1969c10
Forum Newbie
Posts: 44
Loc: california
Reg: 06-24-08
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04-27-12 04:37 PM - Post#2219768
Hello, I have a 355 SBC, stock stroke, 9.1:1 static compression, roughly 7.7:1 dynamic compression, cam duration is 204/214 @ 0.05 and lift of 420/442, quench is .040, 1.5 ratio rocker arms. I'm using the MSD GM small cap computer controlled distributor. The base map for timing that I picked is 25 idle/4? wot. 25 degrees at idle sound high? Maybe thats normal with fuel injection, not sure? What is the best timing base map for my set up. Thanks
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Danny Cabral
Member
Posts: 3144
Loc: Ellington, CT
Reg: 11-03-04
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04-28-12 02:08 AM - Post#2219862
In response to 1969c10
25 degrees at idle sound high?
No, although with that camshaft, you may find it idles better at 20°.
It's not an EFI thing; a mechanical distributor would usually have the initial timing with the vacuum advance (connected to manifold vacuum) providing about the same amount of idle timing advance. This misconception occurs because a carbureted application requires the mechanic to temporarily disconnect & plug the vacuum advance canister to check the initial timing. That's why usually only 8°-12° is seen at idle but the engine normally runs with the additional vacuum advance functioning (+10°-15°).
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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1969c10
Forum Newbie
Posts: 44
Loc: california
Reg: 06-24-08
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04-28-12 11:07 AM - Post#2219961
In response to Danny Cabral
Thanks Danny. I totally brain farted on the plugging the vac line with a nail to set timimng on the old distributors. Hopefully I won't have to change a whole lot with the base timing map during fine tuning.
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zwede
Senior Member
Posts: 1499
Reg: 01-10-03
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04-28-12 11:40 AM - Post#2219972
In response to 1969c10
With such a small cam you need to have a fairly slow advance curve. Have a look at the charts in this manual to see how a small cam needs a slower curve. Page 5 is of special interest:
http://www.google.com/url?sa=t&rct=j&am p;q=&am...
I agree with Danny that 20 dgr idle advance sounds more like it for you.
Edited by zwede on 04-28-12 11:41 AM. Reason for edit: No reason given.
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