Carb Jets On 454
 

I Built A 454 30 Over 9.2 Comp Performer Intake And
The Cam Is 534/556 And A 830 Holley Carb Were Should
I Jet This At?? Thanks

Jet the carbs 5 sizes larger than box stock from holley for a baseline. That will put you close from jump street.

We had jetmech motors on the dyno yesterday. I think his jets were 88 and 92. That was for a 489ci. The only way to do it is with an air/fuel meter. then there is no risk of melting anything.

You have a pretty big carb on 454. You will have to jet it richer than normal because of that.

Also, are you running powervalves in both primaries and secondaries. That will make a difference.

I know every boat/engine is different, but just for a baseline reference that may help a bit,----I know of someone who has a pair of 454's bored .030" over, with some Holley 830cfm carbs with annular discharge and 4-corner idling adjustment screws. The engines also have mild flat tappet hydraulic cams (218*/226*), dual plane intakes, cast iron heads, 8.6 comp ratio, stock Merc Thunderbolt ignition---in the boat probably makes about 425-440hp @5100rpm.

He runs the engines in a 32' Baja and uses GIL dry exhausts, but he thinks he's running a little too rich and is fouling out spark plugs at times and black transom....too much jet in the carbs....using power valves on both sides and #86's on all 4 corners. He's going to try some #84's and see how it goes.

1 power valve.

I would start with about 82 primaries and 92 secondaries since there is no PV in the secondaries.

I had a similar spec hopped up 454 mag with a cam close to yours and milled heads for 8.9CR. I was using an 800cfm Holley.


Take plug readings at max cruise before the secondaries open to adjust the primary jets. When those are dialed in, take WOT plug readings and adjust secondary jets as needed.

THANKS GRIFF....

Annular discharge needs a smaller jet, due to the strong signal. try 80 in the frt. with power valve and 86 in rear no valve .

That could be. The reason for bigger jets on a carb that is slightly too large is because of a weaker signal.