Subject: Re: [Fot] Advance BTDC for 1296 Spit?

From: Mike Harmuth via Fot <[email-masked]>
Date: Sat, 21 Nov 2020 15:41:12 -0500

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Bud, I'm running 34 degrees from 3500 up and could probably go more. I used
to run 36 with an older, lower compression engine, but that was with a
pertronix set up. Currently using a points system from Jeff at Advanced set
up (19 degrees mechanical advance up to 3500) for this cam (APT-BK74) and
compression ~ 13.2.  No knocking, no overheating, could probably go some
more still tweaking the fuel system.

mike h

On Sat, Nov 21, 2020 at 1:46 PM Bud Rolofson via Fot <[email-masked]>
wrote:

> Listerati,
>
> I=E2=80=99m curious what total advance you Spifire racers are using @3000=
-4000 RPM
> and up?
>
> I had someone in New Mexico swear that he runs 48 degrees @4000 RPM and
> backs down by 2 degrees until it doesn=E2=80=99t knock on WOT. I=E2=80=99=
m not sure I=E2=80=99m
> brave enough to run that much advance.
>
> What say you list? What total advance are you running at what RPM. And
> what compression ratio?
>
> I=E2=80=99m running 36 degrees total advance @ 3000 RPM for a 12.52 compr=
ession
> engine and that=E2=80=99s worked pretty good so far. But I=E2=80=99m alwa=
ys looking to get
> out of the corners faster yet pull hard in the straights sooo=E2=80=A6=E2=
=80=A6??
>
> Thanks
> Bud Rolofson
>
> Extreme Parts Racing (more than just a haircut)
>
> 71TR6 CC57365 (Good 6)
> 71 Spitfire MK IV Race Car #3
> 69 Spitfire MK III (back up FE engine/dinghy car)
> 93 Minnie Winnie Race Support Vehicle
> 77 Z-50A Hardly Davidson Honda Mini-Trail Bike (Triumph Pit Bike)
>
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<div dir=3D"ltr">Bud, I&#39;m running 34 degrees from 3500 up and could pro=
bably go more. I used to run 36 with an older, lower compression engine, bu=
t that was with a pertronix set up. Currently using a points system from Je=
ff at Advanced set up=C2=A0(19 degrees mechanical advance up to 3500) for t=
his cam (APT-BK74) and compression ~ 13.2.=C2=A0 No knocking, no overheatin=
g, could probably go some more still tweaking the fuel system.<div><br></di=
v><div>mike h</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" cl=
ass=3D"gmail_attr">On Sat, Nov 21, 2020 at 1:46 PM Bud Rolofson via Fot &lt=
;<a href=3D"mailto:[email-masked]">[email-masked]</a>&gt; wrote:<br=
></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;=
border-left:1px solid rgb(204,204,204);padding-left:1ex">Listerati,<br>
<br>
I=E2=80=99m curious what total advance you Spifire racers are using @3000-4=
000 RPM and up? <br>
<br>
I had someone in New Mexico swear that he runs 48 degrees @4000 RPM and bac=
ks down by 2 degrees until it doesn=E2=80=99t knock on WOT. I=E2=80=99m not=
 sure I=E2=80=99m brave enough to run that much advance.<br>
<br>
What say you list? What total advance are you running at what RPM. And what=
 compression ratio?<br>
<br>
I=E2=80=99m running 36 degrees total advance @ 3000 RPM for a 12.52 compres=
sion engine and that=E2=80=99s worked pretty good so far. But I=E2=80=99m a=
lways looking to get out of the corners faster yet pull hard in the straigh=
ts sooo=E2=80=A6=E2=80=A6??<br>
<br>
Thanks<br>
Bud Rolofson<br>
<br>
Extreme Parts Racing (more than just a haircut)<br>
<br>
71TR6 CC57365 (Good 6)<br>
71 Spitfire MK IV Race Car #3<br>
69 Spitfire MK III (back up FE engine/dinghy car)<br>
93 Minnie Winnie Race Support Vehicle <br>
77 Z-50A Hardly Davidson Honda Mini-Trail Bike (Triumph Pit Bike)<br>
<br>
_______________________________________________<br>
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<br>
</blockquote></div>

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From: Greg Hilyer via Fot <[email-masked]>
Date: Sat, 21 Nov 2020 15:10:02 -0700

Hi Bud,
I can’t speak to a 12.5 1296 but I can speak to tuning for altitude. I do a fair amount of dyno tuning at 5500’ here in Albuquerque. Be it a 40hp Formula Vee or a 500hp V8, if the engine was properly timed at sea level I’ll usually end up 4-5 degrees advanced from where it was. I’ll go up 2 degrees per pull until the power goes backwards and then set it for peak power minus maybe one degree for safety sake. The one caveat is to remember to dial it back when going to the lowlands!
Starting at 48(!) degrees and backing down sounds like a recipe for disaster. Must be hell on starters too - if it will even crank over with that much timing.
A chassis dyno is your friend and doesn’t lie.
People seem to think it’s expensive but that’s really not the case - maybe my dyno guy treats me exceptionally well, but I can get two “base-line” pulls for $40 (and sometimes that’s all I’ll do for the session) and rarely over $150 for extensive tuning (8-10 pulls. 
My $.02 worth,
Greg “Lunker” Hilyer 
Albuquerque NM

> On Nov 21, 2020, at 11:42 AM, Bud Rolofson via Fot <[email-masked]> wrote:
> 
> Listerati,
> 
> I’m curious what total advance you Spifire racers are using @3000-4000 RPM and up? 
> 
> I had someone in New Mexico swear that he runs 48 degrees @4000 RPM and backs down by 2 degrees until it doesn’t knock on WOT. I’m not sure I’m brave enough to run that much advance.
> 
> What say you list? What total advance are you running at what RPM. And what compression ratio?
> 
> I’m running 36 degrees total advance @ 3000 RPM for a 12.52 compression engine and that’s worked pretty good so far. But I’m always looking to get out of the corners faster yet pull hard in the straights sooo……??
> 
> Thanks
> Bud Rolofson
> 
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/[email-masked]
> 
> 

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