Changing a V8 to a V4

Thanks gentleman for taking the time to answer my question. This is what I am I have gleamed so far. Using the firing order, I would remove from every other cylinder: the piston, connecting rod, pushrods and rocker arms. This should reduce drag from the rings, eliminate any pumping losses, and seal off the manifolds with the valves. I would leave the lifters in place (off the cam lobe) with Loctite and maybe a setscrew if there is room. I can manufacture a collar for the crankshaft journals to maintain oil pressure and locate the remaining rods. Maybe, cutoff the large end of the rod and use that. I would leave the sparkplug in, but, remove the wire. The whole point of this exercise is to improve the gas mileage for those driving vehicle with V8's. I'm thinking these cars/trucks have a lot more horsepower than they need to haul one person to work/store. Of course, if you need the HP for hauling a load, then you will just have to pay the price. And yes, you could just put in a smaller engine. But, the cost for that would in the thousands. You might as well spend that money on gas. Thanks again for your input.

let us know how it works out for you

The machine shop work for the conversion is likely to run quite a bit too, unless you have a very well-equipped shop yourself, in which case you could buy a well-used four, rebuild it yourself, and install it.

Yea, but where's the fun in that.

PS. I own and operate a fully equipped machine shop. Just furnished converting a rotary engine for use on an airplane. I'm sure I can handle any machine work. But, I had completely over looked the oil pressure problem. That why I posted the question. Thanks again.

I still think that while it may be a "fun" project the balance issues and the weight of the unused portions of the block will make it less efficient and durable than, say, simply adapting a four or six cylinder engine.

nate

If you think it might be a fun project,,,,, Go for it. cuhulin

You're still gonna need to pull the engine. Every car I've had with a V8 has a crossmember under the oilpan. Won't pulling rods off the crank kill the balance? Seriously, this sounds like a lot more work than buying a car with a smaller engine.

A flex-fuel project would be a far more workable vehicle. Plus... GM already brought back it's V4-6-8 with modern engine controls. If you really want the V4 concept the best route is probably getting one of those engines (and its associated control system bits) and put that in. (the new version of course)

Yep, if you pull a rod and piston assemby off the crankshaft, you would have to make up a bob weight for best balance and to restrain the oil flow.

In the example I gave, the piston was removed to keep the rod from going through the block on the way home, and was intended as a short term patch, not a cure. The kid got himself and wife home, but it was probably nip and tuck that they made it.

Re another post, leaving lifters in a bore without a pushrod or whatever is not, IMO, a good idea. You could work out a situation to pull the lifter up off the cam face and hold it off, while still restraining oil flow, but if you leave that lifter banging off the cam and possible being slung out, that is not good hot rodding.

As do the numerous systems in use today (Chrysler MDS, GM DoD, etc). The difference being that the Caddy V-8-6-4 used electric solenoids to release and re-engage the fulcrums of the rocker arms, and that system was very trouble prone. Today's systems divert oil pressure in a way that causes the lifters to either lift or not lift, and that system is EXTREMELY reliable.

Right. Some engines (most straight-sixes, for example) are balanced independent of the weight of the piston and conrod (the "bob weight."). But a v8 cannot be balanced independent of the bob weight. If you change from a heavy piston to a lighter one in a v8, you have to rebalance the whole rotating assembly. Not so with a straight six.

In fact, on many engines the oil "leak" you cause by removing a lifter is many many times greater than the "leak" you'd cause by removing a connecting rod! Take a Mopar or Ford v8- the lifters bores actually protrude into the main left and right bank oil galleys, so you essentially would de-pressurize the whole oiling system by leaving out one lifter. On the other hand, each rod bearing has a fairly small hole, and a healthy oil pump might easily keep up with the "leak" it would cause.

At the other extreme, there's the slant-6. The solid lifter version oils the lifter bores by splash from the overhead, and oils the lifter/cam contact face by squirt from below. Removing a lifter wouldn't affect oil pressure or flow at all.

And watch it shake itself to a million tiny bits because its now horribly mechanically imbalanced due to the missing weight of pistons and connecting rods......

Steve, could you expound on this. I can see that the large end of the rod affects balance because it is rotating. But, the small end and the piston are moving linearly. What exactly is meant by "mechanically imbalanced"? Thanks

Was there ever a slant six with a hydraulic cam?

nate

I'm not Steve, but...

If it's moving, it has a definite effect on balance. As-built, any given engine "expects" to be needing to move the piston, rod, and rings up and down the bore, along with having the large end of the rod spinning with the crank. Remove the weight of rod, piston, and rings, and you massively (err... no pun intended, but since it's laying there...) alter the balance of the engine.

Pulling out pistons and rods is going to make at least SOME mess of the balance in pretty much any engine, but particularly so for the "V"s due to the fact that the masses are flying in two planes, rather than one. Straights and flats (like the old VW Bug or today's Subarus) as well as slants (which are effectively just a straight that's tilted) all have their pistons "only" going up and down (or in the case of a flat, "in and out") on a single plane of motion. Depending on where it is in the cycle, a V's pistons are moving either "up and out" or "down and in" - moving on two planes of motion simultaneously. Which complicates things quite a bit as far as balance goes. Take away some weight that's "supposed to be" moving up and out as another weight that compensates for is is supposed to be going down and in (or vice-versa) and the vibration is gonna get real ugly real fast, and it's only going to get worse the faster the crank spins.

In the 1970s, I owned an ex Dolly Madison 1967 International walk in cube delivery van.The slant four International 152 cubic inch engine was the right hand bank of Internationals 304 cubic inch V8 engine, it had a five main bearings.Some International Scout vehicles also used the same engine.It wasen't a very smooth running engine either. cuhulin

All of them from somewhere around 1978 onward through end-of-production (where's Stern when you need him?)

And the way they managed to pressurize the lifters is amusing, to say the least. Putting a galley in the block to side-feed the lifters the usual way would have meant a big re-tooling, but the top-end was well supplied with oil via the rocker shaft. So they adopted a sort of "reverse Chevrolet" oiling system where pressurized oil was tapped from the rocker shaft, fed through a passage in the rocker arms, sent down hollow pushrods and into the lifters. Rube Goldberg smiled at that one, I'm sure, but it worked flawlessly (as did pretty much everything about the slant-six).