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Author Topic:   Timing ??
steve'66
Gearhead

Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000

posted 04-27-2002 12:20 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Guys,

This 408w doesn't want to idle with less than 30 degrees advance at idle. I double checked the timing pointer w/my tdc gauge tonight. I locked it out at 35 degrees and it is very happy. But what do you think is the reason it won't idle lower? I checked for vac leaks and didn't find any, it runs great locked out. Am I missing something? This cam isn't that radical.

SteveW

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Larry Jennings
Gearhead

Posts: 540
From: Redwood City, Ca. USA
Registered: Apr 2000

posted 04-27-2002 12:30 AM     Click Here to See the Profile for Larry Jennings   Click Here to Email Larry Jennings     Edit/Delete Message   Reply w/Quote
Rotor phase?

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No matter what's happening, there's always somebody that takes it way too seriously.

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steve'66
Gearhead

Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000

posted 04-27-2002 12:45 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
I dunno Larry,

At tdc the rotor is pointing directly at the #1 plug wire. Could it be a vacumm leak? I didn't assemble this long block, but I trust the guy who did.
It'll work locked out and starts fine, so maybe I won't worry about it. Any ideas?

SteveW

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Larry Jennings
Gearhead

Posts: 540
From: Redwood City, Ca. USA
Registered: Apr 2000

posted 04-27-2002 01:09 AM     Click Here to See the Profile for Larry Jennings   Click Here to Email Larry Jennings     Edit/Delete Message   Reply w/Quote
Did you find TDC with a piston stop by turning the engine in each direction and marking the stops then dividing the rusults? Or did you make a small assumption as to where true TDC might be? The damper is not used for anything during assembly and can easily be off a few degrees, and it doesn't mean the builder was on crack if it is. they're off so often that it's on our regular check list now.

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No matter what's happening, there's always somebody that takes it way too seriously.

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bluestreek
Gearhead

Posts: 1460
From: Athens,GA
Registered: Jul 2001

posted 04-27-2002 01:14 AM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
What rpm are you trying to idle it at? The only times I have seen one that won't idle at timing under 30 degrees was because the cam was retarded too much, the compression was too low for the duration of the cam, or the idle mixture was wrong. 22-28 degrees base timing is pretty normal for a racing cam, but 30 degrees don't seem normal in your situation.

Get it going hero... We want to see some 10s.

[This message has been edited by bluestreek (edited 04-27-2002).]

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67Coupster
Gearhead

Posts: 179
From: Fortson, GA, USA
Registered: Oct 2001

posted 04-27-2002 06:50 AM     Click Here to See the Profile for 67Coupster   Click Here to Email 67Coupster     Edit/Delete Message   Reply w/Quote
Steve the cam in my 393W is very similiar to your duration @ .050. I had to work at mine a little bit to get a decent idle. Mine was pig rich or it was in the transition circuit. I ended up opening up the secondary plate a little and also drilling some holes in all four throttle plates to get enough air in so it would work on the idle circuit. Then I added some more initial timing, it currently is at 16 degrees initial and 35 total all in by about 2500 rpm. It has a very nice 1100 rpm idle now. Just a little more info for you to ponder. Later

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James
67 Coupe
393W, AFR 185, 4 Speed, 4.11 9 inch
7.09 @ 97MPH 1/8
1.55 60'
'66 Fairlane 500XL
Daily Driver

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steve'66
Gearhead

Posts: 7226
From: Sonoma,CA,USA
Registered: Mar 2000

posted 04-27-2002 10:38 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Thanks,

Yeah I'll try the secondary idle circuit on the 850 dp that should help. Also I used a stop and checked it both direction. TDC was off on my pointer by 5 degrees.

I works fine locked out though.

SteveW

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