68 tri-power idles at 3000 rpm

[Ted K.]

Have a 68 427/400 hp that had been sitting for quite some time. I took off the carbs and went thru them to clean out the funky. Put it all back together and when I start the car it immediately revs up to about 3000 rpm. All linkage is disconnected, idle set screw completely backed off and auto choke off the fast idle cam. Choke was converted to manual but have cable disconnected. I'm baffled, could something not be assembled correctly in the carb?

[Norris W.]

Re: 68 tri-power idles at 3000 rpm

Look for a vacuum leak.

[Rich G.]

Re: 68 tri-power idles at 3000 rpm

Are you sure the two secondary carbs are not active? I would cover each one and see if that does anything. Also, I think there is an issue with getting the base gasket right, but I can't remember the details. Sorry, not much help but I bet the guys who really know something will have an answer for you soon.

Rich

[Timothy B.]

Re: 68 tri-power idles at 3000 rpm

Ted,

I have read somewhere about two base gaskets (carburetor to throttle plate) and they can be mixed up so double check.

IMO, remove and block the secondary carburetor bores and tune the center carburetor first. After that install the secondarys and start with the correct linkage adjustment as this was discussed just recently so check archives.

There are too many variables and things that can make vacuum leaks so eliminate things one at a time.

[Ted K.]

Re: 68 tri-power idles at 3000 rpm

Discovered the problem, The secondarys were not closed all the way. When I pushed them closed by hand the rpms slowed right down. They looked closed but I guess just a fraction open effects the rpms. I also believe the vacuum lines for the secondarys are not hooked up correctly.

What is the correct source of the vacuum from the center carb for the secondarys? There are 3 vacuum ports.