US spec Spider CS1 Cams?

Road-race engines and ancillaries - general discussion
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Mark W
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US spec Spider CS1 Cams?

Post by Mark W »

I’ve just bought a 1977 US spec Fiat Spider 124 CS1 and am looking to freshen up the engine. From various publications, it would seem that this spec 1800 engine has the lowest output of any of the units fitted to Spiders. It certainly doesn’t ‘sparkle’ on the road.

From what I understand, to bring the unit up to 115 bhp euro spec, I need to raise the compression and fit the 4-2-1 cast exhaust manifold along with a more suitable carb. I am thinking along the lines of a Weber 28/36. Obviously, all the air injection plumbing will be removed as well.

Am I correct in thinking that the US spec cams are different and need to be swapped, or can I retain them? I find it hard to believe that an exhaust and compression change would account for the lost 30 bhp.

Regards

Mark
Guy Croft
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Re: US spec Spider CS1 Cams?

Post by Guy Croft »

I have a feeling (only ever seen one pair) that the cams may be lower lift than Euro-spec..

As far as comparative bHP goes, I think the 118bhp spec you mention is the 9.8/1 CR 124BC series with twin Weber 40IDFs.

G
Mark W
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Re: US spec Spider CS1 Cams?

Post by Mark W »

Thanks Guy.
I had a feeling that the cams would be different. At least lift is an easy parameter to measure.

A pair of Euro spec cams on the shopping list as well then.

Mark
vandor
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Re: US spec Spider CS1 Cams?

Post by vandor »

Guy Croft wrote: I think the 118bhp spec you mention is the 9.8/1 CR 124BC series with twin Weber 40IDFs.
The 124BC (and 124BS) had the 1608 engine with twin IDFs, and was rated at 110 BHP.
The 124CC (and 124CS) had the 1756cc engine with single 34mm 2-barrel single carb, and was rated at 118 BHP.

In the US the 1756 engine had lower compression (8.0:1 vs 9.8:1), as smaller carb (32mm single 2-barrel), more restrictive exhaust manifold, air injection, and EGR. The ignition advance was also different.
The 49-state version was rated at 86 BHP. A well running, stock, US-spec 1800 still feels peppy.

It is hard to compare Fiat cams, because Fiat changed the clearance at which they measure cam timing. For the US 1608, cam timing was measured at running clearance, and it was 26/66-66/26. For the 1800 it was measured at a much larger clearance (forget the figure, maybe 2mm?), and it was published as 5/55-55/5. However, when measured, both cams had the same profile.

If I were you, I'd leave the cams for last. I'd get a larger carb (the Weber 32/36DFEV works very well), upgrade the exhaust manifold, and convert to electronic ignition (you can use a later distributor with a better advance curve).
When it come to rebuilding the engine you can use domed pistons to get the compression back to Euro specs. Just be cautious of pistons with too high domes (8mm), as they give a CR around 11:1.
bye,

Csaba
Auto Ricambi, LLC - 124 Spider Specialists
http://www.autoricambi.us
GC book #288
emil
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Re: US spec Spider CS1 Cams?

Post by emil »

Hello Mark,
I don't know if this is still of interest to you. I have measured a number of Fiat cams, including those from a 1979 2L US Smog engine, a 1974 Euro 1800cc and a Euro 1608cc engine. The cam profiles were all identical (I'll gladly post the profiles if anyone is interested)! I have read in numerous places that the 1608 cams are "the hottest standard Fiat cam" etc. etc. My opinion is that this is not true. What does differ however, is the cam timing. There were huge differences in the timing of the cams between the engines. If I were you I'd stick with the stock cams for now, and get a pair of adjustable cam wheels instead. If you feel like upgrading to hotter cams in the future the cam wheels will still be useful.

In addition, like Csaba wrote, there is a significant difference in the cam timing (at least between the Euro 1608cc and the 2L US engine) and I would strongly recommend that you replace or rebuild the distributor.

Regards,
Emil
'74 Fiat 124 Spider
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