Carb and air cleaner issues

[Ewing]

Hi all - looking for a bit of insight. I have a 70 Cuda 383. Recently having trouble getting it started and feels restricted when driving. When starting, it cranks, and cranks, and cranks, you get the idea. It will eventually start but sounds like it is limping and might shut off at any point. While driving, it feels underpowered compared to what if felt like when I bought it.

So I thought maybe timing. Checked yesterday with some buddies and it was at 15 degrees BTDC. We backed it down to 10-12.

THEN, I noticed hey, with the air cleaner off this thing sounds and responds to throttle just like the day I bought it. So we played around with the air cleaner (top off with filter, top on no filter etc.) The result was with the air cleaner off it was back to "normal". Put it back on and it sounds like it wants to take a nap. Now, this is a 383 dual snorkel with a K&N filter that maybe has 100 miles on it. So can't be a dirty filter, and both snorkels are clear (no blockages).

So now I am thinking this is a carb thing where I am not getting enough air. Has anyone experienced this? My buddy said he looked at the carb and it looked like there was some leakage in one of the gaskets, so I am thinking I might need a carb rebuild.

Looking to understand if anyone has heard of this and if this is properly diagnosed as a carb issue, where would you trust for a rebuild and tune?

I am in a Los Angeles, vehicle is a 70 Cuda 383, Edelbrock Dp4b, Carter 750 cfm (has elec. choke but not hooked up), mild cam (so I'm told..). Initial timing 10-12 BTDC.

Thanks for your feedback and I hope everyone has a great Christmas/holiday season with family and friends.

-Ewing.

[Cuda Cody]

Kinda hard to tune a car through the internet.  But first I would make sure the carb is functioning right.  Then I would set my initial timing and the all in timing.  Also, make sure your plugs are clean and not fouled.

[70 Challenger Lover]

Timing doesn't change on it's own. You have something going on and you need to go through everything systematically rather than doing this and that. We would also need more information to help you.

Does your car have points? If so, I would upgrade them with an electronic conversion kit. It's cheap. I know some guys say points are just fine but you will need the skill to gap them and set dwell. If you do not have points (or once you convert to electronic), get your timing light and do the following:


-Inspect distributor cap, rotor, plugs and wires for good condition
-Remove air cleaner and disconnect vacuum advance. Plug at carb for now
-Set initial timing at 15 degrees. Reset idle to 750
-Check the total advance at various rpms. You want to see a grand total of about 36 degrees before 3000 rpms, 2500 would be better. If you are a little over or under 36, you can readjust the initial advance setting a little.
-get a vacuum gauge and connect it to manifold vacuum. Ideally a fitting on the intake rather than the carb. It will show immediate reading at idle.
-before you start the engine again, turn the idle mixtures screw in (clockwise) until they stop. Measure how many turns on each and write it down. They should be equal. Put them back where you found them and make sure they are equal if they weren't before.
-start car and Carefully adjust the screws in 1/8 turn on both sides. You are looking to see if the engine speeds up or slows down. You are also looking for the same in vacuum reading. If you get a change within the first 1/8 change, then they were too far in and start doing the same thing in backing them out, looking for increased idle and vacuum. Keep doing this until you get the most it will give you.

Doing this stuff will give you a good starting point for the rest of us to work with.

[Cudamike]

I tighten by K&N air filter lid too tight once and the butterfly hit the bottom of air cleaner.

[73chalngr]

I had a similar problem and it was the butterfly hitting the air cleaner lid.  Do you smell gas on shut down ?