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Pinto carb test
We all know that a pair of DCOE carbs will give more power than a single downdraught on a 2-litre Pinto, but how much, and are 45s better than 40s?
Times have changed, we are all online and it seems everyone has a rolling road.We certainly live in enlightened times but something which amazes me is when it comes to old-school Ford stuff is that people are still repeating the same unsubstantiated made-up numbers that were circulating when I was young!
So having grown up with car mags I have a soft spot for them and finding myself in a position to install at my work place an iconic Superflow 901 dyno just like tuning guru and author, DavidVizard used to write about, I just had to put a few old myths to the test — starting with the power gains available from swapping carbs on 2-litre Pintos.
For this test I was to compare twinWeber 40 and 45 DCOE carb upgrades against a standardWeber 32/36 on a bog-standard, not even rebuilt, 2-litre Pinto with an injection head. As soon as I dreamt up the test in my head
I could hear all the experts saying it was a waste of time even trying such upgrades — especially the 45s — but I wasn’t so sure. Back when I sold go faster bits, I had access to, and in fact still have, the paper jet settings given by the Dell’Orto importer for all manor of engines, and on the data sheet for twin 40s and a Pinto it said, ‘45s may be better even on a standard engine’. I had to put it to the test.
The 32/36
So the Pinto was bolted to the dyno, a cheapo 4-2-1 exhaust manifold fitted along with a 32/36 carb and initially a K&N filter. I pretty soon left the K&N off because it made rejetting the carb easier and made no difference to the power. I optimised the ignition timing without any vacuum advance and left it the same for all the tests.
With the 32/36 the engine made peak of 107.4 bhp and 125.3 lb.ft.
The 40s
Next up the 40s were fitted with 32 mm chokes (going any bigger is pointless). Surprisingly, there was no loss of lowdown power, peak torque jumped by 6 lb.ft and we now had a peak power of 117.6 bhp.
The 45s
For the 45’s I removed the 36 mm chokes already fitted and installed 34s — the reason being the 36s will support well over 150 bhp and this slightly-worn, standard engine was never going to get anywhere near that. Did the 45s work?They certainly did, in fact through most of the rev range they gave more torque than either the 40s or 32/36,
“WAS IT A WASTE OF TIME TRYING THE WEBER 45s? I WASN’T SO SURE...”
only losing out slightly down at around 2000-2500 rpm. Peak power was up another 3 bhp to 120.3 bhp, but what was very noticeable is they held onto the power a full 500 rpm longer than the 40s.
Worth it?
So is it worth putting sidedraughts on a standard Pinto? Below 4000 rpm there is little difference, so unless your going to modify the engine further or rev it, then no. But if you are planning further upgrades or like living life between 4000 and 6000 rpm, then hell yes!
So 40s or 45s? In my test between 4000-5000 rpm the curves for the two carbs sizes swapped a couple of times, as the AFRs wandered around a bit, but the differences are small and the ability to rev on better certainly wins the day for the 45s.
Downsides of the 45s?Well, a couple: you have to be a gentler applying full throttle at low speed or the engine will just sulk, but if you are flooring it down at 2000 rpm you are either in the wrong gear or need to buy a diesel! So I don’t count that one. One difference is definitely jetting them — with 40s my first guess is often close enough, but the 45s are a lot harder to get right.You are unlikely to be able to buy a pair of 45s and use then without a re-jet but can often do that with 40s.The big carbs cost more, too, but if you feel the need for speed…
So is there an elephant in the room?Yes, the good old 38 DGAS! My old boss used to tell everyone you will gain 10 bhp by fitting one to a standard engine — well, you wont! I didn’t include it in this test but I have run one on this engine and it made no noticeable difference to power — exactly the same thing DaveWalker controversially stated in the 1980s!
“THE ABILITY TO REV ON BETTER WINS THE DAY FOR THE 45s”