are. Good luck and let us know how it goes. J.Rob
 
Also last but not least:

If engine checks fine but you search for more HP -Do NOT and I repeat DO NOT re-create the Magnum 380. The move to that big lazy single plane and that big stupid lazy cam on a truck long block WILL result in less performance. Believe it or not the performance starts in correcting all the shitty machining in the short block--then the Magnum heads can be improved easily or move to EQ's and then a bump in cam and you will pickup about 100 hp. Your carb is not too small, you don't need a different intake etc... J.Rob
 
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