I'm getting a LQ9 with 40k miles tomorrow and the last few weeks I've been trying to wrap my head around a strong street combo that's somewhat budget (not unlimited, but I have some money to spend). I know what's streetable is objective, but I need something that idles at least decently, won't require new springs all the time, something that will last a few miles.
I plan to drive the crap out of the car. It's not a daily driver, but a solid weekend car. I plan on maybe taking it to the strip a couple time to see what it has, but not to be competitive. Probably take it to autocross events more than the drag strip as that's how I have set the suspension up. The car is a '69 Chevelle.

My plan:
LQ9 shortblock
PRC L92 CNC'd heads with stiffer springs (patriot springs?)
LS3 intake (ported), injectors (39lb), fuel rail ect. (there are some good take offs on ebay)
90mm cable tb (yet to be decided)
cam (Hot Cam???)
T56 with centerforce dual friction clutch
3.73 rear gears

Now I have definitely searched and have read a lot about these heads, and LQ4 & LQ9s. I want something with a lot of average HP and torque. Most people here seem to run pretty radical cams (especially me being used to cam specs for flat tappet SBCs). I'm trying to figure out what would be just a moderate cam that makes good average power with this combo. Probably less than .570 lift so I don't have to go through springs, plus I don't want to have to worry about PTV clearance. From what I have read, you can get away with a pretty mild cam on these heads and make a lot of power, but is a Hot Cam too mild? When I've read small cam on other threads they're talking about .610 lift. As in this thread

I don't know if I should just call Comp to get a custom grind? Seems overkill if I just want a mild cam. If I am going for more of a street setup, would getting ported heads give me much advantage? Or would throwing some stock L92's with some stiffer springs probably do as well? I am willing to spend the extra to get ported heads, but only if I see some benefit.

 

IMO for a 6.0 setup, no need to port the heads as they flow 300cfm stock and that is plenty.
What I would invest in is a good valve job and light valves, that is it. Springs with light valves PAC 1518s.
As for cam, you do not need mega cams to make power with these heads. You need a proprly matched cam so custom is what I would go with.
Do not be afraid of lift but avoid real harsh lobes like LSK; XFI and LSL or XE-R will do nicely (that depends on cam designer) some use other lobes.
mid 220 range cam is enough to gt you 450+rwhp and 430+ rwtq which seems plenty for what you have in mind.
Then you can put your $$ in nice headers/exhaust.
I myself prefer to keep the car FI (for below curve street trq)

 

I agree, in fact I'm doing the exact build right now on my LQ9. I had a set of L92 heads, and bought the upgraded lightweight LS3 valves from the dealership. Then Sent them to Lingenfelter to be CNC ported, more for the exhaust gains because the intakes flow really well as already stated.

I too went with a single beehive spring because a dual isn't required with a mild cam and the weight of the spring matter too. I run Comp 26918s with their new lightweight Tool Steel Retainer. It weighs about the same as Titanium but wont wear, it weighed 6.7g IIRC.

I wouldn't run a GM hot cam either. Lift is good for these heads, duration is where most people on the forum and I disagree. My perfect cam has low duration and high lift which means lots area under the curve. Most people on here will want you to put a ginormous cam in this thing 240 dur @ .050 and that's not what your describing as being what you want. I went with an Comp LSR cam (LSL Lobes) 219/235 .607/.621lift 113LSA +4. I like tons of power,drivability, easy tunability, good vacuum, and brakes.

I also think you might be pushin it with stock LS3/LS7 shorty style 39lb injectors. Im going with 46lb/hr in mine. But thats something thats up to you, just be careful and watch your duty cycle.

 

I'm totally intending to keep it fuel injected, that's one of the reasons I'm going Gen III over my old small block. Adding fuel injection to an sbc gets more expensive than just getting an LQ4 in the first place.

I was thinking 39lb injectors would be appropriate for a 450hp or so engine. Plus getting a new set of injectors is $350 I could put elsewhere.

Would I really need really light weight valves? I don't intend to be spinning this thing above 6k very frequently. Or are the stock valves just crappy? The heads I'm looking at have 106 gram intake valves, are these L92 valves or the LS3 valves you're talking about. They have an option for hollow stem intake valves which save 15 grams. That's adding another $180, on top of $1124 + cost of stiffer springs (assuming the ones that come with are not adequate for the cam I run).

I guess I will call comp to get a custom cam when the time comes and I have settled on the exact heads and intake I'm going to use. The heads have been out for long enough now that I'd assume they'd probably have something in mind for this combination.

 

Calling Comp for a custom cam would be the biggest mistake of it all.

And IMO yes, light valves and top notch beehives are the way to go

 

if it were me a 224/230 .609/.604 112+4 would be decent but have pred z spec you a cam! not comp!

 

A XFI lobe 224/230 .609/.604 112+4 would seem about right then based on what Predator said.

That would be a custom cam though wouldn't it, or is that a production cam? Where would be a good place to get PAC springs? They look kinda pricey on the first couple sites Google came up with.

I'm guessing I might as well start with some bare heads if I were to replace the valves and springs (if beehive, I'd need different retainers correct?)

 

not trying to ya, but i was under the impression that the L92 heads favored a little more exhaust. Like 10 - 15 degrees. say a 228 / 240 ? This was due to the heads flowing small (comparatively) on the exhaust side?

Pred Z, am i correct in this assumption?

 

It depends on the rest of the exhaust but yes they do favor a bit of added exhaust with the right valve events and overlap for the cubes.

 

something like a 224/238 .609/.605 112+4?

 

well i'm no cam expert, nor do i claim to be. But.... I think the cam that you mentioned above would be very streetable. I know with some of the larger cams with L92's people have trouble getting them to idle, just because of the huge amount of air that is still coming into the engine at low rpms.

 

oh maybe pred z can chime in here

 

That cam is only 7* overlap, very streetable low 6300+ shifts

 

didnt someone have good results with a 224/230 cam?

 

I think you're on the right track however I'd go WITHOUT the cnc ported heads. It's a waste on such a small motor. When I get my L92's I'm not planning on having them ported either. Secondly, are you planning on milling the heads at all to bump your compression up? Any idea what head gasket you're going to use? I myself am curious as to what point you'd have to flycut the pistons for a mild cam since the L92 has such a monsterous intake valve. I wonder if it's safe to run we'll say a mild 224/228 cam with a 112LSA with the heads milled .040 and a thinner .040 head gasket. FYI the stocker is actually .056" compressed.

 

This is the dyno I was refering to

https://ls1tech.com/forums/dynamomet...p-446rwtq.html

Its a ls2 dont they have the same compression as lq9's?

 

They have flat top pistons yes, L92s are ~69cc so ~ 10.4 SCR.

Would anyone know valve drop value on L92 heads?

 

Well, turns out the engine I got is a LQ4... I have a pair of new L92 heads and an LS3 intake. Now I'm going to try to make due with what I have. I'm thinking of milling the heads a bit to get my compression back up to what the LQ9 would have been (mill .030?)

With that being said, would the cam mentioned earlier (224/230 .609/.604 112+4) likely have interference with the head milled .030? Should I not worry about the compression and just put a little more cam? I'd have the piston fly cut if I knew someone in Dallas that could do it with L92 heads... but I don't.

 

Your compession milled .030 will be ~ 10.35:1 SCR (with L92 gasket)
As for cam I would go with something like this:

227/235 111+1 LSA
9* overlap

 

Looking at Texas Speed the cam that may fit would be:

226 (.585)/234 (.598) XE-R lobes
111 LSA
110 ICL

Or.

224 (.609)/236 (.607) XFI lobes
111 LSA
110 ICL

Is the XE-R more aggressive than the XFI? Is 111 LSA bad for the street?