301 Main Bearings

Pontiac V8 301 Main Bearings

Its Own Family — 301 Main Bearings for Pontiac V8s

The 301 is Pontiac's own late small-displacement V8, and it is its own animal. It does not share a main bearing set with the 326 through 400, and it does not share one with the 421, 428 or 455 — which is exactly why it gets a separate page rather than being buried in a larger listing.

Main bearings for this engine are catalogued as a 265-301 family, sold as complete sets and sized to the crankshaft's finished grind. If you are rebuilding a 301 and are not certain what the crank measures, that is the call to make before anything is ordered.

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More About 301 Main Bearings

1. Why the 301 is listed separately

Pontiac built the 301 as a distinct engine, not a destroked 350, and the bottom end reflects that.

Not interchangeable	A 326-350-389-400 main bearing set does not fit, and neither does a 421-428-455 set. Shopping the 301 out of a general Pontiac listing is how people end up with a box they cannot use.
Catalogued as 265-301	Bearing manufacturers group this engine with the 265 rather than with the larger Pontiac V8s. If you are cross-referencing a part number elsewhere, that is the family to look in.
Sets, not shells	Like every main bearing on this site, these are complete sets for the engine.

2. Sizing to the crank

The same rule that governs every other main bearing page applies here, and on a low-production engine it matters more because there is less margin for a second attempt.

Measure before you order	Main bearing sets are made in standard and in undersizes for cranks that have been ground. The finished journal size on your crank decides which one, not the engine's year or badge.
Get it in writing	If the crank is at a machine shop, wait for the finished sizes. Guessing an undersize on a 301 wastes a set you may wait on.
Tolerance matters	Racing bearing lines built for this family are marketed on tolerance control — King's AM series, for example, advertises tolerance control up to plus or minus .0001". That is only useful if the journal it is going on has been measured properly.

3. What else the 301 needs

The bearings are one line on a short list, and the rest of that list is worth planning at the same time.

Rod bearings	Ordered to the rod journal diameter, from the rod bearing pages. Do not assume they come out of the same family as the mains.
Cam bearings	Chosen by year and cam journal size, and pressed in before anything else goes together.
Call on availability	The 301 is a low-volume rebuild compared to the rest of the Pontiac V8 range, so stock here moves differently than it does on a 400 or 455. A phone call is faster than a guess.

If you are putting a 301 back together, give us the measured main journal size and what the crank was ground to. That is the whole conversation, and it saves a return.

Not sure what your Pontiac needs?

Email our tech team at tech@butlerperformance.com. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.