Seal Solutions
Q.I'm rebuilding a 322-inch Buick V-8 for my '40 Ford and I'm concerned about the rope-style rear main seal. Some friends claim they leak no matter what you do; others say soaking them in oil before installation is the trick to making them seal.
I noticed in the blown Hemi engine build featured in the June issue of SRM that you used a lip-style seal from BESTgasket instead of the original rope style, does that mean you prefer not to use rope seals? Is there a rubber seal that will work in my Nailhead, lacking that got any tricks to make rope seals work?Ken WaltonVia the Internet
A.Over the years I've actually had good results with rope seals. Like many such things, every mechanic I asked over the years had their own special tricks for installing them, but one grizzled old-timer who had been turning wrenches long before I came on the scene had a simple but effective procedure. He simply dropped the seals in a can of oil and let them soak over night. However, the real trick was how they were installed in the block and cap. He used a series of custom-made half-round installation tools and a rawhide mallet to press the seals into place, making them flush with the bearing surfaces. (Something similar could be made out of tubing, solid aluminum, or even hardwood. In some cases a large socket will work.) Once the seals were pressed in place a sharp blade was used to trim the ends, allowing them to extend approximately 1/8-inch past the mating surfaces.
While soaking rope seals worked with the older materials, today things have changed. To get the latest update on rope seals and retrofitting early engines with lip seals, we contacted Armin Brown of BESTgasket and asked for his comments. Here's what he had to say:
"Rope seals were once made from asbestos, but in the 1980s the fallout from asbestos lawsuits caused the automotive industry to seek alternatives, and by 1997 the manufacturing of asbestos rope rear main seals had ceased.
"As an alternative the industry came up with synthetic rope seals, unfortunately they are difficult to trim and have mixed results when it comes to sealing. Comments from failed synthetic rope users range from 'it turned to mush' to 'oil runs right through it.' But, I've also heard from some customers that they seal just fine. This has been the single most frustrating sealing-related aspect of rebuilding vintage engines that were not designed for a rubber rear main seal.
"In most cases, tooling costs for rubber rear main seals (where only ropes have been available) are cost prohibitive. Even where tooling has been made, there are cautions of which to be aware. A rope seal is forgiving, filling in any machining inconsistencies, whereas a rubber seal is not. Rear main seal housing machining tolerances, when designed for a rope seal, often reflect this. Rubber replacement seals will not always produce the desired fix because of machining inconsistencies. Either the seal ends will not meet together properly or a lack of concentricity foils the deal; trying to use a later rubber seal in some earlier Chevy six-cylinders is a good example. The 216-235 engines from '40-55 use a rope seal and have the same seal journal/cap-block dimensions, so they could theoretically use the '56-62 rubber seal, but machining variances make the success rate too low for BESTgasket to advertise this as a match."