Not the original Motor

[GsKaWa]

Hey Guys/Girls,

I have a 1966 Bonneville and the owner I bought it from said the engine was changed out and a Pontiac 400 was installed, big block.

How do I go about finding out what the existing motor is(I wanna fix)?

How do I find out the Original Motor Was(Just curious)?

I am not a Motor Builder, just a Backyard Mech. I did rebuild a few motors in High School, but that was 20+ years ago. I do plan on rebuilding the present engine but I need a good place to start. I'm not interested in spending a bunch of money on a new motor unless this one is junk. It runs but it has a spun rod bearing, pretty common for a 400, I have herd.

Thanks in advanced.

[94SilverSSEi]

Your car probably had a 389 originally. That was the standard engine for a '66.
The 400 is a tough engine I've got one in our '68 Bonneville and they were used from from '67 on as the base engine but you could option for larger.

Also try looking on wikipedia under Pontiac Bonneville. Lots of info about all model years on there.

[00Beast]

Not sure exactly where, but there will be a stamping number on the block which will tell you what year and size the engine is. There might also be a number on the car somewhere. I'm not terribly familiar with the old bonnevilles. These new cars make it easy on us with VIN numbers and RPO codes.