Olin,
FWIW, it has been my experience with high compression pistons, in any older
engine (read as cast iron heads) you will need a different vac unit. What
you want in the end is for less total vacuum advance timing to come in
earlier, but have overall less advance maximum when you add vacuum and
mechanical.
Cheers,
Chris
BJ8...prepping to move yet again
----- Original Message -----
From: <olin.brimberry@talecris.com>
To: <healeys@autox.team.net>
Sent: Tuesday, October 18, 2005 1:37 PM
Subject: Vacuum Advance Units - High Compression
> My problem is that over long runs at 3000+ rpm in OD, I am getting some
> pinging and overheating. Everything below 3000 is great. I want to avoid
> advancing too much, but I am thinking that maybe I need to have my
> distributor set up for hi-compression. I have high compression pistons
> (arias) and my cam was suppose to be ground to BJ8 specs. From memory, my
> timing is advancing to approx 30-35 degrees around 2000 RPM. I still have
> the stock distributor and assume the same advance unit. I am running the
> 3.54 rear end with a 28% OD, so I am sure that it adds to the torque
> requirements.
>
> Per the email from Curt below, I would be interested in knowing the vacuum
> settings (normally 5-12-8 for MKII) for the "High compression special
> orders" vacuum units. IE, the start of advance, max advance, etc. If
> anyone could relay that information I would certainly appreciate it.
> Better yet, if you have a good one lying around for sale, email directly.
>
> What do the racers do when they keep the stock distributor and have high
> performance guts?
>
> Regards,
>
> Olin Brimberry
> Raleigh, NC
> 62 BT7
>
>
>
> Date: Sun, 16 Oct 2005 18:20:31 EDT
> From: CNAArndt@aol.com
> Subject: Re: Distributor Vacuum Units
>
> Josef,
>
> Off the top of my head ;) here is a short list through 1960.
>
> BN1/2
>
> 1953-55 Early distributor 40320A - vacuum 420006
>
> 1955 Early 100M distributor 40422 - vacuum 420755
>
> 1956 Later distributor 40495A - vacuum 54411727
>
> 1956 Later 100M distributor 40520A - vacuum 54411233
>
> BN4/6
>
> 1957 For distributor 40532A - the vacuum control unit is 54412033. I
> believe
> that this the one for the BN4.
>
> 1958-59 For distributor 40581A/B - the vacuum contol unit is 421189, which
> should be for the BN6.
>
>
> 3000 Mk1
>
> 1959-60 distributor 40662A/D - vacuum 421189
>
> AN5
>
> 1958-59 distributor 40561D/H - vacuum 54411100
>
> 1960 distributor 40561J vacuum 54411100
>
> "High compression special orders."
>
> 1958-59 distributor 40656A/B & E - vacuum 425700
>
> 1960 distributor 40656D & F - vacuum 425700
>
> Cheers,
>
> Curt Arndt
> Carlsbad, CA
> '55 BN1, '60 AN5 :{) '72 RWA Midget
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