Ferd/289 Posted June 5, 2012 Share Posted June 5, 2012 using a high performance cam thusly lowering vacuum to lets say 7 inches, wouold the use of a power valve 6.5 cause the smf engine to flood and not start? Also, can you get a valid vacuum reading by using a vaccum guage on a cranking ( but not running) engine? Quote Link to comment Share on other sites More sharing options...
jap tin Posted June 5, 2012 Share Posted June 5, 2012 No and No. Quote Link to comment Share on other sites More sharing options...
Scarab73 Posted June 6, 2012 Share Posted June 6, 2012 HI, First, you are not going to get any accurate vac readings from simply cranking the engine over. As far as that power valve is concerned, it's use comes into play when the engine is running and and additional fuel is required. See this article:http://www.chevyhiperformance.com/techarticles/74058_carburetor_valve_problems/index.html If you suspect the engine is flooding, check your float settings. There could be trash in the bowls, the needle tips could be worn etc. The idle could be too high, thus exposing the transition slots. You might consider an outright carb rebuild. Regarding the cam. What do you know about the cam that it's events are causing that low of vac? That wold make for one terrible street ride. Good luck! Quote Link to comment Share on other sites More sharing options...
Ferd/289 Posted June 6, 2012 Author Share Posted June 6, 2012 HI, First, you are not going to get any accurate vac readings from simply cranking the engine over. As far as that power valve is concerned, it's use comes into play when the engine is running and and additional fuel is required. See this article:http://www.chevyhiperformance.com/techarticles/74058_carburetor_valve_problems/index.html If you suspect the engine is flooding, check your float settings. There could be trash in the bowls, the needle tips could be worn etc. The idle could be too high, thus exposing the transition slots. You might consider an outright carb rebuild. Regarding the cam. What do you know about the cam that it's events are causing that low of vac? That wold make for one terrible street ride. Good luck! I rebuilt the carb. Put a holley trick kit in, ie new needle valves, gaskets, floats look fine and adjusted good. Just trying to figure out why engine wont start. Timing seems good, checked firing order etc., geting spark. Thats why the only thing I can think of is big vacuujm leak so little atomized fuel mixture getting to cylinders. Stumped. Quote Link to comment Share on other sites More sharing options...
Scarab73 Posted June 6, 2012 Share Posted June 6, 2012 I rebuilt the carb. Put a holley trick kit in, ie new needle valves, gaskets, floats look fine and adjusted good. Just trying to figure out why engine wont start. Timing seems good, checked firing order etc., geting spark. Thats why the only thing I can think of is big vacuujm leak so little atomized fuel mixture getting to cylinders. Stumped. Hi, OK, Let's sort through this. 1. Cranks fine? 2. AT TDC, the rotor is pointing at #1 plug location on the cap? 3. You have spark at any given plug when you ground the lead? 4. You see fuel squirting atop the throttle plates when you manually rotate the throttle? 5. You have compression because you've removed a pug and felt the compression when rotating the engine manually? Just keep in mind, you need compression, ignition, and fuel for an engine to fire. It may not run correctly, but it will fire. When was the last time this engine ran? Why did you add a "trick Kit". You may need to verify, the cam timing is correct, that is, with the rotor pointing at # 1 the crank at TDC, both #1 valves should be closed. Quote Link to comment Share on other sites More sharing options...
Pyro Posted June 8, 2012 Share Posted June 8, 2012 The wrong power valve will not stop it from starting. However, it will make it run super rich. I would use a power valve rated at 1/2 the vacuum at idle. Does it start with staring fluid? Is gas squirting out of the carb with you pump the throttle? Quote Link to comment Share on other sites More sharing options...
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