Big Block heads Rectangular or Oval

[kgblazerfive]

If my exhaust is a square hole does that mean I have Rectangular port heads. I'm not in the mood to pull a valve cover to get the # so I was checking to see if anybody know's. The round headers that I bought won't fit the square exhaust ports so look in the sale forunm soon for them.

 

[u2slow]

I have seen heads with all 3 intake port types (rect, oval, round) but I don't recall they're being a shape difference between the exhaust ports.

However, if the heads are newer than ~'75 (and they're not from a marine engine) you can bet they're the small round 'peanut' ports.

 

[Lonnie P]

The rectangle/oval port refers to the intake ports.

Most common big block heads have a square shaped exhaust port, athough round & "D" ports do exist. Your headers, as do most smaller tube truck style headers are round. You probably have 1-3/4" tubes. These will work fine on your vehicle. Do not worry about the mismatch. Just buy small diameter round port header gasket. I ran the 1-3/4" Hedmans on mine (like you are describing) with no problems.

 

[kgblazerfive]

It doesn't appear to me that they will even match up so I put the manifolds back on, with new gaskets. The round is way small.

 

[sweetk30]

However, if the heads are newer than ~'75 (and they're not from a marine engine) you can bet they're the small round 'peanut' ports.

nope i got a 78 1/2 ton burban with 10k tow package . it has large oval non emisions 454 in it.

and for ports go oval for bottom end power.

 

[u2slow]

nope i got a 78 1/2 ton burban with 10k tow package . it has large oval non emisions 454 in it.

Lucky dog. Certainly the exception and not the rule.

 

[sweetk30]

yep drove the 454 a/c cruise and 400 turbo tranny home for 600 bucks. ha ha