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Author Topic:   CAM With Performance and Vacuum
WinFan
Dirt Roller

Total posts: 10
posted April 26, 2004 05:13 PM  
Can anyone shead some light on a Camshaft that has performance yet will pull 13lbs of Vacuum @1000 RPM? My local track has implimented a 13lb of vacuum @1000 RPM, and no 305 heads. I am currently running a Chevy 350 bored 30 over with 202 heads and a CAM with intake lift of .442 and exhaust of .465 and the duration @ .050 is intake @ 214 degrees, exhaust @ 224 degrees, and I am barly meeting the vacuum requirements. I have heard there is cheeter cams but I cant seam to find them. Does anyone know where I can gain some HP, or find a cam that will serve the purpose of my vacuum rule and perform at 3500 to 5000 RPM.

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WinFan Racing

Busch
Dirt Full Roller

Total posts: 46
posted April 26, 2004 07:58 PM  
Call COMP cams and give them your specifics and they will give you a great edge Also play with your base timing and idle bleeds on the carb theres a whole lot more if you will just ask around Hope this helps Busch

waltonjr1
Dirt Forum Champ
Total posts: 516
posted April 26, 2004 08:28 PM  
You should be pulling more vaccumm than that with that cam.


WinFan
Dirt Roller

Total posts: 10
posted April 26, 2004 08:39 PM  
What could be my problem that I am not pulling more than that in vacuum. I put in step down smaller cam this season when I rebuilt because I was too close running 2 races last season. I had 305 heads and one up from the cam in question, but by going leagle I can't seam to catch the top 2 cars in the class.

Special Ed
Dirt Full Roller

Total posts: 63
posted April 26, 2004 08:43 PM  
waltonjr1 is right, you should be pulling WAY more vacume with that cam. We had a 500-496 with 224-226 @ 50 and it pulled 21 inches with stock lifters. We also tinkered with the vacume on a large solid lifter cam and managed to make it pull 13 inches just by adjusting the carb.

WinFan
Dirt Roller

Total posts: 10
posted April 26, 2004 09:06 PM  
quote:
Originally posted by Special Ed:
waltonjr1 is right, you should be pulling WAY more vacume with that cam. We had a 500-496 with 224-226 @ 50 and it pulled 21 inches with stock lifters. We also tinkered with the vacume on a large solid lifter cam and managed to make it pull 13 inches just by adjusting the carb.

What kind of carb you running, I am running a rochester 2 bbl carb.

77k
Dirt Maniac

Total posts: 174
posted April 27, 2004 12:11 AM  
midwest 510 hyd pulled 15lbs last time I checked

waltonjr1
Dirt Forum Champ
Total posts: 516
posted April 27, 2004 01:36 AM  
WinFan, the only thing I can think of is that your valves could be set to tight. You should have stayed with your original cam and installed anti pump or rhoades lifters to get your extra vaccum needed. Also have you checked with more than one gauge?


WinFan
Dirt Roller

Total posts: 10
posted April 27, 2004 05:17 AM  
I have only checked once this season with one gauge. The tech at the track has yet to check so I am not even sure where they are taking the measurement from. If my Valves are a little to snug would that gice me a decreese in HP. besides lowering my vacuum?

hobby39
Dirt Maniac

Total posts: 112
posted April 27, 2004 08:11 AM  
Winfan, 38Y here their taking the measurement off one of carb ports or since mine are all blocked off i put a valve in the intake right under the carb and they use that. they'll pretty much use whatever you want them too so i'd find out where your getting the best reading and direct them there.

WinFan
Dirt Roller

Total posts: 10
posted April 27, 2004 09:13 AM  
Hobby39, you know this is 17, are you running a rochester carb? I really want to catch that darn 72. lol

Special Ed
Dirt Full Roller

Total posts: 63
posted April 27, 2004 09:54 AM  
Winfab we are running a Holley 4412. I would not waste the money for expensive lifters. You can get more than enough vacume with stock ones. Our cam had more duration than yours and we were pulling 21 inches with stock rebuilder lifters.

WinFan
Dirt Roller

Total posts: 10
posted April 27, 2004 10:59 AM  
By the way, I am at 4800ft elevation here where I race, I have also heard that elevation makes a noticable difference on the vacuum. Does anyone know if this is true???

    

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