which cam for lq4 and l92 heads, w/o flycutting
11-03-2010, 12:20 AM
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which cam for lq4 and l92 heads, w/o flycutting I have a stock lq4 and would like to put the l92 heads on but I have no idea which cams to even be looking at without having to flycut the pistons. The heads have such big valves campared to the 317,s . I was not sure where to ask this question so ill start here. thanks I plan on running the stock l92 truck intake also.
11-03-2010, 09:32 AM
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Mostly for drag/street. This is in a 67 chevelle and not a daily driver. 4.10 gears and 4l80e with 3500 stall. I would like to go out to the strip on the weekends. thanks
11-03-2010, 12:16 PM
#5
After looking at it a bit I really don't like the L92 heads for an LQ4 with the stock dished pistons. The large intake valve makes it hard to get the compression up and maintain safe PTV clearance. If you are dead set on the l92's I'd suggest a 228/240-112+2, but even this puts the DCR at an anemic 7.2:1. Some 243/799 heads with a moderate camshaft(something in the mid 230's) would make much better power.
11-04-2010, 12:01 AM
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Texas speed posted on the engine forum that answered my question. I thought the l92 heads had a smaller chamber than the 317 heads? with 317 heads the engine is 9.6 to 1 according to gm specs.
11-04-2010, 09:13 AM
#7
The LQ4 actually has a 9.4:1CR with the 317 heads(72cc) and the L92(70cc) will bump it up to 9.6:1. I did see your other thread and agree with the last post about wanting more compression. To me an unported L92 head would need more exhaust duration to overcome the lazy exhaust port, but TSP has done the research.
For comparisons sake a 243/799 head unmilled would net you a 10.2:1CR. The LS6 castings are very good with just a 5 angle valve job and a back cut on the intake valve. Plus you don't need to buy another set of rockers. Hell for just about the same as what the L92 heads and rockers would cost you could get a set of PRC stg1 LS6 heads.
For comparisons sake a 243/799 head unmilled would net you a 10.2:1CR. The LS6 castings are very good with just a 5 angle valve job and a back cut on the intake valve. Plus you don't need to buy another set of rockers. Hell for just about the same as what the L92 heads and rockers would cost you could get a set of PRC stg1 LS6 heads.
