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 Post Posted: Thu Jun 16, 2011 8:05 am 
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My regulator has a vacuum ref port, My intake and carb do not, Is it worth it to drill a port in my intake?
It also has a "Idle Bleed For Vapor Lock Prevention" I don't this will be a problem only running 1/8mi, Your thoughts?
I know it's been said a 7-10* change in the 1/4 is good,What would be a good temp rise in the 1/8mi?

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 Post Posted: Thu Jun 16, 2011 8:30 am 
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Drilling into the intake will not work. As the top end of the track the vacumm will increase as the load on the engine decreases and will cause an unsafe drop in fuel pressure.

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 Post Posted: Wed Jun 22, 2011 10:24 am 
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Still trying to get this straight. Where would you get vacuum for a regulator then?

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 Post Posted: Wed Jun 22, 2011 11:10 am 
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"Plumbing the 1/8” barbed fitting to a vacuum port below the carburetor base plate will reduce fuel pressure at high RPM off throttle conditions (corner entry). This will make the engine “cleaner” when you pick up the throttle on corner exit. Idle pressure will also be reduced."

Found this off the "racepump"web site.
I think I'll just leave it unpluged.

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 Post Posted: Thu Jun 23, 2011 9:29 am 
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Your talking circle jerking as apposed to drag racing. Different applications. They may want it to go lean going into the corners and be that way until picking up the throttle coming out. Going lean on a strip will cause problems. If you are running alcohol fuel it is a good idea to use a vacuum referenced regulator. Best explanation I have seen is on the pro systems website. http://www.prosystemsracing.com/frienddom.html If on gas just set it to what ever psi you run and go for it. They use a specially drilled port in the carb to keep vacuum low as long as you are on the throttle .

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 Post Posted: Fri Jun 24, 2011 7:49 am 
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Good read? /\ /\ /\

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 Post Posted: Fri Jun 24, 2011 2:28 pm 
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But that only holds true to Pro systems and how they meter the fuel in they're blocks and carb...Not all carb builders use this method.. Not saying Pro systems is bad, butthis set-up is not needed to run alcohol.. ;)

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 Post Posted: Sat Jun 25, 2011 12:56 pm 
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I've never seen a successful alcohol racer using a regulator with any sort of vacuum reference.

I think the best alcohol fuel system is a belt drive pump and either a diaphragm or poppet style return regulator. I use a diaphragm BG.

People also have success with the big electric pumps and deadhead regulators. I just like the ease, reliability, and decreased electrical draw that belt pumps offer.


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 Post Posted: Sun Jun 26, 2011 11:58 pm 
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bbc-olds wrote:
Your talking circle jerking as apposed to drag racing. Different applications. They may want it to go lean going into the corners and be that way until picking up the throttle coming out. Going lean on a strip will cause problems. If you are running alcohol fuel it is a good idea to use a vacuum referenced regulator. Best explanation I have seen is on the pro systems website. http://www.prosystemsracing.com/frienddom.html If on gas just set it to what ever psi you run and go for it. They use a specially drilled port in the carb to keep vacuum low as long as you are on the throttle .



Thats odd. I bought my carb from Patrick in February and even asked him about a recomendation on a regulator and he didnt mention this at all to me. Oh well I am doing fine with what I have...


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 Post Posted: Mon Jun 27, 2011 8:39 am 
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We made it to the track!!!
It rained every test session since we got the car running, So all we had was one hour of open time trials and then two qualifying rounds before eliminations. We left the car set up the same as before to get a comparison as close as we could get it. So the shift was only at 5200 and four threads showing on the bolt under the throttle. (to run the 7.00 index)
We staged the car at 160* and 6.80 seconds later it was still at 160* even back to the pits. I was expecting to make a jet change but my son (the driver) said he left the fan on. After talking to some guys that run close to the same setup as ours, we left it alone as this is how they did it.
So that's a two tenths gain not counting the air temp was 20* warmer.

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 Post Posted: Mon Jun 27, 2011 7:19 pm 
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That's two tenths gain and it's probably still fat on jetting. You're going to have to find a 6.50 index class to run soon. :D Lee

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 Post Posted: Tue Jun 28, 2011 6:15 am 
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racecar77 wrote:
That's two tenths gain and it's probably still fat on jetting. You're going to have to find a 6.50 index class to run soon. :D Lee



Leaving the fans on won't make it hold the same temp from staging back to the pits...
either way as Lee stated sounds like the carb is still very fat,,and too gain .2 arlready on a fat tune,,means there probably another .2-.3 still there was you get it dialed in.. 8)

Congrats and good luck.. 8)

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 Post Posted: Tue Jun 28, 2011 1:09 pm 
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I never had any luck with my prosystems carb and their vacuum regulator set up. I ended up ditching it and putting my Magnafuel back on to make sure I didn't have an issue. Fuel pressure was all over the place. Now I am running an aeromotive return regulator on ethanol.

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