Something is wrong. (and I wish you did have a better angle). No way when you hit the throttle should it go down first and then up. It should shoot up when you hit the throttle, and then down for a second after you let off.


EDIT: And by shooting up , I mean in the direction the needle goes(that's why I was wishing your vid was better). Not the HG. (that should go towards zero when throttle is hit)

 

Here's a crappy video of how the needle should react when you hit the throttle. No sound, but you can see my hand push/pull the throttle. As you can see, it does NOT go down until after I let off. Hope the vid works.

 

well, here's a video with the engine hot. I pulled right over when the sputter started, but in park with no load on the engine, it wouldn't sputter at all:

https://www.youtube.com/watch?v=PSGJ...e_gdata_player

For reference, the lower vac readings are to the left, high vacuum is to the right.

There's a long spot in the middle where I just let it idle, and the needle would go down slowly and then right back up. Weird.

 

OK, now that we have the correct orientation, . The needle still goes the wrong way at first(up,down,sideways doesn't really matter) when throttle is applied. Either the gauge is not reading right, or according to the manual, you have an exhaust restriction. Are you still using that original Magna Flow cat me and you know is a problem?

 

Vacuum looks normal to me. It falls when he hits the gas then as RPMs rise at the same throttle angle the vacuum increases.

Has it done this since the cam install? Tune not proper for the cam?

 

I'm not sure about that. You are right that it should fall when you hit the throttle, but his rises first big time.

 

No, the lesser vacuum is to the left, it dips down toward 10 "hg or lower then starts climbing.

It didn't do this when I first installed the cam, it only seems to have happened recently.

 

I wonder if just maybe the push rods are a hair too long. Do they stretch longer with more heat?

The reason I ask is that I was originally using the stock length 6.925" pushrod, but it was a wee bit noisy with the cam. I have a non adjustable valve train as the rocker arms are the HS pedestal mount non adjustables. Marty from KRC recommended a slightly longer pushrod so I went with the 6.936" edelbrock pushrod to quiet them down and it worked. I can't recall if it was around that time I started having issues or not, but I think it was running fine for a good while even after that switch. besides if the push rod got hot and opened the valve just a crack, I would think it would always be a problem, not just off idle.

We had one hell of a hot summer here and the truck got closer to 210° more times than I would have liked, but as I said, none of the typical signs of a popped head gasket have arisen.

 

I don't know. All I do know is, when you hit the throttle in that vid, the needle goes up(Hg) or in the opposite direction it should go for a moment. Maybe that's normal with an airgap and cam. It's just not normal on a stock motor as per the crappy vid I provided.

 

I don't think 210 deg would effect pushrods. Any metal expansion at 210 would shrink after cooling.