Jetting baseline for new 302 build

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Jetting baseline for new 302 build Empty Jetting baseline for new 302 build

Post  HorsinAround on April 26th 2018, 10:34 am

Hey guys, I'm finishing my Ranger project and am looking to get a baseline set up for the carb. Engine is a stock 302 mustang bottom end, GT40x heads with just clean up porting, F303 cam 226 dur at .050, .512 lift with factory rocker ratio. Weiand dual plane and a Holley 4777-5 650dp carb. Currently have 68 primary jets and 74 secondaries with a 6.5 pv and 28 nozzles.

Is this jetting a good place to start?
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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  dfree383 on April 26th 2018, 11:08 am

Yep
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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  nuclearcobra on May 17th 2018, 4:10 pm

On the 302 in my 76 mustang which had the same carb 4777 but with a victor jr intake and the jegs/kaase heads on a stock bottom end and a flat hyd cam 244 and 534 lift the jetting was best at 70-78 for me.
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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  DeepRoots on November 14th 2018, 8:07 pm

4777-4 and -5 are roughly the same...  here is my data on it:

List number 4777-4
Type 4150
Primary
Float Center hung brass
Booster Straight leg .139
Pump nozzle .028
Pump type and cam 30cc pink#1
Idle air bleed .075
High speed bleed        .030
Metering block# 11170
Main Jet        67
Power valve 6.5
PVCR       .039
Emulsion       2@.027
Kill Bleed upper dogleg (plugged by me with 4-40 set screw)
Idle Feed restriction .035
Needle and seat .110
Throttle plate size 172/173

Secondary
Mechanical or Vacuum? MS
Spring color na
Diapghram length na
Float Center hung brass
Booster Straight let .139
Pump Nozzle .028
Pump type and cam 30cc Pink#1
Idle air bleed .055
High speed bleed        .030
Metering block/plate# 11166
Idle Feed Restriction .039
Secondary jet                      73
Emulsion setup 2@.027 each side.  Upper dogleg was drilled, I plugged with 4-40 set screw
Needle and seat .110


67 is the stock main jet, if your cruise vac is way down due to massive camshaft you might go as big as 70, otherwise I'd enlarge the PVCR as it's pretty small as delivered, I'd go as large as .050 and keep the jet low at the lean limit. Plugging the old emulsion tube feed is nice, seems I get a cruise surge sometimes if it isn't plugged.

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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  rmcomprandy on November 14th 2018, 8:12 pm

Original jetting when new would be a good place to start.

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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  HorsinAround on March 19th 2019, 9:45 am

If the plugs show lean (whiteish color) how many jet sizes would you go up to start?
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Jetting baseline for new 302 build Empty Re: Jetting baseline for new 302 build

Post  stanger68 on March 20th 2019, 5:13 pm

I always go 4-5 sizes at a time you’ll find the rich or lean side of the tuning window a lot faster. After you find the rich side of the window back up until the plugs stay clean.

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