Can you make a V4 from a V8?


#1

I’ve heard of a V-4 being made from a V-8. Of course, half the displacement, half the Hp/torque? Is the V-8 to V-4 possible, or is this an old Wrench’s tale?


#2

Sure, both Cadillac and Chrysler used cylinder deactivation to improve mileage but the improvement is relatively small. Their systems automatically switched to more or less cylinders depending on throttle openings and operating conditions.

About the closest you could come to this at home is to remove the pushrods from every other cylinder in the firing order. Expect half the power and I am guessing maybe a 10% gain in economy. Doesn’t seem to be worth it. This car only got 21 mpg when driven moderatly with the smallest six.


#3

Not clear if you are asking if the V8 in your garage can be made INTO a V4 with some modification or if you are asking if a V4 was ever made by a manufacturer from a V8 design.

Ford of Europe made a V4 in the late 60’s but it was not based on any V8. Lancia made a V4 in the 1920’s, also not based on a V8 design. Pontiac had a straight 4 in the early 60’s that WAS based on their V8 with half the cylinders cut off from the driver’s side of the engine.

I agree with @oldtimer_11, you don’t really want to yank the pushrods and pistons from a V8 to MAKE a V4. You won’t gain much and you’ll still be dragging around all that extra iron you aren’t using anymore.


#4

Not on point, but back in the day American inline 6s did not generally have flow-through breathing, in other words, the intake and exhaust manifolds were on the same side of the block. I don’t know about other manufacturers, but the Chevy 6s and V8s had the same cylinder spacing and head bolt pattern. The 230 CI I6 had the same bore and stroke as the 307 V8. If you really wanted to get a little extra power from the 230, you could take the cylinder heads from a 307, cut off 1 cylinder from each head, weld them together and they would bolt right on to the 230, and voila, instant flow-through breathing. I would imagine that somewhere along the line the after market just starting casting flow-through cylinder heads for the I6s.


#5

I’m pretty sure that with enough time, money, and motivation, you could indeed make a half V-8 based on a car engine. A lot of ultralight aircraft use half VW engines, A two cylinder boxer twin made out of a VW crankcase sawed in half. But why not make a 7 cylinder radial out of VW engine jugs?

Oh dear God! Did he use an electric starter to fire up that engine?


#6

In theory anyway it should be possible to disable 4 cylinders of a v8 engine, and it would still run ok. How to disable the cylinders for spark, fuel, and air would need some invention. The cylinder’s you disable would depend on the firing order. I think you’d disable every other one from the firing order list. So there are two ways to do it.


#7

40 years ago in a gas price crisis a company offered a kit that disabled half of a V-8 engine for all the obvious reasons. Common Ford and GM engine kits were advertised to be in stock and installation was supposed to be somewhat simple. The front and rear piston on one back and the center 2 piston on the opposite side would be replaced with dummy pistons with holes in the top. The rockers on disabled cylinders were removed and a spring loaded cap replaced them and the exhaust valves were left out. half the carburetor no longer operated due to lack of vacuum. I never saw an engine with such a kit installed and never had much confidence that installing it would ever be worth the cost. I seem to recall a Transmaro in the ad and wonder just how a 175 cubic inch 4 cylinder would get that car out of a light ahead of a bicycle.

While that kit was advertised in auto magazine a “Solar Clothes Dryer” was offered in Better Housekeeping. A friend bought that drier for about $50. It was 50 feet of cord, 2 eye bolts and a sack of clothes pins.


#8

How about one of these? A little pricey, but you would have the only one on the block:


#9

There is no need to do anything with pistons, once the pushrods are removed the valves are held cosed by the springs. No air or fuel flowing into the cylinder, The soark plugs fire on a cylinder with no fuel in it so no harm. The cylinder acts like an air spring, compressing the air until TDC which helps push the piston down.

You can remove the plug wires if you want but leave the plugs in place or you will be spraying an oil mist out he plug hples.


#10

Not to mention dramatically increasing the pumping losses of the engine which would likely result in lower, not higher fuel economy, and it would be noisy, like a Jake brake, while stealing just about as much energy from the system.


#11

Convert an existing V8 to a V4 - Not worth it.

I think there are some V4 engines still around - mainly in Marine engines or Generators. Don’t know of any V4 auto engines still around.


#12

It seems there were many efforts to turn gas guzzlers into economy cars by disabling cylinders 40 years ago


#13

$50? Sounds like $5 - he was ripped off.

Can’t you get another V4 cheap and add it to the power train?


#14

That reminds me of the old straight four that pontiac made from the V-8. Good job I thought.


#15

For a while BMW considered their engines ‘modular’, with 0.5 L cylinders being used in 2.0 L 4, 3.0 L 6, 4.0 L V8, and even a 5.0 L V10, with same bore x stroke for all. They claimed a 0.5 L cylinder was ‘optimal’. I don’t know if that still is the case.