[sharkey]

The best way to know if the power valve is blown? I have weird symptoms off idle to maby 1800 then smooths some. Also how is the best way to know if the intake manifold has a leak. Would greately appreciate any thoughts. Thanks. Sharkey 5557.

 

[jwmbishop]

Intake man leaks can be found by spraying around with a fuel - a can of carb cleaner, etc works but can be messy - and easily start a fire. I like to use a micro butane torch (UNLIT) - but its not as sensitive. they make leak finders - I had a snap on leak finder years ago. When the fuel hits the leak the engine speeds up or slows down. Check mix by a small hit of your checking fuel straight at the air entry of carb - a lean engine will speed up when the fuel gets it - a rich one will slow down. Then you know which response you are looking for when you start leak hunting. If a quick half second blast is enough to kill the engine - you may have a PV blown.

the most common carb problem is not hard parts related - its crap in the fuel collecting in the carb. A good cleanout solves many ills. A lot of tune issues are blamed on the carb - bad ign tune drastically changes the signal the carb uses to meter.

Power valve symptoms are excessive rich - all the time. Runs real bad - so I doubt its your problem (unless just slightly leaking and not blown). Check mix as above - but bring engine to about 1800 then give a quick hit with the carb cleaner - it should slow slightly - if it drops real fast and almost dies on a half second blast you are already excessively rich - quite possibly blown PV - but if it drops and recovers quickly (normal operation) you are still not completely out of the woods. On a holley the best way is to pull the metering body, pull the PV and check it - you should be able to draw a suction (yuck this involves kissing a carb part) on the big side and pull the valve shut. You have just verified the vacc side - but this does not verify the fuel side! Last PV I bought was like $4.50. In other words just go ahead and replace it if your alkready in there! (if same issue after reassemble - you now have a spare PV - newer holleys have a check valve in em - but older ones this is a very common issue if you ever have a backfire it pops the valve real easy.
9 times out of ten if you are careful your gaskets will reuse - but you should have some on standby anyway - most holley owners keep a couple hanging around just in case (this is the most commonly tweaked carb). On other carbs (not called power valve but enrichment valve and does same thing) its much more difficult. By the time your in there a jiffy kit is due.

 

[sharkey]

JWMBISHOP. Thanks for the info. The engine is camed up pretty good but i think it idles OK. Its just off idle that it seems to almost lose one cylender then a thousand rpm's or so improves. Plugs are sooty and maby one has a touch of wetness (i think oil) . I did a compression test and 4 cylenders were 170 and 7and 8 were 165 but that does not eliminate guides. I'm trying to do one thing at a time here before I get to deep. I first had a look at the distributer (pertronix conversion). I think i'm OK there. I guess I'll just keep trying. I guess I could take it to a real mach, but then I wouldn't learn much. Thanks again. Sharkey 5557.

 

[Hafrod]

Your problem is fouled plugs.

 

[3 Tri-Fives]

The power valve will definitely richen the idle and low end since if it is blown it will allow fuel to flow when it shouldn't.

 

[jwmbishop]

170-165 is in good range maybe a little high unless upper 9's:1 or higher compression - obviously oiled rings (bead of oil as opposed to film). Try another test using just the easiest cyl to get to, one round as is, one with a little oil. If it does not go up slightly then the rings are already wet. then do a leakdown - set the cyl at bottom dead center (point of greatest taper) of the power stroke and add 120 psi shop air - listen for vapor coming out of the oil breathers. None = bad guide seals, air flow = bad rings cyl wall as possible source of the oil (I have seen good compression rings with toasted oil rings - and vice versa though). Some time guides tattle on themselves with a puff of smoke on warm starts - sometimes the only way to be sure which (rings or guides) is to ether drive it till it shows sure symptoms or tear it down.

remember extra oil = extra fuel so can mask carb lean.

How fresh and how "abused" is the engine? (I know - it ain't abuse - it's hot roddin")

 

[sharkey]

Hey guys thanks for the input. A little bit more on the engine. It has only a couple hundred miles on it. I did not do the rebuild on it.Its a 30 over 400 with a comp cam and cast over the counter angle plug heads with roller rockers. the manifold is an Edlebrok with a 4160 holley. The didiz is an old points style that has apertronix II conversion. I put a 45000 volt coil on it today and got rid of the ballest resistor to get 12 volts to the coil all the time. I also opened the plug gap to .050 and reinstalled. I ran the engine and it did much better. But its not right yet. I did hook up a vacuum guage and had 18 inches steady, even with that cam. Ill do the timeing tomorrow(around 10 12 initial) and put in a new set of plugs and then
,frankley, I do not know where to go from there. By the way I'm kind of rueling out the power valve because it actually idles pretty well for that cam. Any, thanks for all the help so far. Sharkey 5557.

 

[sharkey]

By the way, this car ran very well when I got it (2years ago). Also, I'm running ave gas in thes car , 100 octane low led. this fuel has more led in it than our automotive fuel had before they took the led out . Maby this is not good. What is your guys thinking on that. Sharkey 5557.

 

[Hafrod]

Are you running a PCV in a valve cover? If you are, do your valve covers have baffles in them? Non baffled valve covers with a PCV valve will suck oil into the engine and make you think your engine's toast. Not saying this is your problem, but could be one of a couple different issues. Not looking for a peeing contest here.

 

[sharkey]

Halfrod!!! That is exactly how it is, nobaffles in the valve covers and also a PCV in the valve covers. Typically are stock valve covers non baffled, as I have a set of those to experament with. No peeing match here, all input is greatly appreciated. Just click off one variable at a time. If I have to go inside the engine then I will, but will eliminate all else first if possible.Sharkey 5557.

 

[jwmbishop]

THere it is - your probably sucking oil through the PCV - by chance is the oily plug the one with the closest shot from the manifold vacc port? Plug that bad boy off - make a run and see what it does (with new plugs would be best). THen clean up the oil mess and figgure out an alternative venting. I have seen some guys weld a A.I.R. Gulp valve at an angle in the header collector and connect the hose to a pcv - this used the exhaust flow as the vacc source for venting.

note: NOT legal for higway use in any state - does not meet C.A.R.B requirements.

200 miles? the rings ain't even set in yet! take bad rings off the list - they can leak like crazy for some 500 miles depending on the agression of the cross hatch in the cyl hone job, and the ring material.

 

[56owner]

baffles

I have the tall Chevrolet insignia valve covers (Powder coated to match orginal 56 Chevy engine red not orange ) that I installed baffles from Edelbrock that were made to attach with screws to the inside of certain Edelbrock valve covers and heliarced them to the inside of my valve covers. PCV is after market an fits into grommet very snuggley. Looks like it will work great but results unknown as engine hasn't been fired yet.