Cam setup

[Cox]

I have a 1973 Fiat 124 CSA with following specifications:

10.5:1 CR
Alquati 087 42/82 camshafts
43.5 inlet valve
36.5 exhaust valve
cylinder head inlet and exhaust ported
OE inlet manifold ported
OE exhaust manifold
Weber 44 IDF with trumpets and free flow air filter


To do the setup I have following questions:

Are the Alquatis a good choice?
What timing would you suggest? (in and ex cam)

The Car is running well. What I¢ž¢m missing is the top end power in forth and fifth.
Maybe a free flow exhaust will change things.

Thanks Paul

[Guy Croft]

Paul, hi

Assume 1800cc? Those Alquati cams are certainly good (for what they are) but are just a mild StII. I think stock figure is 110 deg but for max top end power with best torque - overall - I'd time them at 104deg inlet and 108 deg ex.

You will certainly get benefit from 4-2-1 header, and a single straight-thru 2.5" bore silencer is imperative. Say 18" x 8" x 5" flat oval. The George Polley AX891 is ideal for that car. I'd go ex header bores 1.5" primary, 1.75" secondary, 2" tailpipe. Use py length with that cam timing 23" and 10" secondary. Link 1&4 py and 2&3.

Pipe lengths are pipe chord length only (ie: measurement of bore axis around bends) and do not include the length of the collector joints which are independent of pipe pressure-wave criteria.

GC

[Cox]

Hi Guy,

Thanks for the prompt answer. I have a 4-2-1 Manifold, the OE one Fiat No. 4306618 for the 124 CSA, but the silencers are aftermarket ones. While browsing in the net, I've seen a setup from Quicksilver exhausts with only one silencer and a single exit. Ok Abarth like would be the dual exit, which I have. But that don't help much if the flow is restricted. I'll weld a layout like you recommend, out of my aftermarket ones.
The cam timing that you recommended I'll try and will give the results later.

Thanks
Paul

[Guy Croft]

I know the OE production header from Fiat-Abarth because I used to own a 124CSA, but that is pretty useless really. I have seen 'works' ex headers on some 1800 124CSA units which are 4-2-1 with much longer and equalise pipes 17" py and 17" sy dims, similar bores to those I gave above. They seemed to worked fine and sure, I copied those layouts for quite a while.
But my suggested specs come from recent software analysis and dyno test and that has proved over and over that the best 'area under the torque curve' comes from long py short sy in the overall 32-35" range, py/sy lengths varied within a fixed overall length according to engine spec - eg: cam timing and inlet tract length and where you want the optimum power band.

GC

[sumplug]

Guy.
Noticed there is a growing band of tuners using unequal length primary Pipes. Have you any knowledge on this?

Andy.

[Guy Croft]

Yes, Andy.

& I know about people trying to 'copy' techniques from er, 'Touring Cars' etc etc - like odd pairings of the 4-2-1, thinking that if works on a touring car it will work for them. I have no doubt that if you played around with the header characteristics - that is if you had very advanced software to examine such a thing in the requisite detail - you could generate particularly strong torque results within quite specific engine speeds to match a particular circuit and gearset, yes. And that system might well look very different from anything else.

Most of us have to make do with a system that copes especially well across as wide a range as possible. As for the 'guessers' and 'copiers' out there, even assuming the setup they are copying is fully optimised - and they are unlikely ever to have access to that kind of highly confidential information - if you don't copy the engine setup top-to-bottomit won't work at all well compared with a more contemporary setup and yes, I have seen examples.

If a reader - for reasons best known to them - deviates radically from the kind of advice re lengths, equalisations and pairings that I give on this site, well, good luck to them, I really don't want to know...!

GC