well i have a 216/224 on a 114 lsa cam and i beleive it is bleeding off a bit of boost. i was originally running about 11-12 psi with this blower and pulley on the old stock lq9 and now on this motor( 370 9.25-1 cr) im only seeign about 7-8 psi with the same pulley . im thinking the cam may be bleeding off alot of boost and i may be looking for something more agrressive but nothing crazy. any ideas .

 

I dont think the cam is bleeding off any boost. More of a combination of things. Your comparing it to the stock LQ9 you had. Slightly larger cubes,lower compression,plus the cam is why I think the boost dropped some. Time for a smaller pulley.
I went from a 216/218 114lsa cam to my current cam which ALOT larger and still on a 114lsa. We thought I may need to pulley down , but made the same boost.

 

but i still think its kind of alot to loose. what determines the boost lost? does anyone have any dyno graphs with cam swaps on fi ls based motors?

 

i don't see how going from a LQ9 to a punch out LQ4, running the same came you had in the LQ9 will cause this kind of loss.
more then likely the LQ4 came with same heads you had on the LQ9.
something here is diffrent other then compression.

 

What heads did you end up going with? Are you still seeing the same amount of air past the maf?

 

Larger CI engine+lower CR = lower intake mainfold pressure all other things the same. Boost is measured residual manifold pressure. Another cam might be more efficient.

 

do you still have stock heads?

 

Excactly. His LQ9 was completely stock, including cam. I'm still betting on the combo of......lower CR,slightly bigger cam, and larger cubes.

 

here is the engine specs

patriot stg 3 heads
probe i beam rods 6.125
eagle forged crank 3.622 stroke
diamond -15 cc dished pistons
cam mentione above.

.060 head gaskets .

guys its only 6 cubes imo thats not much.

 

Its not just the larger cubes its the lower compression too. Also you didnt give us enough specs for valve events. ICL, EVC, EVO, IVC, IVO etc