[alfa] Re: 105.48 Cam Timing

["Dean" <tessiedog@xxxxxxxxxxxxx>]

Thanks George.
Pats book is very informative however some information given is not correct.
Overlap is of course important however with the duration of the 10548 Cam it
serves no use to increase it. With the settings you describe you can obtain
an effect of supercharging the chamber at high rpm.
I am interested in your opinion on the engine dyno software. How accurate
this may be in calculating HP.
Cheers,
Dean
----- Original Message -----
From: "George Beston" <gbeston@domain.elided>
To: <tessiedog@domain.elided>
Sent: Monday, March 01, 2004 11:20 AM
Subject: 105.48 Cam Timing


> Hi Dean,
>
> I was glad to see your comments about  an unquestioned error in modern
> Alfa lore regarding cam timing.  I'm not sure of the original source of
> this.  It might be Joe Benson, the author of the Buyer's Guide.  Back
> in the 1970's, Joe was the technical editor of Alfa Owner, the US AROC
> publication.  Whoever the author was, my best guess is that this
> suggestion was a reaction to camshaft and timing changes made in the
> mid 1970's as part of keeping emissions within US requirements.  I
> think it was an attempt to make valve overlap more like it had been in
> prior years, as if it was a worthwhile criterion in the first place!
>
>   They would definitely have been better to focus on ignition timing
> which was 9 degrees ATC at idle!
>
> I have done a lot of work with 105.48 cam timing in my Alfetta guided
> by a friend who is skillful with an engine simulation software package
> called Dynomation.  The lobe centres I'm now using are intake 123 ATC,
> and exhaust 103 BTC.  This works very well.  I have published these
> results a number of times on the digest, but I have yet to make a dent
> in the armor of the  cam timing myth that Pat perpetuated in his book.
>
> No one has ever come back to me and questioned my conclusions.  I'm
> ready to invite anyone to make their own cam timing choice and compare
> data with them.  By the way, Dynomation says that the Braden
> recommendations will result in about a 10 hp loss.  Quite significant
> when the baseline is only 110 hp, which was all the de-smogged mid
> '70's 2L would deliver.
>
> If you want more detail on the work I have done, I can send you
> electronic versions of some articles I have written for the Canadian
> Alfa Club's newsletter.
>
> Regards;
>
> George
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