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Author Topic: camshaft ponderings  (Read 1966 times)
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RobD
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« on: 22 November, 2014, 10:46:59 AM »

Having only recently acquired the Fulvia I'm still  familiarising myself with idiosyncrasies of the marque so please bear with me if some of my queries are a bit naive.
I knew the Fulvia had two camshafts but up until this morning I'd assumed it was in essence a SOHC V4. It was only whilst staring at a diagram in the owners booklet it dawned on me the engine was a true DOHC. This opens up opportunities for cam timing experiments which could be useful for me.
I've picked up from other threads that early Fulvias had vernier adjustment on the cams and I wondered if the later cars could be adapted to accept the earlier cam timing arrangement.
The reason for asking is from previous experience with Italian race bikes I've noticed Italian engine designers often favour quite aggressive cam timing . On one particular bike we built for endurance racing we reduced the cam overlap and ended up with an engine which had a much improved midrange with negligible adverse effect on top end power. It didn't come on the cam quite as dramatically but the lap times were quicker because the power was so much more accessible .
I'm hoping to enter my Fulvia in hillclimbs next season and the ability to finely adjust the cams is of interest, if anybody has experience of this I'd really like to hear about it.
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'75 Fulvia 1.3S
'68 works Laverda 125cc ISDT
KTM 640 Adventure
Yamaha TDM 900
Numerous Gas Gas trail bikes...
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roddy
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« Reply #1 on: 14 December, 2014, 06:32:31 PM »

Hello Robb

Welcome to Fulvia ownership.  I see it is some weeks since you posted this question, and you may have got the answer already?  You may now be aware that the S3 Fulvia has slotted key-ways for fitting the chain-wheels to the camshafts, which can only allow the cam timing to be adjusted by a complete chain link.  A Series 2 coupé will have cams with the same profiles, but using the vernier adjustment chain-wheels.  This allows infinitely adjustable alteration of the individual camshafts.  Remember, adjusting an inlet cam will require the distributor timing to also be re-set.  Be aware, Series 1 cars have a different timing chain / wheel / sprockets (the rollers of the chain are a larger diameter than the S2 units).

Good luck experimenting, but very often, the factory got it just right.....

Regards - Roddy Young
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Roddy Young
Dunfermline, Fife

1970 Fulvia Sport S1 1.3S
1972 Fulvia Sport 1600
lancialulu
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« Reply #2 on: 14 December, 2014, 08:18:11 PM »

Am I right in remembering the a chain link equals 11 degrees?
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Its not the winning but taking part! or is it taking apart?
1955 Aurelia B12
1967 Flavia Vignale iniezione
1967 Fulvia 1.3HFR
1972 Fulvia 1600HF
1972 Fulvia 1600HF
1972 1600 Fulvia Sport
1979 2500 Gamma Coupe
1988 Delta 1.6GTi
1998 Zeta
RobD
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« Reply #3 on: 16 December, 2014, 12:05:02 AM »

Hi Roddy,
Thanks for the info. On some engines I've worked on in the past it's possible to flip the cam chain wheel over 180 degrees and this provides half a tooth of adjustment. I wonder if that's possible with the Fulvia?
I think I'll keep an eye open for some Series 2 camshafts... perhaps the lack of adjustment on the series 3 camshafts is evidence of FIAT cost cutting.
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You're all entitled to my opinion.
'75 Fulvia 1.3S
'68 works Laverda 125cc ISDT
KTM 640 Adventure
Yamaha TDM 900
Numerous Gas Gas trail bikes...
www.adventureride.co.uk
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