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Mikey 97Z M6 · 10-02-2008, 01:42 PM

I decided to go with L92 heads, so I breathed on them a bit with some porting burs. I spent most of my time porting the exhaust, which everyone knows the L92's are a bit weak on the exhaust flow. My goals were to do a mild port on the intake runners, and do what I'd call a stage III port on the exhaust runners to help get them up to speed with the incredible flowing intakes.

For the intake, I basically just removed the bumps from the rocker boss, and valvespring pocket, blended the entire port with a cartridge roll, opened up the area around the valve guide, and very slightly opened up the outside bowl edges.

The exhaust side got a decent amount of work done, but the area between the intake runner and the exhaust runner ports in the bowl is pretty thin from the factory, so it limits the amount of bowl work done on that side of the bowl (intake and exhaust). The exhaust runner tends to "lean" away from the intake runner anyway, so it's really no big deal, but if anyone ever ports these themselves, be careful in that area.

Here are the before/after flow numbers. They use a Superflow 600. All flow numbers are at 28". They test with a 5" long exhaust pipe, so these exhaust numbers are a little higher than you're probably used to seeing for stock L92's. Valves used for testing are stainless REV, the intake valves have a backcut performed by West Coast Cylinder Head (thanks Richard).

Stock L92 Heads
Lift.....intake.....exhaust
.200...160.........122
.300...214.........173
.400...268.........200
.500...302.........216
.550...315.........222
.600...319.........226
.650...321.........229

Ported L92 Heads
Lift.....intake.....exhaust
.200...164.........130
.300...228.........179
.400...280.........223
.500...317.........252
.550...335.........260
.600...350.........266
.650...357.........270
.700...357.........274

The decks were cut 0.025". I'm shooting for 11.3:1 for this combo. Once I get the heads back from the shop, The are assembled with the REV valves, Patriot Gold springs, and install them on the shortblock with the new Cometic head gaskets.

Here are some updated pictures of mocking up the accessory drives onto the engine. I had to piece-meal all the front belt driven accessories since I didn't have an LS1 to begin with. I wanted to make sure I had all the nuts/bolts and brackets etc. The headers are 1-3/4" super-old Grotyohahns (sp?). They should really go in a museum but I need them...

Mike

10-02-2008, 01:42 PM	#3
Mikey 97Z M6 11 Second Club 1997 Chevrolet Camaro Trader Rating: 15 Join Date: Mar 2004 Location: Vancouver, WA Posts: 1,502	I decided to go with L92 heads, so I breathed on them a bit with some porting burs. I spent most of my time porting the exhaust, which everyone knows the L92's are a bit weak on the exhaust flow. My goals were to do a mild port on the intake runners, and do what I'd call a stage III port on the exhaust runners to help get them up to speed with the incredible flowing intakes. For the intake, I basically just removed the bumps from the rocker boss, and valvespring pocket, blended the entire port with a cartridge roll, opened up the area around the valve guide, and very slightly opened up the outside bowl edges. The exhaust side got a decent amount of work done, but the area between the intake runner and the exhaust runner ports in the bowl is pretty thin from the factory, so it limits the amount of bowl work done on that side of the bowl (intake and exhaust). The exhaust runner tends to "lean" away from the intake runner anyway, so it's really no big deal, but if anyone ever ports these themselves, be careful in that area. Here are the before/after flow numbers. They use a Superflow 600. All flow numbers are at 28". They test with a 5" long exhaust pipe, so these exhaust numbers are a little higher than you're probably used to seeing for stock L92's. Valves used for testing are stainless REV, the intake valves have a backcut performed by West Coast Cylinder Head (thanks Richard). Stock L92 Heads Lift.....intake.....exhaust .200...160.........122 .300...214.........173 .400...268.........200 .500...302.........216 .550...315.........222 .600...319.........226 .650...321.........229 Ported L92 Heads Lift.....intake.....exhaust .200...164.........130 .300...228.........179 .400...280.........223 .500...317.........252 .550...335.........260 .600...350.........266 .650...357.........270 .700...357.........274 The decks were cut 0.025". I'm shooting for 11.3:1 for this combo. Once I get the heads back from the shop, The are assembled with the REV valves, Patriot Gold springs, and install them on the shortblock with the new Cometic head gaskets. Here are some updated pictures of mocking up the accessory drives onto the engine. I had to piece-meal all the front belt driven accessories since I didn't have an LS1 to begin with. I wanted to make sure I had all the nuts/bolts and brackets etc. The headers are 1-3/4" super-old Grotyohahns (sp?). They should really go in a museum but I need them... Mike __________________ -97 Z28 - 387 LS1 Darton MID-Sleeved, 236/236, DIY Ported L92's w/L76, Grott LT's, True-Duals, Quick Performance 9", 3.89's, 3" Chromoly DS, Monster Level 3, 6pt Rollbar, Spohn Suspension, N/A - 11.03 @ 125.55mph My FQuick \ My LS1 Swap Thread -00 Tahoe LT - Stock 5.3 -02 VW GTI VR6 - H&R's, Konis and 18's Last edited by Mikey 97Z M6; 10-02-2008 at 06:05 PM..