Too much cam?
Thread Starter
Intermediate
Joined: Jun 2001
Posts: 33
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From: clarksville, TN, USA tn
Too much cam?
I've always heard that if you have too aggressive a cam, you will have problems maintaing vacum pressure. Since C-3 vettes use vacum to opperate the headlight mechanism, this has extra importance to us. At what point is a cam too extreme to be practical on a street C-3? Has anybody had experience with weak vacum due to a big cam?
Burning Brakes
Joined: Aug 2000
Posts: 852
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From: Katy TX
Re: Too much cam? (HFP073)
Well the cam will definitely affect vacuum and if you go too big your brakes and headlights will not work well. I can tell you that my car runs right at 15" vacuum at idle and everything works fine. Not sure how low you can go. Others here have described running auxillary vacuum systems in order to run a big cam. In fact there is a post about a brake booster in the linked post.
http://forums.corvetteforum.com/zerothread?id=241946
http://forums.corvetteforum.com/zerothread?id=241946
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Re: Too much cam? (Smokehouse69)
My vette used to pull 9", still operated the lights and wiper door, just a little slower :D:D
Edit, and power brakes too...
[Modified by 427V8, 10:03 PM 2/26/2002]
Edit, and power brakes too...
[Modified by 427V8, 10:03 PM 2/26/2002]
Racer
Joined: Feb 2002
Posts: 272
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From: MOBILE ALA
Re: Too much cam? (HFP073)
A rule of thumb is 12 inches manifold vacuum for street,MINIMUM.The idea that a really large cam is best depends on your intended use.A cam with lots of durration may soon good at idle,but will have poor street manners and driveabilty to say the least.For street use you would be best served by a cam with durration of no more than 230 @.50.A wider lobe seperation of 112-114 will as help smooth idle and aid low speed driveabilty.You can run lift up to .500-.510 with the correct valve springs.Durration and overlap affect vacuum. :chevy
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Too much cam? (HFP073)
You will never have to much cam if it's a proper combo. Hydro cams with to little lobe center cause low vacuum and drivability problems. all you have to do is have enough compression and free flowing intake and exhaust and things run great. You also have to think of props like gearing and higher stall converters and keep carb cfm within reason
Team Owner
Joined: Feb 1999
Posts: 34,454
Likes: 665
From: Republic of Texas
Re: Too much cam? (gkull)
I plan to run a vaccum booster to be safe. I remember my father telling me that in in 1970 he switched his '69 L89 cam for a 300/300 duration and when he raced at night he had to lock the headlights in because at the top of each gear the light would go down and then come back when he shifted. :lol:
Race Director
Joined: Apr 1999
Posts: 11,520
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From: CORVETTE 77 385 C.I. TEXAS
Re: Too much cam? (HFP073)
It may have importance to some, but not all. :cool: Yes, have run low vac. setups. :cool: Never too much cam, just not enough engine.
A big cam will act smaller w/ more C.I. You need to pick a cam that matches you setup. If you give your setup, can cam.
For many 230 @.050 110LS is a good street limit, however this is not a rec. w/o knowing the setup.
:cool:
A big cam will act smaller w/ more C.I. You need to pick a cam that matches you setup. If you give your setup, can cam.
For many 230 @.050 110LS is a good street limit, however this is not a rec. w/o knowing the setup.
:cool:
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Safety Car
Joined: Feb 2000
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From: Massachusetts , USA,
Re: Too much cam? (HFP073)
My understanding is a strong vacuum signal will usually result in smooth idle & crisp part throttle response and driveability & good low end tourque.........on the street torque is king,............................. reference>>> comp cams 252 , 600 rpm idle 17/18 ins, comp cams 268 850 rpm idle 16 ins, comp cams 280 , 850 idle 12 ins , comp cams 292 950 rpm idle & 10 ins of vacuum at idle.................The Dog Woof woof. :seeya
Team Owner
Joined: Jun 2001
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From: Thomson Georgia
Re: Too much cam? (StrayDog)
My understanding is a strong vacuum signal will usually result in smooth idle & crisp part throttle response and driveability & good low end tourque.........on the street torque is king,............................. reference>>> comp cams 252 , 600 rpm idle 17/18 ins, comp cams 268 850 rpm idle 16 ins, comp cams 280 , 850 idle 12 ins , comp cams 292 950 rpm idle & 10 ins of vacuum at idle.................The Dog Woof woof. :seeya
Safety Car
Joined: Feb 2000
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From: Massachusetts , USA,
Re: Too much cam? (427V8)
NOTE.....the vaccum readings etc & cam info, was from an article ..in Super Chevy Magazine April 1998 issue , page 42....on basis of dyno tests after various cam changes,,,,,,,,,, :yesnod: i reccomend this magazine great tech info :seeya :flag
Melting Slicks
Joined: Mar 2001
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From: Exiled Tampa Bay Misfit
Re: Too much cam? (Alwyn678)
I guess I am a lost bulldog.................... :seeya :flag
SWEET......... :cheers:
SWEET......... :cheers:
GATOR BAIT!!
Melting Slicks
Joined: Mar 2001
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From: Exiled Tampa Bay Misfit
Re: Too much cam? (xfactor974)
Just a point of interest.... When dealing with vacuum (I do on a daily basis but in an industrial setting) there are TWO factors. Suction and Flow. While you may be drawing 13"Hg your flow way be very low and therefore it will take a long time to pumpdown to this level. Conversley you may have a low vacuum suction pressure but a high flow. I think that it is this aspect that can partially explain why two cars witht the same pressure reading act so much differently...
Team Owner
Joined: Jun 2001
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From: Thomson Georgia
Re: Too much cam? (Monkeywrench)
I guess I am a lost bulldog.................... :seeya :flag
SWEET......... :cheers:
Oh dear Lord. As if Alwyn's Georgia fanatacism wasn't enough... :lol:
GATOR BAIT!!
SWEET......... :cheers:
Oh dear Lord. As if Alwyn's Georgia fanatacism wasn't enough... :lol:
GATOR BAIT!!
Go DAAAAAAAAAWWWWWWWWWWWWWGGGGGGGGGGGGGGSSS SSSSSS :lol: