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LB9 Cam swap

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Old Apr 24, 2012 | 01:33 PM
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LB9 Cam swap

In my efforts to make my 305 have a more practical use than a boat anchor, lawn ornament, or scrap metal, I'm doing a bit of upgrading. I have an 89 LB9 auto Firebird, and as most of you know, the stock cam is . So after modifying the air box and getting a new rear gear, that's my next project. This is what I'm looking at:

http://www.compcams.com/Company/CC/c...?csid=208&sb=0



As the factory heads came with 1.5:1 rockers, I'm moving up to 1.6:1 along with new springs. But, will this cam work? I have no intentions of replacing the heads, I'd get a 350 before that. Eventually I will port the heads. I also have a new cat-back exhaust. This car is not a daily driver. It's main use will be cruising around on nice days, and a fair amount of track time.

If this cam won't work well/at all, what should I look at instead?
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Old Apr 24, 2012 | 02:45 PM
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Re: LB9 Cam swap

Overlap will be 46 degrees w/that camshaft...
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Old Apr 24, 2012 | 04:35 PM
  #3  
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Transmission: Full Manual TH350
Axle/Gears: Moser 9" 3.70
Re: LB9 Cam swap

Originally Posted by Street Lethal
Overlap will be 46 degrees w/that camshaft...
I'm not sure if that's good/bad, can you elaborate? Sorry, I'm still learning

Called Summit and talked to them a bit, and they said it should work good for my intended use. I figured I would verify that here, because you guys are experts
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Old Apr 24, 2012 | 06:12 PM
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From: NYC / Jersey
Car: 1990 Trans Am GTA
Engine: Turbo 305 w/MS2
Transmission: 700R4
Re: LB9 Cam swap

Originally Posted by PhoenixFirebird
I'm not sure if that's good/bad, can you elaborate? Sorry, I'm still learning Called Summit and talked to them a bit, and they said it should work good for my intended use. I figured I would verify that here, because you guys are experts
I don't know who you spoke to at Summit Racing, but I don't see how it should work good for your intended use. On a plus side, overlap causes a scavenging effect, which is great at higher RPM's, but then again your running Tuned Port Injection which chokes the engine above 4500-RPM, so you won't be able to take advantage of that. Overlap also causes reversion, which pushes up on the intake charge essentially slowing the down the velocity of the charge. There are better cams to go with for your application.
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Old Apr 24, 2012 | 07:03 PM
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From: Norwalk, Ohio
Car: 1989 Firebird Formula
Engine: 385
Transmission: Full Manual TH350
Axle/Gears: Moser 9" 3.70
Re: LB9 Cam swap

Originally Posted by Street Lethal
I don't know who you spoke to at Summit Racing, but I don't see how it should work good for your intended use. On a plus side, overlap causes a scavenging effect, which is great at higher RPM's, but then again your running Tuned Port Injection which chokes the engine above 4500-RPM, so you won't be able to take advantage of that. Overlap also causes reversion, which pushes up on the intake charge essentially slowing the down the velocity of the charge. There are better cams to go with for your application.
I actually talked to 2 different people from Summit, maybe they were just trying to get the sale or misinterpreted my intended use of it. What sort of specs am I looking for then? Eventually I plan on porting the heads, and possibly going with a Holley Stealth Ram manifold. Shouldn't that bump me up a bit as far as RPM's go? I'd hate to end up with making higher RPM's than the cam RPM range. But then again, I don't know how much of a gain there is with HSR + ported heads.

http://www.compcams.com/Company/CC/c...?csid=212&sb=2

Thoughts on that?
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