Collector Size & Length - how short is too short?

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John_Heard
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Collector Size & Length - how short is too short?

#1 Post by John_Heard » Thu Dec 20, 2012 10:36 am

I decided to try a larger collector on my car for next year, switching from a 2 3/8" x 4" to a 2 3/8" x 5", this time with a shorter muffler. I want to cut the collector down to get it as short as I can to help with ground clearance, but not to sure how short is to short, or if it matters.

Going to use the Vibrant 5" x 5" this time - anyone got an idea how short is too short? Or would it matter much?
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Re: Collector Size & Length - how short is too short?

#2 Post by ytnova » Thu Dec 20, 2012 4:04 pm

I had thought about doing the same thing when the BBC was still in the nova so I called lemons. He said with my cubic inch and weight of the car It probably wouldn't help and might even hurt it. Your combo is bigger by about 40 cubes and you make more power, so I would try it. As for length??? I would cut the length of the muffler off and start there, anymore and I think you would be losing the scaveging effect of the collector, might as well go with zoomies then, lol.
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Re: Collector Size & Length - how short is too short?

#3 Post by John_Heard » Thu Dec 20, 2012 4:32 pm

That's kinda what I was thinking too, keep overall length about the same as the collector itself. I think it will be real hard to tell much difference, but gotta start cutting somewhere.

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Re: Collector Size & Length - how short is too short?

#4 Post by Mike Peters » Fri Dec 21, 2012 12:05 pm

I don't think there's any scavenging effect with big time power adder cars. NA cars run tight lobe separation angles but, there's very little overlap in cam designs when boost or spray is maxed. Make 'em as short as possible and spray the crap out it!!! What's your lobe separation angle on your cam John?
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Re: Collector Size & Length - how short is too short?

#5 Post by John_Heard » Fri Dec 21, 2012 12:10 pm

114 right now

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Re: Collector Size & Length - how short is too short?

#6 Post by Mike Peters » Fri Dec 21, 2012 12:15 pm

John_Heard wrote:114 right now
Wow. I figured it would have been 117 or better. My cam for my tiny engine is 114.
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Re: Collector Size & Length - how short is too short?

#7 Post by John_Heard » Fri Dec 21, 2012 12:32 pm

I've ran more before and had issues with reversion. I'd consider a different cam sometime, but this one seems to be working ok.

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Re: Collector Size & Length - how short is too short?

#8 Post by Mike Peters » Fri Dec 21, 2012 12:36 pm

John_Heard wrote:I've ran more before and had issues with reversion. I'd consider a different cam sometime, but this one seems to be working ok.

That's 'cuz you had too much exhaust back pressure!!! LOL

Wider lobe separation angle in the same engine size or a smaller engine?
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Re: Collector Size & Length - how short is too short?

#9 Post by John_Heard » Fri Dec 21, 2012 12:44 pm

That was on a smaller engine, not this one. The wider angle might have worked better on this one, don't know. I haven't experimented with it. Might try something different next time it's apart.

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Re: Collector Size & Length - how short is too short?

#10 Post by Mike Peters » Fri Dec 21, 2012 1:20 pm

John_Heard wrote:That was on a smaller engine, not this one. The wider angle might have worked better on this one, don't know. I haven't experimented with it. Might try something different next time it's apart.
Big difference between a 505 and 615. I'm no cam expert but, it might be worth investigating for the next version of Frank.
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Re: Collector Size & Length - how short is too short?

#11 Post by John_Heard » Fri Dec 21, 2012 1:32 pm

I think a big clue will be if it don't want to go faster with more juice, if that happens the cam will be something I'll certainly be looking at.

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Re: Collector Size & Length - how short is too short?

#12 Post by supernova » Sat Jan 12, 2013 7:29 am

Mine's a 572 and my cam is 112. Had a 114 in it last year, changed it to the 112 and went a .10th faster........
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Re: Collector Size & Length - how short is too short?

#13 Post by Craig W. » Sat Jan 12, 2013 2:46 pm

supernova wrote:Mine's a 572 and my cam is 112. Had a 114 in it last year, changed it to the 112 and went a .10th faster........
Is that on the bottle or off? How hard are you spraying it?
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Re: Collector Size & Length - how short is too short?

#14 Post by Mike Peters » Mon Jan 14, 2013 7:32 am

supernova wrote:Mine's a 572 and my cam is 112. Had a 114 in it last year, changed it to the 112 and went a .10th faster........
Cam was the only thing you changed? Like Craig said, on the bottle or off and how much juice?
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Re: Collector Size & Length - how short is too short?

#15 Post by BracketNova » Wed Jan 23, 2013 9:49 pm

I thought there was a sweet spot for collectors? I looked through my notes and found a formula for tubes, but not collectors.
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