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I'm stumped, please give me some ideas...
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Thu Mar 03, 2011 10:26 am    Post subject: Reply with quote

I do agree there might be air getting into the motor from another source. Knarely's test would prove that the under side of the intake is leaking or not.

I have seen bad HEI's before too that had rusty ground bars under the coil not giving it a good ground also causing spark issues. I just don't care for them. They are too big and there are better "dizzys" out there.

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10.78@122 MPH 1/4mi
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SMOKEmUP
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1979 Chevrolet Camaro

PostPosted: Thu Mar 03, 2011 12:23 pm    Post subject: Reply with quote

Knarley Darley wrote:
Smoke brings up another good point with the under side of the manifold. A easy way to check this is to pull the PCV and temporarily seal all other breathers/ openings (I just put the palms of my hands or tape over the valve cover holes) If the manifold is leaking it will quickly build vacuum in the crank case and your idle will get better. When you pull your hand off one of the covers you will hear a big woosh of air suck into the motor. If it builds pressure, then the mani is probably sealed pretty good. This test is done with the engine running of course. good luck and keep us posted


I'll have to remember that.

The reason I say this because this bit me when I switched from stock GM heads to Darts with and Edelbrock intake. Funny thing is I switched the intake to a Weiand and it fit perfect, no machining required. One of the reasons I'm not a big fan of Edelbrock stuff.

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disturbthepeace1
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Joined: 14 Jun 2003
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Location: Stanton, CA
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1965 Volkswagen Beetle

PostPosted: Thu Mar 03, 2011 2:18 pm    Post subject: Reply with quote

Fired it up this morning, warmed it up and checked it out. Crankcase pressure is def positive Mad

Another clue that has developed is that I'm getting a top end nose but it doesn't sound like valvetrain. It sounds more like piston slap in a LS motor. I have ignored it cause oil pressure is spot on and it was faint. Idk

Joe

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squeeezer
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1991 Chevrolet Camaro

PostPosted: Thu Mar 03, 2011 9:37 pm    Post subject: Reply with quote

you say positive crankcase presure.....what was the reading????
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squeeezer
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1991 Chevrolet Camaro

PostPosted: Thu Mar 03, 2011 9:39 pm    Post subject: Reply with quote

disturbthepeace1 wrote:
Fired it up this morning, warmed it up and checked it out. Crankcase pressure is def positive Mad

Another clue that has developed is that I'm getting a top end nose but it doesn't sound like valvetrain. It sounds more like piston slap in a LS motor. I have ignored it cause oil pressure is spot on and it was faint. Idk

Joe





you have a butted/er broken ring in there
what pistons did ya use , and whats the side clearance?????

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disturbthepeace1
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1965 Volkswagen Beetle

PostPosted: Thu Mar 03, 2011 9:49 pm    Post subject: Reply with quote

Didn't build the motor, If I did it wouldn't be noisey.

It was done by a machine shop and if the dizzy swap doesn't clear it up Im going to give them a call. Will a leak down test show me a cracked ring? The comp test was dead even and the plugs show a heathy mixture with no oil burn. Confused

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clay
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1972 Chevrolet Nova

PostPosted: Fri Mar 04, 2011 9:12 pm    Post subject: Reply with quote

I can't think of anything to add on the idle issues yet but I can offer something to look for on the knock. I was helping a friend see what offset wheel would fit on his car which isn't important. Anyway he brought it on a trailer and of course I wanted to hear it run. When he cranked it up you could hear something knocking. This was also a very fresh engine - oil pressure good. Turned out was started looking and you could see the valve covers flexing on the side next to the carburetor. It was one of those cheap chrome kits with the valve covers, timing cover, breather, etc. and the rocker arms were hitting them. When we took them off it actually looked like the chrome job was so crappy it looked like they touched them up with spray paint. The 3310 should actually be a little rich on the cruise / idle circut. It was originally a BBC spec'd carburetor I believe. I'll keep thinking on the rough idle. Clay
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Knarley Darley
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PostPosted: Fri Mar 04, 2011 10:22 pm    Post subject: Reply with quote

LOL Clay I have seen that too on the cheap covers. They actually hit the sides and you can see them moving around.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Fri Mar 04, 2011 11:00 pm    Post subject: Reply with quote

disturbthepeace1 wrote:
Just re adjusted the valves to 1/2 turn after 0 lash. No change Mad

Joe


i had one that i ultimately had to just adjust the valves to 0 lash and leave it. if i went 1/4 turn more it would hold the valves open and run like sh!t at idle. never figured out why but the customer was happy so that was good enough for me.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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clay
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1972 Chevrolet Nova

PostPosted: Sat Mar 05, 2011 11:42 am    Post subject: Reply with quote

Where is initial timing set? Granted with those mild cam specs it shouldn't need a lot of initial but I would still shoot for 15 to maybe 20. Maybe something weird going on with the advance weights in the distributor? Clay
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squeeezer
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1991 Chevrolet Camaro

PostPosted: Sat Mar 05, 2011 4:55 pm    Post subject: Reply with quote

i do as little preload as possible (like a solid)
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coppergmc
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PostPosted: Sun Mar 06, 2011 11:00 am    Post subject: Reply with quote

You could pressurize each cylinder and listen for air leaking from some place other than rings. Might be something to do with the valve seat. I know that you said it will crank 170 psi but it might not be holding that pressure.

I'd probably check all the valve train components including the lifters and pushrods. If this is an old set of remanned heads there might be too much clearance in the guides. I've see some heads that would actually knock while running. You could actually move the valve spring back and forth on the head. The valves can't do what they are supposed to if they don't hit the same place every time.

Did you adjust the valves while it was running?
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squeeezer
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1991 Chevrolet Camaro

PostPosted: Sun Mar 06, 2011 12:47 pm    Post subject: Reply with quote

squeeezer wrote:
disturbthepeace1 wrote:
Fired it up this morning, warmed it up and checked it out. Crankcase pressure is def positive Mad

Another clue that has developed is that I'm getting a top end nose but it doesn't sound like valvetrain. It sounds more like piston slap in a LS motor. I have ignored it cause oil pressure is spot on and it was faint. Idk

Joe





you have a butted/er broken ring in there
what pistons did ya use , and whats the side clearance?????




i take this one back
you stated........
it has 170 cold cranking psi dead even on all cylinders

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osmiumfoot
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PostPosted: Wed Mar 09, 2011 2:00 am    Post subject: Reply with quote

Did you put a light on it with the advance working and then blocked off? Funky springs in the mechanical will sometimes do this. Whoops, Clay already called this one. I'll learn to read first and type second. Maybe not.
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disturbthepeace1
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Joined: 14 Jun 2003
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Location: Stanton, CA
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1965 Volkswagen Beetle

PostPosted: Mon Mar 14, 2011 4:45 pm    Post subject: Reply with quote

swapped back the factory dizzy with the tach drive and a pertronix unit and........


17-18in of vacuum, steady needle, and a smooth idle Cool Cool Cool


found out that the previous shop had left this car out in the rain with the hood off for weeks unknown. Rolling Eyes

any one want to buy a MSD hei with slight water damage??? Laughing


thanks for the help, this was a strange one

Joe

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