LQ4 into a 3rd Gen/1972 Nova by frojoe

5 minute(s) of a 891 minute read

Hey Clint,

People laugh when I say that one of the driving reasons for twins is to gain room to make/install inner fenders, but when I break down the waterfall effect of engine bay pressure combined with more rad/fan/intercooler room, they get it.

The lag before was existent, but not unbearable. I would say if I started in 2nd gear at 2000rpm, it would go something like this:

2000-2800rpm = boost instantly spikes from pulling vacuum to 0 or even 1 psi boost
2800-3000rpm = 2-3psi
3000-3400rpm = 5-6psi
3400-3800rpm = 6-10psi
3800-4500rpm = 10-14psi
4500-5000rpm = 15-16psi
5000-6200rpm = steady 16psi, occasional 17psi, but the acceleration dies off due to backpressure from restrictive 2.5" dual exhaust, I'm sure

I know what you mean about the symmetry of twins and then a centered 3.5" charge pipe going right into the throttlebody. I'm still not counting it out, but from my above wooden measurements, it looks like I'd have to limit myself to a 16.5" high radiator core located in the same spot as current, in order to bend a 3.5" round pipe over it and have ~0.25" gap below the pipeand 0.5" gap above to the hood. I've also considered fabricating an aluminum charge pipe version of the cobra-looking Corvette cold air intaketubes (like below), but I'd have to squish it quite a bit just to gain room to increase the rad core 1-1.5" taller.

On Monday I put in an order for some weld elbows of several sizes, schedules, and bend radii, to test fit and see which ones will work for my envisioned turbo piping setup. I figured if I'm shipping some stuff to my PO box in the states, might as well ship some more, and I ordered a bunch of 2.5" and 3.5" intercooler couplers, elbows, and piping that I know I'll need anyways.  

It was also very hard for me to not pull the trigger on a new rad+fans setup last night as I researched setups for hours, but I knew I needed to measure real life with as many items mocked up in place. I'll hopefully remove the current intercooler and rad this weekend, and mock up hotside piping as well as routes and clearances for charge piping, to figure out the thickest/tallest rad+fans combo I could get.

Unless proven/measured otherwise, my current thinking is a 2-row 2-pass C&R radiator (P/N 802-31191) and likely dual 14" fan, but maybe a single 18" fan. It's terrible trying to choose fans online based off all the sketchy CFM ratings (like Zirgo.. 3600cfm and 10amp draw? Yeah right!).

 

Possible fan options currently are:

1) dual Spal 1900cfm 21amp 14" fans (P/N 30102042). But Spal consistently has tech specs for all their fans, and although 2400cfm isn't the highest draw I found for a fan, it's from a company with good reviews (more specifically, a lack of reviews say their CFM's are full of ****) and is the highest amp draw I could find.

2) dual Derale 2200cfm 22amp fans (P/N 18214) as I've good success with that brand and that's the highest CFM 14" fan they make, and it's a good price.

 

3) for a single 18" fan, there's very limited options available.. I would likely be looking at an OEM SUV or truck fan, so it would be hard to get CFM/amperage data for one. A fan that comes to mind is the Cadillac SRXfan (I forget the exact details at the moment) but they're crazy expensive at I think $600, and require PWM management.. but apparently pull crazy amounts of air. I'll search my subscriptions and try to find the Mark Steilow build thread that has more specific info for it

EDIT: looks like the fan I was thinking of is from a Cadillac SRX, and is huge(fan shroud is 23"x24"). But here's some interesting info anyways...