What psi do you set the tester at for a leak down?
I finally was able to buy a leak down tester and want to check it

 

It doesn't really matter since you are just looking at the ratio, but I typically set mine to 80psi. You are supposed to lock the piston at TDC (or some time early in the power stroke) to ensure both valves are closed, but I'm lazy, so I just set the pressure high enough so it forces the piston to BDC. If you have a cam that opens the exhaust valve super early you may have an issue, but what you are really looking for is a cylinder that is drastically different from the others.

 

Ok
At 100 psi I am even at around 7-10% on that bank

 

So they all read between 90 and 93?

How about the other bank?

 

That's cold to
I have a dual gauge and it shows me leak %
I am gonna check the other bank right now

 

Second bank checks out the same as the first bank
6-10%

 

Hmm, so im running out of ideas. Has it ever worked properly with the 408? Do you have cats still?

 

The truck ran amazing last year with the 408 with different heads, cam and headers
But towards the end of the year I thought the race gas messed up my o2s cause my a/F gauge was running richer, plugs looked fine tho
Basically runs same A/F as last year on idle when I thought the o2 was bad.
Got it all buttoned up again but I am gonna try my other computer

 

So it hasn't run good since the new heads, cam, and headers?

Did you degree in the cam, or are otherwise sure its installed correctly?

 

Yeah its over fueling since the new parts
I lined the dots up like I have for the other 5 cams swaps I have done.
Won't hurt for me to check it again tho but it's gonna have to wait for another day as that's more time then I have left today. Lol
The computer I have apprently isn't comparable so I gonna have to get a different one.
I really really appreciate the help tho man