[Badgoat64]

Will 3” headers for a 1973 400 block, also fit a 1964 389 block?

[tom s]

3 in what?

[b-man]

3” headers?

Is that the collector size because it sure can’t be the primary pipe size.

All Pontiac blocks are dimensionally the same externally, the same physical size. If both have D-port heads (used on 99.99999% of Pontiac engines) which is highly likely then yes of course. Pontiac heads can be interchanged onto any Pontiac block.

And please let’s not bring up the short-deck 301 and 265 blocks that 99.99999999% of us don’t want or use.

[Badgoat64]

Originally Posted by b-man

3” headers?

Is that the collector size because it sure can’t be the primary pipe size.

All Pontiac blocks are dimensionally the same. If both have D-port heads which is highly likely then yes of course. Pontiac heads can be interchanged onto any Pontiac block.

And please let’s not bring up the short-deck 301 and 265 blocks that 99.99999999%’of us don’t want or use.

My 64 GTO has a 461 stroker (built from a 400 block) with Edelbrock heads. It is 3” exhaust from the headers to the tail pipes. Yes that’s the collector size. I’m just trying to figure out if I put the original 389 back in the car, will the headers on the 461 bolt up to the 389, or am I going to need to make exhaust mods.

This is my first Pontiac, so please forgive my lack of knowledge on the subject. Thanks.

[b-man]

If your Edelbrock heads have round exhaust ports then the 389 would have to have round port heads too for the headers to work. 389 engines never came with round port heads.

Edelbrock in recent years did produce D-port heads (two center exhaust ports look like the letter D back to back) so it’s possible your headers from your 461 would work.

As long as the type of head as in exhaust port style match your headers will work.

Keep in mind that round port Edelbrock heads will have a flat on the exhaust port floor at the port exit flange but they’re still considered round port.

[Badgoat64]

Originally Posted by b-man

If your Edelbrock heads have round exhaust ports then the 389 would have to have round port heads too for the headers to work. 389 engines never came with round port heads.

Edelbrock in recent years did produce D-port heads (two center exhaust ports look like the letter D back to back) so it’s possible your headers from your 461 would work.

As long as the type of head as in exhaust port style match your headers will work.

Keep in mind that round port Edelbrock heads will have a flat on the exhaust port floor at the port exit flange but they’re still considered round port.

Thanks for the response. That helps. The car is still new to me, so I’ll figure out exactly what heads I have now (whether D-port or not).

[b-man]

http://forums.maxperformanceinc.com/...d.php?t=636309

From the Street forum Tech Thread Archive, round port and D-port head differences.

The differences between them are pretty easy to spot.