Exhaust port, size comparison request

[timspu]

Could anyone advise if the 3.2 engine exhaust ports are larger than a 3.3 Turbo exhaust port. The size i am after is the diameter where the header mates with the port.

Reason for my question,if an exhaust jig was made off a 3.2 head would the header tubes then be a perfect fit on a 3.3 turbo head?

Thanks as usual.

[Tippy]

I am 99% sure the Carrera's are bigger but that last 1%, you have to take my word with a grain of salt.

I know someone has posted a chart here with all of the port dims between all heads - maybe this was in the engine rebuilding section.

[RarlyL8]

930 exhaust port is 38mm, Carrera is 42mm. You get a nice bump porting the 930 heads to Carrera size.

[timspu]

Brian, Tippy,

Thank you very much for the responses. That should help.

Cheers

TIM

[JFairman]

930's have have tiny little intake and exhaust ports.

It's pathetic as far as high rpm performance goes and they made the intake ports small to increase intake airflow velocity at low speeds to help get the slow responding very low at low rpm K jetronic injection pressure to atomize fuel better at low speeds so it could pass emissions.
The increased intake velocity from small intake ports improves low rpm turbulance and swirl in the combustion chambers to mix and atomize the fuel better but larger intake ports make way more power at high rpms.

I don't know why they had such small exhaust ports.

From 1975 through 1977 930 exhaust ports are 36mm.

Then for some reason they got even smaller.. .

From 1978 through 1989 930 exhaust ports are 34mm.

1984-1989 Carrera exhaust ports are 38mm.

[Tippy]

There's conflicting data posted, now I'm confused.

[GJF]

[quote=

from 1975 through 1977 930 exhaust ports are 36mm.

Then for some reason they got even smaller.. .

From 1978 through 1989 930 exhaust ports are 34mm.

1984-1989 carrera exhaust ports are 38mm.[/quote]

correct

[JFairman]

Thats what happens around here... frequently.

I have a set of origonal 1976 930 cylinder heads and I measured the intake and exhaust ports with dial calipers.
The 1987 cylinder heads on my car are also origonal and I measured the exhaust ports with the same calipers when I had the headers off the motor.

My measuraments agree with the port size specs in Waynes 911 engine rebuilding book.
The Carrera exhaust port spec I posted is from Waynes book.

You can believe what you want but I know whats correct.

[GJF]

The Carrera head is 38mm once the headers are indexed onto the port. The actual size of the opening is 42mm but that is for the index of the header flange. If you wanted to run 1 3/4 primaries the ports on a Carrera head needs to be opened up to blend the port shaft to the 41mm or larger. But stock for stock 38mm is correct on Carrera heads with a 42mm step for the header flange index.

[Tippy]

Ok, the step size for the header was the discrepancy.

So port size is still larger for the Carrera vs 930's.

[Tom F2]

So, are the tubes on the factory exhaust pipes that stick into the ports 2 mm larger on the 3.0 Turbo heat exchangers, as compared with the 3.3? I notice that the heat exchangers have different part numbers.

[kenikh]

I used Carrera HEs on my 930, so the port was machined to 38mm, while the step was 41mm, IIRC.

[Tom F2]

Originally Posted by kenikh

I used Carrera HEs on my 930, so the pretty wad machined to 38mm, while the step was 41mm, IIRC.

Thank you, Kenik, but I am not sure what "pretty wad" means. I'm sure that someone on this forum can offer a humorous take on it...

[kenikh]

Originally Posted by Tom F2

Thank you, Kenik, but I am not sure what "pretty wad" means. I'm sure that someone on this forum can offer a humorous take on it...

While Paul and Ronnie can wax poetic about the "pretty wads" that pass as articles of entertainment for them, the above was a simple typo, now fixed.

[RarlyL8]

The sizes I quoted are primary exhaust tubes per application. The measured port size before the gasket protector step is 34mm 930 and 38mm Carrera.
Sorry for the confusion.

[Ronnie's.930]

Originally Posted by kenikh

I used Carrera HEs on my 930, so the pretty wad machined to 38mm, while the step was 41mm, IIRC.

Originally Posted by Tom F2

Thank you, Kenik, but I am not sure what "pretty wad" means. I'm sure that someone on this forum can offer a humorous take on it...

Originally Posted by kenikh

. . . the above was a simple typo, now fixed.

^^^
Ya', right!


Paging Dr. Freud to the courtesy phone - one Mr. Kenikh needs your assistance!

[Tom F2]

So, when I put heat exchangers from a 1986 Turbo on my 1977 930, I ended up with sleeves that fit correctly into the ports, but exhaust pipes that were 2 mm smaller than the functional exhaust ports, is that right?

[onboost]

Originally Posted by JFairman

Thats what happens around here... frequently.

I have a set of origonal 1976 930 cylinder heads and I measured the intake and exhaust ports with dial calipers.
The 1987 cylinder heads on my car are also origonal and I measured the exhaust ports with the same calipers when I had the headers off the motor.

My measuraments agree with the port size specs in Waynes 911 engine rebuilding book.
The Carrera exhaust port spec I posted is from Waynes book.

You can believe what you want but I know whats correct.

Funny, I just went through this ordeal last month as I continued to receive the wrong header gaskets from several sources after asking them to verify gasket inside diameter before shipment.
I too measured with dial calipers and provided each supplier with those numbers and most thought I was nuts or didn't know what I was talking about.

3.0 was 39mm
3.3 was 39mm
3.2 was 42mm

Mine ended up being 45mm No it ain't stock

[RarlyL8]

This is the source of confusion. The port sizes I quoted were gasket protector OD, the size Jim quoted are functional port ID, and the sizes you are looking for are gasket ID which are largest of all.

[clutch-monkey]

are the ports on a 964 3.3 any different?