Slightly lean? It's a 461 9.6:1, Lunati Voodoo 262/268. Stock Quadrajet from a '68 Toronado.
Thanks.

 

A little lean.

Are those duration figures @ 0.050? That would be a lot of camshaft.

 

Thanks. Yes, at 0.050".

 

Whoo! Amazing the thing even idles.

Do all the plugs look like the one pictured?

 

The couple that I looked at did.
It doesn't run bad at all.

 

Probably time for a change.

 

Needs more fuel

 

What would be the best way to enrich the primaries a bit? Jets? Rods? Softer power piston spring?
Thanks.

 

I have no skill for reading plugs but you’re definitely looking lean to me. That carb wasn’t exactly intended to deal with a cam like that, but it will. I don’t know if it will optimize without getting into the idle air bleeds & down channels but it’s easy enough to do the simple changes and see what happens. I depend on an air/fuel gauge when tuning carbs and love that you can always see what is going on with any “circuit” that is primarily engaged and the transitions from one to another. Consider getting one (I like the AEM for fwiw) and putting a bung in the exhaust. If you opt to obtain a gauge, start with it before you do anything, get a baseline, know your numbers.

If you get serious with the tuning, disable the secondary air flap and concentrate on the primary side until it is good, then play with the secondaries. The primaries are most of your driving and have a strong effect on secondary mixture.

ASSuming you have a 71 jet, 49 rod, AU secondary rods in a stock 68 Toro Qjet, I would start with a rebuild kit if carb hasn’t been recently refreshed. I would collect a couple of base gaskets and choke horn gaskets, might want one for the throttle plate to bowl as well. When tuning Qjet primaries you will be popping the top a number of times to optimize or once or twice for “good enough.” Put a light film of grease or anti seize on gaskets so they will release cleanly on disassembly. Don’t over torque anything on reassembly, positively snugged is where things want to be.

To start recalibration I would put in 72 primary jets, maybe a softer piston spring and see what happens. You could even end up in 73 territory, rods would have to be sized accordingly for the in betweens but you have to do it in steps. If you want to get into it and you’re tuning with a gauge, uncover the APT screw in center/front throttle plate and break it loose, warning - they can be stubborn, don’t wreck it! If not using a gauge, leave the APT alone, you won’t need that precision.

This will get you started. Primary jets make a pretty big difference, rods make smaller differences. Secondary rods make noticeable differences, hangers make smaller differences.

quadrajetparts.com
quadrajetpower.com
everydayperformance.com

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Light ash deposits on a spark plug indicate too much fuel or oil contamination. Or, they simply have been in there a long time.

 

Plug reading can be hard to do like this. It is also best to do plug readings with new plugs. Are you looking for the reading at WOT or idle or general driving? Should also do all 8 plugs to have the total picture.

 

I resealed this carburetor a couple of years ago and it runs flawlessly. I will check to see what primary rods and jets it has now.

I hear that pre-ethanol carburetors are going to run lean with their original settings on modern gas. Is this correct?

Thank you.

 

99% of my driving is on the primaries (and idle circuit). I will pull the rest of the plugs to confirm.

Thank you.

 

Thanks. The engine does not consume abnormal amounts of oil, but I'll have a closer look.

 

Yes, even 10% ethanol requires a richer mixture.

 

From 71 jets to 75.

 

I always have to refer to this when I check my plugs. Hope it helps someone else.

 

No they’re not, those are advertised numbers. I’m pretty sure they don’t make @.050 lobes that big in the VooDoo series. Your @.050’s are somewhere in the high teens to 220 range.
And by the looks of these they’re not really that lean at all.
But you can stop the guesswork and buy a wideband Instead.

 

Yes, advertised duration: (Int/Exh): 262/268; Duration @ .050 (Int/Exh): 219/227;

 

I ended up installing a wideband O2 gauge.

Light and medium throttle were both very lean. WOT was spot on.

I fiddled with the power piston spring to maintain a relatively lean cruising mixture and quickly enrich once more throttle is applied. Engine is happier now and I got 14MPG with my Toro last weekend!

Well worth the money. I was thinking on getting a Sniper EFI unit and now I'm having second thoughts.