[formula_73]

I havea block question. What blocks did pontiac acctually have? I've heard that they didn't really have a big or small block, just a "general perpose" block that houseed a 350-455. If so then is it a two or four bolt? I have a 73 formula 400 and have been told that I have a 350 by some people mostly those familiar with Chevy engines.I was told by the previouse owner that it was a 400 He said it was four bolt maiun and that to prove it all I had to do was look for thew bolts. I looked up the VIN and it said I had a formula 400. The heads read "4X" I haven't got a chance to lift up the car to see if it's a two or four bolt, but it pontiac used the same block wouldn't it be the same on all of them? So what's the deal on that? Any experts know the facts? Just trying to make sense of it all...

[formula_73]

I havea block question. What blocks did pontiac acctually have? I've heard that they didn't really have a big or small block, just a "general perpose" block that houseed a 350-455. If so then is it a two or four bolt? I have a 73 formula 400 and have been told that I have a 350 by some people mostly those familiar with Chevy engines.I was told by the previouse owner that it was a 400 He said it was four bolt maiun and that to prove it all I had to do was look for thew bolts. I looked up the VIN and it said I had a formula 400. The heads read "4X" I haven't got a chance to lift up the car to see if it's a two or four bolt, but it pontiac used the same block wouldn't it be the same on all of them? So what's the deal on that? Any experts know the facts? Just trying to make sense of it all...

[NW S/D]

If this is the orignal motor you would most likley a two bolt main.look for the code stamped
on the front right area of the block under cyl. head,will have two charcters , Such as "XD". lookup code in shop manual or post back.

[formula_73]

The numbers "D N" are shown under the valve covers and above the exhaust manifold. I have a picture of this but I don't know how to post it. I tried attaching it as afile, don't know if that's the right way.

[johnta1]

New S/D was talking about looking on the front of the block,below where the passenger head sits.



There will be some numbers and below that 2 digits.

Then try this link.
Engine Code Search

[x-bird2]

the D N is for Day or Night shift production at the foundry. as far as 2 or four bolt mains, teh block code will tell you, vehicle application and whether or not it's a 4-bot. pontiacs are easy to convert to 4 bolt from 2 bolt.

[formula_73]

What's the advantage, if any? More durability?

[formula_73]

I think the numbers read 889450 X N. I couldn't make it work on the site you provided johnta1. I don't have all the required info. Does the info I provided help?

[formula_73]

I finally got the info to pop upo on the website. All i had to type in was XN on the block code section and this info , along with other year engines came up. But how does this info tell me it's a four bolt BIG BLOCK? It did help though, now I know and can prove that it's a 400 and I know that the heads are the right code. Thanks! But can anyone else help me figure out what I have?
YEAR: 1973 ENGINE:400 HP200,230 ENG. CODE:XN TRANS:A CR:8.0 CAM:066 HEAD:4X BBL:1-4 CARB NO:7043264 MISC Block Casting # 481988

[johnta1]

1970 was basically the last year to get a 4 bolt main 400 engine.
Service replacements might have them.

Yours appears to be the original 400 for the car. It's 2 bolt main.
No "big" block or "small" block,this is generally a Chevy term.

Your 400 is a small main journal bearing block compared to the large journal bearing 455.

[formula_73]

Cool, thanks! But what's the addvantage a a 4 bolt? Should I consider a conversion if I want to modify it for more power?

[johnta1]

A 4 bolt will be more stable.
The 400 doesn't really need 4 bolt compared to the 455.
Unless you're making over 600 HP I wouldn't worry about it.

[formula_73]

Oh, I'm only looking to make around 450 HP, if possible. It's a street car. Anyway, thanks a lot for the info and the education!