Alright...another SI vs SII question... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-17-2005, 10:45 PM   #1
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Default Alright...another SI vs SII question...

Alright so i've heard all kindsa **** is different from SI and SII engines...Are the piston sizes even the same? I'm curious if the whole upper part of the engine is swappable from a Series II onto a Series one..like heads...lower/upper manifolds, etc. Like SII mani/heads onto an SI engine. Plausibe? I just don't know the dif in sizes of pistons/combustion chambers
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Old 04-17-2005, 10:58 PM   #2
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The bore is still 231cubic inch, or 3800 CC'*. The compression ratios differ. Check the Techinfo link above, Specifications. There'* some information there. Also run some part numbers through www.gmpartsdirect.com

Ultimately, you'll be better off just swapping in a S2 for all that trouble, but for the car you're talking about, I'd do the 93 L67 with it'* fantastic PCM and Full OBD1. You can get chips for it, too. 93 was the first year of the upgraded valvetrain, and the last year for the PCM 'flash' feature.
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Old 04-18-2005, 02:16 AM   #3
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BonnedGP I am currently looking at the SII topend onto the SI block issie as we speak and will be dedicating a day to experimenting on a few SI and II 3800 in the Jyard, I will also be bringing all my micrometers and CC'ing equipment as one of the things I am curious about is the SII combustion chamber volume compared to the SI.
with the SII having less of a dish on the pistons, I am guessing that the SII head chambers may be larger which would be perfect for us as the 3800 SI engine in the rear of our 94 olds cutlass 442 project will be getting Turbocharged...

I will be doing a full writup of what we find at the Jyard, and post specs and pics that can be added to techinfo when everything is all said and done.

It'* all a matter of some research....

I will be posting more as I find out at this thread:

http://www.bonnevilleclub.com/forum/...ic.php?t=33178

James
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Old 04-18-2005, 02:25 AM   #4
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Quote:
Originally Posted by willwren
The bore is still 231cubic inch, or 3800 CC'*. The compression ratios differ. Check the Techinfo link above, Specifications. There'* some information there. Also run some part numbers through www.gmpartsdirect.com
Not all 231CI engines will have the same Bore. Here are some 93 L27 pistons specs (as per Factory service manual) These are just abot the diameter, it still doesnt' mean you can get a pin/piston setup that will work between SII and SI parts (rods, pistons).

Cyl Specs = 96.5mm (3.8 inches)
Out of round (Max) = .010mm
Taper = (.0013mm/.0005 inches)
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Old 04-18-2005, 10:03 PM   #5
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The bore should be the same, Series I and Series II, but there is a substantial difference in compression height due to the lower deck on the later model. Vin "L" pistons can be fitted to the Vin "C" engine for more compression ratio. The piston will be approximately flush to .005" above with the stock deck height on the Vin "C". The "L" pistons use a slightly thinner ring set too. When I cc'd my "C" engine heads, they were all approx. 38-39 cc'*. I don't know what the Series II heads might be. I did port my heads but unfortunately I hadn't built my flow bench to see what the effect was, plus or minus. They certainly looked better. The engine could use more cam to wake it up, particularly the upper rpm range. The stocker has essentially no overlap and substantially less than 200 degrees duration @ .050". It'* works very well for a clean running engine and good low end torque but has no top end. These are the specs I got when I degree'd the stock '90 cam: Intake open 20.5* ATDC, close 27.5* ABDC, Exhaust open 30* BBDC, close 26* BTDC. All readings @ .050" lobe lift. Intake lobe lift .250" and exhaust .255". I hope this info helps.
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Old 04-18-2005, 10:06 PM   #6
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2seater- that definately helps, as i planned on getting a cam for this engine as well, so that definately helps! Thanks!
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