Budget turbo rebuild
This article ties two ongoing projects together. Bob O’Neill needs a fresh turbo for his Daytona, and our Slant-6 project needs a fresh turbo, too. Since both turbos are nearly identical, this article covers the rebuild on both projects. Differences between the two will be noted where applicable. I’ll even toss in a few cheap or free upgrade tricks with the purchase of this article.
Turbochargers utilize the normally wasted heat energy from the exhaust to help engines make more power. That’s how Stephane Beauregard can go 8.04 at 174.30 mph in a 2.2 liter Shelby Charger! It will be a key component in helping Bob achieve his “modest” goals as well. Converting to a blow through intake manifold, Bob has decided to use a TII Garett T3 turbo (.42 A/R intake, .48 A/R exhaust). The specs are the same for the Slant-6 turbo.
Start by removing the lines and fittings from the turbo, then remove the housings from the center section. It would be a good idea to soak all of the bolts with PB Blaster or equivalent a couple of days ahead of time to help them break loose. Set everything aside except for the center section. Mark both wheels so they can be reinstalled with the same indexing. This will at least restore the original balance the turbo came with. If you’re shooting for an extreme performance turbo, have it professionally balanced. Turbos Unleashed (www.turbosunleashed.com) can handle the balancing for you.
Using an air gun and wrench, remove the nut holding the impeller on the center shaft on the intake side. There are 4 bolts holding the back of the intake scroll to the center section. Remove those now. At this point, you should be able to remove the turbine and shaft by sliding it out the exhaust side. Sometimes the shaft needs some persuasion to come out. With some very small snap ring pliers, remove the rings holding the bearings in place. You will find that there are a total of 4 snap rings. Only the outside ones need removed. The inside ones are a bugger to get to and really don’t need to come out.
With all of your small parts laid out, compare them with what comes with the new rebuild kit to make sure you have the right stuff. If everything is in order, put all of your bolts and small hardware aside for now. The best place I’ve found for the kits is www.gpopshop.com. They are about ½ the price of Turbo City.
As a performance upgrade, the bell of the swing valve housing can be ported. The stock 2.25” swing valve measures an actual 2.1” across. The later TII 2.5” swing valve measures an actual 2.3” across. The smaller 2.25” swing valve can be ported to 2.4” across, making it flow even better than the larger 2.5” version.
For better boost control, the wastegate port can be opened up to flow a bit more. I shoot for about 1/8” larger than stock. Going too large can create sealing issues and make the boost control somewhat eratic. Blend the sharp edges while you’re in there.
On the Slant-6 turbo, the early TI intake scroll has provisions for EGR. This simply gets tapped and plugged. I start with a reamer, then the 3/8” NPT tap. The plug will then screw right in place.
Considering these turbos are around 20 years old, the wastegate can arm will be rusty. In some cases, the eyelet that goes on the control arm may be rusted clean off. An easy fix is to cut the shaft about 3” from the can, thread for ¼” X 20, and replace the end. I made one out of dowel material with a hammer and drill. Using a long nut you can reconnect the 2 ends together and you have an adjustable wastegate. Be sure to add a lock nut to keep it from working loose.
With the modifications performed, it’s time to sand blast everything clean. Plug the nipple on the wastegate can to prevent sand from getting in there. The center section can be blasted providing you clean it thoroughly afterwards. The blasting will remove old baked on grease and oil, and provide a surface texture that will help our new coatings to adhere properly.
The center section, exhaust scroll, and swing valve get Tech Line’s Color Guard High Temp Titanium coating on the outside. The scroll and swing valve get Tech Line’s Cermit ceramic thermal barrier coating on the inside. The intake scroll and backing plate will be powder coated. Bob’s turbo was powder coated Gold Glaze, while the Slant-6 turbo was coated Tropic Orange. The folks that bought the Slant-6 turbo requested that I re-coat the orange a Lollipop Blue to match their 1973 Swinger’s stock engine. Nevertheless, it’s orange for now.
Other articles will cover coating the intake scroll and the exhaust.
All of the small parts should be cleaned up and coated as well. There are brackets that hold the center section to the scrolls, there are bolts, fittings, oil drain tube, etc that can be spruced up for a better looking and longer lasting end product. A wire wheel on a bench grinder will tackle most of this for you, and the sand blaster will do wonders on the rest. To paint the bolts I take a box and punch small holes into it. The bolts are pushed into these holes where I can spray them without having the finish marred by them rolling around. Brackets can be hung from wire and sprayed (or powder coated).
Before reassembling, tap all of the holes in the exhaust and intake scrolls to keep the bolts from bottoming out on crud and not sealing properly. This extra step is highly recommended. I use stainless steel bolts on the exhaust side in case it ever has to come apart again.
By now you have a pile of impressive looking pieces and parts. Reassembly should be done with care to ensure everything is right on. Liberally oil all internal parts as they go together. I suggest using STP Oil Treatment or Lucas as it is thicker and won’t run off as quickly as engine oil will. Just assemble in the reverse order you took it apart. Be sure to realign your turbine marks to maintain some semblance of balance. Also be sure to get all of the parts clocked or indexed properly. Bob’s turbo is indexed the same as it came apart. A “before” picture can save you headaches at this point. Another trick is to grind notches into the different pieces where they should go together. The Slant-6 turbo gets indexed entirely differently. This one can be tightened upon installation if you are unsure.
The Slant-6 turbo required a special oil drain tube to be made that comes straight out instead of on a sharp angle. I made a flange that closely duplicates the stock oil drain flange, pressed in a piece of ¾” tubing, tack welded the tube in place, then sprayed it black.
All of the fittings for the oil and coolant should be coated to prevent leaks. I use Permatex Super “300” Form-A-Gasket Sealant. Reattach the fittings and lines and it is ready to bolt on. Not as hard as one might think.
|Mike Holler, known on Allpar forums as mpgmike, also contributes to mpgResearch.com. He has contributed many columns to Allpar:|
|Interiors||Budget interior restoration: making the inside of your car look like new again
Red carpet treatment: Installing new carpet in an old car
|Porting||Porting heads for performance: step by step
Head porting example, part 1 | part 2
Intake manifold porting
Exhaust manifold porting (turbo)
Poly Quad heads: porting revisited
|Turbochargers||Turbochargers - all you need to know (interview)
Turbocharging the slant six for power and economy • Revisiting the turbocharged slant six
Budget turbocharger rebuilding (and Turbo Rebirth)
Installing a boost gauge
|Other||Powder-coating for a brilliant, durable finish
Custom pistons: roll your own!
Prepping valves for performance: grinding and polishing
Old cars: an opinion
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