Ported Chevy 781 heads

[Carnut1]

I have seen 049's with two different combustion chambers. This Chamber looks identical to my 781 chambers and the ports in the cutaways look the same too.

[Ron E]

I think the question about what the engineers were thinking is not a bad vs. a good port. But, its about having both in the same head. the newer Suburbans have heads with all long ports. So, they have made all short, all long, and mixed port versions. its kind of difficult to know what they prefer.

[Carnut1]

I think the question about what the engineers were thinking is not a bad vs. a good port. But, its about having both in the same head. the newer Suburbans have heads with all long ports. So, they have made all short, all long, and mixed port versions. its kind of difficult to know what they prefer.

I had to look that up. I did not know the 8.1L used all long ports.
They make aftermarket aluminum heads for that and they flow nearly 400 cfm.

[Adger Smith]

Just depends on which Engineering group is trying to prove their position with GM as to what we get from them. Applies to body style, too.
It is the Corp. way. I don't put much stock in saying what we see is the best because it will change in 3-5 years.
BTY: I think the 8.1 is great for what it was designed to do. Pull heavy loads. To me it is a great gas engine for a 3/4 -1 ton or mid sized MH.

[Ron E]

Adger, i agree on the 8.1. To me, its about as good as a gasoline truck engine gets.Good power vs. economy.

[Carnut1]

0329161915.jpg

Decided to do some more work to the Corvair 781's. Bad port ssr before.

[Carnut1]

0329161924.jpg

Bad port ssr after. Photos nearly look the same but quite a bit of metal removed.

[Carnut1]

0329161926.jpg

Good port ssr before.

[Carnut1]

0329161935.jpg

Good port ssr after.

[Carnut1]

0329161954.jpg

Floor after pic.

[pdq67]

I think the question about what the engineers were thinking is not a bad vs. a good port. But, its about having both in the same head. the newer Suburbans have heads with all long ports. So, they have made all short, all long, and mixed port versions. its kind of difficult to know what they prefer.

I had to look that up. I did not know the 8.1L used all long ports.
They make aftermarket aluminum heads for that and they flow nearly 400 cfm.

Doesn't the Vortec 8.1 L. engine have, same length, "non-siamesed", LS- type intake ports instead of regular log/short siamesed ports like regular large oval -781 heads have?

As well as the head-bolt deck pattern being just enough off that it is a pain to switch heads from new back to old or the other way...

pdq67

[vortecpro]

On your bad port short turn, the more you can move the left side over the more it will flow, but you have to listen to the port as you port, you will hear when its getting thin. Hope this helps.

[Carnut1]

I think the question about what the engineers were thinking is not a bad vs. a good port. But, its about having both in the same head. the newer Suburbans have heads with all long ports. So, they have made all short, all long, and mixed port versions. its kind of difficult to know what they prefer.

I had to look that up. I did not know the 8.1L used all long ports.
They make aftermarket aluminum heads for that and they flow nearly 400 cfm.

Doesn't the Vortec 8.1 L. engine have, same length, "non-siamesed", LS- type intake ports instead of regular log/short siamesed ports like regular large oval -781 heads have?

As well as the head-bolt deck pattern being just enough off that it is a pain to switch heads from new back to old or the other way...

pdq67

You are right, 8.1 has 8 Bad ports!

[Carnut1]

On your bad port short turn, the more you can move the left side over the more it will flow, but you have to listen to the port as you port, you will hear when its getting thin. Hope this helps.

I am nervous about finding water. I need to Upgrade to a better ultrasonic thickness gauge. Thanks for your help Mark.

[Bob Hollinshead]

On your bad port short turn, the more you can move the left side over the more it will flow, but you have to listen to the port as you port, you will hear when its getting thin. Hope this helps.

Mark, just to be clear on this you mean the cylinder wall side of the port right?