A question about header size... 1 3/4" vs. 1 7/8"

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10scnd70
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A question about header size... 1 3/4" vs. 1 7/8"

#1 Post by 10scnd70 » Wed May 11, 2011 9:05 am

We've got a new Shafiroff 14.4:1 434 with a .727" solid roller going in a '70 Camaro, with AFR 227heads. It seems as though everyone suggests 1 7/8" headers. In a perfect situation, I'd love to have a set, but the only one's I can find start at $600. We have a perfectly good set of 1 3/4" headers that were on the old 386. I ran 10.83 @ 125 MPH with that combo. This was an 11.2:1 destroked 400 with Dart 230CC Iron Eagles, and a .646" roller...but...I shifted it at 7600 RPM's. The 434's max will be 7000.
This car is a weekend play toy, that is always ran with open headers. We're not looking for a max effort deal here, but in the real world, how much HP would we be leaving on the table with the 1 3/4" headers?

Frank
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With the old 386 and single Predator
With the old 386 and single Predator
The old 386 with tunnel ram and 2 Predators
The old 386 with tunnel ram and 2 Predators
Just another 10 second Camaro...

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wikd69
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#2 Post by wikd69 » Wed May 11, 2011 10:45 am

Frank,

What carbs are those ?
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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10scnd70
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#3 Post by 10scnd70 » Wed May 11, 2011 12:19 pm

wikd69 wrote:Frank,

What carbs are those ?
Those are Predators. In my opinion, the best carburetors made. When we first built this motor, we had 3 different holleys on it the first season. We went though "adjusting this and changing that".. I had some of the Holley "experts" look at them, and tune them. We made the switch to a single predator and never looked back. The car went from a previous best 10.90 to a 10.83, and it started easier, and idled better. I have NEVER felt ANY holley with the throttle response of a Predator either. Predators offer many advantages over a Holley. They're "variable nenturi" carburetors, which means they work off engine demand. This means that you're never over or under carbureted. They will draw anywhere between 390-930 CFM...Whatever the engine wants. The Predator has exactly 2 adjustments... Main idle adjustment and idle air adjustment. You adjust idle air, and the way you tell when it's correct is to stick your thumb in the air door, rapidly. If the engine gains idle speed, you adjust one way...If it losses speed, you go the other. Once it stays steady, it's adjusted corectly. This takes about 15 minutes. TThe Predator uses no jets, power valves, squirters, idle air bleeds, etc. They do have a replaceable pump cam that usually doesn't need to be changed. We only needed it when we went to the twin set-up, because we were a little lean on the dyno. I called Predator, told them what we had, and they suggested the correct pump cams and sent me a set. Just the cam change fixed it perfectly. When I ordered the cams they told me, "If this doesn't fix it, bring the car to us, we'll fix it for nothing!" A great product that outperforms the competition AND great customer service! There are a few disadvantages to the Predator. They have no provisions for a TV/ kickdown cable, and they're taller than a Holley. In David Vizards book "How to build horepower" He states that the Predator MAY be down a few HP when compared to a PERFECTLY TUNED Holley. When was the last time you seen a PERFECTLY TUNED Holley?...LOL. BTW, you can buy a new Predator for around $530. http://callieskustoms.com/CalliesKustoms-Predator.html http://predatorcarb.com/performance/carburetor.html
Here's a picture of what I ran 10.83 @ 125 MPH with. The Predator worked great, off idle all the way to 7600 RPMs.
Image
Here's a close up pf the 2 of them.
Image
Image
Just another 10 second Camaro...

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10scnd70
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#4 Post by 10scnd70 » Wed May 11, 2011 12:30 pm

Also...The carbs we use are the ones WITHOUT an idle circuit...but...They still idle at 1000 RPM's. They idle better than any of the Holleys did...LOL
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wikd69
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#5 Post by wikd69 » Wed May 11, 2011 1:59 pm

So I take it you like your Predator carbs better than the Holley carbs you used in the past ? :mrgreen: :mrgreen: :mrgreen:
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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10scnd70
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#6 Post by 10scnd70 » Wed May 11, 2011 3:03 pm

wikd69 wrote:So I take it you like your Predator carbs better than the Holley carbs you used in the past ? :mrgreen: :mrgreen: :mrgreen:

Yeah... I guess you could say that...LOL :lol:
Just another 10 second Camaro...

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10scnd70
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#7 Post by 10scnd70 » Sat May 14, 2011 2:35 pm

Oh well...Gotta buy new headers anyway. The old set won't fit angle plug heads... I guess I'll be calloing Schoenfeld for a set of 1 7/8"
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chpcamaro
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#8 Post by chpcamaro » Sat May 14, 2011 9:38 pm

wow i haven't seen a predator carb in years
best to date N/A 8.91@153
psca westcoast heads up racing open comp
67 Camaro RS/SS
BBC Powerglide 4800 stall 4.11 29.5x10.5W
http://www.chpdragracing.com

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10scnd70
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Re: A question about header size... 1 3/4" vs. 1 7/8"

#9 Post by 10scnd70 » Sat May 14, 2011 10:14 pm

chpcamaro wrote:wow i haven't seen a predator carb in years
Yeah, we get that alot...LOL There's alot of "what the hell is that?" in the pits :lol: Everyone asks how it works. We always told them to watch us run. After consistant high 10 second passes, most were convinced it worked.

Frank
Just another 10 second Camaro...

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