Is Header up-grade worth doing?
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Pretty much anything is better than the S3 one piece manifold if yours is so equipped.
Unless a set of the ubercool tuned equal length pipes is going in, the current idea seems to be that the 2 piece stock S2 manifold is as good as an aftermarket header or vice~versa.
Unlikely you'll notice a sound difference as the cans deal with that and powerwise you might see a bit up high, or you might not depending on what manifold system you're thinking of getting rid of. Down low might be less than w/stock manifolds, or it might not.
Lotta variables make for a lotta different potential results.
If nothing else, the header is prolly a bit physically lighter than stock manifolds.
Unless a set of the ubercool tuned equal length pipes is going in, the current idea seems to be that the 2 piece stock S2 manifold is as good as an aftermarket header or vice~versa.
Unlikely you'll notice a sound difference as the cans deal with that and powerwise you might see a bit up high, or you might not depending on what manifold system you're thinking of getting rid of. Down low might be less than w/stock manifolds, or it might not.
Lotta variables make for a lotta different potential results.
If nothing else, the header is prolly a bit physically lighter than stock manifolds.
Thanks Darren, yes i have the original one piece manifold. The centerline catalog says 10-15% power increase with their header. The guy I spoke to at centerline says 5-7 HP increase. I'm inclined to believe the 5-7 HP is more accurate.
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Dyno tests in the 80s here in the Bay Area showed the stock Weber/Spica cast 4-2-1 piece through 1974 was the best normal-rpm manifold. Tube headers were better at very high rpm, generally worse down low. We're talking on the order of 3-5%, not a ton.
This is covered in the Vandenburg papers in extreme detail in the AROC Spica manual. He tested air filters, induction systems, headers, cams, pumps, CO levels, all kinds of variables. It was all pre-Bosch, but the results apply to exhaust.
Some tube headers are very poor quality; some are fine. I have IAP headers on my track car, and they fit surprisingly well, and have not cracked in 7-8 years.
Andrew
This is covered in the Vandenburg papers in extreme detail in the AROC Spica manual. He tested air filters, induction systems, headers, cams, pumps, CO levels, all kinds of variables. It was all pre-Bosch, but the results apply to exhaust.
Some tube headers are very poor quality; some are fine. I have IAP headers on my track car, and they fit surprisingly well, and have not cracked in 7-8 years.
Andrew
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I say pre-'75 4-2-1 manifolds with the accompanying non-cat pre-'75 OEM exhaust. You'll need to weld in a bung for an O2 sensor, but that's cheap and easy to do. This setup made a very positive change on my '87 Spider.
I noticed IAP now sells new 2 piece manifolds. I do not think they sold them a year ago. Just checked the website and do not see them but they are in the spring IAP catalog. Seperate parts numbers - inner branches part 14252 and outer branches 14253. Each is $219 so $498 total. IAP header is only $298. If you go with the 2 peice manifold route I assume you can just put on a pre-cat stock or magna flow exhaust system, assuming you do not have to worry about emissions. This seems like a good option. You more than make back your mainfold vs header premium on the pre-cat front piece of the exhaust system. IAP prices are $219 vs $445. Again this seems like a good option.
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If you ordered the Centerline headers, you made an excellent choice... I have ordered their units several times, and the most recent order was 2 years ago. It is a bolt-on piece that fits well (nothing to cut or weld, with the O2 sensor bung already built-in) and will make a difference in what you can get out of your 1983 stock engine. That said, the manifold / header upgrade is just one component of the system. It alone will not give you a "wow" effect in real world driving conditions, although you will notice the improvement.
The next component that you need to address is the catalytic converter. I have not kept up with what is available, but how they are constructed does make a huge difference. Today's cat have a free flow design, which the OEM unit did not. Thus, just about anything will be an improvement, but units vary in price considerably and they are certainly not made the same. Along those same lines, a free flow design muffler will also make a difference. Upgrade all these components, and you will be very happy that you did, although once you total the cost you may be surprised at how expensive it is to get a few more hp.
Last, I would suggest that you send the new headers to Jet-Hot for a coating. That will keep your headers looking like new for the rest of their life.
Best regards,
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990 Posts
I haven't installed headers on an Alfa but wanted to chime in here on the noise. Every car I've installed headers on has had a considerable noise increase in noticeable noise coming from the engine bay. Not so much that it is a lot louder, just more annoying. I'm sure the Alfa folks will chime in here about this but my thinking is that it depends on what you are trying to do with the car. If you are going to be continually trying to improve engine performance and don't mind such changes, then headers make sense. But if you aren't going to be doing other improvements then I personally would leave something cast iron in place.
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