In the last issue we presented 18 engine assembly Do's and Don'ts related to the bottom end using an early 389 Tri-Power engine for illustration purposes. For this installment, we returned to DCI Motorsports in Atwater, Ohio, to photograph more and learn the details from experienced engine builder Don Johnston.
Keep in mind this is not an Engine Building 101 article that will detail each step of the process. Rather it provides more advanced techniques a pro employs when pre-assembling and assembling a Pontiac engine. The tips in the story should be used in addition to the basic-engine-building procedures.
As we did in Part 1, we will also discuss a few more common assembly mistakes that Don sees frequently in engines that come into his shop, so you can better avoid them. Top-end info will be covered in the next issue.
Get Roped In
Use sealer behind the rope seal.
Drill a 3⁄16-inch-deep hole in the center of the rear main seal groove with a 0.120-inch drill bit and install a 1⁄8x3⁄8-inch roll pin to keep the seal from rotating. It’s added insurance to work with the anti-rotation grooves already in the block. (Note the pin shown has not been installed yet and is just sitting where the hole should be drilled for illustration purposes.)
Install the rope seal leaving material sticking up on each side so both can be cut perfectly flat. Work the seal into the groove with a socket or a dowel or something with a smooth, round surface. It must seat the seal properly so the anti-rotation grooves and roll pin keep it in place but not crush it too much because it still must seal the crank. This rope seal from Best Gasket (PN 6380 S) is impregnated with graphite, which the company says reduces drag and helps seal against the crank.
Trim the seal with the cutter and with the shim in place to ensure the end of the seal extends slightly above the block surface. This allows the finish crush to be done by the crank upon installation. The wood stick protects the finger from the blade. All these tools are provided in the Best Gasket kit. After cutting, roll any slightly frayed edges too short to trim back into the seal. Repeat steps 1 through 3 for the cap.
Use a little RTV on each seal end and between the cap and the block to avoid leaks.
The tips in the story should be used in addition to the basic-engine-building procedures.
Torque all the main caps properly to draw the rear cap down so you don’t bend the crank. (See how it’s sitting up off the block in the photo?) First, install the main cap bolts and hand tighten. Next, tighten them in this order: #5 (rear), #3, #1, #4, and #2; then repeat until torqued to spec. The number 1 to 4 caps are torqued to 100 ft-lb, the rear cap is 120 ft-lb. Torque the bolts in increments—50 ft-lb, then 75 ft-lb, then 100 ft-lb, and finally the rear cap to 120 ft-lb when using factory fasteners. Studs require different torque settings.
Rings and Things
Make sure the ring gaps are opposite one another when installed on the pistons to get a better seal for initial startup, despite the fact that they will ultimately rotate on the pistons. Yes this is an easy one, but it’s forgotten many times, according to Don. Stagger the oil-ring wipers as well at 10 o’clock and 2 o’clock relative to the wristpin position at 12.
When using gapless rings, remember that the second ring is a two-piece (the top may be as well), so install it with the gaps opposite one another and with the thinner ring on the bottom.
Install the rings upside down. If there is a dot on the ring like this one, it should be facing up. No dot? Check with manufacturer.
Get the rings mixed up. When using gapless rings, the oil ring is similar in size and material to the second zero-gap ring assembly (the top may be as well). However, the oil ring is wider (left).