Home › Forum › Ask A Member › ’67 80 hp; hey, wait a minute.
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fleetwin.
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September 20, 2020 at 6:56 pm #216940
Long story short; motor seems to starve out at the upper ranges of the throttle. Lots and lots of work; can’t seem to iron it out.
Thought I’d inspect the carb on the way in to the leaf assemblies.
Pulled the orifice plugs, (which I’d carefully replaced; even ordered a jet tool).
They are different sizes. Not only by eye, but by carefully inserting a tapered probe. Goes about twice as far into one as the other.
I see the numbers are written in different script, but they’re the same numbers.
I’ll replace both, and take a hard look at them first. But if anyone has any insight on this I’d sure appreciate it. All opinions welcome,
Many thanks and happy motoring.
AlanSeptember 20, 2020 at 7:05 pm #216945Alan, which jets have the larger holes?? The new ones, or the ones that were in your carb? Someone before you, may have enlarged the holes in your jets with a drill, which is a big no no.
Do the new jets have a “D” or “C” stamped next to the number? It doesn’t look that way to me, but the two different letters indicate opposite fuel flow directions. Keep in mind that the fuel inlets may be tapered slightly which is normal…But, your pictures sure make it seem like the actual hole diameter is different on the two jets…September 20, 2020 at 8:13 pm #216949I’d wager that somebody has drilled one or both out. The number designated the hole diameter, or .064″ A number 52 drill is .0635″ if you have one for a gage. Or, of course 1/16″ is .0625″.
September 20, 2020 at 9:32 pm #216956Replies appreciated.
These were purportedly new and OMC NOS. I wouldn’t dream of drilling a jet, myself. Like I say, I even sprang for the jet tool, and actually waited.Each one feeds a carb throat, so the fuel goes in the same direction for both.
They were shiny, and appeared new, with smooth orifices. I looked at the numbers, and quit there. Won’t do that again.
My shadetree guess is this was a manufacturing error, but I don’t claim to know much. If someone drilled ’em, they did good work, with a pretty little chamfer. Since I’m making stuff up, I’ll guess the larger of the two is correct. It looks a lot closer to 1/16″ to me. That big ‘ol V4 is thirsty.The fact that the stamped numbers are in a different script is interesting.
I won’t complain about the lost time. Maybe.
Thanks for the opportunity to vent.
Peace.
AlanSeptember 21, 2020 at 5:29 am #216975Going back to the original condition, did you ever get around to shooting fuel down the carb throat when the condition manifested itself? Did the speed pick up when you shot fuel down the throat fed by the smaller jet?
This all goes to prove that no matter how careful and conscientious your are, the Big Guy is gonna find a way to test you.
Long live American manufacturing!
September 21, 2020 at 7:27 am #216981I am not saying the new jets were drilled out, am saying the old jets may have been drilled out….I am assssuming that the old jets have the larger holes, perhaps this is not the case. And yes, back then there was only one direction of fuel flow for fixed jets, so there was no need for “C” or “D” indicators. But, there have been many different styles of carbs used since then.
If your new jets have the larger holes, I would find a number 52 drill like Frank described, measure it, and see which jets are correct.
Good work on the jet screwdriver, it is nice when folks follow through on our advice…. -
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