Holley 600 carb jetting

[JL8Jeff]

I'm wondering how much I need to go up on the primary jets on the Holley 600 vac secondary carb that is on the ZZ3 motor in my jet boat. I did a quick run yesterday and had a bad stumble off idle and found it has .025 pump nozzle which seems way too small so I'll try .031 and then .035 if necessary. The carb has 66 primary jets and I'm not sure what the rear plate is until I can open it up again but it says it has the silver spring in the vacuum secondary. Here are the plugs which look pretty lean but I think they are platinum and only 1 of them had the bottom puck left on it so most of them were .050 or larger gap. I just put the recommended AC MR43LTS plugs in gapped closer to .042 like stock. The distributor is a MSD street unit with no vacuum advance connected. I can't get the engine to idle with the open headers so I can't verify the timing right now. I have some 72 jets but I'm thinking I should try 68 or 70 first to see how the plugs look.

[WildBillyT]

You mentioned you are changing the squirters- what pump cam do you have?

FYI:

[JL8Jeff]

It has one of the white cams but I'm not sure which one. I think the arm was misadjusted and was too tight which may have allowed fuel to drip out at idle. I read that the 600 should have the .031 squirter stock and it has a .025 which is pretty small. I found the baseplate gasket was the wrong one and it's too small and sticking into the carb so I replaced that. I put the 72 jets in today and I'm waiting on the squirters to try them. But I can't run the motor at the house, I need to put the jet drive in the water so it doesn't burn up the new cutlass bearing. I need the muffler inserts before I will run it at the ramp again. The secondary metering plate was the 34R 9716B with a 6 stamped into it and that looks like it's equal to 69 rear jets so that might not be too bad for now. The jet drive will limit the rpm's the motor can actually use so I think the 600 should work. It should be fun getting this dialed in.

[PolarBear]

Jeff, I have a whole squirter and pump arm kit, it has all of them. You can borrow it so you can try different things out if you want.
It is this one
https://www.summitracing.com/parts/hly-36-184/overview/

[JL8Jeff]

Nice! I may take you up on it once I have the exhaust quiet enough to start to do some tuning. You remember how loud that speed skiff was? This is way louder than that right now so I can't really run it this way.

[PolarBear]

Originally Posted by JL8Jeff

Nice! I may take you up on it once I have the exhaust quiet enough to start to do some tuning. You remember how loud that speed skiff was? This is way louder than that right now so I can't really run it this way.

Yeah, i think I had ear plugs and still got bad ringing in my ears, lol. I can't imagine this one

Originally Posted by JL8Jeff

It has one of the white cams but I'm not sure which one.

Just FYI, there is only one cam of each color(except pink maybe?), it just has two holes in it and depending which hole you use you get the different fuel profile.

[JL8Jeff]

It turns out the primary throttle shaft was twisted and the throttle plates were a bit corroded. So I got some new plates and a new shaft. Installed the .031 nozzle and 72 jets along with new plugs. It still didn't want to idle below 1000 rpm's yet but it would at least idle so I could check the timing. It's too loud with the headers and the muffler inserts so I need to switch to the water cooled exhaust. But the hesitation is gone and it runs strong. It was either breaking up or I was getting a sudden vibration from the driveline or pump at the higher rpm's so I couldn't stay in it. I think it might be the HEI because the wire harness only had either 14 or 16 gauge wire in it so I ran a new 12 gauge wire to the HEI and need to recheck it. I'll try opening the secondary throttle blades a little bit to see if it helps the idle.

[BonzoHansen]

I fought all sorts of vibration issues that ended up being caused by problems with a god awful expensive MSD HEI. New Davis HEI and problems solved.

[JL8Jeff]

Originally Posted by BonzoHansen

I fought all sorts of vibration issues that ended up being caused by problems with a god awful expensive MSD HEI. New Davis HEI and problems solved.

I've read the same thing in several places so I'm already thinking that may be the culprit. I have to see what old parts I have sitting around to possibly swap out for testing.

[WildBillyT]

Originally Posted by BonzoHansen

I fought all sorts of vibration issues that ended up being caused by problems with a god awful expensive MSD HEI. New Davis HEI and problems solved.

I thought it was an Accel dizzy?

[BonzoHansen]

Originally Posted by WildBillyT

I thought it was an Accel dizzy?

you are a distributor behind.....

[WildBillyT]

Jesus christ.

[BonzoHansen]

you have no idea.

[JL8Jeff]

I ran a heavier gauge wire to the HEI and took it out for a run today and the vibration/breaking up seems to be gone. Now to get some quieter exhaust so I can run it for more than 5 minutes!

[JL8Jeff]

Figured I would update this. I gave up on the used carb and I ended up getting a refurbished 600 from Holley and the engine ran a lot better right away. I picked up 1000 rpm's from 5000 max to 6000 now. Turns out the check ball for the secondaries was jammed in place and not allowing them to open at all. I did a little more tuning and I'm currently running 76 primary jets and the purple spring for the secondaries. The boat almost jumps out of the water when you floor it from idle and it feels like the top speed is in the 70-75 mph range.

[BonzoHansen]

Where do we send the flowers? Glad you got it fixed