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Old 10-23-2001, 05:12 PM   #1
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LT4 hot cam & advance/retard install

Hey guys.
I have decided to get a LT4 hot cam to go with my AFR 190s and my SuperRam on my new 357. My question is what are you finding to be the best way to install these cams? Straight up, or advanced.
It seems to me that straight up would work fine. Let me know what works and what doesn't.

------------------
'88 RS (originally 2.8)
-350, .040 over, vette alum. L98s, stock tpi.
-305 injectors & chip
-TES headers & edelbrock cat back
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Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
on a 2.050 60 ft.
(Damn the 2.8!)
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Old 10-23-2001, 11:54 PM   #2
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probably straight up is the most common install.
Advancing and retarding the cam can move the power band up or down a few hundred rpm. Advance for more bottom end and retard for more top end. It usually takes about a 4-degree change for a driver to feel it. When making these changes, increases at one end mean decreases at the other end.
Some thoughts on choosing the proper cam.
1. Longer rod engines seem to prefer shorter durations and wider lobe separation.
2. Short duration cams with wider lobe separations usually yield much flatter torque curves.
3. Longer duration cams require tighter lobe separation to have any mid-range power.
4. Stock exhaust manifolds or a highly restricted exhaust usually respond well to shorter exhaust duration and wider lobe separation
5. Most unported heads approach 85 or 95 % of peak flow at .400 to .450 lift and do not need or want a maximum valve lift over .540 to.555. Often a low cam lift with 1.65 or 1.7 ratio rockers is very helpful on the intake side as long as lift is kept to about .550. Exhaust is less critical with 1.5 or 1.55 being the most popular.
6. Dyno testing doesn't test drivability or throttle response of the engine.
7. The important numbers on a dyno sheet are about a thousand RPM above and below peak torque and peak horsepower. Peak numbers are for bragging purposes and high peak numbers do not win races.
8. The benefit of high ratio rockers is faster valve movement and the added lift is frequently detrimental in unported heads. It often helps to utilize a lower cam lift with high ratio rockers.
airdeano
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Old 10-24-2001, 02:13 AM   #3
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Mine is installed straight up.....

------------------
1987 GTA L98 MD8
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Old 10-24-2001, 09:23 AM   #4
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Mine is straight up. Haven't tried any other way.
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Old 10-24-2001, 10:25 AM   #5
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thanx guys. straight up is what i was leaning towards.
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Old 10-25-2001, 07:08 PM   #6
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In your car with those heads and SuperRam, straight up is the way to go. But I installed mine 2 advanced because I have the LTR's still, and the cam's peak is higher than the runner's peak. Installing it advanced helps to bring the power band of the cam down a little, and gives it a touch more vacuum, both good things for a speed density LTR TPI.

------------------
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Old 10-26-2001, 08:09 AM   #7
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Get that cam in and get some times for me!
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Old 10-26-2001, 08:29 AM   #8
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I just got my new cam. The specs are similer to the LT4 and in the directions it said my cam was already advanced for more midrange and low end TQ. The specs on my cam are 218/224 496/502 112 lsa. With it already being advanced it should work well with my LTR setup.
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Old 10-26-2001, 11:29 AM   #9
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Which cam did you get?

Bob
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Old 10-26-2001, 11:35 AM   #10
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Most cams that i am familiar with already come with 4 degrees advanced ground into them. On my 81 Z with my 383, Dart heads, RPM intake, Holley Street Avenger 770cfm, 4:10, 2800 stall in a TH350 would only hit 13.6's on the track because it couldn't pull any mph. I had the cam installed 4 deg advanced on the timing chain. I took it apart & re-installed it stright up. Went 13.400 and picked up 3 mph. Something you should consider. Know your cam before you install it.

Hope this helps
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Old 10-26-2001, 11:46 AM   #11
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I got the Comp XR269HR
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Old 10-26-2001, 03:13 PM   #12
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when i installed it into the car t was straght up,however i feel i should have put it 1.5-2 degrees adv. with that intake setup.with the superram straight up is where you'd want it.

------------------
87 trans am,gm crate 350(4 bolt mains 10to1),L98 aluminum heads,LT4 hot cam,slp runners,slp 1 5/8 headers,3in.y-pipe,edelbrock base,hi flo cat,air foil,afpr,as&m ported plenum,gutted airbox,t-5 tranny w/centerforce clutch and a 3.27 9bolt(11.9in. brakes),ed wright's fastchip,relocated iat sensor,160 fan switch&t-stat,tb bypass,accel supercoil,cap& rotor,slp 3in. catbcak,a/c delete.

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Old 10-26-2001, 06:27 PM   #13
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OK good deal, sounds like a majority winner. My last Comp cam was ground with 4 degrees advance also, it went in straight up with the stock intake.
Do you guys know if the hot cam has advance already ground into it?

[This message has been edited by '87FAKE-IROC-Z (edited October 26, 2001).]
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Old 10-27-2001, 12:05 PM   #14
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I bought my hot cam used, and when I degreed it, it turned out to be 3 degrees retarded! I was shocked, and measured it twice to be sure. I put in a 4 degree advance key to bring it back.
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Old 10-27-2001, 12:05 PM
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