Propane Into Valve Cover... Looking For Vac Leak... Is It SAFE??

[Guest Mike]

Check and make absolutely certain #5 & 7 plug wires aren't crossed' date=' or that any spark is jumping between these two wires. A dark garage is best for checking for sparks jumping wire to wire.

 

John[/quote']

 

...assuming the cam is a standard grind. I guess I could try switching plugs 4 & 7 just in case this is a swap grind cam. The wires are new as are the rotor, cap, condenser, and module. I'll look for little blue glowing thingies none-the-less :^)

[jt1]

A 4 - 7 swap wired up incorrectly will give a dead skip. 5 - 7 are close enought it just does goofy things like you describe.

 

No need to discuss how I know this!

 

Edit: If it's a hydraulic cam motor, check and make sure the rockers are adjusted so that the plungers in the lifters aren't bottoming out. Cam timing is another possibility.

 

John

[MONGO510]

Are you saying that the crank case shows no vacuum unless there's a valley leak? Is there a general guideline as to how much it should/shouldn't have?

 

No. A sealed crankcase will always build pressure. The pressure is caused by ring leakage. If it has a vacuum it has to be caused by a leak from the intake! A minor leak may not show up if the vacuum leak is about equal to the ring leakage. But a leak that minor would probably not cause the problems you are having. This is on a SEALED crankcase! No vents, no pcv, etc.

FWIW!

[Guest Mike]

A 4 - 7 swap wired up incorrectly will give a dead skip. 5 - 7 are close enought it just does goofy things like you describe.

 

No need to discuss how I know this!

 

Edit: If it's a hydraulic cam motor' date=' check and make sure the rockers are adjusted so that the plungers in the lifters aren't bottoming out. Cam timing is another possibility.

 

John[/quote']

 

The rough idle is manifested as dead cylinders... at least two. Sorry if I was unclear:rolleyesg

 

I think this is a hydraulic flat tappet cam but I'm not sure. I didn't build the engine. I'll check rocker adjustment this weekend. Cam timing is later... if this is off, then the chain has slipped:sad:

[Guest Mike]

No. A sealed crankcase will always build pressure. The pressure is caused by ring leakage. If it has a vacuum it has to be caused by a leak from the intake! A minor leak may not show up if the vacuum leak is about equal to the ring leakage. But a leak that minor would probably not cause the problems you are having. This is on a SEALED crankcase! No vents' date=' no pcv, etc.

FWIW![/quote']

 

...but I can temporarily plug those.

[grumpyvette]

IVE NEVER EVER SUGGESTED PROPANE as a method to find leaks INSIDE the engine, OUTSIDE YES, INSIDE NO!

if IT was my engine and I suspected the intake to head was not sealed ID PULL AND INSPECT THE INTAKE, its that simple

[Guest Mike]

IVE NEVER EVER SUGGESTED PROPANE as a method to find leaks INSIDE the engine' date=' OUTSIDE YES, INSIDE NO!

if IT was my engine and I suspected the intake to head was not sealed ID PULL AND INSPECT THE INTAKE, its that simple[/quote']

 

...I'll pull the intake and inspect this weekend.

[Pop N Wood]

Check and make absolutely certain #5 & 7 plug wires aren't crossed' date=' or that any spark is jumping between these two wires. A dark garage is best for checking for sparks jumping wire to wire.

 

John[/quote']

 

I was thinking cross firing betweent the cylinders also.

 

Check the inside of the dist cap for carbon tracing. A solid indication of cross firing.

 

Dark garage is an excellent idea. I found a crack in a coil cap that I never would have found if the sun hadn't set on me. Make sure wires are in good shape and not crossing at odd angles.

[Guest Mike]

I was thinking cross firing betweent the cylinders also.

 

Check the inside of the dist cap for carbon tracing. A solid indication of cross firing.

 

Dark garage is an excellent idea. I found a crack in a coil cap that I never would have found if the sun hadn't set on me. Make sure wires are in good shape and not crossing at odd angles.

 

...new plugs, cap, rotar, module, condenser, and wires. I'll look for arcing tonight.

[Sparks280zt]

IVE NEVER EVER SUGGESTED PROPANE as a method to find leaks INSIDE the engine' date=' OUTSIDE YES, INSIDE NO!

if IT was my engine and I suspected the intake to head was not sealed ID PULL AND INSPECT THE INTAKE, its that simple[/quote']

 

Opps sry!

[LLave]

sort of reminds me of the old fire cracker in a open hand does nothing, in a closed hand is a world of pain.... sbc pipe bomb... yikes

[Guest Mike]

sort of reminds me of the old fire cracker in a open hand does nothing, in a closed hand is a world of pain.... sbc pipe bomb... yikes

 

Yeah... I want to do this right. I wouldn't want to blow it!!