stevewix

Car is 2007 corvette with STOCK L92 heads with 918 springs mated to an L76 complete intake assembly, then with B&B headers connection to the STOCK h-pipe and mufflers. Car will retain stock converter on 6-speed auto. Z-51 Gearset.

The cam i have chosen is an XE-R 220/232 581/595 112LSA 108ICL (4 deg advance ground in) Yielding 2 degrees overlap and 8.64:1 DCR from 10.66:1 SCR.

A very close second place is an LSK- intake lobed 218/230 XER .605 int/.592 ex 111 LSA 107 ICL (4 degrees advance) Yielding 2 degrees overlap and an 8.73:1 DCR from 10.66:1 SCR.

thoughts? this will be a stock combustion chamber which i have found to be 70cc, with a .041 mls head gasket.

1. With cats (starting out it won't have them) who wants to take bets this car will pass vegas/CA emissions?

2. Will it need to idle fast enough to effectively 'push' through the stock converter when stopped? i'm projecting 800 rpm or perhaps 850-875 rpm maximum idle speed.

3. Are there any suggestions regarding cam specs/valve events/SCR/mild head porting that someone could justify for me?

EDIT: this car/motor should be completed in the next 5 weeks.

Patrick G

iTrader: (14)

Lots of questions. First off, why in the world would you put a lightweight 918 spring over a heavywieght L92 valve (especially when considering those fast ramped cams)?

Second, why run such a low compression ratio when milling is worth so much power?

Third, is your goal to remain emissions legal?

If emissions compliance is your goal, then you might be pleased with those cam selections. Otherwise, they are really, really small. Basically, subtract 10-12 degrees of duration and you'll have an equivalent cam in a 346. We're talking 208/220 cams here. The cams will make your motor very torquey and fun to drive around town, but will lack a little bit up top because of the very early intake valve closing point. Really depends on your goals. If you want stump pulling torque and emissions compliance, then you're on the right track. If you want emissions compliance and top-end pulling power, I think you're off the mark.

If you don't care about emissions compliance, I think you're leaving lots of power on the table with your current selections.

stevewix

tell me where YOU would want to be, the primary factor here is we have to do this on a stock converter, it would be nice if the car were able to meet emissions, but not necessary.

i personally thought the 918 was weak for the 2.160 valve also BUT that was simply how SDPC was selling them.

i'll bounce yet another off you here:

EDIT:

XE-R 230/244 116 LSA 112icl heads milled to 64cc acheiving 11.47:1 SCR and 8.61:1 DCR. I'm trying to stay away from too much overlap in order to contend with fuel mileage and smooth idle/NVH.

Patrick G

iTrader: (14)

If you're wanting to cut back overlap, you may want to consider running a little bit less of a split between intake and exhaust. Something more like 230/236 114LSA +2 might satisfy your drivability and emissions goals while still putting down some good power with nearly stock street manners.

For maximum area under the curve, you would want to narrow the LSA more and run another 10-15 degrees of duration, but it doesn't sound like you want this type of build.

cybernco

I ran the Comp Cams 918 valve springs, push rods and XR275HR 222/224 duration, .566/.568 lift, 112 LSA on my 2005 GTO. The 918 valve spring broke, allowing my valve to drop into the #3 cylinder, ruining my whole longblock. Yeah, I'd say the 918 valve spring is way too weak to run on the L92 heads. I'm running the 921 springs on my L92 heads.

JakeFusion

iTrader: (7)

No converters available yet for the A6?

Also is this a 6L build with L92 heads on top?

If so, I'd go with a Comp XE-R 224/238 115+0 Camshaft.

tmoneyr007

iTrader: (2)

You get that L92 setup running in your GTO yet? Haven't heard any HP numbers yet. Hope the islands are treating you well (besides the spring/valve issue on the LS2)!

stevewix

yep, l92-headed LS2. have you got a dyno sheet of the 224-238 cam i could look at?