V8 to V4 Conversion: Get 40 Percent Better Gas Mileage

A V8 to V4 engine conversion will give you much better gas mileage for a small reduction in performance.

| July/August 1979

Back in the early '70s most Americans drove large, two-ton cars with muscular V8 engines lodged under their hoods. However, over the last 10 years, attitudes — as well as economic necessities — have changed. Today's outrageous gasoline cost and limited fuel availability have made such "solid" sedans look like real dinosaurs.

Yet many folks still own the overpowered runabouts; the unfortunate old tanks just flat refuse to die, and they're next to impossible to sell for a reasonable price. But if you're one of the people who've suddenly found themselves with too much car, take heart! Before you put the Detroit workhorse out to pasture, there may be a way to get better gas mileage from them. Consider trying Joe Lawyer's V8 to V4 conversion.

As crazy as it may sound, you can actually achieve a 40% improvement in fuel economy by putting four of the eight-bagger's cylinders to sleep without any loss of engine reliability. The job is not difficult to perform, either. If you have moderate shade-tree mechanical skills — say, enough to complete a valve-job on that V8 — you can do all the necessary wrenching by using the instructions that follow. And best of all, the conversion is inexpensive. All you'll need is a top-end gasket set, a couple of feet of 1/8" x 1" x 1" angle aluminum, a 1 1/4" rubber expansion (or freeze) plug, four 3/8" x 3" fine-thread bolts with nuts and washers, some brass shim stock, and eight 1" aviation-type hose clamps.

Kansas Ingenuity

I paid a visit to Jim Clark's Chrysler/Plymouth dealership in Topeka, KS to look over mechanic Joe Lawyer's shoulder while he converted a 400-cubic inch, eight-cylinder gas  guzzler into a 200-cubic-inch, four-cylinder sipper. Joe has done about 10 of these changeovers since 1973 and can claim a 100% reliability record for the altered eights. In fact, some improvement in engine longevity can be expected because when one set of four cylinders starts to "feel tired," the other quartet of "snoozing" holes can be put back into action.

The ex-Army maintenance mechanic experimented with several different conversion schemes before he settled on the one I witnessed. Joe even tried removing the pistons from the car's four deactivated bores, but found that the balance of the engine was too radically altered by that process. Besides, the ace "wrench" theorizes that there may be some power-producing combustion in the "dead" cylinders caused by the induction and ignition of incompletely burned fumes from the exhaust manifold.

Essentially, Joe's transformation involves de-energizing every other power pulse in the V8's firing order by "immobilizing" the valve train for cylinders two, three, five and eight. Of course, the inlet valves had to stay put to prevent air from being pumped into the intake manifold by the rising pistons. And — in order to maintain pressure in the valve lifter oil gallery — the hydraulic lifters were raised out of the cam shaft's reach and locked in position. (The spark plugs and wires serving the inactive cylinders were also retained — they produce a "waste" arc which ignites any lingering vapors, helps to clean up emissions, and keeps the electronic ignition from overheating.)

James Herrin
9/19/2009 6:08:52 AM

Hey Mr Roach, I am seriously planning on doing a conversion like this on my car i was wondering if there was a way i could get a hold of the gentleman you interviewed for this article. i understand if you cant give me his information, but you have my email. if you can ask him if he would be willing to speak with me on the subject, if so i would be willing to give you my phone number so he can call me.

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