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Dowel Pins
Pontiac V8 Dowel Pins
Locate It Before You Clamp It — Dowel Pins for Pontiac V8s
Dowel pins locate parts that bolts only clamp. On a Pontiac V8 they index the cylinder heads to the deck, the main caps to the block saddle, and the bellhousing to the back of the block — and every one of those locations has a length and a fit that has to be right.
Butler stocks Pontiac head deck dowel pins in 5/16" x 5/8" and extra-long 5/16" x 3/4", main cap dowel pin kits for 2-bolt and 4-bolt blocks, singles in 3/4" and 1" for the center three caps, and extra-long bellhousing dowels including an offset pair.
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More About Dowel Pins
1. Ream the Hole — This Is Not Optional
The single most important thing on this page: the 5/16" dowel pins measure .3125", and the original Pontiac hole is .310". The pin is slightly oversized on purpose, and the hole has to be reamed to accept it.
| What happens if you skip it | driving an oversized pin into an unreamed main cap hole damages and can crack the cap. That is a block-out-of-the-car mistake to fix. |
| When it comes up | any time you are installing dowels into main caps, and any time caps have been cut, splayed or replaced. |
| Do it with the machine work | reaming the cap holes belongs in the same visit as align honing, not after the short block is assembled. |
2. Head and Block Deck Dowels
Deck dowels index the head gasket and the head to the block. Milled decks and thicker gaskets can change how much pin is left standing proud.
| Standard length | 5/16" x 5/8" block and head deck dowel pins, sold as a single (MSC-06025068) or as a set of four (BPI-Bolt-Head-Dowel-Pin-Set) for a pair of heads. |
| Extra long | MSC-06025076 is the 5/16" x 3/4" extra-long deck dowel, sold singly, for decks where the standard pin does not stand far enough into the head. |
| Why it matters | the gasket and the head both locate off these pins. A missing or short dowel lets a head walk during assembly, which is not something you find out until it leaks. |
3. Main Cap Dowels, 2-Bolt and 4-Bolt
Pontiac uses different lengths for the center caps than for the front and rear, and 4-bolt blocks are not the same as 2-bolt.
| 2-bolt main kit | BPI-Bolt-Main-Dowel-Pin-2B-Set covers the center three caps with 5/16" x 5/8" pins (set of six) plus 5/16" x 5/8" pins for front and rear (set of four). |
| 4-bolt main kit | BPI-Bolt-Main-Dowel-Pin-4B-Set uses longer 5/16" x 3/4" pins on the center three caps (set of six), with the same 5/16" x 5/8" pins front and rear (set of four). |
| Extra-long center pins | BPI-Bolt-Main-Dowel-Pin-XL-Set is a set of six 5/16" x 1" pins for the center three caps on a 4-bolt block, with MSC-06025100 available as a single. |
| Singles | MSC-06025084 is the 5/16" x 3/4" center-cap pin sold one at a time, for replacing a damaged pin rather than a whole set. |
4. Bellhousing Dowels
The bellhousing dowels set transmission alignment to the crank. Worn or missing pins let the bellhousing sit off center, which shows up as input shaft and front bearing wear.
| Extra-long pins | TCI-930055 extra-long bellhousing dowel pins give more engagement than a worn factory pin, useful with thicker blow-proof housings and adapter plates. |
| Offset pins | MOR-37938 is a .625" diameter pair with .021" offset, used to move the bellhousing when a dial indicator says the bore is not concentric with the crank. |
Dowels are the cheapest parts in this whole section and the ones most often reused because they looked fine. If the engine is apart, replace them, ream what needs reaming, and put everything back where the factory put it.
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.