Does a drag race only car need exhaust boxes?

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Your countryman David Vizard has an excellent section on exh systems in his small block Chev book, SA books #57. Well worth getting. He also explodes the myth about having equal length pri pipes. There is a dyno test in his big block book, equal v un-equal, with unequal making up to 29 HP more [ & never less hp ] on a 525 ci engine
 
I run Pypes race pro’s through a full 2.5” exhaust with 340 manifolds and run 11.39 at 117 mph. If you go Pypes, avoid the Violators. They sound HORRIBLE. Drove 1000 miles on Dragweek with the race pro’s. It was fine.
 
furrystump said:
I run Pypes race pro’s through a full 2.5” exhaust with 340 manifolds and run 11.39 at 117 mph. If you go Pypes, avoid the Violators. They sound HORRIBLE. Drove 1000 miles on Dragweek with the race pro’s. It was fine.
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I run the Pypes race pros too and love them. Great sounds and I’ve been 5.98 in the 1/8 with them. I put a good dose of engine oil through them last year from in intake oil leak and took them off till I had the problem fixed. I sure hope I didn’t mess them up because I welded my whole exhaust system.
 
Oldmanmopar said:
All I can tell you is that is what it weigh when I drove it over the scale at the track. From what I remember my 70 Duster original 340 auto car weighed a tad over 3200 No cage or options . I know My orange 71 Duster was quite heavy. Add ons and all the options add up quick.
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It was all that badassary. That adds a lot of weight. lol
 
Big men…. Loaded car w/A/C, PB, PS, spare tire, etc….
Later A bodies with heavier impact bumpers weigh in more.
 
The car was all original with the spare in the trunk and all insulation in place. Mild steel cage. 4 big speaker with a stereo and amp. High nickle race block. complete 3 1/2 exhaust with 2" tube headers and tail pipes with tips, Trans and engine coolers, Large be-cool rad, all braided steel lines , No fiberglass parts at all. Driver was 220. There was at least 50 lbs of battery cable and wire in the car. including the monster cables for the stereo, I believe most of these 340 cars came in at 3300 - 3400 with auto trans, Don't forget the 8 quart pan and the remote filter and then the heavy deep trans pan cast aluminum . Large Diameter steel drive shaft and frame ties. scoop , wing, and all the other options I am forgetting like the map light harness, trunk mat, **** starts adding up quick.

None the less the car went over the scales with my son in it at #3850 what is hard to believe about that. We want the new car to be around "2200 with the small block.

You can see and hear the car is heavy in the video below.


dvw said:
How do you get a Duster to 3850 raceweight? 3 200lb people in the car?
Doug
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Sweet! Almost the same direction I’m going in. IDK about the back halting for myself…. Juuuuuuzsst yet.
 
Oldmanmopar said:
Well every option the car came with was in the car it was loaded minus air. It was all original metal no glass parts. Complete mild steel cage took 2 of us to carry it without the swing outs or rear down tubes. Large after market stereo with 4 huge magnets. Heavy wall 3 1/2 inch exhaust with mufflers and tail pipes. Full factory bucket seat interior. Every hose was braided . . Oil and Trans coolers. Stabilizer bar still in place. Trunk mat and spare with jack in trunk.

And most important if you look I said with driver. You never asked me what my son or I weighed. He is 6'4" around 240. I am just a tad rounder. If you look close at the one video you can see it is turning the tires through second. It did not hook on the feathered street driven tires.

The new car will be very light all chrome moly steel we are only using the roof ,firewall, and quarters, AJE front race suspension with Strange light weight brakes. The rest from glass tech. The engine now will be all alluminum, Titanium, internals except for the light weight crank. Ordered the titanium valves tonight they are on sale right now $140.00 each. Everything else is here
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years ago when I had my 70 Duster,( factory 340 air car) I raced it with 8 point mild steel cage, frame connectors, all steel except bumpers( so likely 50 pounds savings total there.
full bench seat/ carpet interior, full stock gas tank full of gas( didn’t want any slosh, no spare tire, I weighed probably 310 at the time, car weighed almost 3450 at the line with 3 inch exhaust out to the back, 727 transmission.
3850 is something I would love see go over the scales at my track, 400 pounds more than mine weighed( and I weighed more as a driver) is something I would stand at the scales and bet 100 bucks on
 
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Markh said:
My 340 drag only dart has exhaust cut outs with plates that unbolt.
The car was ran on a rolling road for a base line figure and the afr showed a steady 12.
The car then had 2 runs with the cut outs opened. Afr dropped to 11 and then 10. Hp was down 5% and torque down 10% on both runs. Carb is a 750dp. If the carb was rejetted to get the afr back to 12 would the hp and torque be better with the open exhaust or does a car make more power with exhaust boxes over an open exhaust? Or do I need a bigger carb? I suppose what I want to know is what is going to make the most power, an open exhaust or one with boxes or is it not that simple?
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If it's a race only car why not just get rid of the extra weight and tune it from there. One way I used to tune extensions (before all the data) were to cut them where the paint burned off. Also, if you want to use both exhausts just get a second carb. and tune one for each exhaust. And do get the 2nd o2 sensor. And last it will run better with a proper tune.
 
Demonracer said:
My car is a bracket car only, it never sees any street time. I have multiple length collector extensions that I swap around according to the weather and track conditions. There are going to be nay sayers out there who disagree with me, but I know what works for ME. Everyone has their own ideas and things that work for them. Try your car out multiple ways and see what works best for you.
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:thumbsup:
 
B3422w5 said:
years ago when I had my 70 Duster,( factory 340 air car) I raced it with 8 point mild steel cage, frame connectors, all steel except bumpers( so likely 50 pounds savings total there.
full bench seat/ carpet interior, full stock gas tank full of gas( didn’t want any slosh, no spare tire, I weighed probably 310 at the time, car weighed almost 3450 at the line with 3 inch exhaust out to the back, 727 transmission.
3850 is something I would love see go over the scales at my track, 400 pounds more than mine weighed( and I weighed more as a driver) is something I would stand at the scales and bet 100 bucks on
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I try to weight most of my cars and my darts usually weight in around 3450 -3580 stock with at least 3/4 tank of fuel. These have been G/T's (bucket seats/consolewith no options. Stock exhaust. My dusters were always lighter 100 -150 lbs. I currently want to weight my 69 Cuda, 340 Auto. Dana 60 8 point ms cage all steel. I'll bet she;s 3650 or so w/o driver.
 
B3422w5 said:
years ago when I had my 70 Duster,( factory 340 air car) I raced it with 8 point mild steel cage, frame connectors, all steel except bumpers( so likely 50 pounds savings total there.
full bench seat/ carpet interior, full stock gas tank full of gas( didn’t want any slosh, no spare tire, I weighed probably 310 at the time, car weighed almost 3450 at the line with 3 inch exhaust out to the back, 727 transmission.
3850 is something I would love see go over the scales at my track, 400 pounds more than mine weighed( and I weighed more as a driver) is something I would stand at the scales and bet 100 bucks on
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Your dad must have had helium in the car. These cars weighed up to 3400 from the factory depending on engines. In 73 and newer they were all over 3200. My car with all the add ons weighed 3630 without my son in the car. So what you are saying is there is no way we added 230 lbs in extra weight with what we added to the car. What do you think the lightest these cars weighed base bare bones with small brakes and no extras? I would say the lightest would be 3000 wouldn't you say that. and 3400 with a 340 727

Are you telling me I am lying about the weight after all the things we added to the car. Or are you just misinformed and calling me out to be a smart *** to me. I have seen these cars with 383's and AC weigh over 3500. I have taken many across the scales, 383 cars with no options weigh 3200 at the lightest. My race block weighs almost double of a 383. start adding the options up the parts don't contain helium . I don't care what your dads car weighed I am telling you what ours weighed . Why would I say something thats not true. I have the list of weights for these cars in a folder from mopar bare bones as they came. None weighed under 3000 not even the bare bones light weights.

Where would I collect my $100
 
Oldmanmopar said:
Your dad must have had helium in the car. These cars weighed up to 3400 from the factory depending on engines. In 73 and newer they were all over 3200. My car with all the add ons weighed 3630 without my son in the car. So what you are saying is there is no way we added 230 lbs in extra weight with what we added to the car. What do you think the lightest these cars weighed base bare bones with small brakes and no extras? I would say the lightest would be 3000 wouldn't you say that. and 3400 with a 340 727

Are you telling me I am lying about the weight after all the things we added to the car. Or are you just misinformed and calling me out to be a smart *** to me. I have seen these cars with 383's and AC weigh over 3500. I have taken many across the scales, 383 cars with no options weigh 3200 at the lightest. My race block weighs almost double of a 383. start adding the options up the parts don't contain helium . I don't care what your dads car weighed I am telling you what ours weighed . Why would I say something thats not true. I have the list of weights for these cars in a folder from mopar bare bones as they came. None weighed under 3000 not even the bare bones light weights.

Where would I collect my $100
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You are correct. My lightweight 68 Dart weighted in at 3180 with a 1/4 tank of fuel auto/8 3/4.
 
 
My 67 barracuda fastback with 383, no options, no cage no fuel weighed 3275# .
With me in the seat ,1/4 tank fuel 3475 #
This was my street/strip car in early 80's.
As it evolved over the years it still weighs over 3200#
 
If your exhaust boxes are crappy and restrictive you could very well need a different tune up for when the exhaust is open. My car is fuel injected, with the cutouts open it uses 3% more fuel to hit the same AFR target, it is about .1 and 1mph faster with the cutouts open vs running through an exhaust system. This is a 3550lb A body Barracuda with a 418" small block that runs 10.40s.
 
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