Hello,

Some of you guys may remember me putting together a LQ4 with stock 799 heads, 220/224, 0.575 lift cam, Pac 1218 springs, and I just bought a DLS2 intake. It's still on the stand waiting for the completion of a ls swap.
Now I picked up a LQ9, so far I have the heads off, and cylinder walls look good. Still need to pull the rod and main bearings. So here is my dilemma, I have a set rectangle port truck heads, and LS3 intake, going to run an off the shelf Summit Racing Cam. This will be for a daily driver street car, would this be worth doing? I'm a big fan of using parts from the stock parts bin, but I want the best bang for the buck.

Thanks.

 

Hey you have a decent compression LQ9, some GREAT truck heads, and a GREAT intake setup. Which cam do you have in mind? You won't need much! I too am all for using "talented" OEM parts if that's what will get the job done.

 

I'm really looking at the SUM-8715 or the SUM 8707 camshafts, Ithink either one will suit me just fine. If I could stop buying **** I don't really need verses what I want, my swap might be farther along then what it is. I still want an under drive crank pulley and an aluminum flywheel.

Stampede.

 

I think the 8715 will do you the most good. More flexible than the 8707, and will still deliver the power. Look up Mavn, a poster on these forums. He races hard, yet was impressed with this cam.

 

Well, that's the cam I'm really thinking about, and I will be milling the heads some.

Stampede.

 

The LQ9 is already 10.1:1 compression. How much more do you want?

 

I would like to be at 11:1.

Stampede.

 

the lq9 with rectangle port head will be 10.4:1 without milling

also the 8707 cam will have MUCH more thump at idle.... just so you know

 

Personally, I wouldn't do anything more than just a clean up mill on those heads. You can get into piston to valve clearance problems in a hurry when using milled square ports on stock LQ4/LQ9 pistons and an aftermarket cam, unless you plan on fly cutting the pistons.

 

He'll need a square port intake for square port heads.

 

he has a ls3 intake already

 

Yes, I forgot about having 2.165" dia valves, glad I said something.

Thanks.

 

Be sure to pick up dual springs with 150# seat pressure and 400#open, 11/32 pushrods and a decent lifter.

 

Why the larger pushrods, and dual springs? I planned on running LS7 lifters with 1218 springs.

Thanks.

 

I would call a reputable manufacturer of these products for information but from the info I have gathered after lots of research:

Pushrods are engine columns and can deflect/bend under stress. Thicker pushrods do a much better job at maintaining proper control of the lifter as it runs over the lobe. The consequence to the pushrod bending is the lifter can lift over the lobe and crash down causing a loss of power and possibly lifted damage. 11/32 pushrods are much stronger then the 5/16 pushrods people like to use and fit without modifications and are maybe a few bucks more.

I recommend dual springs for multiple reasons. For one, if a spring breaks the engine will begin to misfire at high rpms, run poorly and should start making some weird noises. But there is a greater chance that it won't completely fail and drop a valve, get munched up and annihilate everything but the intake...if your lucky. Dual springs maintain fantastic control. They can maintain higher seat and open pressure for control of more radical cam lobes and higher lift rates of the cam. You can run beehives if you want, modern lobes are pretty gentle and dont need lots of spring pressure for proper valve control but if that spring breaks...kaboom.

Stock rockers with trunnion upgrades should be okay with modern less than .630 lift cams and springs with 150# seat and 400# open pressures. Otherwise, TSPs steel roller rockers are a great option. I'd recommend them for their strength and durability over stockers along with improved guide wear and more controlled wipe patterns.

Lifters are a big one. Ls7 lifters are designed for running long term in OEM applications. Through heavy springs and a faster lobe in the mix and now its out of its element. The lifter will not bleed down fast enough and will pump up. Causing an excess amount of oil to reside within it and over extend the valve. So imagine the valve needing to be closed but cant, due to pump up. Disaster for high rpm power. The lifter can also end up turning in the tray which will cause catastrophic engine faliure. A quality lifter will eliminate these issues and provide better valve control over high rpms. Less noise at idle and resist pump up at low rpms as well providing more accurate use of the lift of the cam to the valve across the entire rpm range. Running something like a 2116lsr is what I'd recommend. Better lifter capable of higher rpms, better control of the valve and maintains full lift characteristics offered by the cam across the entire rpm range, quieter and gets lessens the chance of a lifter rotating in the bore due to a link bar.

 

Well some may disagree with me , and I'm not bashing L92 heads and they're a good value but I like them for big bore , not 4". You would get better results for a street car to go with good set cnc cathedral heads more power low and mid-range .If you decide to stay with the L92 head get a good valve job , give some attention to exhaust side clean up, put LS3 intake valves in and the best exhaust valves you can afford. And on cams I don't like low lift cams like the 8714 with those heads.