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Old 09-14-2011, 09:34 AM
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Cam decision in stock 305 HO

I am rebuilding a 85 Monte Carlo SS motor and it is remaining essentially stock with air injection removed. I'm considering using the Comp XE254 with 210/218 duration and 111 lobe seperation. I'm wanting to add a little more power capability while I'm in the engine, but don't want much effect on the idle. Not looking to create a ton more power, but I can't help but want to improve some over factory while I'm in the engine. I know I could go the 204/214 route and be sure there's no idle change, but that is only a couple degrees differnet than the 202/212 it had from the factory.

So will the 210/218 duration cause me any noticable change in idle? Or decrease the low end torque. The SS has a faily high rear end, 3.73 I believe.

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Old 09-14-2011, 09:41 AM
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That's a fine cam for a daily driver, BUT I would look into a good set of headers and a good single 3" exhaust first, exhaust is the first place to do upgrades on those older cars. 1 5/8" long tube headers would be well suited, and then consider a cam.

BTW, if properly retuned you'll see a slight bump in mileage too (not a huge gain but about 5%)
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Old 09-14-2011, 09:49 AM
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I'll probably inprove a lot of things later including the exhaust. I understand improving the exhaust makes a big difference on these cars.

But I had to rebuild the engine and, you know, while you're there.
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Old 09-14-2011, 09:56 AM
How fast is fast enough?
 
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Quote:
Originally Posted by TNshadetree
I'll probably inprove a lot of things later including the exhaust. I understand improving the exhaust makes a big difference on these cars.

But I had to rebuild the engine and, you know, while you're there.

The cam you're looking at is fine for a daily driver, the idle will change slightly but nothing of real significance.
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Old 09-14-2011, 11:22 AM
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If your really concerned about keeping your idle about the same, and you plan to upgrade the exhaust later(remove cat converter) (add headers/true duals) I would shorten the exhaust duration to the same as the intake 210* IMO. I put a 350 in mine with a Comp HE260 (212*@0.050 in&ex) and its allot more "lumpy" than the stock almost silent "HO"305 ever was.
Then again I have tri-y headers and 2-1/2" dual exhaust with sonic turbos.
I just can't help but think that a 305 will act like its got a lot bigger cam.
Don't get me wrong. I'm not saying it won't run. But if you want an idle as smooth as a baby's butt, you better back off IMO.
ssmonty
PS If you go with the comp cam you might want to go with their springs too.
Even on a short duration like that with the stock springs I wouldn't be surprised if they bounced at 4500rpm.IMO

Last edited by ssmonty; 09-14-2011 at 11:27 AM.
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Old 09-14-2011, 08:47 PM
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Quote:
Originally Posted by TNshadetree
I am rebuilding a 85 Monte Carlo SS motor and it is remaining essentially stock with air injection removed. I'm considering using the Comp XE254 with 210/218 duration and 111 lobe seperation. I'm wanting to add a little more power capability while I'm in the engine, but don't want much effect on the idle. Not looking to create a ton more power, but I can't help but want to improve some over factory while I'm in the engine. I know I could go the 204/214 route and be sure there's no idle change, but that is only a couple degrees differnet than the 202/212 it had from the factory.

So will the 210/218 duration cause me any noticable change in idle? Or decrease the low end torque. The SS has a faily high rear end, 3.73 I believe.
If you are retaining use of the stock ECM, be VERY careful! A relatively small change in engine vacuum can throw things off and require a chip change to allow the cam to work.

BTW, the 3.73 rear end would be said to be fairly low (high numerically). Not pickin', just sayin'
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Old 09-14-2011, 09:20 PM
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Try things like Aluminum driveshafts reducing rotational wt 6-9 lbs. SMOOTH ride.

Aluminum pullies, and if needed electric fan. Somebody said pullies help, not sure who.

Aluminum cross drilled brake drums. That is reducing 20lbs of rotating weight, it is lots. Impresive braking performance and low heat fade.
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Old 09-14-2011, 11:15 PM
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85 should have 3.73 gears i had a 86 and 88 do u have emision laws in wva we dont thank god i both had 5.0 the 88 was a roller cam thought but a edlbrock performer intake and 600 carb works great true dual exhaust i had 2 1/4 pipes and small tube headers the 88 ran 14.5 at 99 i did swap out the 200r for a th350 bad move for the hiway 3400 rpm at 70 and the closest drag strip was 2 hrs away but it was quicker but a few mods i should of done was a msd box a 2000rpm stall converter and 1.6 rockers and stronger valve springs
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Old 09-16-2011, 08:02 AM
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Quote:
Originally Posted by cobalt327
If you are retaining use of the stock ECM, be VERY careful! A relatively small change in engine vacuum can throw things off and require a chip change to allow the cam to work.
True, too much duration can cause computer issues. But it isn't as tight as you think. I am currently running a Vortec headed 350 in the car using the GM Hot Cam 218/228 and the computer is actually very happy. I was nervous, but I don't have any codes coming up. My only issue is the ccc quadrajet could use some fattening of the idle circuit so it doesn't flat spot when coming up from idle. But I left the carb alone because I knew I was going to go back to the original motor eventually.
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Old 09-16-2011, 08:09 AM
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You are very fortunate. From Scoggin-Dickey's site:

LT4 Hot Cam can be used in any late model (1986 and newer) Small Block Chevrolet block for a significant horsepower gain at a reasonable price. This camshaft offer a slightly rough idle in most applications. Computer modifications are usually required, can be used in non computer controlled engines.
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