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Discussion Starter #1
My car is running.:D, but I do not have the power I would expect from it, this is associated with occasional back firing in the tail pipe.

I have followed all of the procedures in Wes's book and the only thing I can think of at this time is the fuel mixture adjustment. I start at the recommended 8 turns in from the first thread catch on the FCS, and I usually need to rich it up (ccw) to get it running to where it sounds good, but I can see the teltale rich running smoke in the tailpipe.

Wes's procedure calls for deviding the (2) reference marks in half but he only describes 1 mark in step 2.

Thoughts?:confused:
 

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In my copy of Wes' book, Step 3 says "Unscrew the de-cel (ccw) past the highest speed. continue in 1/8 turn increments until the engine slows down again (Acts lazy).

My technique is to lean (cw) until the engine sounds "fluffy" when the throttle is blipped, mark, then richen (ccw) until it slows down. Blipping the throttle will give an instant response instead of a slight hesitation. Your looking for a very hesitation when blipping the throttle. A too rich mixture will result in a more carb-like throttle response.

With regards to lack of power, you need to make sure that when the pedal is on the floor stop, that the throttle butterflies are full open. There are A LOT of cars out there with maladjusted throttle linkages that are only getting partial throttle at best.

Regarding the backfiring, have you set the stop screws with the Stop Screw Tool? Need to make sure that with the throttle not being pressed by your foot that the throttle butterflies are completely closed. If not you'll get some burbling and backfiring.

BTW, are you finished with the Throttle Stop Screw Tool? Have you sent it on?
 

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First let me acknowledge John's expertise with the SPICA FI and all things Alfa. I would also be looking for exhaust leaks, they will cause both lack of power and backfiring, the nuts on the exhaust manifold should be brass with washers, they often need tightening, an "s" wrench is essential and to limit the damage to your hands they should be tightened when the engine is cold. I don't know if you have the stock single collector pipe or the earlier manifold with the dual down-pipes, but in either case the joint between them is suseptable the leaking, usually that joint is leaking it will need a new gasket(s), wheras the manifold to head gaskets can usually just be re-tightened. You also want to look for leaks all the way through the rest of the system. Having the correct hangers helps to keep the system from vibrating and coming loose, the bracket with bushings between the tranny and front pipe is very important. Small holes can be welded by an exhaust shop.
 

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Discussion Starter #4
No, No, No, you are not going to add yet another variable to the nightmare that is a spica tune up are you?
 

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I know how tough it can seem with your first Alfa, hang in there! Once your sure you have no exhaust leaks you eliminate a variable. At the down-pipe joint(s) the joints between the different sections of the exhaust system and small leaks from holes in the pipes & mufflers themselves are often indentifiable from the small areas of black carbon build-up.
 

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Discussion Starter #6
Actually this car has been in the family since new. Over the years I have replaced the head gasket, water pump adjusted the valves, converted it to webbers but seem to be having particular difficulty returning the car to spica form. Oh, well the life of the alfisti.
 

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Alfadan,

The best way to check the mixture if to measure the Air/Fuel ratio (A/F). Wes used to sell a "Dynograph" that indicated A/F as measured by an Oxygen sensor, but these are no longer available. I found an equivalent product, and welded a bung in the tailpipe for an Oxygen sensor, in order to properly tune my new HP pump. This, and the A/F measurement from some chassis dyno runs, indicated an over rich condition so I leaned the mixture considerably. When all else fails, spark plug color is a good indicatior of mixture, so I emailed some pictures to Wes for his analysis. The comment was "too lean, add richness". I did this, ran an autocross yesterday, and the plug read indicated a very light grey as desired (but I forgot to bring my camera). The picture below shows an earlier plug color from a slightly lean mixture. For maximum accuracy, a plug read needs to be right after some full throttle time.

Don't forget to put a little "Anti Sieze" compound on the plug threads to prevent galling...

My car is running.:D, but I do not have the power I would expect from it, this is associated with occasional back firing in the tail pipe.

I have followed all of the procedures in Wes's book and the only thing I can think of at this time is the fuel mixture adjustment. I start at the recommended 8 turns in from the first thread catch on the FCS, and I usually need to rich it up (ccw) to get it running to where it sounds good, but I can see the teltale rich running smoke in the tailpipe.

Wes's procedure calls for deviding the (2) reference marks in half but he only describes 1 mark in step 2.

Thoughts?:confused:
 

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The best way to check the mixture if to measure the Air/Fuel ratio (A/F). Wes used to sell a "Dynograph" that indicated A/F as measured by an Oxygen sensor, but these are no longer available.
There's a nifty little tool I got from the UK called a "Colourtune". It's a spark plug with a clear top that displays the combustiion process. It's great for tuning Spicas and Webers as well. A blue-white flame signals a good mixture. It's very easy to use, although I don't know if they're still being sold.

I first read about Colourtunes in an old David Vizard article in Cars and Car Conversions (a long, long, time ago). Oddly, I found that someone has posted the article on the internet. In it he describes using a Colourtune to "dyno" an engine without actually hooking up to a real dyno. Basically, he put a car on jackstands and then used the car's brakes in the same way a real dyno uses it brakes to put a car under load. While it was under load at various rps he checked the mixture with the Colourtune. I can see how it would work, but---zow---I'm not sure I want to crank up 6000 rpms with my car on jackstands. If anyone is interested, do a google search for David Vizard. The article is on the first page.

Addenum: international has Colourtunes on their website.
 
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