Q. I am the owner of a 1957 Pontiac Custom Safari, VIN K757H2913, but it appears that the engine is from a 1958 Pontiac – engine number K758H7777. The engine has a Tri-Power setup but it is difficult to adjust the carburetors because they are set so close. Any information on the engine or tips on adjustment would be appreciated.
— Bert Hansen, Boulder City, Nev.
A. You’re right. You have a 1958 engine, which gives you more displacement than the original ’57 engine. Both your car and the engine donor, however, are Kansas City-built Series 27 122-inch wheelbase cars (Chieftain, Super Chief or station wagon) with Hydra-Matic. Tri-Power, however, is completely outside my experience, so I’m going to have to get help from our readers. Tri-Power gurus, how do you adjust your carbs?
Q. Attached are a couple photos we took of a two-piece finned aluminum intake part that has us and many of our car buddies stumped. We took these to Iola and had them in our booth. They were a big conversation piece with many veteran car guys looking them over closely. We had guesses that include the basis for some aftermarket heater, a way to cool the exhaust gases, just something that would look cool and an intake isolator – but no one could be positive about their guess. If you look at the close-up photo, you can clearly see the exhaust sections are hollow and circulate the hot exhaust gases up to the finned area.
They are cast in two separate pieces and appear to be for a Chevrolet six-cylinder “Stovebolt” engine but could be other early GM sixes. There are no markings on either piece. We found them in an antique store awhile back. Someone had painted them at some point. We have showed so many folks at cruise nights and car shows that we are getting inquiries from them days and weeks later asking if we’ve found the answer. Your Q&A section of Old Cars Weekly looks like our best chance to get to the bottom of these pieces. We’ve been subscribers for nearly 20 years and the wealth of knowledge OCW readers share constantly amazes us.
— Tom & Kathy Truhlar, Fort Atkinson, Wis.
A. Hmmmm. They certainly look like they will fit a “Stovebolt” Chevy, but it was not immediately obvious to me why they were made. The only possible effect they could have is to warm the area around finned “heat exchanger.” There would be some cooling of the exhaust gases, but not much because they’re merely a “side pocket” with no real outlet. The vast preponderance of the exhaust gases will pass right through into the manifold.
I think they are part of an exhaust heater, probably with a ducted cover, which is missing. There was an accessory for Model A Fords that consisted of a replacement exhaust manifold with a raised, finned section. A cover fitted over this, with an inlet behind the radiator and an outlet ducted to a hole in the firewall. These pieces seem like a similar arrangement for an early Chevy six.
Q. With reference to Gordon Wolford’ s concern about engine performance with E-10 gas at high altitudes (Aug. 1), the energy content of gasoline is expressed in British Thermal Units (BTUs). All gasolines are not equal and they don’t have the same BTU content. Also, a particular brand will not perform equally well in all engines. At any altitude, the only way to know for sure which brand and grade of gasoline works best in a particular car is by trying a few tankfuls of each brand and see how they compare.
— John Singleton, Houston, Texas
A. When I was in Colorado a few years ago, I noticed that the least expensive grade of gasoline was rated at 85 octane, vs. the 87 we have on the East Coast. As I understand it, it’s because of the altitude. Air is less dense at high altitudes, which has the effect of lowering the compression.
To submit questions to this column: E-mail firstname.lastname@example.org or mail to: Q&A, c/o Angelo Van Bogart, 700 E. State St., Iola, WI 54990-0001.
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