7 psi standing still?

so i noticed this the other day - i can build ~7psi just revving my engine up [MSnS]. i'm guessing my cam timing is off and this is causing the mixture to burn in the exhaust housing... any ideas?

problem with the cam timing is that i have a 530 head on a b21ft block so there is no mark to line up the cam with...

specifics:
manual transmission
b21ft
V cam
3" exhaust
my adjustable cam gear [+/- 7*]
my exahust manifold
42/48 [63? can't recall]
Megasquirt N Spark [v290i]
48# injectors
3bar regulator
etc

jao said:

so i noticed this the other day - i can build ~7psi just revving my engine up [MSnS]. i'm guessing my cam timing is off and this is causing the mixture to burn in the exhaust housing... any ideas?

problem with the cam timing is that i have a 530 head on a b21ft block so there is no mark to line up the cam with...

specifics:
manual transmission
b21ft
V cam
3" exhaust
my adjustable cam gear [+/- 7*]
my exahust manifold
42/48 [63? can't recall]
Megasquirt N Spark [v290i]
48# injectors
3bar regulator
etc

Click to expand...

you'll want to fix that soon. yes, extremely retarded, burning fuel in the header, dangerous heat build-up in exhaust. fire hazard. bad.

if the cam isn't marked and there is no alternative cam to run or clever fix known to other lovers of the volvo, i guess you'll need to degree it in. search "degree in" + "cam" on the web and you'll find some good comprehensive instructions from the usual suspects, e.g., crane et al. the circle track and v8 magazine websites have good info, too (usually regurgitated instructions from their advertisers who sell cams).

don't mess with your adjustable gear until you have the cam degreed in.

One way to see if it's close is to make sure the crank is at TDC (measure the position of the piston using a chopstick if you've got a B230) and the cam is pointed so #1 is on overlap. Both valves should be lifted roughly the same, give or take a few thousandths of an inch. If the exhaust valve is quite a bit further down, the cam is retarded by at least one tooth.

Or you could take off the cam sprocket and dab a paint mark (chaulk, a scratch, whatever) on the face of the sprocket that lines up with the pin in the camshaft, plus a mark 180* away from that point. With the sprocket installed and the crank at TDC, the marks should line up with the crankshaft. If you understand what I'm saying, that's probably easiest 'cause you don't have to take off the valve cover, etc.

It could also be your spark timing that's retarded, but that will make it rev slowly at the same time (does it?). Since you have MSnS I wouldn't be surprised if it's your spark that's off.
-Ben

random spark drop for launch control can give you way beyond what your wg is set for in terms of boost.

So it makes boost early....... Be thankful.
Get it on a chassis dyno and use your current settings that are making boost early for power off the line, and make sure that you dial it in for max power, torque and drivability whilst driving down the road.........You are already well on your way to the big fun that we can have with programmable management.

JL

re-eye balled my cam timing. this time i eyed it up and used the teeth on the belt itself to get it close. i am pulling 20" Hg now at idle and my VE table has been bumped up nearly 10 points in most places. it also opens up the wastegate sooner and produces boost earlier.

when i get some $$ i will be going to PnP to get some parts

thanks for the input guys - oh BTW my timing map is pretty aggressive