LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Alternating Roller Rocker Ratios

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Old 03-31-2008 | 09:04 PM
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Originally Posted by Ken95Z28
I have 1.65 on the intake and 1.5 on the exhaust. Times in signature. No since of opening the exhaust valve any more then you have to. Not to mention by opening the exhaust valve more you are running risk of bring the valve closer to the piston on the exhaust stroke.
Car car thinks differently then yours It LIKES .608 lift and picked up TQ through the entire range.
Old 04-01-2008 | 11:35 AM
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when i bought my cam i was told to at least put 1.6's on the intake side
Old 04-01-2008 | 08:10 PM
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I've done tons of R&D on this and the LT1 loves exhaust. I picked up over a tenth and 2 mph going from 1.6s to 1.7s. BUT, now that Comp Cams makes 1.8 rockers that fit the LT1, the playing field will be changed again.
I know plenty of guys that run GM847s on stock bottom end LT1s and that's ~.595 on the exhaust end. With 1.8s on a stock cam the lift will be .536/.551so no worries on the piston-to-valve clearance. That's awesome and only have to remove the valve covers to do it and not spend an entire weekend in the garage.
Old 04-01-2008 | 09:36 PM
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^ Or you could have just gotten a cam ground that way to begin with. I agree with who ever said it before. Alternating rocker ratios is simply a tuning tool or a patch for a previous mistake.
Old 04-02-2008 | 12:52 AM
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Originally Posted by Beaflag VonRathburg
^ Or you could have just gotten a cam ground that way to begin with. I agree with who ever said it before. Alternating rocker ratios is simply a tuning tool or a patch for a previous mistake.
basically, yeah.
Old 04-02-2008 | 02:20 AM
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If it adds power in itself, then how is it ONLY a tuning tool? Obviously if it makes you lose power or retain the same then it's pointless, but if you found it to work would you take them out? I wouldn't.

They actually do this same thing in the 3800 Series II motors... the N/A ones.
Old 04-02-2008 | 01:22 PM
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where might i find these 1.8's you speak about?
Old 04-02-2008 | 03:40 PM
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I would just go with 1.6s all-around and you'll gain a few HP.

WD
Old 04-02-2008 | 10:04 PM
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When I can I have it cut into the shaft along with the correct ICL.


NASCAR is running 2.0-2.3 ratio's. they don not have to move the lifter as far in the bore
Old 04-03-2008 | 05:22 AM
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Originally Posted by Formula96
where might i find these 1.8's you speak about?
Just google Comp Cams 1.8 rockers for SBC/LT1 and you should get the correct results.
Old 04-03-2008 | 05:28 AM
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Originally Posted by Beaflag VonRathburg
^ Or you could have just gotten a cam ground that way to begin with. I agree with who ever said it before. Alternating rocker ratios is simply a tuning tool or a patch for a previous mistake.


Yeah, if I wasn't running bolt ons only. So, a custom grind cam is out of the
question. Alternating rockers is a method to obtain more horsepower, especially for us bolt on guys who are looking for every .0002 horsepower we can find.
Old 04-03-2008 | 12:49 PM
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Why not do 1.6/1.7 or 1.7/1.7 for me this seems like a better way to do since I dont want to tear into my motor now and prefer to build a specific setup when a rebuild is needed.
Old 04-03-2008 | 01:03 PM
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Would it be wise to put 1.6's all around in the car on a stock cam while I wait and save for a new cam?
Old 04-04-2008 | 07:16 PM
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Originally Posted by Skidd
Why not do 1.6/1.7 or 1.7/1.7 for me this seems like a better way to do since I dont want to tear into my motor now and prefer to build a specific setup when a rebuild is needed.
Exactly. I believe in getting every single hp I can out of the car. Going bolt ons is easy on the budget, allows you to do alot of R&D, and keeps the car easily streetable. It feels good to run above average ETs and know that it didn't cost you a fortune.
Old 04-04-2008 | 10:27 PM
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Originally Posted by LT14LIFE JT
Has anyone tried installing alternating roller rockers with 2 different ratios on their LT1? Meaning like

1.6s on intake and 1.5s on exhaust or
1.5s on intake and 1.6s on exhaust or
1.7s on intake and 1.6s on exhaust or
1.6s on intake and 1.7s on exhaust

Well, you get the idea. If anyone has tried this please post gains or loses in power, ET, etc. Thanks
i run tpis's zz-9 cam(212/226-483/520 112lsa)and use 1.6 intake 1.5 exaust and love it
Old 04-05-2008 | 09:17 AM
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Originally Posted by LT14LIFE JT
I've done tons of R&D on this and the LT1 loves exhaust. I picked up over a tenth and 2 mph going from 1.6s to 1.7s. BUT, now that Comp Cams makes 1.8 rockers that fit the LT1, the playing field will be changed again.
I know plenty of guys that run GM847s on stock bottom end LT1s and that's ~.595 on the exhaust end. With 1.8s on a stock cam the lift will be .536/.551so no worries on the piston-to-valve clearance. That's awesome and only have to remove the valve covers to do it and not spend an entire weekend in the garage.
how much is too much? the higher the ratio the higher the stress on the valve train right? what do you guys think an LT1 can handle w/o running into longevity problems? I realize every lil bit helps if your going the bolt-on only route but im getting cammed soon so basically what ratio should I draw the line at? dang nascar uses some giant RR's but their engines get rebuilt on a regular basis.
Old 04-05-2008 | 03:50 PM
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Originally Posted by z_speedfreak
how much is too much? the higher the ratio the higher the stress on the valve train right? what do you guys think an LT1 can handle w/o running into longevity problems? I realize every lil bit helps if your going the bolt-on only route but im getting cammed soon so basically what ratio should I draw the line at? dang nascar uses some giant RR's but their engines get rebuilt on a regular basis.
I've talked to engine builders and the higher ratio does stress the geometry. BUT, all internal moving engine parts are prone to stress and valve guides will wear quicker along with other valvetrain components, but I look at the big picture. I have no $3000+ forged bottom end, no $2000+ aftermarket ported heads, and no $300+ custom grind cam. So I'm not putting strain in anything but a stock engine. So, it won't hurt as much if/when it needs attention.
Old 04-05-2008 | 04:02 PM
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Originally Posted by gotjuice?
i run tpis's zz-9 cam(212/226-483/520 112lsa)and use 1.6 intake 1.5 exaust and love it
Got any video footage of it idling? With that staggering you will have a .515 intake lift and the exhuast remains at .520, so .515/.520 on a 112. That's tighter LSA than a hot cam, but less lift, and different duration. Good choice.
Old 04-05-2008 | 04:10 PM
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Im considering it. It has to be worth something if you change the springs and run the 1.7 or possibly even the 1.8's the only question I have is changing pushrod length. .536/.551 with the 1.8 does sound good to me no need for changing the cam and getting into the lift area I would like to be in. So and opinions?
Old 04-06-2008 | 11:50 AM
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Originally Posted by Skidd
Im considering it. It has to be worth something if you change the springs and run the 1.7 or possibly even the 1.8's the only question I have is changing pushrod length. .536/.551 with the 1.8 does sound good to me no need for changing the cam and getting into the lift area I would like to be in. So and opinions?
I'll be doing R&D on the 1.8s very soon. I know the engine will benefit from the extra lift, but I will want to change the lift and run 1.7int/1.8exh(.507/.551). I think(hope) it will benefit more from the increased exhaust lift.


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