View Full Version : hmmm...carb jetting??

03-10-2003, 07:53 AM
Okay, good questions from before..

Griz, I am working on a 1992 22C with an OMC 454-340hp. The original Holley carb came stock with 73 primaries and 56 secondaries, which I thought was slightly bizarre..

I called Holley tech in Bowling Green, and they say it should be 56 primary and 73 secondary, according to their *books*. Since the carb is 100% original and never before opened up, I made another call to Holley Restoration in Springfield, Tenn where they said to ignore the BG tech guys, and put it back exactly like it was. *Their* books say what I started with is correct. The Tenn tech says *ALL* the marine carbs are jetted way lean like this on the secondaries. I could buy that theory, except 17 sizes down is a BIG number...

Whatta ya think?? This engine has factory *original style* manifolds with thru transom only exit.


Still in Criterion EFI remorse..

<small>[ March 10, 2003, 06:55 AM: Message edited by: BUIZILLA ]</small>

03-11-2003, 12:30 PM
I don't like it but it works because the power valve actually richens up the circuit. If you check the powervalve it is really big and eliminates the transistion bogg. I said I didn't like it because I wan't more control, I ysually do a smaller power valve and richer secondaries. I do think you need to call holley in Ca. and get a third openion. Mine has a bigger secondary jet in my stocker. Mine is older but had a 75 in the secondaries but had been apart. In any event DO not put the small jets in the primaries. it has no power valve!!!

<small>[ March 13, 2003, 08:45 AM: Message edited by: Harbormaster ]</small>

03-11-2003, 01:14 PM
Griz, this carb DOES have front and rear power valves, it was built new that way, and they are both 2.5's. They ARE the high flow power valves..

I'm just having a hard time accepting the 17 size smaller jets on the secondary circuit... eek!

Anybody else run into this malady? :confused:


03-11-2003, 03:29 PM
like I said I would cal Ca for 3rd opinion. The thing is your bosat runs fine right?

03-11-2003, 05:16 PM
actually, it wouldn't idle without belching smoke...both PV's were broken..
I'll call Callyfor and see what they say..

thanx, J

03-11-2003, 06:00 PM
That doesn't sound right to me. I would think that you could fry that engine because it has to go way lean on the secondaries. I have bigger jets than that in my Holley on a 351 Ford. 68's in the primaries and 76's in the secondaries. They have been running ok for years that way. That is how the carb came from Holley. I don't believe they jet them that lean.
Bill G

03-11-2003, 06:40 PM
Are we talking about a jet plate on the secondaries or does it have a drilled metering plate. If it is a drilled plate the number doesn't correspond to a jet no.
Bill G

03-11-2003, 08:59 PM
Is this square flange holley or Quadrajet style? The difference between a high flow and regular power valve would not have anything to do with your jetting or even effect your engine at all at your power level. The number corresponds to the inches of vacum it opens up. Is this vacum operated secondaries? I am not big boat guy but I can only assume it is due to boat constantly lugging around in that primary range? Buy a $10 power valve protector and invest in a $35 BG rebuild kit with reuseable gaskets if you plan on playing with jetting. By the way at idle the carb is not running through your jets yet. Jets are used to meter off idle and up circuits. Holley's are notorious for fat idle due to stock power valves opening to early or being damaged from minor backfire. Good luck

03-11-2003, 09:45 PM
Bill, it's a 4150 series square bore 750 cfm with transfer tube and has a jet block and vacuum secondary's.. Poodle and I confirmed every piece/number/code is factory original..
I bought the correct Holley kit, but the cheapskates don't include the nylon throttle shaft seal rings anymore.. :rolleyes: I've been waiting 2 weeks for those already..
I've built over 200 Holleys b4 and I have at least 10 in the garage now, and this particular *parts stackup* just seems wierd. I could see a 4-6 number spread...but 17 smaller?? :confused:
If anyone has an ORIGINAL distributor for an OMC 454 laying around, I would be interested in purchasing it.

thanx , J

03-12-2003, 11:51 AM
I can't find any Holley 750 carbs that run a jet that small. For every jet size change there is an approximate 4.5% change in fuel flow. Assuming a 17 size change,that is 76% less fuel being delivered to those barrels. I'm assuming that the venturi sizes are the same front and rear. That just doesn't seem even close to the correct jet size.
Bill G

03-12-2003, 12:20 PM
Bill, I gotta believe this 56 thing is wrong. It has to be..


03-13-2003, 01:03 AM
I checked tonight and that is correct thr powervalves take up the slack. that is why they are so big. in front and back. I was told that this works because the powervalves work together and stops hesitation on acceleration and is good for fuel economy on that carb set-up. Guys don't get creative and change yours to match this comfiguration-there is more involved than just this. On my blower motor since it is a blower motor,I took them out because it is a blow through and the venturies are always under pressure they don't work as designed. So I must run big jets.

Formula Jr
03-13-2003, 02:59 AM
Buizilla, your post sent me on the quest of the "I know I have that thingy" search. Well two hours later, I found the remains of my old style 4150/60 holley rebuild kit. The contents of which are your's if you send me a place to send it to via e-mail. :)
Its got these little teflon/nylon? wrap thingys in it. I guess that's the part you seek.
"Bushings." Man, I love that word. "Bushings.....", "Bushings....." :)

Big Griz eats carbs for breakfast. wink

<small>[ March 13, 2003, 02:22 AM: Message edited by: Formula Jr ]</small>

03-13-2003, 07:38 AM
Jr....u got mail..

thanx :)

Griz...I hear ya loud and clear....obviously, it doesn't make common sense to any of us gearheads. wink


03-13-2003, 09:48 AM
This is one hell of an interesting thread.