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Author Topic:   vac rule cams
racer17j
Dirt Forum Champ
Total posts: 5390
posted June 29, 2005 09:54 PM  
They **** I can tell you that much. lol I was getting 15 inches with my 187 jr hyd cam using rhodes lifters. If I remember right I beleive you have this cam already, if not I have one sitting on the shelf with matching lifters I would sell real cheap. Theres plenty you can do to gain or lose vacuum. Timing,jets, valve lash, carb adjustment, total seal rings. After 6 years I had enough of the vacuum rule so I sold my streetstock and bought a superstock. Good luck


4jw
Dirt Roller

Total posts: 10
posted June 30, 2005 08:39 AM  
If you are worried about vac rule, the best thing you can do is use the anti-pump up lifters. The other things listed above do also affect vac as well, but not as much. Use the anti pump lifters, see what ya have and then make small changes to the other things like timing and jets for small adjustments. Also alway make sure you pull vac off of intake not carb.

b4racing
Dirt Forum Champ
Total posts: 626
posted June 30, 2005 12:18 PM  
also you need to set the idle screws on the carb using a vacuum gauge. start with the basic 1.25 turn out and work your way out a .25 turn if it ups the vacuum do it again until you reach max vacuum. If it goes down go the other way not only will you gain vacuum but it will help getting off the corner. Bobby

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 01, 2005 09:12 PM  
have you tried the bullet vacum cam? i beleive a solid lift will run you 150-175.. but if you want the cam number i will get it for you..

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 01, 2005 11:55 PM  

Brand: Competition Cams
Product Line: Competition Cams Xtreme Energy Camshafts
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,800-6,000 RPM
Intake Duration 050 inch Lift: 230
Exhaust Duration 050 inch Lift: 236
Duration at 050 inch Lift: 230 int./236 exh.
Advertised Intake Duration: 274
Advertised Exhaust Duration: 286
Advertised Duration: 274 int./286 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.487
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.490
Valve Lift with Factory Rocker Arm Ratio: 0.487 int./0.490 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash (in): 0.000
Exhaust Valve Lash (in): 0.000
Computer Controlled: No
Grind Number: CS XE274H-10
Quantity: Sold individually.

Camshaft, Hydraulic Flat Tappet, Advertised Duration 274/286

This cam will give you 15 with no problem.

J3
Dirt Maniac

Total posts: 188
posted July 02, 2005 01:20 PM  
[QUOTE
This cam will give you 15 with no problem.[/B][/QUOTE]

I disagree. I had this cam and only pulled 14 to 14.5 @ 1000 r's. However, that was with a 350 CFM carb. With a bigger carb, I don't know if that would make it pull more vac or not. Now, if you step down one size cam to the XE268, I know that one will pull 17 with a 350 cfm carb.

Now, will running a bigger carb increase the amount of vac you can pull????

waltonjr1
Dirt Forum Champ
Total posts: 516
posted July 02, 2005 02:17 PM  
Different engines do different things. Ring seal is a key factor. You should definitly be able to get fifteen from that cam. I got 15 out of a .510/.510 244* @50 108 LS hyd cam. I also used the 268 and pulled 18 w/ anti pumps, 17 with regular hyd lifters.
Thank God I dont have to worry with vacuum anymore.

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 02, 2005 06:48 PM  
I USE THE A SPEED PRO CAM ITS THE ONE PTM AND JRS SELL ITS THE 465 LIFT ONE IT COST ABOUT 69.00 I THINK I LOST MY CATOLOG MY MOTOR PULLS 15 WITH STOCK TYPE LIFTERS

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 03, 2005 03:58 PM  
YES THERE IS A ENDURO RACE THIS WENSDAY NIGHT 500 TO WIN

racer17j
Dirt Forum Champ
Total posts: 5390
posted July 04, 2005 01:15 PM  
to bad my motor is not fixed or i would bring the econo over and give her one last ride

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