LQ4 engine with LS2 Top End
05-15-2011, 05:32 AM
#1
LQ4 engine with LS2 Top End Hi everyone,,
I got a low mileage LQ4 short block pulled out off a 2006 Yukon Denali and installed on a Lumina SS (has the same look and chassis as 2005 GTO but with 4 doors). Stock LQ4 engine have 9.4:1 SCR with the following specs:
Stock 317 heads 71.06cc
Stock MLS gasket 0.052
Dished pistons -6.45
Pistons are ~ 0.004 - 0.010 out of the hole (-) value for piston to deck clearance.
So, to pump up my static compression, I replaced the 317 heads and intake with a 799/243 LS2 heads, 90 intake, and a 90 FAST TB. With the 243 heads having smaller chamber 64.4cc compared to the stock 317's 71.06cc chamber, the compression was pumped up to ~ 10.2:1
To reach higher compression, I replaced the stock gasket with a 0.041 gasket which increased the static compression to ~ 10.5:1
However, my quench become on the tight side ~ 0.030 - 0.038 depending on the piston/deck clearance exact value.
My questions is:
The stock LQ9 cam specs are 196/207 duration @ .050 and 0.467/0.479 lift on a 116 LSA and with my current 10.5:1 SCR, it puts my DCR at ~ 8.71:1 (stock is ~ 7.84) which is bit high for resisting detonation in our country's hot weather (100 F - 120 F in summer).
So, What would be a good cam for my setup that will give me good PTV clearance and reduce my DCR to the 8.0 - 8.4:1 range?
I have seen great results for LQ4 engines with stock MLS gasket and 243 heads and cams with these specs on LSL or EPS lobes:
226/234 .63x/.63x on 110 LSA
227/235 .60x/60x on 112 LSA
230/234 .595/595 on 113 LSA
I'm thinking of getting one of those grinds but I don't know if my PTV clearance will allow me?
I know, MEASURE IT..... I will, but for now, I need your opinions and your experience with similar setups and maybe some rwhp numbers
It would be great if I can run TSP's 233/239 cam or even a MS3 cam without having to flycut my pistons
If I have to flycut the pistons anyway to get a decent sized cam, I will get LS2 bottom end (from the same guy as he's rebuilding his stroked engine) and flycut the flat pistons to replace my LQ4 stock bottom end and pump my compression ratio to ~ 11:1
In that case, more cam options are available
I got a low mileage LQ4 short block pulled out off a 2006 Yukon Denali and installed on a Lumina SS (has the same look and chassis as 2005 GTO but with 4 doors). Stock LQ4 engine have 9.4:1 SCR with the following specs:
Stock 317 heads 71.06cc
Stock MLS gasket 0.052
Dished pistons -6.45
Pistons are ~ 0.004 - 0.010 out of the hole (-) value for piston to deck clearance.
So, to pump up my static compression, I replaced the 317 heads and intake with a 799/243 LS2 heads, 90 intake, and a 90 FAST TB. With the 243 heads having smaller chamber 64.4cc compared to the stock 317's 71.06cc chamber, the compression was pumped up to ~ 10.2:1
To reach higher compression, I replaced the stock gasket with a 0.041 gasket which increased the static compression to ~ 10.5:1
However, my quench become on the tight side ~ 0.030 - 0.038 depending on the piston/deck clearance exact value.
My questions is:
The stock LQ9 cam specs are 196/207 duration @ .050 and 0.467/0.479 lift on a 116 LSA and with my current 10.5:1 SCR, it puts my DCR at ~ 8.71:1 (stock is ~ 7.84) which is bit high for resisting detonation in our country's hot weather (100 F - 120 F in summer).
So, What would be a good cam for my setup that will give me good PTV clearance and reduce my DCR to the 8.0 - 8.4:1 range?
I have seen great results for LQ4 engines with stock MLS gasket and 243 heads and cams with these specs on LSL or EPS lobes:
226/234 .63x/.63x on 110 LSA
227/235 .60x/60x on 112 LSA
230/234 .595/595 on 113 LSA
I'm thinking of getting one of those grinds but I don't know if my PTV clearance will allow me?
I know, MEASURE IT..... I will, but for now, I need your opinions and your experience with similar setups and maybe some rwhp numbers
It would be great if I can run TSP's 233/239 cam or even a MS3 cam without having to flycut my pistons
If I have to flycut the pistons anyway to get a decent sized cam, I will get LS2 bottom end (from the same guy as he's rebuilding his stroked engine) and flycut the flat pistons to replace my LQ4 stock bottom end and pump my compression ratio to ~ 11:1
In that case, more cam options are available
