Here’s the latest reader question, along with my reply!
Gary asks: The carb was diagnosed as no good by my mechanic. Was running crappy all of a sudden. That was after they installed a timing chain cover. Can’t understand that one. All of a sudden it was running rough. So rough, I had it towed instead of driving it. Did not want to keep dumping fuel into cylinders. Not good. And it was leaking around the carb too. So after two rebuilt install attempts, the mechanic was told rebuilt’s will not work on a Mark V 460. Must go with new Holley. OK I said. I got it back and it is a half inch taller. Looks weird. They replaced my original wingnut for the air cover with a screw. That sucks. Now it has a hard time making it up a hill. The old carb before it went bad was amazing. Great power even though it is only 200 horses carrying 5000 pounds. So after some research, it looks like it is running way too lean. It also says that is just as bad if not worse than too rich.Premature detonation I think it said can damage engine. The start up when cold stinks too which I can live with. Still annoys me though because the Holley was $900.00 installed. I was hoping the carb would come out of box being new, and not needing any adjustments. It is idling too high as well because it preignited which I have not heard in years. The AC comes on and the idle go’s up which it is suppose to. But it go’s up to about 800 RPM. What should I suggest or demand? Does the half inch extra height indicate the wrong carb? Should I insist on the right one if so? Or just let him try to adjust it which I am sure he will want to do? Never getting a car with a carburetor again. Or maybe it is the mechanic. Sorry for going so long but these damn things are complicated. Thanks Eric. Did David Knight ever mention why he changed his show’s name from Real News to the David Knight Show? Some leftist news organization complained I would bet.
My reply: Hoo-boy…
I suspect the trouble was minor. Stuck float, bad accelerator pump; maybe a clogged jet.
The idea that “rebuilts will not work on a Mark V 460 V8” is nonsense.
Unless the original carburetor was physically damaged (e.g., the casting is warped or cracked) or had severely worn throttle shafts it should have been rebuildable – and if not, you would have done better to find a good rebuildable original and have it gone through by someone who knows carbs.
Because it would fit – and work – like new, as designed.
What you’ve got now is a generic/one-size-fits all carb that doesn’t quite fit – because it’s physically different. I hope the guy did not put a square bore carb onto a spread bore intake… with an adapter or not (sexual chocolate, either way).
Also, the one-size-fits-all carb probably hasn’t been adjusted correctly for your application. It almost certainly would need to be jetted to work correctly on your 460 (or any other engine) and numerous other small adjustments as well.
It might run “out of the box,” but it’s doubtful it would run well.
Also, $900 is outrageous. A new generic Holley or QJet sells for less than $500 or so and it’s redonkulus to charge $400 labor to install the thing. It takes maybe 30 minutes to remove/install a carburetor with basic hand tools.
Based on what you’ve told me, I’d cut my losses and find a shop that has an older mechanic who understands carburetors. Do you still have your original? If so, it might be salvageable.
Very sorry, Gary…
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