Vacuum Gauge ?

[clar2001]

No I have had the miss for a couple of mounths, the car has single exaust with a new free flow cat.
There has been many mods to the car cooling so on,
removed heat riser & blocked open valve,Egr valve only on the manifold to fill the hole,the intake gasket did not have a hole for it.
I will be exempt from smog in anouther year other wise none of the extras would be on the car.

 

[vettenick]

If you cannot have someone look at the car with diagnostic equipment. Then the next best thing to do is that you must determine if the miss is isolated to one cylinder or not. If it's one cylinder only that's misfiring then I would look at the ignition system to that cylinder first, then the mechanicals second.
You can do that by disconnecting each spark plug wire at the plug one at a time to see if the miss gets worse or stays the same. If the miss gets worse, then that's probably not the problem cylinder. If the miss stays the same, then that's the cylinder that has the problem. You must be careful doing this test because you don't want to overload the cat with unburned fuel from the disconnected plug. Try to connect the wire as quickly as possible after you've determined if that's the problem cylinder or not. Another help would be to use a tach to determine which cylinder causes the lowest RPM drop when the wire is disconnected.
One thing about EGR valves...on a street car, they actually help more than hurt performance. They keep cylinder temperatures down which helps helps the valves stay cooler.

 

[clar2001]

well I said I had no vacum leaks, I was wrong removed the carb spacer and just put in a normal gasket thin one,and my vacum jumped to between 17-20lbs and most of the rought idle went away the guage still flutters about a pound.
Now I'm going to order a 1/2" heat spacer for the carb and still in time replace my old 28year old distrubtor .
I wish my egr was hooked up I diden't realise the gasket diden,t have a place for it till it was to late.
So I still have a problem becouse the vacum guage flutters but not as much as a problem any way.........

Nick you have been a real trooper with your help TKS.....

 

[clar2001]

Ok sunday morring I'm ajusting my carb and the vacum drops low agin 14lbs. and a little bit of a rought idle .
Just when I thought things were worked out.............

 

[vettenick]

Let's get back to basics... disconnect and plug every vacuum line from the manifold, including any line that's below the throttle opening. If the gauge comes up, then one of your vacuum lines or the devices that they run are leaking. If the gauge still stays low, get a propane bottle,DON"T LIGHT IT!!!, open it up slightly and point it around the carb base and intake manifold, etc... If the idle smooths out, then the area where you probed with the propane is the source of the leak.
Just another thought.

 

[clar2001]

Ok pluged all vacum lines & there isen't that many on this car and did the proprane thing (good Idea) with no change,so now friday payday I am going to order a 1/2" spacer for my carb and the correct base gaskets one for each side of the spacer.
Got to be a vacum leak on the carb if removing the old spacer temporarily helped the problem ...
The good news is it's a 100 degress here today and the vette runs a steady 190* butt the fans do run more often.
Will post a update after the spacer .............

 

[vettenick]

Good luck! We're running out of simple things, but lets see what happens with the new base gasket.
I hope that does it

 

[clar2001]

Ok did the 1/2 inch 4 hole heat spacer can fell the difference performance wise but still have a miss and bouncing vacum gauge about 15lbs bouncing pretty hard. My edelbrock manifold has one bolt I can,t tighten properly becouse its between the egr&chock even with the manifold stripped and trying a allen bolt still can't tork that one properly ,thinking about changing manifolds.
Just don,t have the money to let a shop play around ands sell me parts..........

 

[Vettetrurian]

Using a Vacuum Gauge for Engine Diagnostics

Have a look at this article on engine diagnosis using a vacuum gauge.

http://autospeed.com/cms/A_2393/article.html