Wrong headers for the street? Ulix?

carl

True Classic
This is picking up from another current thread where Ulix said the old SERRA headers were not good for the street. The headers on my Bertone looked to be essentially the same as shown here:

IMG_0414[2].JPG


Hard to see but the collector is just below and to the rear of the frame member. Ulix is this a "bad" configuration for the street which causes a flat spot around 2,000 to 3,000 rpm? As I had noted in the other exhaust thread my DCOEs ran very rich off idle but jetted OK at idle and higher rpm and I could not find any jetting that would lean out the "flat spot".
 
my DCOEs ran very rich off idle but jetted OK at idle and higher rpm and I could not find any jetting that would lean out the "flat spot".

Carl, I would doubt the headers are causing this problem, it's the DCOE's... progression holes vary between different models and what your describing is classic "progression pause" (stumble due to a rich condition) you should do a bunch of reading on the subject... this is probably a good place to start.
https://www.alfabb.com/bb/forums/carburetors-fuel-injection-air-intake/32856-weber-dcoe45-152-45dcoe-progression-circuit-modification.html

SteveC
 
Steve, I will read that link. It's Ulix's comment in the other exhaust thread about the SERRA header design, which seems the same as mine was causing 2k-3k rpm issues that might have been the cause of my DCOE headache.

I got part way into that Alfa article and they may be chasing a different problem than mine. I don't have an off idle stumble, I have a very rich condition at steady cruising just off idle. I know about off idle progression issues with IDFs on my spiders.

In any event, I'll get back to this when I reinstall the DCOEs after I get the 77X on the road.
 
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This is picking up from another current thread where Ulix said the old SERRA headers were not good for the street. The headers on my Bertone looked to be essentially the same as shown here:

View attachment 14521

Hard to see but the collector is just below and to the rear of the frame member. Ulix is this a "bad" configuration for the street which causes a flat spot around 2,000 to 3,000 rpm? As I had noted in the other exhaust thread my DCOEs ran very rich off idle but jetted OK at idle and higher rpm and I could not find any jetting that would lean out the "flat spot".
That does not look like a Serra header although the collector ends up in about the same place. The Serra header runs a bit more straight back before going down, and cylinders 1 & 4 are the rear downpipes where as this header 2 & 3 are the rear downpipes.
 
This is picking up from another current thread where Ulix said the old SERRA headers were not good for the street. The headers on my Bertone looked to be essentially the same as shown here:

View attachment 14521

Hard to see but the collector is just below and to the rear of the frame member. Ulix is this a "bad" configuration for the street which causes a flat spot around 2,000 to 3,000 rpm? As I had noted in the other exhaust thread my DCOEs ran very rich off idle but jetted OK at idle and higher rpm and I could not find any jetting that would lean out the "flat spot".
I had a flat spot problem with my DCNFs when I first got them. Got rid of it completely by finding the right emulsion tubes to richen the mixture a bit more at that throttle setting.
 
Carl, I don't know the Serra header personally. Only the PBS header which looks very similar and which you may even have on your car.
And I only reported my experiences.
My problem went away completely when I switched from the PBS header and exhaust pictured to a stock 1974 exhaust manifold and muffler.
 
OK. Maybe I'll play with emulsion tubes when I get the carbs back on some time this winter. It also occurred to me to use an infrared thermometer to check header pipes to make sure they are showing the same temps.
 
OK. Maybe I'll play with emulsion tubes when I get the carbs back on some time this winter. It also occurred to me to use an infrared thermometer to check header pipes to make sure they are showing the same temps.

Carl:

Remember, if you are going to IR read exhaust tube temps, they need to me measured at the same distance away from the exhaust manifold flange. The #1 and #4 distances from the flange can be different locations than #2 and #3.
 
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