How much HP would you guess my 340 produces?

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jcolman

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So I finally made contact with the guy who built my '72 Duster and I now have some of the history of this vehicle. Apparently it was a drag car that a previous owner ran somewhere in Florida for the past however many years. The PO decided to retire the car and turn it into a "street" car. The PO rebuilt the engine and refreshed the chassis before selling it to the gentlemen who finished restoring the car. The guy who finished the car then sold it to the dealer from whom I purchased it from.

These are the specs according to the man who finished building the car. He says that he thinks the engine produces about 350hp. I think that given the mods, it should produce closer to 400 but since it hasn't been on a dyno it's anybodys guess.

340 cid Mopar Engine. Blueprinted and balanced. .30 over. TRW flat top pistons. Mopar steel crank, Mopar performance rods. ARP fastners. Holley Sniper EFI with Hyperspark distributor. Professionally tuned. Edlebrock Aluminum Heads. Weiand Aluminum Intake. Comp cams hydraulic roller cam. 490/490 lift, 262 duration. 10.5-1 CR. MSD Blaster SS Coil. 8mm Plug Wires. Aluminum Radiator. 6-Blade Aluminum Cooling Fan. Hooker Ceramic Coated Long Tube Headers. 2.5” Magnaflow exhaust.

I added the Holley Sniper and Hyperspark after I purchased the car. It originally came with an Edlebrock 600cfm carb. I also added the Autometer instrument cluster.

These are the rest of the specs if anyone is interested.

Wilwood 4-Wheel Disc Brakes. 6 piston front, 4 piston rear. Drilled and Slotted Front and Rear Rotors. Power brakes with silent electric rotary vacuum pump in trunk. Special limited edition American Racing classic Torque Thrust “D”18 Inch Wheels. Front Tires: 235/40 ZR/18. Rear Tires: 245/50/ZR18. Backspace 41/2 front, 51/2 rear. Hub stubs.
727 Torqueflite Automatic Transmission. Center Console shift. 3.91 Gear Ratio. 2400 stall converter. Dana 8 3/4 Rear. POSI Rear End. Moser axels w/5 on 4/3/4 hubs, front and rear. QAI powercoated front end with neoprene bushings. Tubular Upper Control Arms. Powder coated sub-frame and K member.

Autometer custom gauges insert. Black 340 Side Stripes. Black Carpeting. Black Dash. Black Door Panels. Black Headliner. Black Vinyl Interior. Chrome Front and Rear Bumpers. Driver Side Mirror. Duster 340 Tail Panel Decals. Fiberglass Hood and front fenders. Estimated 300 lb weight reduction. Hood pins. Front Bucket Seats. Hood Scoop. Matte Black Hood Stripe. Rear Bench Seat. Three point harness seat Belts. Sublime Green Exterior.
 
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Is that 262 duration at .05 lift or .003 ?
 
With that lift, the 262 is advertised duration. That's a mighty small cam for 400HP.
 
My thought was that the Aluminum heads alone should be good for about 40 - 50 hp. The headers another 15 hp. But these are just guesses.
 
Sounds pretty close to 350 hp to me. Maybe a tad more with the good compression number. Maybe up to 375. Why not take it to a chassis dyno and stop all the guessing? Didn’t your “professional tuner” have it on the rollers? If he didn’t he should have.
 
Sounds pretty close to 350 hp to me. Maybe a tad more with the good compression number. Maybe up to 375. Why not take it to a chassis dyno and stop all the guessing? Didn’t your “professional tuner” have it on the rollers? If he didn’t he should have.
The shop that tuned it for me doesn't have a dyno. They are a resto shop that has a lot of experience installing Snipers. One day I would like to dyno it.

According to Motortrend, the stock 340 made 320hp. That's why I though the mods would be good for about 70 more horses.
 
The shop that tuned it for me doesn't have a dyno. They are a resto shop that has a lot of experience installing Snipers. One day I would like to dyno it.

According to Motortrend, the stock 340 made 320hp. That's why I though the mods would be good for about 70 more horses.
On any efi that’s tunable it is very hard to tune WOT without a dyno. Your tuner can ride along with you and make adjustments while you stomp on it but the local police may have a problem with that. So there may be some left in it. Think of the engine as a package instead of adding up the gains from individual performance parts. In my opinion (not worth much mind you) a 10:1 aluminum headed SBM with a 262 cam, sub .500 lift, is 350-400 hp all day long and twice on Sunday.
 
I don't see your combo making over 375hp ,cam duration and lift being the limiting factor.
 
Take it down the track and see what kind of time you can turn, then do some calculating and that will get you close.
 
If you enjoy the car does it really matter, unless your just looking for a impressive to throw out at shows and cruises.

As has been suggested put it on a chassis dyno.
 
Which Weiand intake are you running? If it’s not an Xcellerator single plane, there’s a noticeable improvement to be had with an LD340 or an air gap intake manifold.
 
My thought was that the Aluminum heads alone should be good for about 40 - 50 hp. The headers another 15 hp. But these are just guesses.
Headers = 15 hp. I’ll go for that if not more.
Aluminum heads = 40-50. Not on your ride it ain’t.
360-370 hp is the best ball park I’m going with.
 
Your build sounds somewhat similar to my 340 except i have a 292/508 cam and i made 416hp w 340hp manifolds. Im thinking 370ish on yours
 
Thanks guys for your thoughts. It's helping me to understand my car and it's potential.
 
For sure bigger cam like a comp XR280hr-10 not to big and not to small would really wake this up and even 1.6 roller rockers
 
Just for comparison for you i have 1.6 rockers and im using an air gap with a 750 holley dp
 
So I finally made contact with the guy who built my '72 Duster and I now have some of the history of this vehicle. Apparently it was a drag car that a previous owner ran somewhere in Florida for the past however many years. The PO decided to retire the car and turn it into a "street" car. The PO rebuilt the engine and refreshed the chassis before selling it to the gentlemen who finished restoring the car. The guy who finished the car then sold it to the dealer from whom I purchased it from.

These are the specs according to the man who finished building the car. He says that he thinks the engine produces about 350hp. I think that given the mods, it should produce closer to 400 but since it hasn't been on a dyno it's anybodys guess.

340 cid Mopar Engine. Blueprinted and balanced. .30 over. TRW flat top pistons. Mopar steel crank, Mopar performance rods. ARP fastners. Holley Sniper EFI with Hyperspark distributor. Professionally tuned. Edlebrock Aluminum Heads. Weiand Aluminum Intake. Comp cams hydraulic roller cam. 490/490 lift, 262 duration. 10.5-1 CR. MSD Blaster SS Coil. 8mm Plug Wires. Aluminum Radiator. 6-Blade Aluminum Cooling Fan. Hooker Ceramic Coated Long Tube Headers. 2.5” Magnaflow exhaust.

I added the Holley Sniper and Hyperspark after I purchased the car. It originally came with an Edlebrock 600cfm carb. I also added the Autometer instrument cluster.

These are the rest of the specs if anyone is interested.

Wilwood 4-Wheel Disc Brakes. 6 piston front, 4 piston rear. Drilled and Slotted Front and Rear Rotors. Power brakes with silent electric rotary vacuum pump in trunk. Special limited edition American Racing classic Torque Thrust “D”18 Inch Wheels. Front Tires: 235/40 ZR/18. Rear Tires: 245/50/ZR18. Backspace 41/2 front, 51/2 rear. Hub stubs.
727 Torqueflite Automatic Transmission. Center Console shift. 3.91 Gear Ratio. 2400 stall converter. Dana 8 3/4 Rear. POSI Rear End. Moser axels w/5 on 4/3/4 hubs, front and rear. QAI powercoated front end with neoprene bushings. Tubular Upper Control Arms. Powder coated sub-frame and K member.

Autometer custom gauges insert. Black 340 Side Stripes. Black Carpeting. Black Dash. Black Door Panels. Black Headliner. Black Vinyl Interior. Chrome Front and Rear Bumpers. Driver Side Mirror. Duster 340 Tail Panel Decals. Fiberglass Hood and front fenders. Estimated 300 lb weight reduction. Hood pins. Front Bucket Seats. Hood Scoop. Matte Black Hood Stripe. Rear Bench Seat. Three point harness seat Belts. Sublime Green Exterior.
Only things that pertain directly to the amount of horsepower are the heads,compression ratio,cam, intake.
The rest are bells and whistles.

Id guess 370-385hp, maybe a few more.
 
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These are the specs according to the man who finished building the car. He says that he thinks the engine produces about 350hp. I think that given the mods, it should produce closer to 400 but since it hasn't been on a dyno it's anybodys guess.

340 cid Mopar Engine. Blueprinted and balanced. .30 over. TRW flat top pistons. Mopar steel crank, Mopar performance rods. ARP fastners. Holley Sniper EFI with Hyperspark distributor. Professionally tuned. Edlebrock Aluminum Heads. Weiand Aluminum Intake. Comp cams hydraulic roller cam. 490/490 lift, 262 duration. 10.5-1 CR. MSD Blaster SS Coil. 8mm Plug Wires. Aluminum Radiator. 6-Blade Aluminum Cooling Fan. Hooker Ceramic Coated Long Tube Headers. 2.5” Magnaflow exhaust.

Jcolman,

I just had my 360 +.040, with a larger duration cam, same compression +/- a smidge, a air gap intake, but Indy X iron heads. It made 385 on an honest engine dyno SAE corrected. You have a roller cam so that is a good plus over me, maybe 10 ponies? But you smaller cubes and less of an intake are minuses. Do you have stamped rockers or rollers? Those can give a decent boost too to efficency and HP. I'd say 365 to 375 depending on other factors like windage, max timing, octane etc.

FYI,
Marion
 
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