SC Exhaust Port Sizes ????

patkeefe · 09-14-2009, 06:34 AM

I am a bit confused regarding exhaust manifolds and port sizes for early SC heads. I have what I believe are early SC heads, which use the thin flange heat exchangers. The dates on the heads are all 1-78, which seems correct to me, as the car is a 78. BTW, the SC is a turbo, which shouldn't matter for his discussion, as it is an old BAE kit.

Anyway, I have a set of 930 heat exchangers, and also a set of headers, both of which are the thick flange models, with the last bit of tube protruding from the flange. IIRC, I measured the bit of tube to be 1.170" OD (I could be wrong here). They will not fit into the exhaust port.

Now, not having a 930 or a later SC at my disposal, are these tubes actually supposed to protrude into the exhaust port? Maybe there is some sort of spacer or thick gasket supposed to be there? Am I correct in assuming I'm missing something here?

TIA,
Pat

Flat6pac · 09-14-2009, 07:14 AM

Youre talking about the insert on the heatbox that inserts into the head at the exhaust.
My 76 930 has inserts from the factory as well as thick flanges as do all the 930 s I have worked with. 930 heads, exhaust and tubes are smaller dia to get more rush of exhaust to the turbo
The 77 S used the inserts with the thermal reactors and thick flanges.
78/79 and all rest of the world got thin flange heat boxes.
80 to 83 USA got thick flange and inserts
84 to 89 Carrera are larger tubes and inserted.
The inserts can be remover with a hammer and chisel with only 3 small welds holding the insert to the tube.
The mid cars for California, I do not know.
Bruce

patkeefe · 09-14-2009, 07:26 AM

Thanks, Bruce. I will examine the construction of the 930 HE's when I get home from work. The other headers I picked up have the same protrusion, but I will need to examine it more closely to see if the protrusion is contiguous with the actual exhaust tube. I was actually considering grinding this off on the headers.

I just don't understand why my port is too small to accept the protrusion. It definitely won't fit in a 2.4 exhaust port (I had a 2.4 head lying around). I didn't check the port sizes on my 2.7 heads either, just for the heck of it.
Pat

Flat6pac · 09-14-2009, 07:50 AM

By the time you get to c2/c3 there is no inserts at all
Bruce

fredmeister · fredmeister's Garage

my 79 930 had the inserts into the port. the exhaust gasket slips over this protrusion. this helps with sealing as the turbo exhaust iperates under higher back pressure than NA cars.
the thick flanges are better for thermal expansion stresses in the studs and remaining flat, and are a good thing. as long as exhaust studs are long enuff.
you should be able to grind them off for the sc but realize that the port diameter should match the exhaust inside diameter to flow properly. any restriction or sudden expansion is not ideal.

patkeefe · 09-17-2009, 11:48 AM

I knocked the inserts out of the headers last night with a cold chisel and vise grips. I cleaned up the remaining spot welds inside with my die grinder. The ports seem to match up fairly well. The headers have 10mm holes, and, of course, I have 8mm studs, so I need to make up some conical locators to center the headers in the ports.

Since my old heat exchangers are the n/a variety, I am familiar with the leaks. I found copper coat sealant and lots of nickel anti-seize minimizes the leakage.