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Author Topic:   Cam and RPM Range
LovetheSport
Dirt Roller

Total posts: 5
posted January 16, 2004 06:47 PM  
I need help on what size cam and what the RPM range should be for my 1976 Monte Carlo?
I race on a fast 1/2 mile with a (305 engine
rule) and TH350 (automatic transmission rule).My final gear ratio =[520]on (205/70/15 DOT street tire rule).The tires are 84".I am guessing about 6900 rpm's but have never ran a tach.What size cam do you suggest if I turn between 6,500-7,000 RPM's?

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 16, 2004 10:12 PM  
I had also thought about changing the rear to a 323 to give me a 486 final gear ratio but since I am rebuilding the engine I will make only one change at a time and go with hyraulic cam change with my 305 engine.
Hopefully I will be able to run at other tracks against the 350's but I most run the 305 engine at my home track.This track is not a small 1/2 mile nor a large 1/2 mile.My friend tried the 486 last year and the way to go at my track =512 to 520.Thanks for your help racer17j and I bet for you it was the cam difference.

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted January 17, 2004 11:43 AM  
if you really want a cm that flyes and pulls very hard it is a comp cams 12-330-4 you need to only turn about 6000 and with that 305 and the small heads that you have and not having the breathing capabilities that you would with a 350 cause of the bore size that cam would work excellent for you.
it is a hydralic cam also i can e-mail you the specs on the cam if you need
you wont find a cam that pulls as hard as this i promise

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you never know how fast you are going when your in the lead, until you blow the announcers hat off!!!

LovetheSport
Dirt Roller

Total posts: 5
posted January 17, 2004 12:35 PM  
Comp cams are suppose to be good cams but the cam you are talking about is for a fast 3/8 mile track.I need a cam for a fast 1/2 track.I want to turn minimum 6500 RPM's.Appreciate your help Ms Iowa.

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 17, 2004 02:19 PM  
The 342 seems like the best choice and that is the largest rear I can go with according to my rules.Since I want to keep my final gear around 342 x 1.52 2nd gear in TH350 = (520 not counting for 84" tires).The 323 x 1.52 =491 and will not work on my large 1/2 mile track.The track is .522 exactly.Very much like Martinsville NASCAR track.Now to figure that cam out.racer17j the cam you talked about might work but I would like some more cam suggestions for my application.Where are your buddies at on here.

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted January 17, 2004 05:31 PM  
yes the cam that i was talking about is for a 3/8 mile but works better for a half mile if it didnt i wouldnt have recommended it for you at desmoines 1/2 mile and oskalossa 1/2 mile is what almost everyone is running i would never try to steer you wrong

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted January 17, 2004 05:37 PM  
why would you want to turn 6500 when you can turn 6000 and be faster iam just curious on your thinking

racer17j
Dirt Forum Champ
Total posts: 5390
posted January 17, 2004 10:14 PM  
What intake, carb and exhaust are you running? If it's a stock intake, 2bbl and factory ex. manifolds, over 6000 is slowing you down. Power would peak around 5500-5700 no matter what if it's all stock stuff.

If you post some the other pieces you have to run, it would help with cam choice. A 305's gonna want about 4-6 degrees less duration at .050" compared to a 350 just from the size difference. A 6000 rpm cam in a 350 (around 230-235 duration) would be a 6500 rpm cam in a 305.

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