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Nov 4, 2007 | 11:47 PM

FESTER1st

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Senior User

Joined: Jun 2007

Posts: 239

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390 ignition timing

I have what I believe to be a late 60's 390 (with fresh heads) in a 74 F100 (A DREAM COME TRUE) internal config is unknown, a new Holley 650 dbl pmpr, a new mallory comp 9000, Edelbrock dual plane intake, headers with dual 2.5" pipes, auto trans, 3:7 gears, and 27.5" tires. I'M ONLY GETTING 10 MPG AND MY KIDS COLLEGE FUND IS DEPLETING FAST AT $3.30 A GAL. The carb is tuned and I love it, the engine is solid and I'am pleased. My symptoms are this: base timing is 4 degs BTDC with a good start and good throttle response but pings like crazy at 2900 and up WOT. Dist is set to max additional 20 degs at 2800, total 24 degs. Q: What is the base timing supposed to be and the max mech advance @ what rpm, or better yet does anybody have a mapped mech advance they could share? Also what is the expected redline, max torque and HP @ what RPM on these things? My past experiences have tought me bad ignition is related to bad MPG. I have the tools, parts, and experience I just need the any info at this point. You folks are my hope. God bless and thanks.

Last edited by FESTER1st; Nov 5, 2007 at 12:37 AM. Reason: Learning the site

Nov 5, 2007 | 12:42 AM

Bear 45/70

Post Fiend

Joined: Mar 2004

Posts: 6,056

Likes: 8

From: Union, Washington

Get rid of the DP, it's a race motor item not a street engine carb. Max timing should be about 36° to 38° at about 3000 to 3500 rpm, with vacuum disconnected and plugged. Initial don't mean crap unless your max timing is where it belongs, which yours isn't.

Nov 5, 2007 | 03:15 AM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

Posts: 88,826

Likes: 785

From: Simi Valley, CA

Quote:

Originally Posted by FESTER1st

I'M ONLY GETTING 10 MPG AND MY KIDS COLLEGE FUND IS DEPLETING FAST AT $3.30 A GAL.

Don't expect much of a gain in MPG with whatever you do. 105 octane Chevron Custom Supreme was 33 cents a gallon in the late 1960's, Leaded regular gasoline was 26 cents a gallon. There was no gas shortage, no lines at the pump, and no one then gave a hoot about gas mileage. Your truck is shaped like a brick. 9-12 MPG city is all you're gonna get. You might get 18 MPG on the highway on a good day, but 14-17 is about the norm.

Last edited by NumberDummy; Nov 5, 2007 at 03:25 AM.

Nov 5, 2007 | 04:23 AM

jowilker

Fleet Owner

Joined: Jun 1999

Posts: 24,552

Likes: 74

From: Creedmoor, North Carolina

Agree with the other posts. Too much carb, and the rear ratio is too low for cruising and getting good mpgs.

Get an Escort for a daily driver, and keep the truck for the testosterone rush when needed.

Tell the kids to study hard and earn a scholarship, dads need their fun.