What jets is everyone running in there holley's

-
skep419

skep419

No show, all go!
Joined
Sep 18, 2008
Messages
5,943
Reaction score
5,071
Location
Minesoooota
71's and 80's w/4.5pv here. 750 holley street hp mechanical sec.
It came with 75 and 80
 
750 dp.....84 and 92 on E85.....in vegas

750 dp 73 and 81 on gas....in vegas
 
Without knowing anything about the engine build, this is preposterous. You might as well gamble on "what's out of the box."
 
67Dart273 said:
Without knowing anything about the engine build, this is preposterous. You might as well gamble on "what's out of the box."
Click to expand...


Not looking to copy anyone's jet sizes. Was just curious what split (primary vs secondary) everyone else is using.

Sorry for the misunderstanding
 
skep419 said:
Not looking to copy anyone's jet sizes. Was just curious what split (primary vs secondary) everyone else is using.

Sorry for the misunderstanding
Click to expand...

That's the thing---lots of stuff affects jetting, including type of intake, car weight and gearing, ..........................................
 
normal split between front and back is around 8 jet sizes...if..there is no power valve in the rear but a power valve in the front...

also.....the diameter of Power valve restrictor channel will determine the split between front and rear..

the PVRC is behind the the power valve....must unscrew it to check it....
 
PVCR as tony says.

That carb has a 5 step up spread and that's ideally what you want unless you enlarge the PVCR
 
Gary Busey can tell you what jets to run. He's a carburetor genius.
 
Slap an O2 bung in one of the collectors, "rent" an Innovate LC-1 off of eBay and tune it out.
 
You should keep the difference between primaries and secondaries the same as from the factory unless you start making major changes, like eliminating power valves, cutting off choke towers, etc. Different manifolds and spacers can affect distribution also, but you need to be able to "read" the plugs correctly (not always possible) or have the proper data acquisition instrumentation to compare cylinders.

Here is a lot of good Holley info. For their original carb jetting, click on "Carb Numerical Listing".

http://www.holley.com/TechService/Library.asp

I was lucky once and noticed a difference in plug color using a dual plane intake. Turned out that the cylinders fed by the lower level of the dual plane was running leaner than the upper level. (weaker vacuum signal?) So I adjusted the jets 2-3 numbers on one side of the carb and the car picked up at least a half a tenth. Your results may vary.
 
Altitude makes a difference too. I'm at 5000+ ft elevation, and we have always jetted the carb down a few sizes from stock so it wouldn't be so rich.
 
skep419 said:
71's and 80's w/4.5pv here. 750 holley street hp mechanical sec.
It came with 75 and 80
Click to expand...
Sorry to say this post is useless. Who really looks at what "jets" another is using? I tune my combo and it is what it is.
 
You must log in or register to reply here.
-

Back
Top