Carb Tuning or Something Else
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Senior User
Joined: Aug 2004
Posts: 389
Likes: 0
From: Nassau Co. NY
Carb Tuning or Something Else
Motor:351m
Headers, full lenth
Weiand 8010
Holley 600CFM (80457-S)
Timing set unknown (assume stock) timed at 10 degrees BTDC
Cam unknown (assume stock)
Dizzy stock
So I recently install a new intake and carb on my 351m in a '78 F150. Everything I have read is that the 80457-S is pretty much plug n play with minor tuning needed.
I set the timing to 10BTDC with the vacuum advance disconected from the "spark" port on the carb. Valve cover decal calls for 6 degrees but 10 gave the best vacuum.
The problem I'm having is if I get on the throttle hard from a stop (4 speed so second gear) its kinda boggy and breaks up a bit. At a cruise if I floor it it just falls on its face sputtering. I'm thinking the secondary spring too soft and they are opening up too early. If Im gentle on the throttle she runs well with no sputtering at all anywhere in the RPM range.
I dont have a ton of experience with carbs and wanted to check if there wasnt something Im missing. Possibly with the timing.
Headers, full lenth
Weiand 8010
Holley 600CFM (80457-S)
Timing set unknown (assume stock) timed at 10 degrees BTDC
Cam unknown (assume stock)
Dizzy stock
So I recently install a new intake and carb on my 351m in a '78 F150. Everything I have read is that the 80457-S is pretty much plug n play with minor tuning needed.
I set the timing to 10BTDC with the vacuum advance disconected from the "spark" port on the carb. Valve cover decal calls for 6 degrees but 10 gave the best vacuum.
The problem I'm having is if I get on the throttle hard from a stop (4 speed so second gear) its kinda boggy and breaks up a bit. At a cruise if I floor it it just falls on its face sputtering. I'm thinking the secondary spring too soft and they are opening up too early. If Im gentle on the throttle she runs well with no sputtering at all anywhere in the RPM range.
I dont have a ton of experience with carbs and wanted to check if there wasnt something Im missing. Possibly with the timing.
Elder User
Joined: Nov 2003
Posts: 778
Likes: 2
From: southeast Idaho
If its your timing just go the other way with it and see if that fixes it. Also check to make sure your accelerator pump squirts a good steady stream all thru the throttle stroke for idle to open, with it not running, you'll need to look down the primary bores to see it. Should start as soon as the throttle moves and when all the way open it should have a little play left in the pump so its not bottomed out around .010 or a bit more I think.
If that doesnt help there are several possibilities but one step at a time works best usually
If that doesnt help there are several possibilities but one step at a time works best usually
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