Gen I and Gen II engines with a one-piece rear main seal and matching crank use a single, one-piece oil pan gasket. These are also now available for earlier blocks as well.
To help seal the first-generation small-block oil pans, Chevrolet Performance offers these oil pan rails that help spread the torque of the bolts over the mounting area.
Recommended Bolt Torque
If the engine is going into a vehicle that has an oxygen sensor in the exhaust system, use sealants that are oxygen sensor safe. Some of the sealants on the market produce gases while curing that can damage the oxygen sensor.
Fasteners
Each bolt and stud manufacturer, whether it is from Chevrolet or an aftermarket company specializing in fasteners, has a recommended torque value or stretch value for each type of fastener. Follow the manufacturer’s recommendation for the proper amount of torque or stretch required for the bolt or stud. Also, each fastener type, depending on its application, requires some type of lubricant on the threads in order to achieve the proper torque or stretch amounts. This lubricant could be sealants, oils, anti-seize, or some form of moly-based lubricant. Follow the recommendations.
Each fastener that is torqued must be drawn up to its recommended torque value in stages and in the proper bolt-torquing sequence. This is especially important when tightening main cap fasteners, head fasteners, and rod bolts. Follow the recommendations, take your time, and double-check your work.
Of equal importance is that every fastener must be clean. Clean the threads and holes in the block and remove any rust, corrosion, and old sealants. If a threaded hole is damaged, it needs to be repaired; the threads on a fastener must be spotless as well. Make sure that the fastener threads are not damaged or stripped.
Like many gaskets, if you cannot find a specific fastener from Chevrolet any more, chances are that one of the aftermarket fastener companies such as ARP or Milodon will have what you need.
Main Cap Bolts and Studs
Small-journal Gen I blocks used a different length main cap bolt than later medium- and large-journal Gen I blocks, which were about 1/4 inch longer. Use the correct bolts or aftermarket studs. Also, the main cap bolt spacing is different between the small, medium, and large journal blocks, and so the main caps are not interchangeable between the small, medium, and large journal (400) blocks.
The production main cap bolts used by Chevrolet work just fine in all street applications and you don’t need to use a stud kit in a stock or street performance engine. Stud kits offer the advantage of reducing the amount of wear and tear on block threads, if you are frequently tearing the motor down. Some race situations can benefit by using a stud kit, especially if you are using a two-bolt block. A main cap stud kit adds strength to the bottom end of the two-bolt block. In large nitrous, supercharger, or turbocharger, high-RPM and high-power applications, a four-bolt block with a stud kit can help. Nodular-iron caps are stronger than the production gray iron caps, and steel caps are stronger still. Also, a splayed main cap offers more strength than a straight main cap.
A four-bolt production block uses 10 inner main cap bolts (PN 3932480) and 6 shorter outer bolts (PN 3877669). Chevy Performance offers a Main Bearing Bolt Kit for its Sportsman Blocks as PN 12480108. These bolts are Grade-8 with 12-point heads and an oxide coating.
If you have a small main journal (2.30 inches) two-bolt block, you can use windage tray mounting studs in five of the main cap bolt positions. This stud (PN 3872718) is 51/4 inches long. A similar windage tray stud for use with 2.45 main journal blocks is PN 14087508. These studs are 5⅝ inches long and can be used with two-bolt blocks or as the inner studs on a four-bolt block.
Four-bolt blocks with straight main caps not using a windage tray can use the 7/16-inch main cap stud kit (PN 10185033). PN 14011001 stud is used in the inner position and PN 14011002 in the outer stud position. These outer studs should not be used on splayed main bearing caps. PN 10046007 is a mounting bolt for the oil pump, which has a stud portion that holds the rear edge of a windage tray. Use a hardened steel flat 7/16-inch stud washer (PN 14087508) with 12-point 7/16-inch x 20 nut (PN 3942410) or 6-point 7/16-inch x 20 nut (PN 3942410).
Two main cap stud kits are offered for four-bolt blocks. PN 14011039 has all of the studs required for one block with straight main caps but does not include the washers and nuts.
Main stud kit PN 10185033 includes the washers and nuts and has 10 (7/16-inch) inner studs, 14 (7/16-inch) outboard studs, and 4 (3/8-inch) outboard studs, all of which are made from 4340 steel.
Cylinder Head Bolts and Stud Kits
Cylinder head/block deck dowel pins are used to help position the head on the block. These dowel pins are 5/16 x 9/16-inch (PN 585927). Offset dowel pins (available from aftermarket suppliers) are sometimes used by experienced engine builders and machinists to relocate the combustion chambers on the head in relation to the cylinder barrels.
Gen I production small-blocks use three different length head bolts to secure the cylinder heads to the blocks. Long head bolts (PN 10168525) are 7/16-14 x 3.75 inches. You need 14 of these. The medium-length bolts (PN 10168526) are 7/16-14 x 3.00 inches. Four are required per motor. The bottom row of short head bolts use PN 10168527 and are 7/16-14 x 1.75 inches. Sixteen are used. A kit with all of the bolts is available as PN 12495499.
Aluminum D-port Corvette heads PN 10185086 and 10185087 (casting number 10088113) require different head bolts with flat washers under the bolt head to protect the aluminum surface of the heads. Use long bolt PN 10168525 (7/16-14 x 3¹³⁄₁₆ inches), medium-length bolt PN 10168526 (7/16-14 x 3¹⁄₁₆ inches), and short bolt PN 10168527 (7/17-14 x 1³⁄₄ inches). These bolts come with the correct flat washer.
A cylinder head stud kit is offered under PN 14014408 and can be used on conventional production cast-iron and aluminum raised runner Bowtie heads. This kit does not include flat washers or nuts. Short head studs are available individually as PN 14011035 (7/16-14 x 2.69 inches). Long-length head studs are PN 14011036 (7/16-14 x 4.73 inches). The medium-length studs are PN 14011037 (7/16-14 x 3.99 inches).
These head studs can be used with 1038 steel stud nut PN 3942410, which has six points and is 7/16-20, or the 12-point 4037 steel stud nut PN 14044866 (7/16-20). Both of these stud nuts are magnafluxed at the factory. Hardened steel flat washers are under PN 1005115, which has a 0.45-inch ID and 0.750-inch OD and should be used on Phase 6 Bowtie aluminum heads for clearance, or on other heads, you can use flat washer PN 14011040, which is 0.45-inch ID and 0.778-inch OD.
GM head stud kits are not made for the Bowtie 18-degree, 15-degree, splayed valve, or SB2 race heads. These must be obtained from aftermarket suppliers.
Something to consider when using head stud kits is that you may not be able to remove the cylinder heads from the engine once the engine is in your vehicle. Depending on the size of your engine compartment, firewall position, air conditioner, and heater box size and location, brake boosters, etc., you may not have enough room to slide the heads on or off the studs. You may have to remove the engine from the vehicle in order to get the heads off.
If you are using small-block heads on a race motor and these heads have been angle milled (which is quite common), remember to have the surfaces on the heads, where the head bolt holes are, spot faced to the correct angles to match the angle milling of the head deck surface. If you do not do this or if your machinist fails to do this after angle milling the cylinder heads, the heads of the bolts (or the nuts used with a head stud kit), do not bear down on the head surface squarely and correctly.