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02-25-2010, 03:11 PM
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#1 |
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Registered User
Join Date: Aug 2007
Location: Puyallup, Washington
Posts: 63
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Advance question
I've been trying to get my old 307 tuned and optimized as much as I can lately and I ran into something that is a little confusing.
I've got an old Mallory dual point distributor that I converted to electronic, so that's all good, but the advance has me a little puzzled. Mallory says the vacuum advance should start to come in at about 7". At idle (about 850 rpm) I've got 15-16". If I disconnect the vacuum line to the advance canister, the timing mark doesn't move. Do I have a bad vacuum advance unit or do I need a different one for lower vacuum? Also, at 850 rpm it appears that the mechanical advance is already coming in. Do I want to get a curve kit and put in some stiffer springs to move it up a bit? Tim
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1970 C10 LWB with SB 307 & TH350 |
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02-25-2010, 03:24 PM
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#2 |
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Between Trucks...
Join Date: Mar 2002
Location: Los Angeles, CA.
Posts: 3,830
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Re: Advance question
Are you hooked up to ported or manifold vacuum? The springs in the advance kits aren't that strong really. Might be better to grab some springs out of a distributor at a junk yard. Factory springs are usually stiffer then even the stiff springs in those kits.
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Beat it to fit, Paint it to match... 
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02-25-2010, 04:27 PM
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#3 |
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Registered User
Join Date: Aug 2007
Location: Puyallup, Washington
Posts: 63
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Re: Advance question
Oh yes. I forgot to mention. I'm running full manifold vacuum. Carter AFB, plugged into the port on the drivers side.
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1970 C10 LWB with SB 307 & TH350 |
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02-25-2010, 04:44 PM
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#4 |
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Between Trucks...
Join Date: Mar 2002
Location: Los Angeles, CA.
Posts: 3,830
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Re: Advance question
Might want to test the vacuum advance. This is on an HEI, but should be similar on yours.
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Beat it to fit, Paint it to match...
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