Firehawk441

iTrader: (41)

https://ls1tech.com/forums/drag-raci...s-any-c-i.html

Car # 15 (TEKTRANS) on this list has the fastest L92's listed. CARTEK Built. They might have a good idea what will work.

mike c.

iTrader: (1)

OLDSSSTROKER-What do you mean? It seems you are saying patrick G has no clue from your highlight of the done his homework part. Do you know something I or others don't????? Reverse split,he never told me to use a reverse split.

108dragon

iTrader: (5)

One major issue is that, stock at least, there is a hellacious difference between the intake and exhaust flow. There has been a lot of crap talked about the LS7 stage 3 cam ("bandaid fix" and such), but it seemed GM knew exactly what was required to balance that issue. Camming it like you would an LS1 is not the answer.
TSP, Livernois, Lingenfelter, and Katech, who have done extensive work with LS7 heads/engines, will be able to tell you what you need -and more importantly, why. I'm sure there are more companies out there with this experience, but the ones I mentioned are the ones who first come to mind.
I have never heard anything negative about PatG's work or expertise. Shawn@VA Speed would be someone with valuable information on your combo as well. If his crew pulls thier expected dyno numbers from thier L92 setup, his head would definately be worth picking.
I would also be more concerned about what the heads are flowing at your anticipated lift values for your combo and not the max. This may preclude a lot of cam specs and narrow your choices as well. -ie if you can't run hellacious lift numbers because of valve to piston clearances, or duration for the same reason....

Patrick G

iTrader: (14)

Don't worry about Jon's comments. He is very bright when it comes to engines, but you won't typically see him giving free advice on this board. That would be taking money out of his pocket (as an engine builder). He is an asset to this board if for nothing more than his quick whit and being the grammar police. I don't get offended when he stirs the pot. It's all in good fun.

Back to topic. I've been very vocal in my opinions on L92 heads since they first came out. I was ridiculed early on for my choice to use large splits between intake and exhaust lobes on L92 heads. For the record, I have NEVER advocated reverse splits for L92 heads.

Here are some "general" observations I've seen about the L92 heads:

1. The large port size does not mean that the L92 heads are going to be soft/lazy with low rpm torque. Surprisingly, when cammed correctly, the L92 heads make for some very torquey combos in the low rpm range, often surpassing their cathedral port counterparts.

2. The large intake ports flow so much, you can use a 4-6 degree smaller intake lobe to make the same power as a typical cathedral (LS2) port.

3. The exhaust port of the L92 is not worse than past cathedral port heads. In fact, it is slightly better. In general, you will run a similar exhaust event in an L92 application as an LS2 application, maybe a little smaller, but certainly not more.

4. The robust low lift flow of the intake port means that the L92 heads are very susceptible to reversion from the exhaust during the overlap cycle. This means that excessive overlap is a big no-no. Intake valve opening points are much more critical in L92 applications than they are with cathedral port applications. This is where experience and care needs to be taken when selecting a cam.

5. The L92 heads respond to lift more than cathedral port heads do. While an L92 head will make outstanding power with .472" lift, they tend to make bigger power increases by running a .600" lift cam than a cathedral port head would.

To summarize, you don't need to run a huge intake event to make good power. You don't need to run any bigger of an exhaust event than you would have with an LS2. In fact, you might be able to run slightly smaller. And finally, you must watch the intake valve opening point in the overlap cycle and avoid excessive overlap.

So if a 242/246 112LSA +3 cam is a popular size for a street strip cathedral port 416 application, a 236/244 114LSA +2 cam would be more like what an L92 application would look like. Notice the exhaust lobe is the same or slightly smaller than a cathedral port application, but the intake lobe is quite a bit smaller. In fact, in this illustration, the IVC and EVO are the same between cams, but the L92 cam IVO is 6 degrees later than the cathedral port cam and the overlap is 8 degrees less.

LSXHawk

iTrader: (27)

???? Im very happy with the cam I got from them.

sixt9er

iTrader: (2)

^^^Just curious to know, what exactly "they" spec'd out for you?

WKMCD

iTrader: (2)

I think Patrick did a pretty good job in his post. My only addition would be to note that a tighter lsa and and ICL is not a bad thing with these heads IF you have the valve events right. I run north of .650 lift on the intake and close to that on the exhaust. My overlap is under 10 degrees.

Old SStroker

No offense meant to Pat. Just picking on him a little.

Pat has used some "reverse split" cams on cathedral port heads in the past. Not everyone who does LS cams goes that way. The good thing is that the cathedral port heads seem to give fairly good results with various valve events. My guess is that the L92 style heads may be a bit more sensitive to valve events. Read what Pat wrote above.

I'm not a cam guy, but there is a Holiday Inn Express nearby...


Jon

Stang's Bane

iTrader: (22)

Just a little thought from the bleachers.

I think the reason the heads respond so well to more lift is the valve doesn't get out of it's own way until higher lift numbers.

Just my thoughts

Richard@WCCH

iTrader: (3)

Patrick. Well done sir! This mirrors our observations with camming the L92 heads. And explained with very nice grammar (thanks Jon).

Richard

108dragon

iTrader: (5)

There is a good read on a build like this at http://forums.corvetteforum.com/c6-z...age-3-a-3.html.

It appears to be an LS7 427 build using an LS7 Stage 3 cam. Really high strung, track cam. Probably could have done better with a better set of heads ..WCCH maybe. Definately better with 1 7/8 headers, full exhaust, and fine tuning. I'm not too crazy about idling around town at 1200-1400 rpm though. lol I guess it's that 107 lsa. There are probably better cams for this application.

"Well, the beast is now running. Trying to get this thing to idle and stop hunting for idle has been a challenge, but after playing with the Airflow Minimum Final and Startup Airflow tables, I think it's pretty close now. I sure wouldn't want to drive this thing in 5 o'clock traffic. It only starts to smooth out around 2000 rpm. And lopes like a fueler. =)

Went to the dyno yesterday and made 576 rwhp and 517 rwtq on a Dynojet. Torque curve is flat from 4200-5300 with 460 tq then climbs to a peak of 517 till 5700 rpm then dips. HP starts at 4000 (330 HP) and climbs to a peak of 576 by 5700 then holds till redline.

I have a feeling the LG 1 3/4 headers and stock C6 mufflers are my point of restriction. The Killer Bee and Fast Intake show now restriction on my logs...

I'll try to post a video and dyno sheet soon."

There is a dyno posted in the thread as well.