OK fer the fellow psychotic gearheads out there....
The rear 90 3800 LN3 Vin C engine in our twin engine 94 Olds Cutlass 442 will be getting Turbocharged this winter and get a Mega Squirt EFI setup (90 non PCM controlled trans) and we have already swapped to the Delco ignition, there are plans for an intercooler to be plumbed into the mix to feed a TB located on the belt side of the engine for better plumbing.
One of my goals is to swap the SII cam, heads, intake onto the SI 3800, and have the specific modifications required to make this Hybrid, available to anyone else who might be interested in getting more power from their SI 3800.
All references to SI are taken from a 90 Vin C 3800 and all SII are in reference to a 95 Vin K 3800 engine, these may also correlate to other SI and SII engine years.
SI & SII 3800 differences/similarities: They seem to have the same bolt pattern on the ends of the heads, but different accessory mounts, this would allow the use of the SI accessory’s and belt drive with the SII heads. The 90 LN3 block (all SI) has a taller deck height which with using the series II Lower intake manifold will require spacers with the SII heads on the SI block. The different looking coolant bosses from the block into the heads is not a big deal, the head gaskets will still seal them... at least the SII V6 isn’t reverse flow and have the massive differences like the Gen I (regular) small block Chevy V8 vs. LT1/LS1 Gen II/III V8’s though more than a couple of people have put LT1 heads on the Gen I SBC with just a couple of modifications. Here is a side by side comparison of the SI and SII block surfaces.
The camshaft lifters are hydraulic roller for both engines but the series II has shorter pushrods for its lower deck height, there is a possibility the stock LN3 pushrods will work with the SII heads, but custom length pushrods are not expensive, if they are required. The valve arrangement is different between the SI and SII, i.e. the cam lobe timing events are tailored for the I-E-I-E-I-E valve positions of the SII and not the E-I-I-E-I-E of the LN3, this is one of the only things that I have found different between the cams. The other major change concerns the balance shaft bearings, the sleeve bearings (SII) that got changed from roller bearings (SI) on the balance shaft. The SI & SII cams have identical bearing journal spacing as well as the lobes, so they would line up correctly with the lifter bores. In one manual I found that there are differences in the SI and SII bearing journal diameters, but it also states that it is 97 and later SII that has the larger diameter, whether or not this is the case still remains to be seen.
Series I:
Camshaft Journal Diameter = 1.785-1.786 in
Bearing-to-Journal Clearance = 0.0005-0.0025 in
Series II:
Journal Diameter = 1.8462-1.8448 in
Bearing-to-Journal Clearance = 0.0016-0.0047 in
If this is the case, then it would require the early SII cam to slide into the SI cam bearings or the later SII cam would have to be chucked in a Lathe and cut the journals down and polish them to the correct diameter for proper bearing clearances. The other difference between the SI & SII cams is the snout and timing chain differences. The SI cam (in the 2 SI blocks I have looked at) uses a flange on the front of the cam to keep it from walking back in the block and uses a cam button on a spring to keep it from walking forward into the T chain cover. This pic is of a non balance shaft equipped SI.
The SII cam however (has no front flange and can slid back and forth no problem) slips into the block and has a flat retainer/thrust plate that bolts on with two flush head torx bolts, this keeps the cam from being able to walk forward in the block.
Then after the plate the balance shaft gear slips over the snout of the cam with the cam Timing chain gear going on right after and tightened with a single bolt, and with the Thrust plate behind the balance shaft gear/T chain gear this prevents the cam from walking backward in the block. And yes the SI and SII do have the same cam journal diameters if it's a 95 (and some/all 96?) SII blocks then the cam bearing part #'s change... to the larger ones....no wonder my manual said that the 97+ have the larger cam bearing journal diameters-and this is also shown by the 95 and 96 SII blocks using the same part # cam bearings as the SI blocks. The Cam specs are as follows for a 90 Vin C 3800 duration at .050 is 188 deg on the intake and 191 deg on the exhaust with the lobe separation angle of 114 degrees (no valve lift #’s found-yet). The 95 Vin K SII cam specs out at 180 deg intake and 191 degrees on the exhaust at .050, and the lobe separation of 115 degree’s, the SII cam also lists valve lift at .411/.408, on the intake/exhaust valves respectively.
The other difference that I can see is that the pushrods will have more of a tilt to them than the SI pushrods when the SII heads are placed on the SI block but this shouldn’t be a problem as plenty of engines have been designed with pushrods that are not directly in line with the axis of the lifter bore, the only side effect would be a little more thrust loading on the lifter to bore surface. Did you know the SI and SII use the same lifters? Same part #’s! The pushrods on the SI are 7.965 inches in overall length where the SII pushrods are 6.959 inches in length. This would seem to indicate that the shorter deck height is approx 1 inch on the SII block (presumably for a smaller engine package that will fit into smaller engine bays) but I have yet to verify this through specs or through measurements. This hybrid engine may still require custom length pushrods for proper lifter preload and valvetrain geometry
The SII exhaust manifolds would have to be used with the SII heads, however it seems possible that the SI tubular log manifolds can be cut and modified to fit the SII head, however with the plethora of aftermarket SII headers this wouldn’t be necessary, though the X-over pipe would be a little longer due to the SI blocks taller deck height. Here are pics of the SII front (cast) and rear (tube steel) exhaust manifolds.
SI front manifold made of tubular steel
The pistons in the SI are listed as having two 1.5 mm and one 3 mm ring grooves with a 1.377 compression height rated at 8.5 to 1 Compression ratio with a dish of .260 inch deep x 3.050 inches in diameter. The SII pistons spec out as having, one 1.2 mm, one 1.5 mm, and one 2 mm ring grooves, with a 1.090 inch compression height and having a dish of .050 inch deep x 2.9 inch diameter.
Now for the cylinder heads, the primary difference between the SI and SII heads are the intake and exhaust valve and port locations/order, with the SI head having a EIIEIE arrangement and the SII having a “symmetrical portâ€
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Psychotic Gearhead/Redneck/Mekanik
94 Olds 442 Twin engine's! 6.9L/425 cu inches and 12 cylinders!
13.81 @ over 98 MPH! consistent 1.9s 60'!
