Camshaft selection question
Thread Starter
Instructor
Joined: Aug 2003
Posts: 148
Likes: 0
From: Mitchell, Indiana
Camshaft selection question
Have been going through some hot rod courses in school and got to thinking about something. Has anyone tried to run more duration with essentially the same lift or just a little more on the stock springs? I feel at the strip the lt1 pulls strong but just seems to get weak @5500 plus. Being able to wind it up to about 6300 would seem like it may get a few mph out of it. This is with the thought of using stock valve train due to the lesser tension allowing it to rev more freely. If you stay below the maximum lift spec of the stock springs (which I would like to know) could a custom ground cam like this help? Keep in mind this is for someone wanting to do cam only without modifying other things and this is budget.
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
The stock LT1 springs will only support ~.490 lift, and I wouldn't want to spin the engine higher than 6000 rpms with these springs. If you are going to the trouble of changing the camshaft, get a matching valvetrain. At the very least, LT4 springs will support ~.525 lift, and are very cheap (~$30).
Racer
Joined: Apr 2006
Posts: 405
Likes: 1
From: Twinsburg OH
The stock LT1 springs will only support ~.490 lift, and I wouldn't want to spin the engine higher than 6000 rpms with these springs. If you are going to the trouble of changing the camshaft, get a matching valvetrain. At the very least, LT4 springs will support ~.525 lift, and are very cheap (~$30).
Thread Starter
Instructor
Joined: Aug 2003
Posts: 148
Likes: 0
From: Mitchell, Indiana
yea you guys are probably right, and if i had to change springs why not do some springs that can handle more lift, that way i can get a cam w/ lift to match max flow rate of head. just thought itd be kinda nice to run just a cam and replace the necessary gaskets and get my car down to maybe high 12's for dirt cheap. Best thus far has been 13.3 and its been right around there for close to 4 years now. Guess nothing is cheap though. Does anyone know how big of o.d spring the stock lt1 heads will accept? I have a set of the 99893 Crane double springs sittin around doing nothing but they have the 1.460 o.d
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
Nope, those won't work with the stock seats. In fact, I don't think there is a double spring set that will work with the stock seats.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Have you looked at the complete Hotcam Kit. Every thing is there including cam, RR's and springs that match up for under $600 IIRC. Try
www.summitracing.com
www.summitracing.com
Melting Slicks
Joined: Jul 2004
Posts: 2,695
Likes: 0
From: Chicago Illinois
I agree with just doing hotcam kit. I would never go through the hassel of cam change, and do it half ***. Save up a feww extra buck and do it right. This cam will pull strong up to 6300 rpms and put a smile on your face. Should put you in 12.7 range with proper tune.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
" run more duration with essentially the same lift"
I thought the general idea was to run more lift before increasing duration.
Open- close valve faster- higher rather than longer to achieve the same timing event.That is why the better roller designs have aggressive ramps to get the valve opening sooner
Longer duration brings in idle / drivibility problems you don't get with lift increase only.
I thought the general idea was to run more lift before increasing duration.
Open- close valve faster- higher rather than longer to achieve the same timing event.That is why the better roller designs have aggressive ramps to get the valve opening sooner
Longer duration brings in idle / drivibility problems you don't get with lift increase only.
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From: Former NCM Drag Racing coordinator, National director Corvette Challenge Spring Hill, Tennessee: Whiting, New Jersey
Cruise-In VI Veteran
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NHRA cam rules for Stock require stock lift with any duration. On those cams the lobes are almost SQUARE.