Series I Rockers 1.7 or 1.8? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 02-14-2006, 12:48 AM   #1
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Default Series I Rockers 1.7 or 1.8?

I will be ordering either 1.7 or 1.8:1needle/roller rocker sets for this series engine in a couple of days, and have them hand-carried back from down under.

I have two engines, both 1993, one is NA the other is SC. Without changing cams in either engine, which rockers would you choose and why? Here is more info:

I rebuilt the L27 and has been running strong for ~30,000Km. The 1993 supercharger bits will be removed from the donor L67 and mounted on the L27, along with the donor PCM etc. A 2.2" pulley will be run along with water methanol (above 70% throttle - I designed my own circuit to read TPS).

After this has been accomplished, a 94 SC and throttle body will then replace the 93' version (both SC'* have had the flashing removed with judiscious radiusing in the right places).

So...a set of these aftermarket rockers will be used on this combo to start. I just need to decide which with the help of you folks. I degreed #1 instake/exhasut on both engines, looks like with the OEM cam the 1.8'* will be close, but do-able.

The donor 93 SC engine will eventually be rebuilt with either a 4340 knock-off of the OEM crank, or possibly a 4.3 stroker kit. Then the SC bits would be put back on this powerplant and thrash it for a while...

Is anyone running larger rockers on Series I engines in North America...other thna DrJay?
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Old 02-14-2006, 12:56 AM   #2
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I would do neither.

Rockers only increase lift, and cost twice what a Cam costs. Cams increase duration and lift both.

If you're mechanically inclined, and not afraid to open the sucker up, do a cam.
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Old 02-14-2006, 12:59 AM   #3
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Default Re: Series I Rockers 1.7 or 1.8?

Quote:
Originally Posted by Sukhoi
I rebuilt the L27 and has been running strong for ~30,000Km. The 1993 supercharger bits will be removed from the donor L67 and mounted on the L27, along with the donor PCM etc.
Ummm....its not that easy...there are lots of different parts internally between the 2 engines
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Old 02-14-2006, 01:23 AM   #4
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Actually, there is little difference between the two engines. In fact the build sheets for both marques list precisely the same operational dimensions, clearances, and PN'* (I have have friends at GM, as well as their rebuild center).

I have rebuilt many GM engines over the years, this happens to be the 3rd Buick V6 (the others the original and a GN), so yes I agree a cam would be a more reasonable choice "along" with the benefits of roller rockers to reduce reciprocating loses..

However the L27 is already installed in a vehicle which would require dropping the front clip in order the access the cam, something I am not willing to do at this point. It will be simpler to remove the NA induction system and replace with the SC components, pull out the existing PCM and replace (plus a few more electo-mechanical anomalies).

So given that the recipient engine will be receiving a fine set of aftermarket rockers, which would you choose...the 1.7'* or 1.8'*?

Thanks in advance for the advice...
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Old 02-14-2006, 01:51 AM   #5
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First the pistons are not the same... The SC pistons are hardened from the 2nd ring land groove on up... As well they are 8.5 : 1 compression and there is a diffrence in the way the wrist pins is set up in an L67 as compared to an L27 and if memory serves there are diffrent rod PN'*... The blocks, crank and heads are the same...

There were also some change in size / depth of the dish in the L27 piston and in some cases the L27 may actually be 9.0 : 1 compression ... As well there are some diffrences in the 2.97 SC trans as compared to the 2.84 or 3.06 trans... I think the TC and the Case for the 2.97 is beefed up a bit to handle the added stress...

And as far as I know the only rockers made for a series I is a 1.7..

The 1.8 and 1.9 are for the series II engines as well as series III ...


Have fun and keep us up to date with the pics


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Old 02-14-2006, 03:02 AM   #6
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You have correctly pointed most of the differences within the engine confines, however where it counts...it will accept the L67 SC parts. Indeed my L27 is 8.5:1 compression. The two transmissions share the same PN, at least in my case.

Along with the 1.7:1 ratio currently available, the 1.8'* for series I are now finished.

Should be interesting....it'* in a Lumina APV

So far: Bilstein custom valved F/R struts (Z06), Hotchkiss bars, machined Delrin/Polyurethane endlinks throughout, StopTech crossdrilled discs..front "and" back, modified/lowered coils, solid link panhard rod, steel braided brake lines, cowl induction, ported front to back, reground OEM cam, 40 over, balanced, 5-angle grind, radiused/chamferred magnafluxed, windage tray/baffled pan, 2.5" Borla 350Z exhaust system

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Old 02-14-2006, 03:18 AM   #7
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Here are the 1.8:1'*...
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Old 02-14-2006, 09:22 AM   #8
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Changing the cam does not require dropping the front clip. The cam can be changed through the RF wheelwell. At least on a Bonneville. Can't tell you about the purple people mover.
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Old 02-14-2006, 09:52 AM   #9
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Seems to me that the motor may sit low enough in the van to accomodate the wheel well access as well.
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Old 02-14-2006, 10:38 AM   #10
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