Originally Posted by slow trap

have you thought about checking the cylinder that had 2x% leakdown and see what it is now ? i am thinking that cylinder was the reason for low power. could be rings but i am thinking the head on that hole had a bad valve or something out of whack causing all the leak down. if heads were checked and came out fine then that much leakdown seems alittle excessive but who knows.
glad it is picking up power now.

Originally Posted by 74u

I recently swapped H/C/I. Bottom end was untouched and same supporting parts were used..

="4"%Old combo...
LS3 block w/4.070 bore x 4" stroke
TEA TFS 225 w/nitrous exh port milled to 59cc 11.2:1
Fast 92 with bumps removed, throated to 95mm to match 95mm t-body and port matched to heads
Tick Custom 239/246 - 624/595 - 113+2
TSP 1 7/8
3" true dual over the axle

My old combo made 475/446 and ran 92mph in the 1/8 mile.

="4"%New combo...
LS3 block w/4.070 bore x 4" stroke
LS3 821's - stock runners & chambers - milled to 58cc 11.3:1 and intake flange milled to promote better port alignment
LS3 intake stock no port matching (t-body flange port matched to 95mm t-body)
CamMotion 232/240 - 621/613 - 116+4
TSP 1 7/8
3" true dual over the axle

New combo made 475/460 and went 95mph in the 1/8 mile (121.6mph 1/4 mile)

Unfortunately I don't have the graphs to post (I'll get them next time I see my tuner), but what I found interesting is the big ole rec port 260cc runner LS3 headed combo out torqued the super sonic high velocity TEA TFS 225 Cathedrals from the bottom (15ftlbs rwtq advantage at 3000rpm). In fact the only area the cathedral combo had an advantage was was in "over-rev". Both combos peaked around 5900 - 6100rpm but the cathedral combo didn't fall off as sharply. I'm sure cam timing has a lot to do with the advantages both combos have on the dyno, but the cheaper and more street friendly LS3 CamMotion combo definitely made better MPH at the track.

I pocketed about $1500 dollars after selling the TFS & Fast and buying the LS3 heads/intake...I'm going to use that money to port the LS3's in the future...will report back.

EDIT: forgot to mention, the car is a full weight 99SS M6 (3750lbs) and track times have been on all-season 60,000mile warranty tires (exactly as I drive on the street). Sixty foot times are all 1.95 - 2.0 range.

Originally Posted by big hammer

pretty cool test

Originally Posted by big hammer

pretty cool test

Originally Posted by G Atsma

Four years later???

Originally Posted by Darth_V8r

That is pretty cool. Same power, more torque. Did the rectangles make more torque than the cathedrals? or is it me?

Originally Posted by G Atsma

Similar flow + smaller port volume = increased velocity = more power

Originally Posted by speedtigger

So, what happened here then?

Originally Posted by Darth_V8r

That is pretty cool. Same power, more torque. Did the rectangles make more torque than the cathedrals? or is it me?

Originally Posted by Know It All

Probably has more to do with the cam change IMO.

Tick Custom 239/246 - 624/595 - 113+2 (used with TFS cathedral port heads)
IVO is 8.5 ° BTDC ( - indicates ATDC)
IVC is 50.5 ° ABDC
EVO is 58.0 ° BBDC
EVC is 8.0 ° ATDC ( - indicates BTDC)
Overlap is 16.5 °

CamMotion 232/240 - 621/613 - 116+4 (used with LS3 rectangle port heads)
IVO is 4.0 ° BTDC ( - indicates ATDC)
IVC is 48.0 ° ABDC
EVO is 60.0 ° BBDC
EVC is 0.0 ° ATDC ( - indicates BTDC)
Overlap is 4 °

Originally Posted by Darth_V8r

No doubt.

But ppl like to say ls3 heads do not make torque. They do when properly cammed.

Originally Posted by Tony @ Mamo Motorsports

.....the cathedral crowd got jipped with the original results....
-Tony