When I put everything back together, my compression was 60 50 30 40, with a stock head gasket, (yes, I DID use all three layers). So I did a leakdown. I had the TB all the way open, (no IAB valve body in my intake), & an ITR header on it. I thought that the valves could possibly be not seating, (don't ask why). I figured that if this was the case, the air that I was pumping into the cylinder should have came out of the TB, or header, as there would be less resistance for it to flow that way as opposed to into another cylinder. However, the air was coming out of the third cylinder plug hole, so I figured that the head or block must have gotten warped somewhere in the process of putting everything back together the last time. BUT, when I took it apart & looked for the warpage that I was SURE would be there, I found none. So, I sprayed parts cleaner into the intake ports & all of my valves are leaking - every damn one. So that's obviously the problem & I'll be getting a valve job ASAP. But in the meantime, I'm having trouble understanding why the air that I was pumping into the first cylinder was coming out of the third cylinder plug hole. Perhaps the head gasket was bad along with the leaking valves, but then the air would have been coming out of the SECOND plug hole, not the THIRD, correct? It's just not all computing to me... am I missing something?

 

If the intake valves from #1 and #3 were open at the same time, the air would go from #1 into the intake manifold and right out the intake valves of #3 and then out the plug hole.

 

I can't understand why though? There would be less resistance for the air to flow down the runner, through the plenum & out the TB. So instead of the air taking the path of less resistance & coming out of the TB, it made a u-turn inside the intake & came out of cylinder #3. It would be like a river flowing up over a mountain instead of around it - it doesn't make sense.

 

firing order is 1-3-4-2 .. so #1 was about to close and 3 about to open ... you prolly werent fully on TDC on #1 you were on exh stroke.

greg

 

Your resistence theory is wrong because of the weight and volume of air that must be moved thru the piping. The cylinder is a shorter and quicker route to free atmosphere. Pressure is built up in the mani and just takes the best route. Why travel 3' when you can go 3"?

 

But I didn't have an intake on the TB. So once the air got into the plenum, it could either take a straight shot to a 60mm opening in the TB, leading to open air, or, take a 90° turn, flow down a conduit that is, say 25mm, then out of say, a 15mm hole to open air. Sorry if I'm being redundant, but this still doesn't make sense. Unless...
I did the leakdown a few different ways & the one time that I did it, (which is the time in question), I didn't use a gauge, I just basically took an airhose & attached it to a hose that would screw into the cylinder so there would constantly be air flowing out of the hose. I screwed the hose into the plug hole, then hooked the air hose to it. It built enough pressure to push the piston down, which opened the valves & let the air escape fom cylinder one. Now, this would have in turn, started the #3 piston down the cylinder, creating a bit of a vacuum in said cylinder, thus drawing in the air that was coming out of the first cylinder. Then once the air developed a flow pattern, it just maintained it. Is this what y'all are saying?

 

Are you sure that the air was not coming out of both spots. More noticeable from a small hole than a big hole. No matter what, it will take the path of least resistance. If it was easiest for 75% of the air volume to flow out the plug hole and the balance to go out of the throttle body, that's what it's going to do. It's not about the flow of air, it's about the easiest pressure relief.