marc_w Posted January 21, 2005 Report Share Posted January 21, 2005 Any guys on stock shortblock LQ9's come across an instance where they need to flycut? I'm looking to run 66cc (LS1) AFR 205's. Cam - 210/218 112 LSA, with rockers, a possible .583" at the valves. About the only thing in my favor here is the small durations. I'll certainly still have to spec everything out once it's apart and semi-installed... Just looking to compare setups from someone who's had to 'cut. Thanks, -marc Link to comment Share on other sites More sharing options...
TurbochargedBerserker Posted January 21, 2005 Report Share Posted January 21, 2005 My pistons are flycut a little to clearence the 2.08 valves and .600" lift Link to comment Share on other sites More sharing options...
BigTex Posted January 21, 2005 Report Share Posted January 21, 2005 Its goint to depend on the heads and how far off the deck the valves sit. On stock heads, I had planned on running a Comp 224 XER with .581 lift. I wasn't going to flycut mine. If the valves sit no lower than the valves on stock 317 casting heads, you should be fine. You are right, the low duration helps you out too. On the other hand, I looked at a heads cam upgrade on an SS last year. Durations were in the 230s and lift was near .600. I'm sure the heads had been milled some and larger valves were installed. It required the pistons to be cut. Link to comment Share on other sites More sharing options...
BigTex Posted January 21, 2005 Report Share Posted January 21, 2005 You realize that with a stock gasket you'll have 10.85:1 compression. With that small duration cam, you'll have some pretty high dynamic compression. It should make some strong torque, but might be prone to detonation a bit under high load low rpms in a heavy truck. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 Thanks a lot guys... Tex - Yeah, actually, that's just what I'm catching onto right now. I'm a little bummed - I thought it would be a pretty straight-forward install. I was doing something wrong in my calculations before. I'm getting a DCR around 8.5:1, with an alleged .048 quench on the stock-ish gaskets. What are the exact stock specs? (I managed to lose them). I think 8.5's considered borderline for pump gas, correct? On a .041 gasket, I'm getting 11.15 on an alleged .030 quench... and 8.57 DCR. The VHP guys were recommending the next cam up, if I were to up the compression during the swap. 216/224 on a 115. I think that'll take it down to around 8.25. Or I could do 1cc reliefs in the pistons to cut down about a quarter of a point... Crap. Link to comment Share on other sites More sharing options...
BigTex Posted January 21, 2005 Report Share Posted January 21, 2005 You should probably stick with the stock GM multi-layer steel gasket. Thats .054 compressed thickness and 4.04 bore. You know, the LS2 is 10.9:1 compression. The efficiency of the LS6 head is allowing that higher CR without issues. Its running a small cam too. Your main issue would really be that your truck weighs so much more than a vette. Without a bigger cam, I'd want to drop the compression a little. I wouldn't be worried about upper rpm stuff, but the 1500-2500 range where the truck lugs along. Thats when it would be pinging under the load. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 I definitely agree... This might be a dumb question... Can the 66cc chamber heads be brought out to 70 or 71cc? Easily / cost-effectively? I know the 76's (well, I know they 'should') be able to be brought down to 72cc's with milling (maybe more?), but then that may introduce the issue with the height of the valves in the head, and flycutting. Everyone in the world knows how much I love my small torque cam. If I can keep (or enhance) my power from ~ 1,800- 2,500 by bumping the CR up, and having to throw some more duration at the motor, then I'm all for it... It seems like there are a number of options... I guess this is why the good motor shops get paid all the money. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 Thanks for the stock HG specs too - got it now. I was guesstimating on the piston to deck clearance at 0.0022. I put in all the variable I knew, and worked that variable until I got our rated GM rated 10:1 compression. Still nut getting the same numbers I had, but oh-well. What's the max diameter head gaskets I can use? Link to comment Share on other sites More sharing options...
BigTex Posted January 21, 2005 Report Share Posted January 21, 2005 Stick with the stock head gaskets. If you do the math for the volume of our LQ9 and then calculate the compression, you'll see that we are really about 10.2:1 CR, not 10.0:1. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 Yup, I'm getting that 10.2:1 now. Anyone seen any good deals on Radix's lately? Link to comment Share on other sites More sharing options...
CoolBlueSS Posted January 21, 2005 Report Share Posted January 21, 2005 If you're using LS1 heads, it's not as much of an issue as it would be with iron heads. Aluminum heads are a little more forgiving with high compression, detonation problems, because of their ability to disapate heat much quicker. Are you going forced induction or NA? Link to comment Share on other sites More sharing options...
BigTex Posted January 21, 2005 Report Share Posted January 21, 2005 Yes, you can have the chambers opened up a little to add a couple of CCs to the chamber volume. Will it be cost effective? Maybe. It just depends on who you trust to do the work and how much they charge. Go ahead and put out some calls to head porters and ask. Link to comment Share on other sites More sharing options...
CoolBlueSS Posted January 21, 2005 Report Share Posted January 21, 2005 What are the specs on the stock LQ9 cam? Just curious. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 Thanks for the suggestions... I appreciate it a lot. Arrival - I was planning on staying N/A. I want to build, or mod my motor around brute torque. Small cam, smaller high velocity ports, higher compression, etc. If it gets too involved, I may just go with a Radix -- especially if I can find one used. Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2005 Author Report Share Posted January 21, 2005 What are the specs on the stock LQ9 cam? Just curious. <{POST_SNAPBACK}> I can't remember exactly... something like 190/210 .490/.490 117.5? Maybe 116? Link to comment Share on other sites More sharing options...
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