The Stovebolt Site Forums The Shop Area Engine Shop AGAIN, I NEED YOUR HELP

I just had Patrick’s 3.55 gear set and installation kit installed in my ’51, 3100 w/’58 235 (solid lifters),Fenton headers, Flowmaster 40s and Offy intake with 2 Carter/Weber carbs. I also had 4 new LT235/75R/15 tires installed. The tires have a height of 28 inches.

A few minutes ago I was on the Interstate. My indicated mileage in 10 miles was 8.6 miles. At 55mph by my speedo, the time it took for me to travel one mile was 56 seconds. My math ain’t that good but I think I gained about 14% over the old stuff.

According to the Classic Truck Shop’s RPM Calculater, at 60 mph I should be turning about 2558 rpm.

I take several long trips each year, pulling a 1940 Teardrop Camp Trailer that weighs about 950 pounds with all my gear and my questions are: Can I do this speed all day and not hurt the 235? Can I run 65 at 2770 rpm for short bursts without hurting it?

Thanks in advance for any questions and comments

Thruwurkin
Kennewick, WA

I ran my 59 gmc 270 in the 2700 rpm range. My truck had a 3.07 rear, and the same size tires. I typically drove it between 70 and 80 mph. The engine was comfortable there. The Steering and suspension weren't. I did get that old girl up to 95 mph with the stock gmc 6 cylinder. Downhill with a tailwind of course!

I think you can go 65-70 without hurting the engine. If you take those speed figures to a speedo shop they can make up a ratio adapter to correct it. Or you can find those on practically every manual trans. in a GM truck at the salvage yard. Get several & find the one that comes close to matcheing your correction. If it is the opposite you can take it apart & reverse the gears. The guys at the pick your own parts places don,t know what they are & generally only charge 1-2 dollars for them.

If it's any help, the WW2 270 GMC's were governed to 2750 rpm, & they would often have been operating in a lot less favourable conditions (air-flow through the radiator etc )

Thanks for the input. I was sure I am going to be ok but it sure is nice to get someone else's opinion.

In late Spring, after the snow is all gone, My Brother is flying out from SC and we are gonna tow my Son's '92 Honda Prelude to him in Charleston. When, or IF, the hills get too big, we'll take it off the dolly and drive the Prelude across then put it back on the dolly.

My Son joined the Navy and is going to Electronics School, Nuclear Power School and Submarine School. The least I can do is get his car to him.

Thanks again for the input.

Thruwurkin
Kennewick, WA