DCOE progression circuit for 8V TC

[Nero]

I've been having challenges with getting my 8V TC running as crisply as I would like. The issues comes down to the progression circuit. The first set of DCOE's were 45 model 150's, which were a mistake as they were made for a blow through turbo application and I could never get the progression circuit working properly as there would always be an off-idle stumble. Following advice that the DCOE 152's were not ideal for the TC I found some vintage DCOE Model 13's and these are much, much better. However they have had a hard life and I have some issues with the carbs returning quickly to idle - they do this slowly (there are no air leaks and the quadrant/linkage set is new) and I've been advised to check for a bent throttle shaft.
Given these vintage DCOE's are much sought after by vintage racers I was thinking of moving them on and buying a pair of new DCOE's, the models with the individual throttle bleeds. Now my question is: does an 8V Fiat need a quick enrichment in the progression circuit? 'Normal' DCOE 152's have 3 progression holes and the 152G's have four. The latter are richer in the initial progression and would this be of any advantage?

[Slawo2000]

I had similar problem with 45 DCOE's model 9. These carbs have only two progression holes and there was a terrible stumble in progression circuit. I've tried different things to get rid of it, but the results were rather poor. Finally I sold them and I bought pair of DCOE's 152G. The progression now is much smoother, not yet perfect, but I think carbs need some small adjustment yet to work perfectly.
I know there are also DCOE's 152 with 5 progression holes to work with Ford Zetec engines. Maybe they would be the best for 8v TC?

Here is an interesting article about progression circuit in 45's:
http://www.alfabb.com/bb/forums/carbure ... ation.html

[Nero]

Thanks for that. I have seen the Alfa information before and I had wondered about the specifics. I found that if I got a really good initial idle I had a bad stumble at 2800. When I leaned out and got close to smooth at 2800 the lower end and response was flat...fuel injection is looking damned attractive at the moment! Each engine has it's own requirements I and I wondered about the Fiat TC.

[Guy Croft]

It would be helpful if you could publish your full engine spec incl full carb choke/jettting, cams and header/muffler setup.

GC

[robert kenney]

Definatly agree, to trouble shoot from afar all current settings and jets installed will be helpful. How far out are you on your idle mixture screws at best idle quality? Could help show if your pilots are correct or to small.

Without knowing I would go up 10 on main air correctors and 5 on main fuel jets. and test

I really don't believe the progression holes are the issue as 2800, you are solidly in the pilots and maybe beginning to draw from the emulsion tubes. You will likely benefit from a more powerful air emulsion IE bigger air correctors and comp the top end AFR's with bigger mains

Robert

[Snakeman]

Hi All,

I currently run Electronic Fuel Injection on my S2 Montecarlo, but the club I intend to race with this year,the Classic Sports Car Club will only allow me to compete if I run it on carbs. So, I am looking to install DCOE 45's.

My engine is a an 8V 2.0L, GCT Stage II with GC3A cams, STD valves & cast pistons.

Am I better looking out for vintage DCOE 13's or will the newer 152's be OK for my purposes?

Thanks
Geoff