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February 2012 Techline

Jeep Front Three Quarter
Willie Worthy | Writer
Posted February 1, 2012

Your Tech Questions Answered

Buick V-6 Identity Crisis
I would like to install a Buick V-6 into my early solid-axle Toyota. I have found the kits to do this and plan to use the TH350 automatic transmission. I know they made both an even-fire and an odd-fire version, but I’m not really sure how to tell them apart.
Steve Martin
Austin, TX

You made me do a lot of thinking and a bit of digging through some old notes. I always was a big fan of the Buick V-6 and installed one in my ’62 CJ-5 back in 1964, then I did several more conversions later on.

Here’s a basic rundown of just a few of the obvious differences between the two engines. I’m only referring to the rear-wheel-drive versions built up to the early ’80s. The front wheel drive (modern) motors are considerably different.

Odd-fire:
The valve cover top is slanted at an angle. The timing mark is cast into the accessory cover. The distributor rotor has a dogleg tang on it and the distributor drive gear bolts onto the cam. The rocker shaft is held in place with aluminum towers.

All passenger car versions had only a two-barrel carburetor. I believe there were some marine versions with four-barrel carbs.

The ’62 and ’63 versions were 198 cubic inches, used a different flywheel, and had a rounded bellhousing bolt pattern. Parts for these engines are almost impossible to find. They also used a flywheel design wherein the smallish clutch was recessed (and quite prone to exploding, with disastrous results).

The 225-cubic-inch V-6 was built from 1964 to 1967 for GM vehicles, and from 1968 through 1971 for Jeep. It was then reintroduced by GM at 231 cubic inches for 1975 and 1976.

Even-fire:
This engine was built from 1977 to the early ’80s. It has a totally redesigned crankshaft with individual throws for each rod, which allowed firing pulses to be spaced 90 degrees apart. The block was trimmed down a bit, losing 10 pounds, to give the engine a total of a 435-pound fighting weight. A turbocharged version with a two-barrel carb was introduced in 1977. In 1978 all turbo motors came with a four-barrel carb. The turbo motors also used a much stronger crankshaft.

The even-fire motors are easily identified by the evenly shaped valve covers.

The timing tag bolts onto the accessory cover (note: the covers are interchangeable, and the ones presently available take a metric filter).

There may or may not be an EF cast on the intake manifold. The cylinder heads have a casting plug on the end; the odd-fires don’t. The ’79-and-later heads flow considerably better with their higher ports. The exhaust side is square versus the early rectangular shape.

After 1980 some of the 231s had four-barrel Rochester carbs. The distributor drive gear is part of the camshaft. All the 252ci motors had four-barrel carbs, plus there were three stiffening ribs in the valley chamber area near the front of the block. The rear of the block on all but the 198-cubic-inch motors has a standard BOP mounting bolt pattern.

There was even an odd/even-fire motor built in 1978 of 3.2L (196 cubic inches).

Knock-N-Ping

The 350 V-8 engine (second one) in my ’72 Chevy truck with 120,000 miles on it has been pinging a lot lately and it is getting worse. The only solution I’ve found is to use premium fuel, which is quite expensive. Is it time for a rebuild, as it does use a bit of oil? I do have headers on it and one mechanic said it was the headers’ fault without going into detail.
Mark Pits
Palm Springs, CA

Knocking is no more than irregular combustion—in other words, fuel burning when it shouldn’t, in bursts or small explosions, instead of one continuous smooth burn. The noise you hear is the irregular explosions echoing off the cylinder walls. Pinging, as I’m sure you know, develops hot spots within the combustion chamber and can lead to things like burnt valves or holes in pistons. Other problems could include broken pistons, piston rings, and damage to the upper half of the connecting rod bearings. Pinging is not something that you want to let continue.

Why does an engine ping? Lots of reasons. If the timing is advanced too far, the cylinder will fire before it is completely filled with a proper fuel mixture. In other words, the fuel mixture is too lean, (i.e., having a higher volume of air-to-fuel mixture than is appropriate for proper combustion). It’s possible that the addition of a more free-flowing exhaust without an increase in carburetor jet size could cause a lean condition, but generally not likely. A small vacuum leak either around the base of the carburetor, the intake manifold, or a cracked vacuum line could be other causes. A compression ratio increase beyond the fuel octane requirements the engine was designed for can be a major culprit in pinging. Not only can the compression ratio be increased by milling the cylinder header or the block surface, but also by using a thinner than stock replacement head gasket.

As the engine wears, pistons, rings, valveguides and their seals wear, allowing oil into the combustion chamber. This oil, even in small amounts, not only dilutes the fuel octane rating, but as it burns, leaves a carbon residue within the heads and combustion chamber, on the valves, and on top of the pistons. By taking up space, this carbon deposit can increase the compression ratio to a point where a higher octane fuel is required. These carbon deposits can also retain enough heat to ignite the fuel mixture before the spark plug does, thus causing pre-ignition and engine run-on. In addition, combustion chamber design (including piston design) and camshaft lift, duration, and lobe center design can have an effect on pinging.

Proper ignition and timing is also important and it could be that the advance weights in your distributor have stuck in the full-advance position or that the hold-down bolt and clamp on the distributor has come loose and allowed the distributor to rotate and change the overall timing.

One other thing to check is the EGR valve and make sure that it is functioning properly. If it is staying open and allowing exhaust to enter the combustion chamber under full throttle, then a lean condition can exist and cause pinging.

So while not giving you a direct answer as to why your engine pings, hopefully I have given you enough clues to solve the problem.

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