Summitracing

@72tutone,

We hear ya and like what you're thinking. We wouldn't hesitate to put the 706 heads on this 6.0 for what you're looking to do. If you could snag a set of 243/799's for a good price they would be a good option as well. If you're good with running 93 we would go with the 706 heads. Like @stockA4 said if you want low-end power/torque with crisp throttle response put the 706s on this

Onto a cam. We have a couple of options we could see working here. One of them has already been discussed here.

Option 1 - SUM-8720R1 with specs of .600/.600, 218/227, 112+2 with -1* of overlap. This will have a noticeable lope with a lower idle speed. With the raised compression and converter this 6.0 C10 swap will be very responsive and fun to drive. It will make strong power/torque from 2,000 rpm on up and run well out to 6,500+ with your .660" duals.

Option 2 - A little unorthodox but hear us out. Our Pro LS stage 2 turbo cam SUM-8706R1.Specs on it are .600/.575, 226/230, 113+4 with 2* of overlap. Don't let the turbo cam scare you because of your previous experience. If your 5.3 was an LM7 with 8cc dished pistons and 706 (61cc) heads you'd be around 9.5:1. With that BTR cam that has a 43* IVC that would likely feel lazy down low with that engine setup and your combo. You would have needed a cam with an earlier IVC and earlier EVO to make a combo like that feel responsive down low. However, with this 6.0 and planned 706 heads with 11.44:1 compression you have a different animal. The cubic inches and compression are going to help with power/torque throughout the range. The 8706R1 will have a nice steady lope but tunes well and is easy to live with. It will have a strong mid-range and carry out well to 7,000+ with your .660" lift duals.

Your 3,000-3,200 converter will pair well with either of these cams discussed.

You'll want to check pushrod length. If you already have some 7.400" 5/16" Chromoly pushrods with .080" walls they might work with either of these cams. We always recommend measuring for pushrod length first to make sure you get the proper lifter preload. Trickflow offers the TFS-9501 pushrod length checking tool that is good to have in the toolbox for future builds. If you end up needing different pushrods we offer a variety of brands that carry 5/16" Chromoly pushrods with a .080" wall. You can typically find a set of 16 for around $100. From there you can get into a thicker wall or larger diameter pushrod. For excellent stability and strength check out our 11/32" HDR pushrods with a .120" wall. These have 25% less stress and 28% less deflection than a typical 5/16" x .080" wall Chromoly pushrod.

Something else to help with the install. We have a cam swap install kit. That is part number CMB-09-0029. This includes the timing cover gasket, water pump gaskets, oil pump o-rings, LS2 timing chain, valve cover gaskets, and harmonic balancer bolt. You can always purchase individual parts out of the kit within the kit/combo contents section for the kit.

Let us know if we can be of any further assistance. We'll be happy to help!

Kjduvall

I second summit racings response, there not just some hack trying to sell you parts. They actually care about there costumers and it shows, based on the amount of ( give a ****) I've seen on there part they truly are enthusiast of the (hot rod community)... And I thank you for that.

stockA4

I'm not arguing that either of those cams summit recommended won't work, in fact both of them would work so well that even if he still had a stock stall converter and a taller gear like a 3.08 It still wouldn't matter. The truck is still going to boil the tires off from a dead stop have excellent throttle response and Haul *** matter what cam you put in it, I promise. My point in all this is just that if you look at a mach index calculator and punch in this combo you'll see very quickly that this combo wants a late IVC, I would back both of those cams off four degrees If I had to install them in that combo without second guess. I know summit would agree

I can say this and I know that it's true because I built the same combo years ago before it had caught on. I have an iron LQ4 block 0.065" over with LS3 pistons and bone stock 706 heads on top. LS6 intake, stock f-body exhaust manifolds and magnaflow cat-back. It's in a fat *** 4th gen (3800+ with me in it). And it still has a stock stall and 2.73 gears.

The smaller intake valve and ports, combined with the larger displacement, create an engine that can swallow pretty much any cam on the shelf without really affecting the drivability or low-end response at all. Even with 4° of overlap, It will idle and drive and drive just fine without stalling at 550 RPM with a stock torque converter, I drove mine for a long time and in all kinds of weather before I even had the idle tuning hammered out with a four degree overlap cam because it didn't really matter that much. And I was still at the stock idle speeds, 550 RPM in gear 650 in neutral, I've never had to bump it up with any of the cams I've ran, even with the larger cams. This is an incredibly forgiving combo. I'm running a 2600 stall now and it performs excellent, however even with a larger cam you're missing out on some of that torque and response if you drive it on the street a lot.

This combo is all about torque and response right from idle I spend a lot of time with the converter locked close to there and at varying speeds. I have the converter lock as low as 1100 RPM in third and fourth so I'm getting a lot of feedback with my experiments in that area on the far far left side of the dyno graph that everybody b****** about that they don't get to see. I can assure you that area is way better in that area, way better even than a 243 head.

I have tried a lot of cams in this combo, four so far and the latest one is my own spec a really simple cam spec and It's by far the best. If you can this engine right it will have a usable power band of 1100-7000 RPM with incredible average torque

grubinski

Thanks for this … never heard of this idea before.

The Wallace racing calculator doesn’t suggest an actual IVC … would be more useful/interesting if it did. Do you know of any calculators that provide this?

stockA4

If you throw random numbers at the dynamic compression calculator You quickly find where your Ivc needs to be @ 0.006" to get around 8.5 to 1 dynamic for pump gas.

grinder11

iTrader: (1)

If you read up on cam lobe theory, there's great reading on the theories by Ed Winfield, and Ed Iskenderian (also known as "The Camfather"), on how and why the most important valve event is the intake closing. Fascinating stuff for gearheads.....

stockA4

I agree there's a lot more to it than just targeting a dynamic compression number but I think that's a good place to start for a street engine, however lots of race engines may have very low cranking compression due to a very late IVC event but they are able to scavenge so much at high RPM it makes sense for the application

grinder11

iTrader: (1)

Back when I was young, and a few dinosaurs were still running around, we used to degree a cam using a compression gauge. With an adjustable timing set, you carefully adjusted it until it read the highest cranking compression number, tightened everything, then double checked it all.......

72tutone

Well, looking at my situation and the 706 heads might be too much DCR. Ive also looked at 799/243 heads as well at 64cc.

Messing around compression and DCR calc's they might be on the high side. Which would leave me with these crap 317 heads. If someone can show me a calculator result and show me I'm wrong, I'm all for it.

But, this is what I'm coming up with

Bore - 4.000
Stroke - 3.622
Head CC 61 706 heads
Effective Dome Volume: 0 ?? This is what onallcylinders.com shows for a lq9
Deck Clearance: Guessing and reading .008 above deck???
Compressed Gasket Thickness: .051
# of cylinders 8
Compression - 11.2 : 1

Wallace racing DCR -
Static compression ratio of 11:1.
Effective stroke is 3.31 inches.
Your dynamic compression ratio is 10.14:1 .
Your dynamic cranking pressure is 219.68 PSI.

10.14 is way to high. This is what the 8720r1 @Summitracing recommended on a 39 IVC.

With the compression calc from summit above with a 64cc head this would net me -
10.78 : 1

DCR with 64cc head -
Static compression ratio of 10.78:1.
Effective stroke is 3.30 inches.
Your dynamic compression ratio is 9.97:1 .
Your dynamic cranking pressure is 214.93 PSI.

So, a bit better but still not in that magic quadrant of 8 - 8.5.

Ive looked at summit cams, tsp, cam motion, btr. It seems like I have to have an extreme duration range and or IVC of plus 45 to get anywhere near what i need to do.

I was thinking of milling the heads maybe .020 to get down to maybe 67/68cc. But, then I will need to check pushrod length. I just bought some .080 BTR 7.4 pushrods maybe a few mos ago. I would like to reuse them.

Anyone with a lq9 with 706/799 heads, come on in and suggest a cam or what I can do to mitigate this. I was thinking of running the 706 heads, but with a 0.80 head gasket. That would net me around 10.43 : 1 apparently. But, then I'm not sure if the quench would be right.

Am I over thinking this? I wouldnt think this would be that difficult

I thought 93 octane was near me. Its all 91. So, I need tp stick with 91. I have no issues putting 91 in.

grubinski

That 39° IVC point is at .050” lift. The calculator wants the number at .006” lift. As a pretty close rough guess, add 25° (for the ramp) to the 39° at .050” to get an appropriate IVC at .006” lift. That comes out to about 64° for your IVC … plug **that** into the calculator.

Or else ask Summit for the .006” IVC. The 25° estimate above is a very aggressive ramp. The actual ramp may be slower, especially on the closing side, depending on the lobes used.

G Atsma

72tutone- Summit has a set of calculators on their site, among them being a compression calculator.
Wallace Racing also has one.
Eliminate guessing and use one of them.

grubinski

He’s already using the Wallace racing calculator, he’s just input the wrong numbers.

72tutone

Ive done that. None of these are gospel. For every 4 sites, calculations are different on every single one.

From the wallace DCR at 11.1 with IVC @.006 *65 according to the summit cam 8720r1 this would net arounds 8.83:1 which I guess is ok? Its not in the 8-8.5 range.

I guess I can combat this with thicker headgaskets to lower compression down a bit?

*Note* Just ran 64cc from a DCR with the 8720r1 and comes up at -Your dynamic compression ratio is 8.51:1 which is dead nuts on. This is the route I need to go.

Surprisingly, I would have thought 64cc would have put me around ls2 at 10.9. Summit showing 10.73 with .008 deck clearance. Not sure of this number. .051 gasket, 64cc, effective dome 0. Again, on all cylinders shows volume at '0'. .

stockA4

Absolutely never is the head gasket to be used to adjust the compression ratio. Thicker head gasket would cause detonation issues even with an LS. The reason they sell thicker head gaskets than stock is because sometimes the machine shop has to clean the top of the block deck off and so sometimes the pistons stick out of the hole a little bit so they need a thicker gasket. Some on here measure everything like a spaceship and run a clearance between the top of the piston and the bottom of the combustion chamber somewhere around 0.035"-0.040" and they of course use the thinnest gasket possible. An engine built this way would tolerate and even higher static compression and higher dynamic number because that clearance would maximize chamber efficiency. If you're not doing any machine work a 0.048" blue Fel-Pro head gasket is going to be perfect.

The exact degrees numbers don't matter that much It's all windage, so long as you're close a few digits one way or the other pretty much anywhere it is not going to matter. I have ran LS combos with dynamic compression calculations as low as 6.7 and as high as 9.3 none of them had any issues and were all street-driven combos.

Summitracing

OP,

We don't like to dive too far into dynamic compression as it can muddy the waters. As far as LS engines go we've seen 9:1 dynamic on 93 with no sign of knock. As always you want to have a good custom tune with someone data logging making sure the engine stays happy.

We're comfortable with the 8720R1 in this combo with 706 heads at 11.44:1 using 93 octane. With the 8720R1's 65* IVC at .006" lift that would put you at 9.07:1 dynamic.

If you wanted to go with the 799/243 heads we'd go with some .040" head gaskets to tighten the quench. @stockA4 was alluding to this in post 34. Reducing quench into the optimal .035-.045" promotes a more efficient combustion cycle and reduces the chance of knock. This would put you just under 11.2:1 static and just under 9:1 dynamic. Plenty good for an LS engine on 93 with a good custom tune.

For some reading material on dynamic compression in LS engines check out this Chevy Hardcore article by Jeff Smith.

Let us know if we can be of any further assistance. We'll be happy to help!

Fast355

My aluminum head SBC 383 has 11:1 static and a custom 271/284 @ 0.06, 218/228 @ 0.050 on a 108 LSA and 106 ICL. It has Rhoads V-Max lifters that knock 20° off that cam at low rpm. It cranks at 225 psi compression. Quench is a fairly tight 0.041". I run a fairly aggressive timing map and see almost no knock. Rolling 60 mph on the highway, I saw a little knock retard at 1,800 rpm and 0.44-0.52 gm/cyl load with 38° of timing commanded, but dropped back to 32° there and have not seen any since. WOT I have 16° @ 1,200, 20° @ 1,600, 24° @ 2,400 and 31° @ 3,600 rpm. With a stock diameter converter that stalls 2,800 rpm, 4L85E and 3.73s it has a ton of torque to move the ~6,200 lbs it is pulling around. I actually had to increase the shift points at part throttle at 10-25% throttle. It makes so much torque it was shifting 1-2 @ 10 mph, 2-3 @ 18 mph and 3-4 @ 32 mph at ~15% throttle while the engine sat at 2,500-2,800 rpm. Acceleration is much livelier holding 1-2 to 15 mph, 2-3 to 30 mph, and 3-4 to 45ish and the engine does not rev any higher.

72tutone

So after long deliberation, I'm thinking of just millling my heads 317 down maybe 3CC to 68CC or so. 006/.007 for every C milled is what Ive been told. So with anywhere from 71.5/71 CC now down to 68/68.5 this would put my compression right at 10.89 or so. This is also assuming my piston to deck hovers around -.004 above the deck. From .004-.007 it goes to 10.95 or so compression. DCR is anywhere around 8.65 or 8.61. I would assume this would be acceptable on even 91 octane with somewhat conservative timing?

With the 65 .006 IVC on @Summitracing cam, this certainly helps.

So with .020/.021 milled off, any issue with P-t-v? -218/227 112+2, .600/.600 Lift on this cam with a -1 BTDC I wouldnt think there would be an issue on this lq9? If the magic number of quench is around .0.038 - 0.043 in and I'm milling around .020 what would I look for in compressed thickness on a head gasket?

I hate math and my head hurts trying to figure all this out.

stockA4

This has to stop. You don't need to measure anything You've got 342 gears and a 3200 stall You just need a big cam with those 706 heads.

I keep forgetting you have those crazy 660 springs.

Put the 706 heads on there with a regular fell pro gasket and stop worrying about it.

Summit stage 3 (extra valve clearance so nothing to worry about there) automotive cam ( high horsepower type camshaft)

It's a 230/242 113+3

High compression engines with big cams are often more tolerable of low octane than ones with more conservative valve timing.

You'd be well over 500 horsepower at the crank with this type of cam, and yet you could tune it to run on 89 octane no problem, and if you follow my plan you don't have to measure anything or use any more calculators.

72tutone

Forgive my ignorance, but at .006 seat on that cam its close to 6* BTDC IVO. I thought anything close to 5* then you have to start worrying about P-2-V?

I'm not saying what you are telling me isnt right or wrong. Everything has its tolerances for a reason. At the end of the day I'm the one holding the bag here should I just slap things together, not worrying about SCR or DCR and I grenade this thing because my valve hits the piston. Make sense?

stockA4

It's a summit racing extra valve clearance camshaft, It would still clear even if you had the heads milled a little bit, just Reuse the oe timing gears and put a new LS2 chain on it and you are good to go