Hi everyone,

I installed an edelbrock 750cfm carburetor on my 1968 Coupe Deville. The car makes this sound like it's sucking vacuum when I put it in gear. Did I hook something up wrong or do they make that sound normally when you shift?

Any help would be appreciated... thanks :(

It sounds like you might have a leak.. find out where the sound is coming from.. You can try to spary some carb cleaner around the carb with it running and see if the rpm picks up to find the leak...

Did you use the correct carb to manifold gasket? Hard to diagnose over the internet.

Well, I would hope that I did. I used the aluminum spacer that was recommended for switching to this carburetor. I used the gasket that came with it. I'll probably mess with it some tonight and find out more.

Did you also reuse the stainless steel shim and a new 'lower' gasket under the aluminum adapter? You might be dumping exhaust from the manifold heat crossover right back into the engine (a bad thing).

I think I have this thing figured out, but if you guys have time for one more question... I would really appreciate it, thanks!

My question is prefaced with a story. Today I got a speeding ticket, (I didn't know exactly how fast I was going). The car has a rear limited slip differential from a Fleetwood so the gear ratio is off for the speedometer. The officer said I could have a mechanic sign something saying it was off, and that I would not get any points on my license if I did that. Now I'm trying to figure out the gear ratio for my speedometer to correct this.

According to my shop manual the rear end is a 3.21/1 ratio and for that ratio with 8.90 tires, I need a 41 tooth driven gear with a 19 tooth drive gear.

Original gear ratio would have been 2.94/1 with a 38 tooth driven gear and an 18 tooth drive gear.

Does anyone have any experience replacing these gears or know where I can get them? Is there any other solution? No local parts stores have anything listed and I tried Napa, Carquest, Advance, and Auto Zone.

The equation from TCI
((#drive teeth)(axle ratio)(tire revolutions per mile))/1001
((18)(3.21)(714))/1001=41.21 or 41 tooth driven gear
((19)(3.21)(714))/1001=43.5 or 43 tooth driven gear

Go find an old Ma & Pa tranny shop and ask for the speedo gear for the trans. They will be more helpful then any big box could dream of being. They might even install it quick.

Should have opened a new thread! Any speedo repair shop or trans shop can provide an adaptor that screws onto the trans and the cable attaches to it. They verify error ratio, and make up a set of gears within an adaptor that corrects it. They can also verify the amount of error to sign off the ticket.