[Packy]

, the engine is a 1972 250, carb is monojet bc from the original 66 230 engine. I made some major progress today, #1 the gasket between the carb and intake manifold needs to be thick enough to allow for decent air flow. I noticed the one that came with the rebuild kit was half the thickness of the original, luckily the original one was good enough to put back on. #2 The GAS cap was vented, so I plugged the vent so the fuel pump had to work harder to suck the gas, which slowed down the fuel flow. 3# the kit said to set the float level at 1inch 9/32, after many trial and error, I called my brother and he looked up a shop manual and the float needs to be set at 1inch 19/32. 4# I am using a propane torch to clean my spark plugs for each test. #5 install a pertronix HEI kit , part # 1162a, and also a flamethrower high performance coil. I bought mine off amazon. new plug wires are a must. #5 The timing should be set at 0. #6 install new manifold gasket, and gasket between intake and manifold. #7 new vacuum hoses. #8 make sure the choke is working properly, should be completely open when engine is warmed up. # carb has new needle & seat, and has been gone through carefully with carb cleaner and High pressure hose. # I switched fuel filter to a thicker brass type to slow down fuel pressure. I did all these things and the engine is running a lot better, plugs went from being char broiled, to slightly dusted.

I still have one strange thing going on, my mixture screw is only open by less than a quarter turn. When I tighten it down, the engine does not die, just keeps running fine. Does anyone have any ideas????

The idle screw has me wondering, the carb is from 1966, maybe somebody tighted it down too tight which widened the gap, I don't know, I will try a different mixture needle tomorrow, I actually have one.

 

[jeff swisher]

carb cleaner does not always make the small passages clean and clear.
You need torch tip cleaners to chase all small holes..
or just strip some lamp cord wire and use the copper strands...
sounds like idle tubes are clogged...
If yo find it is just too rich you can also jet it down by inserting some of that lamp cord copper wire strand into the jet or jets...

I make a horse shoe loop and insert one end into 1 jet and the other into the other jet on those gm 2 barrel carbs...

Now i measure the wire diameter with dial calipers....if the wire is too thick you can pinch it between your thumb nail and finger and pull it through..basically stretching the copper wire and this will make it thinner.....you can jet down by .001" real easily like that.

 

[Schurkey]

#2 The GAS cap was vented, so I plugged the vent so the fuel pump had to work harder to suck the gas, which slowed down the fuel flow.

Woof.

 

[Packy]

Thanks for the advice Mr. Jeff, I will probably try what you said soon.

Now, my car won't start, need to find out if still getting good spark, here we go....

Another thing I am going to look at is that when I got the engine, the guy had a fuel regulator that allowed for fuel psi adjustment. It is a mechanical fuel pump. Did he know something I don't? normally mechanical fuel pumps dont need regulators. Weird, might just buy a new fuel pump and see if that does the trick. Maybe my problem has been too much fuel psi?

 

[jeff swisher]

if you are going to play with cars you will need some tools
May i suggest a fuel pressure vacuum tester...those are cheap and will save you buying a fuel pump if you do not need one..
Last thing you need to do it throw parts at it..TUNE TUNE TUNE>

Now a nice timing light like one with a dial back gauge is nice to add to the tool stash...
those 2 items and a multi meter...should have you set ....

I like to have a compression tester also

Amazon.com: Actron CP7802 Vacuum and Fuel Pressure Tester Kit: Automotive

My timing lights are sunpro 7519
read here
http://www.chevelles.com/forums/archive/index.php/t-302358.html

unless you already have these tools in your arsenal.