Worked 317's or L92's
Worked 317's or L92's Here's what I'm working with...
73 Impala, 4k lbs wet with driver
LQ4 stock bottom end (except rod bolts)
Cam will be in the 22x/23x area high lifton a low lsa (110-108), not sure what grind I'm running yet
GM carb mani for whichever head
BG mighty demon 750dp
If I were to have my 317's worked, they would be CNC'ed by PRC with dual valve springs and milled .040, stock valves
If I went with the L92's, they would either be stock or CNC'ed, one of the two. Since I'm leaning towards a lower duration cam, I thought about sticking with the stock L92's as they already flow a crapload.
73 Impala, 4k lbs wet with driver
LQ4 stock bottom end (except rod bolts)
Cam will be in the 22x/23x area high lifton a low lsa (110-108), not sure what grind I'm running yet
GM carb mani for whichever head
BG mighty demon 750dp
If I were to have my 317's worked, they would be CNC'ed by PRC with dual valve springs and milled .040, stock valves
If I went with the L92's, they would either be stock or CNC'ed, one of the two. Since I'm leaning towards a lower duration cam, I thought about sticking with the stock L92's as they already flow a crapload.
Last edited by ramdaspadhye; Jun 14, 2009 at 03:26 PM.
I was asking because of my application and cam choice. Bigger heads aren't always better. I'm wanting a lot of power in the midrange, and larger intake runners tend to perform better up top :/
Anyone else?
Anyone else?
Yeah, I had Pred spec me a cam when i was gonna keep the stock 317 heads. I'll see what he has to say about a cam for the L92's. I just assumed that since the runners flowed so much more than the 317's it would need a lot different cam profile to compensate, since the heads and cam need to match 
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Actualy, the issue here is the dished pistons. L92 would have to be milled considerably to reach 10.5 SCR or above. If you were thinking about getting other heads, 243s would be my choice,
Or Patriot 6.0 castings 59cc (welded chambers) with 2.055 valves. (those might be harder to find, I do not think Patriot still makes them). A nice valve job on those witha bit of hand finish on the bowls would be worth the budget.
Or Patriot 6.0 castings 59cc (welded chambers) with 2.055 valves. (those might be harder to find, I do not think Patriot still makes them). A nice valve job on those witha bit of hand finish on the bowls would be worth the budget.
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Unported L92 heads will work very well. With the L92 heads starting off 2.2cc smaller than unmilled 317s, you're already ahead of the game. LQ9 pistons will raise the compression another .5-.6 of a point which is a good move. An L92 head will generally need around 4 degrees less on the intake duration (but around the same exhaust duration) that you would typically spec for a 317. Just don't go too crazy on overlap as those high flowing intake valves on the L92s are more sensitive to reversion (because of their big flow at low lifts). This makes them a little harder to cam.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
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Verdad Gallardo TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
The LQ4 have about 6.7 cc dish, that would put you around ~9.8 SCR, That is why I said that you would have to mill too much and that 243s would be a more favorable choice (unless you want to change pistons, which mean basicaly a bottom end rebuild)
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Who is joking? I'm just giving you options:
Would L92s with flat tops and the right cam make better power? It depends how much you spend on the 243s.
Would Budget 243s make better power than L92s, NO
Is the LQ4 suited to L92s? NO, piston relief/dish too big. Good for boost.
Would a LS2 or LQ9 do the trick? Yes
Can you just replace the pistons (direct swap with nothing else done)? No, once you remove the crank, rods etc.. on a used motor, it is best to just rebuild since the bearings have seated, and cylinders need honing (doing it otherwise is a backyard fix and will not last long).
What would I do if I were you? I would sell the LQ4, shop around for a LQ9 and take it from there, or I would just rebuild the LQ4 with forged pistons (reliefs), 6.125 rods and take it from there with a stock LS3 headed setup (why LS3, because they have lightweight valves).
I hope this helps
Would L92s with flat tops and the right cam make better power? It depends how much you spend on the 243s.
Would Budget 243s make better power than L92s, NO
Is the LQ4 suited to L92s? NO, piston relief/dish too big. Good for boost.
Would a LS2 or LQ9 do the trick? Yes
Can you just replace the pistons (direct swap with nothing else done)? No, once you remove the crank, rods etc.. on a used motor, it is best to just rebuild since the bearings have seated, and cylinders need honing (doing it otherwise is a backyard fix and will not last long).
What would I do if I were you? I would sell the LQ4, shop around for a LQ9 and take it from there, or I would just rebuild the LQ4 with forged pistons (reliefs), 6.125 rods and take it from there with a stock LS3 headed setup (why LS3, because they have lightweight valves).
I hope this helps
