I've noticed a lot of pontiac 400 blocks for sale locally, made me to start to think about witch block I will make my motor from. So it made me think, what is the difference in the pontiac 400 block and the chevy 400 block, specifically? Will only certain accessories work? What gives?
The pontiac has a different bellhousing bolt pattern, reffered to as the BOP style or Buick Olds, Pontiac style. The motor mounts are the same but will require the frame location mounting to be moved forward about 3/4 inch. Coolant lines are in the same location and are the same size so just use the factory lines. Fuel pump location is also the same, so no new fuel lines needed. You will need either an electric fan, or a fan spacer to get the fan properly located within the shroud. (assuming it is a truck) Power steering pump will need a custom bracket to raise it about an inch or it will hit the frame.
For a 2wd truck, you can use a 2004r transmission, that has provisions for both the chevy bolt pettern and BOP bolt pattern, and is the same length as a th350, requiring no driveshaft cutting. For four wheel drive, your stuck with either getting an adapter plate, or finding the elusive removable bell housing from the early 70's fire birds with a 4 speed, and a removable bellhousing 4 spd top loader. (Those are the only two I have experienced that interchange, although there may be others that will also)
Lastly if you choose to build a pontiac 400, remember to add oil restricters to push more oil to the mains. Get a high volume regular pressure (not high pressure, as high pressure wears out the main bearings unequally) Replace the factory push rods with after market chrome molly ones. Use the HEI style distributor from any 80's model Oldsmobile/buick 301 or 307. Get screw in rocker studs, and be sure to use the correct length head bolts, as 4 of them intersect with exhaust manifold bolt holes.
In all, you'll spend double or triple of the money building and installing the Pontiac 400 for the same power and reliabilty of a small block chevy. Of course you could also go the 5.3 LSx route and get 300 hp, and 20mpg for about 1.5 times the cost of the traditional Small block Chevy.
dont beleive all the haters that say they run too hot. Mine runs at 180* all day long driving and idling and never above 210* playing. Just get a real nice radiator to keep them cool.
