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Old 08-02-2004, 10:37 AM
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Which cam?

I have a zz4 shortblock and fastburn aluminum heads. A friend a mine sold me his GM Hot cam and 1.6 roller rockers. I think they are 525 lift and 218/228 duration. Will this cam give lopey idle sound? I would appreciate any suggestions whether to use this cam or sell it & buy something a little bigger. Also I am using a th350 with 2400 stall speed and 3.73 gears. Thanks

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Old 08-02-2004, 01:20 PM
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two questions:

1. why do you want a lopey idle

2. have you tried searching the forum
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Old 08-02-2004, 03:33 PM
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Yes, it will give you a lopey idle, and if this is going to be a regular street driven car I wouldn't believe on going any bigger. That is a very healthy cam for a 350 especially since your putting 1.6 rockers on it which will give you a .560 lift
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Old 08-02-2004, 06:20 PM
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THANKS! ARE YOU SURE ABOUT THE 560 LIFT. I WAS TOLD 525 AND WAS WAS NOT CLEAR IF THAT IS WITH OR WITHOUT THE 1.6 ROCKERS.
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Old 08-02-2004, 07:59 PM
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You will need to check with the guy you bought it from to determine if he was telling you the cam lift already figured with 1.6 rockers. If not then,

Here's how to figure that:

Divide the lift by 1.5 then multiply the sum by 1.6
.525 / 1.5=.350 X 1.6=.560

Here's a website that deals with some cam basics:
http://www.chevytalk.com/tech/101/Cam_Theory.html

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Old 08-03-2004, 12:16 AM
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The Hot cam is .492 with 1.5 rockers, .525 w/1.6. I heard a Hot-cammed 350 last year & it was slightly lopey, but only slightly.
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Old 08-03-2004, 12:31 AM
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First and foremost, that cam you described will barely lope at all. With proper carb tuning only a hot rodder will know you have a performance cam. How much lope you will get depends on your compression ratio. The higher the ratio the less lope.

You will start noticing a difference in idle quality at around 220 @ .050". At 230o the idle rhythm it gets to where it will lose it's pattern every few seconds. At 240o you get into some serious lope.

These are extremely rough estimates. Lobe separation, compression, initial timing, and duration will change the lope, along with other factors. Lift however is not one of them. Lift does not change idle quality, it only increases efficiency.
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Old 08-03-2004, 12:35 AM
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actually, overlap is what gives the lope, correct?
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Old 08-03-2004, 11:53 AM
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it's a combination of LSA and duration that will give you lope. Check out what the manufacturer has to say about it.

refer to previous posts also:

Hotrodders Post

also try searching for "choppy idle" "rough idle" and you should pull up some useful results.

cheers

tbw
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Old 08-03-2004, 02:16 PM
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I would think that the comp xe274h would give you the sound and performance you are looking for. Although I have seen that hot cam do pretty well for its size, I think you would be happier with the 274 because of the sound. overall performance would probably be similar between the two.

Adam
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