Thread: 383 Stroker low vacuum and sluggish

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Yeah I’m using number 1 spark plug wire. I did your method to try and find a leak from the underside and everything seems good. I’m thinking these marks are off because engine sounds the best when it’s at about 50 degrees timing. Any lower and it starts to stutter. What’s the best method to find TDC with everything installed? Is it possible it just runs a very low vacuum?
Fuel pressure is about 5 pounds. Adjusting the carb doesn’t seem to do very much either way I turn the adjustment screws?
Also I noticed I don’t have a PCV valve hooked up on either side of the carb. Both ports are plugged.

Originally Posted by Devon32

What is the best method to find TDC with everything installed?

There are numerous ways to check TDC.
However, I DO NOT recommend using a spark plug piston stop method on an assembled SBC unless you really know how to do the method, as the piston stop if set wrong can bend valves.
On assembled/installed motors I recommend a non intrusive method (I’ve included a Verify TDC PDF), this is the method I use (modified slightly from other non intrusive methods) and it works well in tight places.

Originally Posted by Devon32

Is it possible it just runs a very low vacuum?

It is possible, if you have a big cam along with low compression, though I suspect other things are also adding to the low vacuum and poor performance, i.e. tight valve lash and carburetor adjustments comes to mind (I've included a valve adjustment PDF).
Is the motor real rummpity at idle (idles rough, has a lot of cam lope)?
What is the compression?
What do the plugs look like?

Originally Posted by Devon32

Fuel pressure is about 5 pounds.

No matter what else you hear, it is important with Edelbrock carbs to have no more than 5 psi. Higher pressure can cause an overly rich idle and very poor performance. Check your pressure, be sure what the pressure is.

Originally Posted by Devon32

Adjusting the carb doesn’t seem to do very much either way I turn the adjustment screws?

Most likely, you have the throttle opened up too far overly exposing the transition slot trying to get it to idle. This can be caused by a large cam or other issues. However, if you use a lot of throttle stop (throttle speed adjustment) to keep it running, it throws the carb out of its idle/transition circuits and screws the low speed performance up and can also add to low vacuum. There are other ways to get the idle speed up without messing up the carb’s idle/transition circuits.

Originally Posted by Devon32

Also I noticed I don’t have a PCV valve hooked up on either side of the carb. Both ports are plugged.

I run PCV on all my motors. Contrary to what some will tell you, the PCV system helps the motor's performance by lowering crankcase pressures (motor spins easier) and it keeps the crankcase cleaner.

VERIFY T.D.C..pdf
Adjusting hydraulic valves .pdf