View Full Version : Twin Turbo Chevy

24-01-15, 09:15 PM
Righto, projects.... Edit: Slight change of plan - building an LQ (iron block LS) motor for this now with the intention of making around 700hp NA. With scope for some forced induction in the future...

Well I can't leave anything alone, so even though my Camaro has only been on the road for a year it's currently in bits waiting for a transmission transplant. I've built a really strong 4L80E for it ready to put some serious horsepower through the chassis. When I rebuilt the car I did it with a similar thing in mind. Substantial subframe connectors, solid body bushings, extra bracing on the front subframe as well. I also fitted a very strong 12 bolt in the back, with Moroso Brute strength posi and forged half shafts. I have a lot more to do yet, but I'm stopping short of fitting any sort of roll cage, for now. As it's predominantly a road car.

Here it is, for those that haven't seen it before. Been to a few shows in 2014, so you might of seen it around. Currently powered by a strong 360 SBC putting out around 425hp. I've made a few underhood changes since the photo was taken, including fitting hydroboost and a different air filter to get rid of that horrible chrome one!

It's got multi-point EFI (I hate carbs with a passion) and wasted spark ignition (crank triggered) with Megasquirt II ECU. This will be getting bigger injectors and the ECU a few modifications for the turbos.



So in the quest for more horsepower, I decided to fit a big pair of hairdriers to it to see if I can blow it up. But that means:
Building a complete new, low CR short block that's strong enough
Building a transmission strong enough
Upgrading the fuel pumps
Making some electronic alterations to the ECU to allow boost control among other things
Making a new exhaust system
Moving all of the ancilliaries on the engine out of the way
Electrical upgrades to cope with the additional cooling fans and fuel pumps
Oil cooler - a big one.

I'm not moving very quickly with the project at all to be honest, lot's of expensive bits and not enough income to share between this and a load of other projects.

I bought a pair of GT35 turbos, they aren't small ones. But equally aren't huge either. I went with recommendations from our friends in the USA who've been using the same ones with good results;
T4 frame with T3 mounting flange
.70 A/R Compressor
.82A/R Turbine
Compressor Wheel: 61.3 /82 mm
Turbine Wheel: 62 /67.8 mm


Along with those I bought some 60mm wastegates - Tial knockoffs - although they look to be very nicely made. These will get controlled by my ECU with a failsafe of an offline boost controller tied into my wideband lambda set up.


And a 50mm BOV


The turbos will end up mounted around here somewhere, although I need to get some exhaust headers made up to put them where I need them to be


So all that stuff is on the shelf to work with as needed. In the mean time I've been working on the other bits.

This is the 4L80 I built to fit. It's not a pretty thing to look at, but inside it's got a load of trick bits that PATC sent over from the USA, including a full set of Alto Red Eagle Power Packs, billet input shaft, valve body modifications and a heap of other stuff.


I also got the Milodon splayed mains fitted to my block after a little machine work


After that I acid cleaned the block and filled it with Moroso Block Filler to the bottom of the water pump holes.

Due to the siting of the turbos both the washer bottle and header tank needed moving out of the way. So I made 2 little stainless ones to fit in the gap next to the radiator on the core support. You can just see it in the pic, the filler neck is easy to spot.


The other things that needed to move are the alternator and power steering pump. So I got a couple of brackets knocked up and fitted an electric water pump. I'm also going to be changing to the modern Saginaw style pump with a remote reservoir as they are a lot neater and offer polyrib drive.


Talking of polyrib, I need to run 2 belts, one for the alternator and one for the steering pump due to their locations. I couldn't find anyone who made a pulley to suit, so I made my own.



A lot of these modifications are being done on my existing engine. There's 2 reasons, the first being I am not going to get the turbo motor built this winter due to financial constraints. And secondly I know it's a reliable motor, so it's a good test bed for the modifications over the next 12-18 months until I get it all swapped out.

When the weather warms up I might get some motivation back and start getting on with this again.

24-01-15, 09:55 PM
Very cool build. Funny how space just seems to disappear when you mess with these things.

24-01-15, 10:15 PM
Great stuff :tup: will be following with interest, does sound like a mountain of work

Been trying to find your first garage thread over the road but cant seen to find it at the min, wouldnt mind checking out the EFI bit again

Found it :tup:

24-01-15, 10:35 PM
EFI side of thing's - might be of interest to a few people so I'll replicate the current set up here. I need to make a few changes to the system for the turbos, but will post details of those as I go.

Air gap manifold, multipoint injection and 1000cfm throttle body. I'm currently running eight 75lb/hr injectors, but these will be getting upgraded again for the turbos as they are very marginal on their size. 90's would be better.


You don't need the distributor, but you do need the oil pump drive off the bottom of it. I modified an old points dizzy to do the job

Stripped the gubbins


Put it in the lathe and turned the top end down and gave it a quick polish up as well


Also had to remove the advance mechanism from the top of the shaft


Made a press fit cap to cover the end up out of a bit of ally bar stock


And a couple of hours later, job done


The ECU - Megasquirt 2. With 4 coil drivers for wasted spark, triggered from 36-1 crank trigger wheel. It also controls things like the radiator fan, tacho etc and feedback for closed loop is via wideband lambda. I ended up modifying the trigger circuit with a JBPerf dual VR board as I had some noise problems which that cured.

Tuning is via Tunerstudio and laptop.

Naked board


USB board plugs into the small 5 pin connector

And some coil drivers, output on a seperate connector


Next up gas tank modifications for fuel injection. Starting with making a small baffled 'sump' for it. Used an old tank that's been well vented and been standing open a good few years. No worries about vapours in this one. This allows me to run an inline fuel pump at the back of the car, with just a feed and return line under the hood. And it's been working well, even when fuel gets a bit low in the tank.

Its about 10"x7", drilled 2 1 1/4" holes in the tank under where the sump is fitted then welded it on. The take off at the front of the tank is the fuel outlet. I added another to use as a tank drain, figured it might come in useful one day. The tank has an old breather line welded into the top, which I plan to use as the fuel return. The gas cap I have has a breather so no problem there either.



I fitted the trigger wheel. I modified it to fit on the back of the damper as its a major job to space everything out if it's mounted on the front. Though it's far from ideal being mounted on the damper, it was good enough to get me running. I'll be mounting a new wheel on that shiny new pulley I made and ditch this one.



You can see the finished bare install here, coil packs are on the fire wall and are Ford ones from escort or fiesta.


Couple of vids after I'd just got it running, shows the software etc.



24-01-15, 11:05 PM

25-01-15, 12:08 PM
Very interesting so far :)

25-01-15, 07:39 PM
love it,great shape camaro too..:tup:

25-01-15, 07:53 PM
Thats going to haul like a north sea trawler.

26-01-15, 07:07 PM
Thank you guys. Hoping to get cracking on with fitting the transmission back in this weekend, weather permitting. :tup:

07-02-15, 07:43 PM
Finally finished that pulley and fitted it! Tomorrow finishing the alternator and PS pump mounts and measuring up for the belts.

Then I'll have a look at sorting out the wiring for the water pump, alternator and fuel pumps.


08-02-15, 05:17 PM
I managed to get the steering pump trial fitted and get it lined up with the crank pulley. Had to modify the fluid feed tube, but it's only pushed into the body of the pump and came out surprisingly easily. I need to add a bend on the end of it toward the inner fender in order to keep the pipework neat and tidy. The pump came off a 5th gen Camaro, but I think it's the same as fitted to many late model GM cars, but I wanted one specifically with the multi-rib pulley. I just need to make some proper spacers (1/4" thick) and paint the bracket to finish the installation.


I didn't get as far as sorting the alternator alignment before it got dark. Really must move the car into the workshop....

Please ignore the rusty engine block.... I'll be fixing that when I swap engines out later in the year. Only I'll be painting the next one with 2k...!

19-02-15, 04:45 PM
Hows things coming along Gothic, rusty engine blocks look cool, far to much shinny stuff going on these days

Didn't notice your for sale add before, looks like the turbo ideas a no go

19-02-15, 05:38 PM
Well, the change of plan is forced by a cash flow issue. I need to get enough money together to get back to Bonneville again this year and scaling back the ideas for the car temporarily is one way of doing that.

I do have a hankering for a forced induction project though, and I have something else in the pipeline for that, albeit on a smaller scale.

However, that doesn't mean I won't be doing something else with the Camaro. I'll either be looking for an LS motor when we are in the USA or doing some serious upgrades to the current small block.

01-03-15, 06:55 PM
And here is the reason all that turbo and small block stuff is for sale.


Its an LQ4/9 (not sure which pistons it has in it). But doesn't have a crank, rods, cam or anything else. Though I do have a sump and some other spares for it that aren't pictured. Got a spare head to replace the badly damaged one. I did get it cheap, and I need to strip it down to check it over, I know there is a small crack near the oil gallery plug at the bottom of the block where one of the sump bolts goes in right at the back (arrowed below - borrowed pic...). Some muppet has broken the boss for the bolt. I might need to do a bit of surgery to fix it, but at least it's not in a critical area. Once I have it in bits I'll check the rest of it over and see if there is any other damage.


So, on the USA trip this year I'll be looking for the other parts I need to build it up into a complete engine and get it installed.

23-03-15, 11:47 AM
This 180lb monster is now fitted, sorta. I need to make a crossmember for it, but before that I need the slip yoke to make sure it's not going to hit the floor pan brace. I am also probably going to regret fitting the stock converter, but funds are currently rather tight.

It's a bit snug in the trans tunnel, only near the cooler lines. But I think it will work out to have about 1/4" clearance.

I also need to get the controller ordered and built - a job for next month.


29-03-15, 06:10 PM
I'm still waiting for the slip yoke to arrive from the USA, and the weather has been really crap this weekend anyway so I decided to make a start on looking at this LQ engine block and figuring out how the hell I am going to fix it.

Pulled all of the pistons out of the bores - all new but missing pins and locks. Not a major problem as I might need to get another set that has valve reliefs cut as I am pretty sure I am going to run into valve to piston clearance with the sort of cam I am planning to run.

Set about checking the rest of the block over for cracks and it all seems to be OK. Checked the bores and water jacket all over and found nothing - messy job with the dye pen fluids. So that just leaves the 2 on the bottom left corner of the block where some muppet has dropped it.

Drilled the ends of the cracks as deep as I dared and ground them out. Haven't gone too mad with them as they aren't really in critical load areas of the block. But one of them is right on the back of the oil passage down the side of the block so it needs sealing up otherwise it'll leak oil. The areas of the block aren't too thick, so it should be possible to get enough heat into it (I hope!). The plan is to use HTS-528 rods for the repairs

This one is pretty simple.


The other is the one on the oil passage. The corner of the block was broken away where the sump bolt hole is. So I drilled it all the way through and then cut off the damaged part - not that it was held on by much anyway. The intention being to make a new threaded boss and dowel it to the hole I drilled through. I'll probably braze it up without the boss fitted and then just fit the boss later as it's not structural, it just needs to hold the back of the sump to the block. This gives the best chance of sealing up the crack... I think...




I've also measured the oil pan and started thinking about modifying that. It's a stock pan from a truck/Escalade and is 8" deep. Too deep for the Camaro. I haven't worked out how much I need to cut off it yet though... I've got the pick up pipe as well, but that's just steel pipe that can be cut to suit. You can buy an LS swap sump kit, but I'm not paying $200 for the privilege of that...