Giving the LS3 More Power With Comp Cams and FAST!

The exhaust valve seat had an odd shallow cut on it which wore this divot into the seating face of the exhaust valves as seen on the left. We replaced them with the oversized Ferrea valve which had a tulip contour and a reduced stem for better flow. This shows that you should never trust your heads to anyone other than the best machinists with the best modern equipment. Our theory is the valve job had been done with old stones instead of cutters. The stones were probably improperly dressed.
To replaced the old corroded, clogged and uncleanable too small injectors that were on the car, we used some Deatschwerks 65 lb/hr injectors.  These injectors are characterized and flow matched in low pulse widths, transitional pulses widths, linear range pulse width and wide open flow to ensure that the set you get is dynamically matched over the injectors entire operating range.

The previous engine builder used injectors that were too small then used a really high fuel pressure to force more fuel out of them.  The side load put on the pintles from high fuel pressures can cause inaccurate and inconsistent response from the injectors and cause them to wear out quickly like the hammered injectors in the motor were. Now that we have proper injectors with headspace in case Rathyna wants to run E85 or Nitrous in the future, we are in a lot better shape fuel system wise.

One good thing is our heads had a nice mild port job from the old engine builder.
We recut the seats using a 3 angle valve job with the proper angles and proper seat width. We hand blended the 70-degree base cut into the port. The heads were slightly warped, too much for the Cometic MLS gaskets we were using so we resurfaced them as well.
Howard installed the new valve seals by tapping them in place using a socket extension and a mallet.
The valve stems were lubed up and dropped in.
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10 comments

  1. The LQ9 isn’t the iron block version of the LS3, they’re not even from the same LS Generation (LQ9 is Gen III and LS3 is Gen IV).

    Reply

  2. Sure the LQ9 is a Gen III and the LS3 is a Gen IV but there are not many differences between the Gen III and Gen IV engines and most parts interchange. The major differences between engine generations here are some to accommodate DOD and VVT options that the LS3 does not use anyway. Where it affects you, in this case, is a single bolt vs 3 bolt cam for the sprocket. The LQ9 has a 4″ bore with the same stroke but its iron block can easily be bored to the LS3’s 4.065, all the internal parts interchange. The heads are the square port, LS3, L92 improved square port configuration and everything interchanges. A lot of Chevy tuners like the LQ9 for an inexpensive forced induction block as the iron block is stiffer under boost. Its cheaper than the LS7 based six head bolt solutions for better head sealing under pressure.

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    1. The Comp Cams Trunion has a lot more bearing area than stock. As you can see in this picture the size difference in bearing area between stock and Comp Cams. You can also see that the stock trunions were beginning to gall on this engine with a stock cam and valvetrain. Installation does require some finesse and proper use of a press. A lot of people have good luck with this kit and perhaps some of the early failures were perhaps caused by improper heat treating and installation.

      I have seen many failures of stock rockers in high-level drifting which is more brutal than drag and road racing in some ways. Check out the pictures and the galling of the stock shafts.

      https://photos.smugmug.com/MotoIQ/Project-Cars/Project-Pink-350z/i-PKXPZXt/0/cf264521/L/DSC_0817-L.jpg

      Your info is good to know and thank you for bringing it to our attention and we will be keeping an eye on them but I don’t think we will have problems. We will report if we have issues.

      Reply

    1. You are completely right, our block is bored out quite a bit to 4.065 and you can go as much as 4.090 as I recall which you can’t do with the aluminum blocks. Everything does interchange between the two motors though.

      Reply

  5. Due to Rathyna’s penchant for not maintaining anything,

    Lol a woman not take care of her car?!!?!?! Unheard of!

    Reply

    2. I unfortunately wasn’t really raised or taught to maintain vehicles. I have always been a driver, and the circles I associated with growing up never emphasized car maintenance. It was all about driving. Luckily I found MotoIQ and they’re teaching me a different way – it’s kind of a running joke with me at this point. I’ve gotten better…not quite good at it yet, but I at least understand the importance of vehicle maintenance and safety now 🙂

      TGI for MotoIQ <3

      Reply

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