LQ4 into a 3rd Gen/1972 Nova by frojoe

5 minute(s) of a 891 minute read

Another decent day in the garage today, ended up spending a bunch of time figuring where wiring, breather hoses, fuel FPR and hoses will go, etc. All this revolved around getting a new intake..

I've been kinda mediocrely pleased with the truck intake this whole time. I originally liked it because it's what I had, and with some trimming I thought it still looked kind of "OEM". But with time and all this attention spent on perfecting the aesthetic of the twin turbo setup, I've been intrigued with getting a nicer looking low-profile car intake.

In my research before deciding to go with twins, I decided that if I were to ever justify replacing the heads, I wouldn't go all the way with crazy CNC AFR heads but instead would go with stock GM LS9 heads due to the better/stronger A356 material they're made of and the casting method, the [slightly] thicker decks, and the all-cool [slightly] larger titanium intake and sodium-filled exhaust valves. Well I found a good deal on BNIB GM CNC LS9 assembled heads... why not! Their combustion chamber size is 66.5cc compared to my old 70.5cc 317 heads, so that will bump my compression up from 9.0:1 to 9.4:1.. I don't foresee this being an issue. Bonus for this is if I end up stroking the engine in the future, I won't have to settle for 8.0:1 to 8.5:1, I could get closer to 9.0:1 with a 4.0" stroke.

This allows me to run an LS3 intake which looks much nicer in my opinion (hey.. I have to pay attention to form sometimes!) and requires a 4-bolt 90mm throttle body which is close to the 3.5" charge piping I'm running. The rectangular ports look honestly almost twice as big as the cathedral ports.. I personally don't see a downside to the upgrade... if I can build the same power but at 0.5psi, 1psi, or even 2+psi less boost produced by the turbos, then that's a win in my books, not to mention the better heat properties of the head material.

I did some reading thinking I'd be smart, and preemptively purchased a 2008+ "gold blade" LS3 throttle body (GM p/n 12605109), reading that its blade is reverse-sweep compared to the previous 2005-2008 "silver blade" LS2 throttle body (GM p/n 12570790) but that Holley is compatible with it. Somehow in my hours of research beforehand I didn't come across the fact that apparently the later "gold blade" TB had much weaker servo motors than the "silver blade", and has a tendency to have the TB blade get forced/stuck open under "high boost" when the foot is taken off the pedal. So looks like I'll be returning the later LS3 TB and buying an earlier LS2 TB.

Checking the angularity of the silicone coupler and the 3.5" piping, with the intake now a bunch lower. It was actually quite easy to stretch the 3.5" 5ply silicone double hump coupler over the 100mm throttlebody OD, so it's nice I can reuse that coupler. With some ovalization of the charge pipe over the radiator I don't think the intake piping angles will look too whacky...

A decent shot to show how close I got the placement of the wastegates, the clocking angles of the wastegate domes, and the angles of the wastegate dump pipes (with flex joints).

Also got started on the passenger side wastegate dump pipe into the downpipe.. I'm pretty happy with it but will think about it a bit to see if I want to slacken out the angles of the bend going into the downpipe...