Cutouts for Strip only, beneficial?

[Kent mosby]

1973 Scamp that is my hotrod and not a race specific car. It has full interior, etc. RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.6 RR, Trick Flow single-plane intake. Holley Super Sniper EFI, HyperSpark ignition, coil & distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with Transgo TF2 valve body mods. B&M Quicksilver shifter. Gear Vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs.Viking Warrior shocks. Pypes exhaust 3" into 2.5". RacePro mufflers. Mickey Thompson ET street SS Drag radials 275/60-15). Current cam specs 244°/252° @ .050”, 282°/290° ADV, .516”/.537” lift (1.5:1 rocker), 112° LSA, .016”/.018” lash, Solid lifter from Oregon Cams.

I took out the x pipe as I needed some room for the gearvendors install. So my exhaust goes straight into the racepro mufflers. The car runs great at the moment. Our last race was 11.46 at 118. Prior to that we were at 11.7-12 sec. Amateur drivers here so there is much to be improved on. Launch and strip manners are good.

I know the cam is not ideal for naturally aspirated without nitrous as it was designed for a bit of boost. This may happen but not this year as I do not want to put a rollcage in. I would like to have consistent 11.50 time.

SO.... Would the installation of cutouts provide a bit of an advantage to take the 11.8s times to be more in the 11.5 times? I would never run open cutouts on the street. Older video of my exhaust sounds.


Last years race.

 

[4mulas]

You probably wouldn’t notice much of a difference at all. Other than cool and confidence factor.

 

[Dbrelee]

Well, From my experience with an amatuer Style Annual Dragtrip Event in My Hometown, Everyone brought out their Street Strip Cars and the Local Bracket racers Mild to Wild brought out their cars without having to tow off to a a dragstrip 250 miles round trip, I would uncap my Headers on a BBC Single Carb , Hot Street motor for the Bracket racing day 1 , then recap my headers for the Street Cruise and Sock Hop at the local Mall with show cars etc . we would then run day 2 bracket eliminations all day on day 2. I have experienced 'noticeable performance gains' with Exhaust Back Pressure' All hooked collectors'.This annual Area wide Drag Race at our Airport Lasted i think 10 or so years until we got our own Track Built . I never went racing open Headers again after I Noticed this Performance Gain. The gains were improved take off response , Better Converter (2800) Results and more Crisp throttle response . wanted to share into your thoughts.

 

[memike]

Yes, especially if you have very restrictive mufflers , add some timing and go racing

 

[Oldmanmopar]

Install and H-pipe I found it to be a big difference over the X-pipe through mufflers.

 

[413]

I wouldn't bother with it. That car has enough to go 11.50 with mufflers.

Plus I don't like all the racket inside the car.

 

[Ironmike]

I have Race Ready cut outs and they won't gain you anything. You might even LOSE a tenth.

Not to mention.........I think they kinda sound crappy. Not even close to that great chest thumping open header sound.

 

[Lefty71]

Honestly only you can answer that question. The drag strip is all experimentation. I personally have never had any luck with cutouts, and have seen more than one of my Mopars do better thru the mufflers (but not restrictive ones).

 

[RustyRatRod]

IMO, the only way cutouts might "add" something when open is if they open the uncapped side while CLOSING the exhaust side off. None do that "that I know of". ......and I haven't looked for any that do, because it's never interested me. But all the ones I've seen basically leave the exhaust side open when they open the uncapped side. This allows the exhaust to go both directions and it seems to me that wouldn't be beneficial to good flow. Now If you could make a dedicated long "collector" on the uncapped side, and somehow fix it so is sealed off the exhaust side while opening the uncapped side, AND that transition was good and smooth then you might be into something.

 

[Kent mosby]

Honestly only you can answer that question. The drag strip is all experimentation. I personally have never had any luck with cutouts, and have seen more than one of my Mopars do better thru the mufflers (but not restrictive ones).

The pypes Race pros are not restrictive so I should be good for now. Still looking for another winter project after my electric power steering install was completed in a weekend. Perhaps front end work is in order!! Thanks everyone

 

[Demonx2]

A 512 in a Scamp? That ought to EASILY run what you're after! I suspect you are traction limited? I'll bet that big motor makes a ton of torque and the car needs some help with traction. The cam is small for that big of a motor so the top end power is likely lower than it's capable of. But my goodness, with that much displacement, I see no reason you can't run what you want without cutouts.

 

[Kent mosby]

A 512 in a Scamp? That ought to EASILY run what you're after! I suspect you are traction limited? I'll bet that big motor makes a ton of torque and the car needs some help with traction. The cam is small for that big of a motor so the top end power is likely lower than it's capable of. But my goodness, with that much displacement, I see no reason you can't run what you want without cutouts.

Yea, the cam was designed with nitrous in mind. We are working on the suspension to get it dialed in better. No prep tracks are harder and that is all we run on. Also working on the EFI tune. Richard Nedbal did the original tune and some advice from Andy Finkbeiner has helped as well. A work in progress. I guess I will skip the cutouts for now and work on the other aspects

 

[Demonx2]

Yea, the cam was designed with nitrous in mind. We are working on the suspension to get it dialed in better. No prep tracks are harder and that is all we run on. Also working on the EFI tune. Richard Nedbal did the original tune and some advice from Andy Finkbeiner has helped as well. A work in progress. I guess I will skip the cutouts for now and work on the other aspects

Indeed an engine with that much torque would be difficult on a no prep track. Getting that to hook will be a challenge every day! But I believe you still have ample power to meet your goal. Good luck!

 

[Oldiron440]

I don’t know why your cam profile is so the way it is but with that many cubes and stroke I would have gone with something around.250 @ 50
110 CL and then close to.600 lift. I’d say you are giving up fifty hp with that cam.
What guys don’t realize when building a long stroke is that what a 383 likes needs to have ten more degrees of duration for a 440 and then the same thing is true for 4.15 or 4.25 stroke engines, add ten more degrees of duration in comparison to the 440 and 20 compared with a 383.
So if a good street cam for a 383” has 230 @ 050 so a 500”+ needs 250 @ 050 and will make 500tq @ 2500rpm.
Another mistake I see made with the big blocks is using a two plane intake, if you have a 4.15 or 4.25 crank you don’t need to worry about low end power only traction. A two plane will kill top end and bottom end on a big inch engine.

 

[str12-340]

Evidently Tom Hoover and the Dodge Ramchargers engineers thought it was worth the effort since they came form the factory on all the Max Wedge and Hemi cars in the early 1960s. The system was designed so that the primary emphasis was on the design when the cut outs were used (soft angled big pipes right to the cut out, and the rest of the system was an almost 90 degree turn off that pipe. This as opposed to a simple turn off for a cut out from a system designed for the overall exhaust system. I am sure that the tuning was done with the cut outs open, and how that fell when they were capped and the whole system was used was an afterthought.

 

[RustyRatRod]

Evidently Tom Hoover and the Dodge Ramchargers engineers thought it was worth the effort since they came form the factory on all the Max Wedge and Hemi cars in the early 1960s. The system was designed so that the primary emphasis was on the design when the cut outs were used (soft angled big pipes right to the cut out, and the rest of the system was an almost 90 degree turn off that pipe. This as opposed to a simple turn off for a cut out from a system designed for the overall exhaust system. I am sure that the tuning was done with the cut outs open, and how that fell when they were capped and the whole system was used was an afterthought.

I cannot disgree, HOWEVER, look at how that factory system was made. The cutouts were on the MAIN BRANCH of the exhaust system, not an offshoot, like modern cutouts. The mufflers and the "rest" of the Max Wedge system was on the offshoot of the factory system, so that system probably did flow better with the caps removed.

 

[Jeremiah (jd)]

I run Doug's 2.25" cutouts on my 68 GTS and they help quite a bit under any conditions especially drag racing. It has a 511" low deck with a n20 grind solid roller.

I'd be cautious taking advice from anyone without direct experience on the matter.

If I was starting all over I'd build the exhaust 3" mid pipes to 2.5" tail pipes with an H. I'd run 3" electric cutouts too.

 

[RustyRatRod]

I run Doug's 2.25" cutouts on my 68 GTS and they help quite a bit under any conditions especially drag racing. It has a 511" low deck with a n20 grind solid roller.

I'd be cautious taking advice from anyone without direct experience on the matter.

If I was starting all over I'd build the exhaust 3" mid pipes to 2.5" tail pipes with an H. I'd run 3" electric cutouts too.

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Man, I've always just loved that car! Have you got some pictures of how you have the cutouts installed?

 

[Demonx2]

I run Doug's 2.25" cutouts on my 68 GTS and they help quite a bit under any conditions especially drag racing. It has a 511" low deck with a n20 grind solid roller.

I'd be cautious taking advice from anyone without direct experience on the matter.

If I was starting all over I'd build the exhaust 3" mid pipes to 2.5" tail pipes with an H. I'd run 3" electric cutouts too.

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A 511 inch low deck in a Dart? That thing must really get it done! What are the et's on it?

My point is if the OP is just wanting to run 11.50, I don't believe he needs the cutouts. He can do it just with the motor. He HAS to be traction-limited!!

 

[Jeremiah (jd)]

A 511 inch low deck in a Dart? That thing must really get it done! What are the et's on it?

My point is if the OP is just wanting to run 11.50, I don't believe he needs the cutouts. He can do it just with the motor. He HAS to be traction-limited!!

It's a no prep/grudge car. I'll probably be more open to share ET's when it has a roll bar this spring : D We might even dig out a pair of Kirkey's for the front.

I agree on the 11.50. A pair of slicks and some cal tracs and/or good shocks should at minimum get it to pull a low 1.60s 60' which is enough to get way into the 11's. It's definitely not happening with BFG T/A's

 

[Jeremiah (jd)]

Man, I've always just loved that car! Have you got some pictures of how you have the cutouts installed?

Thank you sir : D

I will try to find one. It's a hacked up Accurate ststem with Gibson straight through muffs and dougs cutouts grafted to TTI steps. I have not installed the H because.... cutouts lol

I need to install bigger pipes. The AFR changes from 14.5 to 16.1 at idle when I uncork it. The O2's are in thr collecter reducers, cutouts are about half way under the door where the recess in the floor pan is. I do not think the O2 sensor placement is causing a lean reading.

 

[Oldiron440]

I’ve run my Plymouth with just headers and with header extensions and with mufflers . Between header extensions and mufflers it took a little carb tweaking for the best number…

 

[MOPARMAGA]

Thank you sir : D

I will try to find one. It's a hacked up Accurate ststem with Gibson straight through muffs and dougs cutouts grafted to TTI steps. I have not installed the H because.... cutouts lol

I need to install bigger pipes. The AFR changes from 14.5 to 16.1 at idle when I uncork it. The O2's are in thr collecter reducers, cutouts are about half way under the door where the recess in the floor pan is. I do not think the O2 sensor placement is causing a lean reading.

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Those are nice limiters Jeremiah

 

[MOPARMAGA]

1973 Scamp that is my hotrod and not a race specific car. It has full interior, etc. RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.6 RR, Trick Flow single-plane intake. Holley Super Sniper EFI, HyperSpark ignition, coil & distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with Transgo TF2 valve body mods. B&M Quicksilver shifter. Gear Vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs.Viking Warrior shocks. Pypes exhaust 3" into 2.5". RacePro mufflers. Mickey Thompson ET street SS Drag radials 275/60-15). Current cam specs 244°/252° @ .050”, 282°/290° ADV, .516”/.537” lift (1.5:1 rocker), 112° LSA, .016”/.018” lash, Solid lifter from Oregon Cams.

I took out the x pipe as I needed some room for the gearvendors install. So my exhaust goes straight into the racepro mufflers. The car runs great at the moment. Our last race was 11.46 at 118. Prior to that we were at 11.7-12 sec. Amateur drivers here so there is much to be improved on. Launch and strip manners are good.

I know the cam is not ideal for naturally aspirated without nitrous as it was designed for a bit of boost. This may happen but not this year as I do not want to put a rollcage in. I would like to have consistent 11.50 time.

SO.... Would the installation of cutouts provide a bit of an advantage to take the 11.8s times to be more in the 11.5 times? I would never run open cutouts on the street. Older video of my exhaust sounds.


Last years race.

That's not bad for a full dressed street car.

 

[Ironmike]

IMO, the only way cutouts might "add" something when open is if they open the uncapped side while CLOSING the exhaust side off. None do that "that I know of". ......and I haven't looked for any that do, because it's never interested me. But all the ones I've seen basically leave the exhaust side open when they open the uncapped side. This allows the exhaust to go both directions and it seems to me that wouldn't be beneficial to good flow. Now If you could make a dedicated long "collector" on the uncapped side, and somehow fix it so is sealed off the exhaust side while opening the uncapped side, AND that transition was good and smooth then you might be into something.

Been thinkin on that issue myself Rusty. A guy COULD buy 2 sets and rig it up so 1 set closes and the other opens. A little cutting and welding ............not that hard. BUT, the cut outs in the exhaust side would be restrictive when the loud side is opened up. OR.......

Some genius needs to invent a sort of "U" pipe that bolts to the headers, with a blade that just goes back and forth, from the open side to the exhaust side. Doesn't really sound that difficult to engineer if you're already making electric cutouts.