Starter Fluid Makes RPM Go Down? (1 Viewer)

[Von Hayek]

I'm trying to seal up the exhaust on my father's '78 and it seems like every joint leaks. I'm trying to test the intake and exhaust manifolds by spraying some starter fluid on them, and when I spray the joint on the head near the front, i.e. cylinders 1 & 2, the RPM goes down. Can someone explain what this means and/or what I am I doing wrong?

 

[Marn0]

POSSIBLY. Just possibly it is allready running lean. usually an engine will increase in revs as it gets leaner. The starter fluid leaking in may be richening the mixture and dropping the revs. Thats just a theory though and happy to be proven wrong- its all about learning

 

[1911]

I'm trying to seal up the exhaust on my father's '78 and it seems like every joint leaks. I'm trying to test the intake and exhaust manifolds by spraying some starter fluid on them, and when I spray the joint on the head near the front, i.e. cylinders 1 & 2, the RPM goes down. Can someone explain what this means?

It means you have found a leak.

 

[Von Hayek]

It means you have found a leak.

I was assuming that was the case, but I always thought adding fuel to the mix should raise the RPM.

 

[1911]

I was assuming that was the case, but I always thought adding fuel to the mix should raise the RPM.

Whether the rpm goes up or down is immaterial to your problem; the rpm would not change at all if there were no leaks. By feeding a foreign substance into the intake and/or exhaust (through the leak), you are altering the stoichioemtric fuel-air mixture. Whether the rpm goes up or down is dependent on several factors; the original tune of the carb, the rpm of the engine during the test, the condition of the valves, the compression of the cylinders, the amount of foreign reactant (starter fluid in your case) used, etc.

 

[jcj_78FJ40]

I like to use seafoam for to find exaust leaks. This past april, my 60 failed inspection due to a manifold leak. The inspector said he could hear it but couldn't find it. About a 1/3 cup of seafoam sucked through the booster hose did the trick. I found this along with a very leaky weld around the header clamp.

 

[Von Hayek]

That is brilliant.

 

[Steamer]

I like to use seafoam for to find exaust leaks.

Ah! So is it the smoke or the wet spots that show the leaks.

 

[jcj_78FJ40]

Wet spots & drips. Still creates lots of smoke though...