carburettor progession holes

Those are tough to find. Let us know if you find one. I think I would start checking with Eurospares in the UK first though

 

jth5610

A few years ago I replaced the carbs on my 78 GTS (72+), with new, but earlier series (45-48).

In general, the different series differ by progression hole pattern, float level, and jetting. Within a series, the differences are linkage pieces. That is, a 45 is the same as a 48 except for lever arms and series stamping.

I cannot tell you how 45 series carbs performs relative to a 72 series carbs. But intuitively, I believe one should match the series to simplify tuning.

It turns out that I have a spare 45 carb body which appears ok to which you can swap the relative fittings. PM me if interested in the 45 body.

Bill

 

You might be in luck

I think I have one, but will need to verify the progression holes, and I am going on vacation for a week starting tommorow. I might trade you for the newer one you have, what is the number stamped on the back of the mismatched one you have?

Geno

 

I have a new set if you don't come right !! But look what Fchat has already dug up ???

 

The progression holes have a significant impact upon the AFR coming off idle. The size and position relative to other holes and the edge of the butterfly has a big impact upon driveability because, frankly, much of your driving time is spent at very modest throttle openings with slight variations to speed up or slow down a little.

You're destined to have mediocre tune at best if your DCNFs aren't matched, and more likely you'll have poor tune when you factor in all the other variables of the DCNF which can just make things worse.

That said, you're not alone. Mis-matched DCNFs on carb'd 308's is very common place. Why? Because when one carb goes bad (cross threaded jet, corrosion in the bowl, etc.) it's a rare man that takes the time to find a matching carb, and an even rarer one who would take on the expense of replacing all four when a match can't be found.

Good luck in your search!