My Self Ported L92 Heads w/Pics, Flow#'s
09-30-2007, 04:06 PM
#1
My Self Ported L92 Heads w/Pics, Flow#'s Well, as some of you guys might know, I've ported heads before so this is really nothing new to me. This is the first set of L92 heads I've ported though. My experience goes all they back to LT1's.
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 get them up to speed with the incredible flowing intakes. I'm hoping for 340/255 @ .600" lift. If I get anywhere near these numbers I'll be ecstatic.
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 baseline flow numbers I had my machine shop flow for me. 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
Here are the pics from the porting with brief descriptions:
Stock combustion chamber
Semi-finished chamber. Unshrouded the intake/exhaust valves near the seat area ONLY. I did not increase the outside diameter of the chamber at all.
Another shot of the semi-finished chamber.
Stock intake runner. Anyone see room for improvement? I do....
Mildly ported intake runner with bumps removed.
Here's a shot of the heavily worked exhaust runner.
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 get them up to speed with the incredible flowing intakes. I'm hoping for 340/255 @ .600" lift. If I get anywhere near these numbers I'll be ecstatic.
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 baseline flow numbers I had my machine shop flow for me. 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
Here are the pics from the porting with brief descriptions:
Stock combustion chamber
Semi-finished chamber. Unshrouded the intake/exhaust valves near the seat area ONLY. I did not increase the outside diameter of the chamber at all.
Another shot of the semi-finished chamber.
Stock intake runner. Anyone see room for improvement? I do....
Mildly ported intake runner with bumps removed.
Here's a shot of the heavily worked exhaust runner.
Last edited by Mikey 97Z M6; 10-01-2007 at 01:51 PM.
10-01-2007, 01:54 PM
#4
I updated the first post with the new ported flow numbers. I'm very, very happy with these results. The flow bench operator was so surprised by the exhaust numbers, that he checked and double checked for air leaks, then re-tested again, and came up with the same numbers.
I'm one happy camper.
Mike
I'm one happy camper.
Mike
10-01-2007, 02:08 PM
#6
Originally Posted by GoFast908Z
those numbers are CRAZY!
Mine were 350 and 230 @ 650 lift
Mine were 350 and 230 @ 650 lift
Mike
Last edited by Mikey 97Z M6; 10-01-2007 at 07:17 PM.
10-01-2007, 02:19 PM
#7
Good Job,
From talking to a few different head guys it's not hard to make the port flow Huge number on the intake, the exhaust does require a bit more work. However the real challenge is getting those flow number to make the power on the engine. The intake manifold is going to be a huge restriction and requires a lot of porting to make it work. Now you just have to find a cam that works...
Again, Good job
From talking to a few different head guys it's not hard to make the port flow Huge number on the intake, the exhaust does require a bit more work. However the real challenge is getting those flow number to make the power on the engine. The intake manifold is going to be a huge restriction and requires a lot of porting to make it work. Now you just have to find a cam that works...
Again, Good job
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10-01-2007, 02:37 PM
#8
Originally Posted by .ALEX.
Good Job,
From talking to a few different head guys it's not hard to make the port flow Huge number on the intake, the exhaust does require a bit more work. However the real challenge is getting those flow number to make the power on the engine. The intake manifold is going to be a huge restriction and requires a lot of porting to make it work. Now you just have to find a cam that works...
Again, Good job
From talking to a few different head guys it's not hard to make the port flow Huge number on the intake, the exhaust does require a bit more work. However the real challenge is getting those flow number to make the power on the engine. The intake manifold is going to be a huge restriction and requires a lot of porting to make it work. Now you just have to find a cam that works...
Again, Good job
The cam I'm using to start with is a single pattern 236/236 .595/.595 on a 112lsa. This is all going on an all-bore 387.
Mike
10-02-2007, 06:00 PM
#12
Thanks guys, I'm really pleased with the way they turned out. I'll be hoping for some decent HP numbers from this 387 now. 
Probably not gonna happen. The intake won't be much larger than stock,,, +10cc maybe? I really didn't do much in the intake runner at all so I'm pretty surprised by those increases as well. The exhaust side, well ya they're way bigger, but I'm not too concerned about that.
Mike
Mike
10-02-2007, 08:31 PM
#14
thats a fairly mild cam for that setup, you looking for a nice stable daily driver? I think you are leaving alot of power on the table by not going with something slight more aggressive
Especially the exhaust side.
10-04-2007, 12:58 AM
#18
Thanks again,
Mike
10-04-2007, 02:24 AM
#19
i wonder what that exh port would be if u went from the d port to a full O port.
i am going to do the same when i get my L92 heads..just blend everything in and so a lil grinding..from what i've seen they dont need much work to be a sick head..
once i go to an all out short block i will have them ported by curtis at rfd or ricky at jeff naisers shop
i am going to do the same when i get my L92 heads..just blend everything in and so a lil grinding..from what i've seen they dont need much work to be a sick head..
once i go to an all out short block i will have them ported by curtis at rfd or ricky at jeff naisers shop
