<I'm thinking of putting some 1608cc cams in my 1756cc. I have the cams, I think they're good, why not try it? OK. What should I expect? I'd like to hear from people who've done this re: pros, cons, etc.

Okay, you asked for it... Here's a copy of a couple of previous posts of mine on the same topic (although I'm afraid that I don't have any 1756 data). I make no claims to being an expert, I've never actually put a 1608 cam in another motor, but hopefully this will provide some food for thought:

I've heard sources both in NZ and the USA extolling the virtues of the 1608 & 1438 cams, however I'm not convinced. Care needs to be taken when interpreting Fiat cam timing data. The specifications that I have seen for cam timing on early 124s (AC and BC, 1438 and 1608cc versions) are given at running clearances, whereas the valve opening and closing specifications for later engines are normally given at increased clearances (to prevent the quietening ramps on the cam flanks from interfering with the timing measurements?). At the increased checking clearances the duration of the valve opening is LESS than at running clearances: so the later engines "appear" to have less duration. This has caused some confusion among some Fiat tuners who have replaced cams in 2000cc Fiat engines with those from 1438cc versions on the basis that the latter provide greater duration (on paper...), and hence more power. In reality the power improvements have probably only been psychological: at running clearances I believe that the 2000cc cams (okay, there are 2000 cams and 2000 cams...) actually provide greater lift and duration than the 1438cc ones. However if the 1438 cams end up at different timing than the 2000cc ones, then engine characteristics may well change...

To confirm my suspicions I took four different cams, set each up in a cam box, and measured the cam profiles with a dial gauge and protractor. The cams that I compared were from a 1438 cc 124, a 2000cc 131 (=USA Brava) Racing, a 2000cc Lancia HPE (all "Euro spec"), and a 2000cc (unknown model)

USA spec Fiat. The lift vs rotation graphs clearly showed that the 131R cam had the highest lift and duration, and the 124 had the least. The Euro Lancia and USA Fiat cams were VERY similar (shape as well as lift), and were between the 124 and the 131. Moral of the story: read the specifications carefully! Only a very limited sample I know, and I'd be interested in hearing from anybody with other data.

Depending original cam timing of your car, retiming the cams to European specifications may.... provide a performance improvement. One of (USA) Fiat's approaches to lowering emissions during the 1970s was to greatly reduce the overlap of the inlet and exhaust cams. This reduced the emissions, but also virtually destroyed the power output. Fiat, not surprisingly, seems to have taken the easiest route to altering the cam timing and manufactured cam wheels/cams with different timing (I'm not sure if the difference is in the cam wheel or the dowel hole in the end of the cam). I used the USA Fiat cam in the rebuild of my Lancia engine, redrilled a cam wheel to get the timing correct, and measured the resulting timing and duration which matched the Euro specs for my motor.

As my (admittedly crude test on a very small sample size) measurements showed, the USA cams are not necessarily very (any?) different to European cams. How effective is it to retime USA cams to "Euro" specs on a USA engine?

So much for my hypothesis: who's got dyno results to prove me right or wrong?

Side issue: In rebuilding a few Fiat DOHC engines I've been surprised at the variations in actual valve timing compared to spec (I've measured up to 6 degrees out). This is on engines without any head or cam box machining. I have my doubts about how good Fiat's tolerances were on the cams/cam wheels, and recommend checking timing and redrilling cam wheels if required. Oh for adjustable cam wheels like an Alfa!

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Discussion continues:

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<<<Ah HA! Someone is finally onto something:

>>Depending original cam timing of your car, retiming the cams to European specifications may.... provide a performance improvement. One of (USA) Fiat's approaches to lowering emissions during the 1970s was to greatly reduce the overlap of the inlet and exhaust cams. This reduced the emissions, but also virtually destroyed the power output.

<The cam timing is a bigger issue than you may think. For example, (and if Ihave these facts backwards, please correct me) the Lancia Beta (US) uses a timing gear that profiles the cam timing differently than that in the Fiat 2.0. One of the tricks discovered a few years ago is to put the Fiat gear on the Lancia (not to mention the Fiat ones are steel). As I understand it, what you're getting with a "1608" et al cam is not so much a different cam, but a different timing profile, thanks to the dowl pin on the cam in relationship to the hole in your sprocket...

My suspicions exactly Dr Watson.... :-))

<Indeed, what we need is adjustable cam gears to find out just what can be achieved with the stock camshafts. I know they once existed for the SOHC engines, but don't recall ever seeing them for the twin cams.

I've seen twin cam ones advertised in some English catalogue from about 10 years ago..

I made a pair once, by setting the cam wheels up in a dividing head (sort of like a big drill chuck you mount to a mill or drill table, with a handle that you turn and indexed plates you use to accurately rotate the workpiece by the required angle) on a mill and drilling a series of holes (6 from memory) around the wheels at slightly different positions relative to the gear "teeth". By choosing the positions of the holes carefully (can't remember the exact angles off hand, but I think that I have my calculations at home) you end up with a wheel which can be set up at any angle within about 2 degrees. (Similar in concept to the Alfa system, if a bit more of a hassle to use). Fiddly to make, but possible and not too expensive, particularly if you have free access to a machine shop.... For a road use motor which is only going to be used in one state of tune you only have to drill one hole in the correct position relative to the teeth.

This is what I did with my Lancia engine. I set up the motor initially and checked the timing, removed the wheel, indexed the dividing head off the original dowel hole and redrilled a new hole at 180 degrees + whatever was required to get it right. Even drilled another index hole for the timing marks attached to the head to make life easier in the future.

Re metal vs plastic cam wheels.. Rule one when removing a plastic cam wheel is to throw it across the workshop so it hits a hard object and shatters... that way nobody will ever try to reuse it! They can and do fail... whenever possible replace with steel wheels.