BAR EXAM

Q. I've noticed the Panhard bar on the rear of some cars is attached to the left framerail, on others it's on the right. Which is correct?

I've got a homemade four-bar and coilover suspension system on the back of my 1950 Ford. I made the Panhard bar as long as possible and attached it to the right framerail for no reason other than being different. Now I'm concerned I've made a mistake.

Robert Bragg
Via the Internet

A Panhard bar is a lateral locator attached to the frame at one end and the axle housing on the other. While the end attached to the axle housing does swing in an arc, which means there can be some sideways movement of the chassis with exaggerated suspension travel, by making the bar as long as possible you've reduced that to a minimum.

Panhard bars can affect handling as they impact roll center, or the pivot point that the body rolls around when cornering. Raising the Panhard bar raises the roll center, lowering the bar lowers the roll center. In most cases the Panhard bar on a street rod is mounted to the rearend at the centerline of the axles or above. With street rods packaging is usually the major consideration. Space can be tight, so Panhard bars are often put wherever they fit best.

The Panhard bar's attachment point on the frame often varies with the application. Dirt track racers often attach them to the left framerail, asphalt racers usually opt for the right. But keep in mind, these cars are designed to turn left and how they load the rear tires in corners is critical. On a street rod you'll never notice the difference.


THE BUMP STOPS HERE

Not long ago we stopped by a friend's garage to check out his newly completed street rod. A lap around it would make anyone think that no detail had been overlooked but that impression only lasted until it was time to take it for a drive. While the car rode very well, on one particularly harsh bump there was definite suspension to frame contact. While the clearance between the frame and rearend housing was adequate under normal circumstances, when the rear coilovers were completely compressed there was contact between the two. One obvious method to cure the problem was to raise the car—the rebuttal to that suggestion included questions about our mental state. But the obvious remedy was something that should be included in virtually every case—bumpstops. Bumpstops provide a cushion when the suspension bottoms out to prevent that bone-jarring jolt felt by the passengers and possible damage to chassis components.

Energy Suspension offers a variety of Hyper-Flex polyurethane bumpstops in a variety of shapes and durometer (hardness) ratings. They're available in red or black, however the durometer is the same, the only difference is the color.


SHE'S REAL FINE

Q. I know that a small-block is probably a more sensible choice, but I want to put a 348 or 409 in my 1952 Chevy. While I haven't had much luck finding an affordable 409, good buys on 348s don't seem to be that hard to come by.

What years were 348s produced and is there an easy way to tell the difference between a 348 and a 409? Finally, about carburetors, did 348s and 409s come with either three-twos or two-fours?

Brian Carothers
Via the Internet

A. When it comes to making sensible choices there is no question that there are contemporary powerplants that are superior to the 348/409 in most respects, but then no one has written a song about how fine an LS is. W engines, as they were known, are rugged—after all they were originally designed for trucks. Unlike some vintage engines, parts are easy to get and there are not too many other engines as recognizable or as cool as Chevy's original big-block.

We do get questions on these engines, so for more information than we have the room to provide here, refer to the article on 409s in the Aug. 2012 issue of STREET RODDER, check the tech section of streetrodder.com, or pick up a copy of Guide To Building A Tri-Five Chevy, which details the construction of the AMSOIL/STREET RODDER Road Tour 1955 that was powered by a Ron Shaver–built 409.

To answer your specific questions, the Chevrolet 348 was introduced in 1958 and was used in cars through 1961, and trucks through 1964; the 409 was produced from 1961 through 1965. One of the unique features shared by all these engines is the combustion chamber design. The heads are flat, the decks of the block are at a 74-degree angle to the centerline of the bores, and pistons have a slanted crown, all of which combines to create combustion chambers in the cylinders. However, be aware that some marine and truck engines used heads with a small combustion chamber to lower compression.

There are a few visual clues to distinguish a 348 from a 409 and the most obvious is the easiest to change; 348s have the dipstick on the left, 409s on the right. However, since the dipsticks are attached to the pans, and those pans are interchangeable it's easy to make one look like the other. Another telltale indicator is the crankshaft flange. All Ws had a forged crank; the 348 had a round flywheel flange and the 409 was D-shaped. Of course the best way to identify these engines is by the casting numbers on the back of the block behind the left head. There are several Internet sites that can aide in identification.