Series 1 L67 - two different LIMs? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-13-2008, 02:24 PM   #11
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It fooled us for a bit. My 93 came non-walled too.

All 93'* have the digital (old style) EGR and non-roller pivot rockers. 93 L27'* got the rollers though.
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Old 01-13-2008, 02:27 PM   #12
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Quote:
Originally Posted by willwren
It fooled us for a bit. My 93 came non-walled too.

All 93'* have the digital (old style) EGR and non-roller pivot rockers. 93 L27'* got the rollers though.
so will 93-95 L27 and 94-95 L67s all come with roller rockers? how much of a difference in performance would that be over the 92-93 rockers?
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Old 01-13-2008, 02:29 PM   #13
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Yes, 93/94 L27 and 94/95 L67 have rollers. They are a direct swap to 93 L67'*, but NOT 92 L67'* without a cylinder head swap.

Performance? No more than 5hp. If that.
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Old 01-13-2008, 02:48 PM   #14
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Will, are the L27 rockers the same ratio as the L67? I know of a couple scrapped L27s I could steal rockers off of, but no 94/95 L67.
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Old 01-13-2008, 03:01 PM   #15
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I believe the rollers to be more of a longevity and noise reduction move on GMs part. The added HP is a byproduct.

But here is a question for the masses, and it'* a viable one. For the sake of arguement, lets take 2 L67s S1s. Everything between the two are the same, except that one has type "A" intake manifold, and the other type "B". Now then, would GM have created a new PCM instruction set for the new-style intake?

Here is why I ask: The HP/Torque ratings for all of 1993 stayed the same, regardless of the manifold. So, using that logic, no engine is better than the other, performance-wise. Experience tells us that a taller intake *should* net a slightly stronger low-end torque (which, as stated, the walled intake is a tad taller). The walls *should* also provide a straighter path for air to flow into the head, which should increase torque again, and a slight advantage in fuel efficiency. One would think GM would have further exploited that design through modifiying the PCM'* program.

And I haven't seen any S2 L67 LIMs, so I ask the question "Are those intakes walled too?"

Quote:
Originally Posted by Drunken Sailor
Will, are the L27 rockers the same ratio as the L67? I know of a couple scrapped L27s I could steal rockers off of, but no 94/95 L67.
Yes, they are the same ratio. Amazingly, the valvetrains between the two are identical. Same lifters, valves, springs, pushrods, and arms.
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Old 01-13-2008, 03:26 PM   #16
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Keep in mind that rocker bolts are not re-usable. This will require new bolts if you intend to swap.

S2 L67 (both L67 and L32) are non-walled.

The walls in effect create a longer runner, and while they may provide a 'straighter' path, they also provide more of a restriction for the air to enter them to begin with.

I'd personally be very surprised if GM wasted their time in optimizing a PCM for something like this. They sure didn't waste their time cleaning up the ugly L36 LIM.
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Old 01-13-2008, 05:48 PM   #17
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To me it almost looks like the walls hold up the "ceiling" of the 94+ LIM, if you will. Maybe they're a structure/strength thing?
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Old 01-13-2008, 06:03 PM   #18
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As stated before, no. They're very liikely acoustic. There are no strength issues with the non-walled LIM'*. The threaded bosses for the SC attachement are fully reinforced and supported. There have been no issues with a LIM failing either, and the S2 doesn't have them.
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Old 01-13-2008, 08:38 PM   #19
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Good point. I forgot about the Series 2 not having them. Will, do you have both styles? Is there really any acoustic difference? It seems like needless expense for GM to redesign something like this.
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Old 01-13-2008, 10:50 PM   #20
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I have both types. Several of each. My SLE was walled originally, but now has the Zilla'* hand-me-down non-walled, while the Zilla has another version ported for the ported heads.

I never paid much attention to the noise at idle between the two, but the SLE may have been slightly quieter originally.
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