75cutty455

I have a '68 455 with a 4160 750 Holley carb on it and when I start the engine it idles high as if I have it floored. I turned down the fast idle screw and the other idle screw but it did nothing. The engine is still ready to jump out of the car and run down the street.

Can someone advise me on how to fix this problem? I cant do anything else on the car because I cant keep it started for more that 1-2 seconds unless I physically hold the red auto choke lever down.

Tony72Cutlass'S'

Are you sure your throttle bracket/cable/assembly isint stuck on something? Did you just install a new carb or this is a random occurance?

75cutty455

Yes, its a new carb. I checked the cables and nothing is caught anywhere. I appears to be setup perfectly until I start it.

halfmoontrail

Sounds like a vacuum leak and/or a timing issue. Does car have points? The carburetor base gasket might be leaking, or the intake manifold bolts, or perhaps the vac advance or power brake booster vacuum source.
Steve

CQR

Agree on the vacuum leak or possibly the secondarys are held open?

75cutty455

I am new to this so I am not sure what "Points" are but I will take the carb off and thoroughly clean the intake again then place new gaskets between the intake and adapter plate and between the adapter plate and the carb (I'm going from the quad jet to a square).

Then I will double check the air line going from the brake booster to the intake, and check my secondary's are not being held open.

Hopefully that will do it. Thanks Update to follow.

Tony72Cutlass'S'

Points is the type of distributor you have, I it's a 75 I'm guessig you have HEI Which kinda looks like a points distributor but has a little square bit at the top. Points is short for breaker points and HEI is high energy ignition. Both work but are set up quite differently. I'd look down your carb before yanking it off and do a visual inspection on if the throttle plates are stuck open. I'm not familiar with Holley but I'm sure there are linkages that can stuck just like the rest of em'

Rickman48

Personally, I like the Q-jet for a lot of reasons, MPG being #1.
Make sure all the linkage is clear of that adapter plate - especially any no-name plate!

75cutty455

Found out what was happening.

Thanks again for the info.

The secondarys were stuck open. It seems as if the throttle is going back but it actually isnt. It's closing the top flap (not sure what that is called) but the secondary's are still open. As soon as i lifted the carb off the adapter it snapped shut. The intake is too high for it to operate correctly and its getting stuck.

So the next question is, can I add a riser to this even though I already have an adapter on the intake? Or will I have to get a new intake?

CQR

Yes you can (provided you will have proper hood clearance). But for each piece you put in you are adding a place for a vacuum leak to occur.

DJS70cutlass

raising the mount for the throttle cable may get it to move freely in a pinch.