Christopher Question

[moparsofcamelot]

440/6 pack at operating temp w/cam 284/484 what would vaccuum read at 800rpm in park?
Thanks

[Christopher]

That depends on a lot of things...Is the engine sealed real well,do the rings have excessive leakage etc.What is your reading??

[moparsofcamelot]

10-12 on gauge and not absolute steady.

[moparsofcamelot]

Also, during warmup it the v gauge is jumping from 0 to 12. When revs are made goes to 20. After warmup settles to 10-12. Starts great, no backfire, nothing. Fumes can kill though.
Thanks.

[Christopher]

Where are you hooking up your vacuum gauge at??With the fuel problem,it sounds as if a power valve is bad in the center carb.And which power valve is in the carb??

[moparsofcamelot]

Hooking up at large nipple on rear of intake, where the brake booster will go. All rubber hoses are new. Don't know about valve, carbs are brand new with no data. Will check unless you think of something else. Only had 1 small backfire on intial startup after installation of cam and 6 pack. Guess that could have been enough. Although I can't get an increase in rpm using WD40 looking for a leak, I still think I'm going to remove each carb and check for a loose throttle body. Something I always check, but actually forgot this time.

[Christopher]

Usually a back fire will blow out the power valve on a Holley,so you'll need to go ahead and replace it.I'd use a 6.5" valve.I'm betting that's what is in there now.

[moparsofcamelot]

I can't get to it til Sat., but I bet your right. Right or wrong? Even with the cam shouldn't the vacuum drop as rpms go up and settle to 18-22 at idle if everthing is right? Mine seems to be opposite. I bet I blew the valve on initial startup.I'll still check throttle bodies and other possible leaks at the same time. If you have any more ideas, I welcome them.
Thanks in advance.

[340king]

Moparsofcamelot,

Just for kicks I put an engine similar to yours on Engine Analyzer 2.51. It predicted an estimated idle vac. of 15.4" Hg. I don't have the exact dur. specs. for the 509 cam, so I may be off a little.

Sorry, I must have gotten your engine mixed up with petethekiller. What cam do you have and what other mods have been done?

[This message has been edited by 340king (edited October 27, 1999).]

[Christopher]

You have to remember that the cam has a 60 degree overlap,which will reduce the vacuum readings somewhat.

[moparsofcamelot]

340KING, 284/484,6 pack, roller chain, valve springs, h-lifters and pushrods to mate w/6 pack.