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Discussion Starter #1 (Edited)
A couple years ago I bought an 89 Graduate, and the Alfa pro I had check it out before I bought it went on and on about how lucky I was that the number 3 cylinder wasn't "shot" yet. Something about how that particular manifold creates a horrible, imbalanced back pressure in #3, and I better install a free flowing header quick!!! This guy sure sounded like he knew what he was talking about. Unfortunately, he has had to close up his shop, so I cant pick his brain any longer. Anyone know what he was talking about?
 

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Well, if his sign read "Alpha Service", in place of "Alfa Service", it's not too surprising he's out of business.

He probably had a set of headers laying around he wanted to sell you. I've never heard anything about those exhaust manifolds being responsible for such alleged destruction to a motor.
 

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Discussion Starter #3 (Edited)
Hey, thanks for your reply. I will say this about the guy...he was kinda famous in the Seattle Alfa scene. Had to close up cuz rent was going through the roof (and, I think I heard the landlord wasn't renewing the lease anyway...rezoned or something.
 

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I do. He was both right and wrong.

Back when most of these were daily drivers. They would burn an exhaust valve usually between 50,000 and 80,000 miles. Closer to 50,000 if they didn't get there 30,000 valve adjustment. Closer to 80,000 if they got there valve adjustment at 30,000 and 60,000.

The header might have been a tiny bit of the problem. But the real culprit is the fuel mixture setting it had to be set at to pass emissions. On the Bosch system the fuel mixture is set with the O2 sensor unplug to around .70. Then when you plug the O2 sensor back in it would drop the CO mixture from .70 to about .20.

The leaner you run the engine the faster it will go. But the flip side is the leaner it is the hotter the cylinder temps are. Which is why they would burn a exhaust valve in that range. Most of the time it was #3 cylinder. But it would also burn #2 and #4.

Alfa started using that manifold in 1977 or 1978. Those years on the Spica injection system rarely burned valves.
 

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Discussion Starter #5 (Edited)
Another question then. Could I have the set point for the fuel mixture enriched (I hope I said that right)? Could that be done, or is it permanently programed into the system (hope I said that right, too). There isn't a smog test requirement in my county, so I'm not worried about violations:). Alternately, how about just unplugging the O2 sensor. Too rich?
 

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I'm with Eric. The main problem is probably that the L-jet can't compensate if something goes too wrong mixture-wise, and there's no check engine light to let you know there's a problem. I'll add checking for vacuum leaks and making sure your throttle position switch (TPS) is working properly to his list.

Nothing to be gained by unplugging the O2 sensor. Assuming your TPS is working it's ignored when you go full throttle anyway. Keep everything adjusted properly and check it once and again and you'll be fine.
 

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Discussion Starter #8
Great answers.

I will say, for the sake of furthering the discussion, that the Seattle guy made a point that my particular manifold (being in a narrow year range (and CA emissions, possibly)), was a culprit. To his credit, he did stress the valve adjustment issue first and foremost.

I know there are considerations with a header "upgrade", but he really put it in second position as a long term fix...with respect to the back pressure issue on #3. How much was he just trying to drum up work?
 

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The only adjustment is for idle CO (not CO2). Leave the O2 sensor connected (make sure it is working properly), check the valve clearances every so often, make sure there are no exhaust leaks and drive the car. Your valves will be fine.
I meant CO not CO2.

Thanks for catching that.
 
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Great answers.

I will say, for the sake of furthering the discussion, that the Seattle guy made a point that my particular manifold (being in a narrow year range (and CA emissions, possibly)), was a culprit. To his credit, he did stress the valve adjustment issue first and foremost.

I know there are considerations with a header "upgrade", but he really put it in second position as a long term fix...with respect to the back pressure issue on #3. How much was he just trying to drum up work?
The manifold you have was used from 77 or 78 to 89 on all the spiders. So its not really a narrow year range and they were used in all 50 states.
 

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Hey, now that's an answer I can live with...right on point. Merci. Gracias. Thankyou. I half anticipated that answer, gleaned from a parsing of everything I could put together so far. I have to say, I love this site. Hey, for giggles, he also seriously promoted a chassis stiffener. I have just started to really drive this car, and I have to say...I LOVE the flex. It feels wonderful in this little car. And I come from a serious Motor City upbringing (actually grew up in Detroit as a kid in the 50's and 60's. Well wait...that was pre unibody for the most part?
 

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And gosh even other countries :surprise: :wink2:
Pete
Interesting. I thought the rest of the world kept using the 2 piece cast iron headers and not the 4 into 2 one piece manifolds. Which are restrictive but not as restrictive as the 75/77 4 into 1 one piece manifolds.

In Alfa training classes that the manifolds form 75 on were U.S. spec for meeting emissions.

Heres a link to the one were talking about on this thread.

Classic Alfa labels it as a USA spec. manifold.

https://classicalfa.com/products.php?product=EX045-USA-SPECIFICATION-EXHAUST-MANIFOLD-%2d-SPIDER-1978%2d89
 

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Interesting. I thought the rest of the world kept using the 2 piece cast iron headers and not the 4 into 2 one piece manifolds. Which are restrictive but not as restrictive as the 75/77 4 into 1 one piece manifolds.

In Alfa training classes that the manifolds form 75 on were U.S. spec for meeting emissions.

Heres a link to the one were talking about on this thread.

Classic Alfa labels it as a USA spec. manifold.

https://classicalfa.com/products.php?product=EX045-USA-SPECIFICATION-EXHAUST-MANIFOLD-%2d-SPIDER-1978%2d89
Well happy to be wrong but I thought once we got to the Bosch L-Jet engines they were all the same. Australia had/has emission requirements too ... not sure about NZ back then, but they do now.

Would be stupid for Alfa Romeo to make different engines for different countries, especially when emissions mattered there too! But yeah, maybe that is why Alfa Romeo kicked the bucket :(
Pete
 
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