My Turbo'ed 8V 4G64, Complete Write-UP

[Low9Life4]

So, it's been quite a few years since I've posted an update on this forum. Since then I have sold the truck, bought it back, and completely rebuilt it again. This thread is to showcase my 400whp ballpark 8V 4G64, provide all he information on how you can do it as well, and answer any questions that you may have. Currently the truck is on a Microsquirt ECU. Stock head/cam/intake. I rebuilt the engine 2 years or so ago with OE CR cast 0.020" oversized pistons and factory rods. Images and documents will be posted below. This will be pretty lengthy.


Let's begin with how/why these engines are able to actually make great power for relatively cheap and the upgrades I'm currently planning to aim for the 500-600whp mark now that E85 is available local to me. I will also go into detail on what can be done to your engine, and how to setup your 4G64 truck for Microsquirt.


A lot of people believe the 8V head is too "restrictive" to be useful. In reality, on a turbo setup, that doesn't matter entirely, because you are forcing the air in. Yes, efficiency of how fast you can get it in/out is important, but the stock head does that just fine! Sure, a 4G63 head flows better and has some more aftermarket support, but the 4G64 has some things we can do to make improvements as well. I'm taking a spare head off to my local machine shop and we are going to flow bench test it to see what the numbers are and maybe where we can make any improvements, but so far I haven't found the need for it.


Cam and springs? Schneider can do you a cam grind and sell you some 6610 valve springs. RPW also sells billet cams, but they are super pricey. G54B chromoly beehive springs can also be used. As far as the valves themselves, I'm waiting to see if any over-sized valves will even help or hurt the performance of these heads. But in stock form, they perform better than they're credited.


The engines come with a factory CR of 8.5:1. Factory forged cranks, cast pistons, and same big rods as the 1G 4G63T. The main limiting factors are the pistons and head bolts up to 400whp, and I'll explain why once we talk about boost. Rods should be good to 500~ You will need to make sure you gap your rings accordingly as well.


Max boost? Due to the 8.5:1CR these engines will hold 15psi reliably on pump gas (91-93oct) all day. The pictures shown are the calculations for EFC (Effective Compression Ratio). This is the formula primarily used and considered most accurate when calculating levels of CR increase with boost. At 15psi we are around 12:1. This is easily achieved with lower total timing, and should net you around 350whp on these engines. The biggest complaint I've seen are people not making over 20psi because the head gets too "restrictive". This isn't the case. It's because we are outside the realm of running pump gas anymore! At 20psi we are seeing around 13:1 CR. This can be run on pump, but you have to have a GREAT tune. This will put you around the 400whp area. I've run 20, but for no longer than 1/4 mile pulls until I move to a different fuel. This is also why I lifted my head at 22psi before. Cylinder pressure is too great, and factory head bolts/cast pistons should not be used above 20psi. The safe area on these engines is generally 15-18psi depending how good your tuner or you are.


Head studs? I am still working with ARP on studs and have yet to try the ones I posted before. 4G63 studs will not work for our engines.


Fuel system? DSM injectors fit our rails. Go with the high impedance so you don't have to run a resistor box. A walbro 190 LPH fuel pump is what majority of the people will need. It will be good for around 400-ish HP +/-. You'll also want an AFPR (adjustable fuel pressure regulator) that has a 1:1 rising rate for boost. I believe the evo X fittings work, or you can have an AN fitting tigged to the rail.


Ignition? Stock distributor. It has the same CAS as a 1G 4G63T in the base. It will pulse crank and cam signal. It can also be used to trigger waste-spark coils.


Turbo manifold? Would need to be custom made. What I did is had a buddy cut me out an exhaust manifold flange, and I built my own.


The 5spd transmission (R5M21) will need the tuff pan on anything close to 350hp or greater to prevent the case from expanding/seperating. I recommend DFab designs. Their billet pan is amazing! (Images will be posted below). For the clutch and flywheel. I'm currently running the heavy stock flywheel. Ebay 'stage 5' 6 puck unsprung clutch. It's supposedly rated for 350hp and 380tq, I have spun it at the top of 20psi, but I would recommend a traditional sprung style for street driving. I'm going to get in contact with Centerforce to see if they can hook me up with a lighter flywheel and sprung clutch combo.


ECU? I'm running the Microsquirt AMP'd V3. I have created and am providing a full PDF write-up on how to Microsquirt your truck as well. Of course this isn't the only ECU option available, but is very budget friendly/gets the job done without issues. You could go with Link, ECMLink, Haltech, etc. Though, I will say for the cost of ECMLink and the little it offers, I would choose one of the others.

I HIGHLY recommend the AMP'd version Microsquirt because it has the built-in pull-up resistors we need for our distributor to function properly so you don't have to wire your own resistors in. More detail is in the PDF.


My next goal is 500whp. I will be going forged pistons and eagle rods. Also going with an E85 fuel setup if my local gas station continues to test good quality. If not it will probably be seeing alcohol injection. I'll see if the R5M21 will hold up, but if not I will probably swap to a Mazda R trans used behind the G54B in the Mazda pickups.


I have been beating on this truck HARD for the past year on 18-20psi and have had no issues. The one time I lifted the head was on a piggy back fuel system before switching to a standalone ECU, and roughly 22psi+ hit. 15psi is perfect daily potential for reliability and fun!