dyno #s seem low ?

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brsmustng99

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Took my 71 340 duster to get dyno tuned, end result 271 HP & 277 tq on a dyno jet. This seems pretty low to me, I was looking for a little over 300. Mods are ld340 intake, voodoo cam, 650 quick fuel carb, headers, 2.5" exhaust, fbo ignition, stock J heads. Do these numbers seem right?? Motor was just rebuilt to factory specs 2k miles ago.
 
That's pretty good from the wheels for a mild small block.
 
They figure 15-20% difference between rear wheel hp and engine so that puts you around 200. You said stock rebuild which was 275 if I remember right.
 
The intake is not much better than a stock 71 intake, the carb also is about a draw with properly set up thermoquad maybe the quad is slightly better in the HP department. Can't comment on cam don't know the grind but that should be a good improvement. Headers should be good for 20hp + or -, FBO ign meh... J heads a wash may even flow worse if they have has a few valve jobs and the intake valve has sunk. I would guess your hp is about 325, remember the 71 340 real world HP is closer to 310 than the advertised 275hp
 
I feel your pain, but it's basically stock with a few mods, thats still a nice engine and should be fun. I'm hoping to break 300 on mine when I get it tuned but as long as it runs great and breaks the tires without to much issue Ill be happy, my first build so just the run great part will be a plus.
 
Guy dyno tuning said I need a set of aluminum with a smaller cc chamber to get compression around 11 to 1. You guys have any suggestions on heads ?
 
Was this a chassis dyno or an engine dyno?
 
brsmustng99 said:
Guy dyno tuning said I need a set of aluminum with a smaller cc chamber to get compression around 11 to 1. You guys have any suggestions on heads ?
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Before going too far with that thought...... while the heads idea is 'heading' in the right direction, you need to say what is the use for this car? Drag race only? Or street? Daily driving? Cruising?

From the HP numbers, the cam looks to be a street use cam, and 11:1 would be a mistake. Do you have the cam part number or specs? Any info on the pistons used?
 
if that is at the rear wheels you should be happy.
..i have seen some pretty hi dyno numbers on modest builds...usually builders or
magazine guys.
 
Results are from a chassis dyno so numbers are at the wheels, Max rpm pulled to 5700rpm. Pistons are speed pro forged .30 over and cam specs are duration 226/234, 110 lobe separation, lift .494 intake .513 exhaust.
 
Then that's pretty snappy. Let it break in good and then you can put the super tune on it. Don't start throwin money out the window.
 
brsmustng99 said:
Took my 71 340 duster to get dyno tuned, end result 271 HP & 277 tq on a dyno jet. This seems pretty low to me, I was looking for a little over 300. Mods are ld340 intake, voodoo cam, 650 quick fuel carb, headers, 2.5" exhaust, fbo ignition, stock J heads. Do these numbers seem right?? Motor was just rebuilt to factory specs 2k miles ago.
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forget the dyno, I think you have a nice street combo going. run it
my lowly lol, 383 powered barracuda has smoked many 500- 600 hp, that's dyno hp cars lol
I see alot of cars on this forum I put in that catagory based on times posted.lol
 
Just keep going from one chassis dyno to another until you find one that gives you the numbers your looking for:) LOL I've seen them as much as 40 HP out , on the same car , on the same day.
 
better set of heads and dome headers would definitely work together and up the hp and tq.Either one by themselves would help some as well.That being said you have respectable numbers and if it runs well it is up to you to decide if is enough power to keep you happy.

These days I would rather drive a car than have it torn down chasing a number.
 
RustyRatRod said:
Then that's pretty snappy. Let it break in good and then you can put the super tune on it. Don't start throwin money out the window.
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277 @ the rear wheels, is strong for a basic daily street /strip car. Remember the cost/machine work/ extra effort, to worry about numbers.. I would tune what you have,& see if you enjoy it.. I went here,did this with Chev Rats.., never had any fun ,chasing high h.p. numbers & the lowest E.T. ( costs too much,IMO..)
 
If you are happy with how it drives who cares about dyno #'s? Only bench racers and Internet enthusiasts who never have set foot on a track, that's who. Go collect a handful of time slips.
 
If it's an auto it's where it should be: 320hp at the crank. I use 18% loss for an automatic, 15% for manual trans.
 
I have a 440 in my dart. I never had the opportunity to dyno it when it was built so I put it on a chassis dyno. It made 314/450. It runs 11's.

I wouldn't' get too caught up in chassis dyno numbers. What I would pay attention to is where it makes power and that your AF ratio is spot on.
 
Fixed...lol

"I wouldn't' get too caught up in any dyno numbers. What I would pay attention to is where it makes power and that your AF ratio is spot on. "
 
Stock 340 = 275 hp plus 25 headers plus 30 for cam = 330 hp - 18% = 271hp
If you really just looking for numbers a 750 probably will get you some more, but to me you got a great little package tune drive it then every year or so you can do upgrades if need like heads.
 
brsmustng99 said:
Results are from a chassis dyno so numbers are at the wheels, Max rpm pulled to 5700rpm. Pistons are speed pro forged .30 over and cam specs are duration 226/234, 110 lobe separation, lift .494 intake .513 exhaust.
Click to expand...
Roger. Looks like you have about 9.1:1 static CR now with your parts, and a 7.4 dynamic CR. Going to 65 cc heads would get you to 9.8:1 SCR and 8.0 DCR; those numbers would be good to go with. (And I am assuming you have the standard FelPro head gasket with .053 compressed thickness. It might be thinner.)

The Edelbrock Performer AL head choices are the 65 cc open chamber or 63 cc closed chamber ones. The 65 cc ones have the open area milled in the head to accomodate your pistons up out of the deck and you could go for a thinner head gasket and more SCR and DCR; you would be around 10.1 SCR and 8.2 DCR with those heads and the .039" thick head gasket. I personally would not push past that, and maybe back off to the 9.8/8.0 SCR/DCR with the thicker head gasket since you won't have quench with that head.

Or the RHS heads would flow good too; I'd get the 2.02" vavles. Being iron, I'd stick with the lower SCR/DCR combo. With your Speed Pro forged pistons being up out of the deck, you need to keep the .053" head gasket thickness with these closed chamber heads. (Unless the block was decked much; in that case you may need a thicker head gasket to keep the pistons away from the heads.) But you would have a decent quench gap.

Either head will flow better, and the flow and better CR will push your torque and HP up. Maybe a 50-60 HP increase at the wheels with no special porting added to the Edelbrocks, and similar for the RHS/2.02" valves.

All depends if you want to spend the $$ for more and what yo want to do with the car. I am assuming a street driven, pump gas car on all the above. Hence the 'no 11:1' CR thinking.... Besides, you'd have to go with 58 cc heads to get even close to 11:1 unless you changed to domed pistons. And then you are moving out of pump-gas-land unless you cam up, and rev up, and there go the street manners out the window.

If too much info, just ignore! LOL
 
Did they do any fine tuning on the engine? What did the air fuel ratio look like? If they were going to give you a couple of pulls I would have dialed in another 2 degrees of timing to see if the engine wanted more.

Your HP number is OK, but your torque number seems low. I would expect the torque to be more in the 320-340 range.
 
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