New Garrett for my Slant 6!!

[85lebaront2]

Opps, missed one. "clocking" of either end (turbine or compressor) of a turbo involves undoing the clamp bolts and rotating (clocking as in clock rotation) the housing untill it is oriented where you need it. Just be sure the oil lines are correct, inlet on top, drain on bottom. For oil supply, run a line from the oil pump where the pressure switch/sender is (tee in the sender) over the valve cover to the turbo oil inlet. The drain needs to be as straight and direct as possible, probably to the side of your oil pan.

[TRRBOJEEP]

Take it from someone whos been there and done that, get yourself some good quality gages, and get them hooked up to monitor things like EGT & A/F ratio. If you don't, you definately won't get to enjoy the fruits of your labor.
A turbo can ruin a motor (even a freshly rebuilt one) as quickly as NOS, if the fuel isn't right! Your 225ci six on 10psi of boost will effectively be like 330ci. I think you'll find that the 390cfm Holly isn't large enough. It's always safer to start out too rich and lean down, than to go the other way.
Good luck and let us know how you're making out.

[finnman1]

thanks bill,...no, i decided against blow-thru, i dont know why someone posted that
ive already bought the A/F and Boost gauge.
EGT = exh. gas temp. Right?? how would i know what's to hot for my particular engine? and how's this hooked up? tapped into the exhaust like an o2 sensor? is it really needed since ive got the A/F gauge?

[moparzrule]

I was gonna use the 500 CFM edelbrock, I think you should too. Edelbrock carb use rods and jet system and is very easy to tune if you buy a calibration kit.

[85lebaront2]

I personally prefer Holley carbs, you can plumb the power valve vaccuum source to the manifold side of the turbo to keep it rich under boost. That's a trick Oldsmobile used on the Jetfires to keep from leaning out the mixture. They also used alcohol/water injection to keep from detonation with 10.25:1 compression.

[moparzrule]

Vacuum secondaries blow (unless you go double pumper), nothing like the throttle response of mechanical.

[doc440]

A slant 6 should be able to handle 5-7 psi. no problem. If it is a '74 engine it should have the steel crank, I think they started with cast cranks sometime around 1976 or so. All slant 6 engines have 4 main bearings, 4 very large main bearings, I wouldn't be concerned about the bottom end at all. Get a 4bbl intake and 500 cfm holley. Have the carburetor linearized- a trick they use in airplane carbs- so it adapts to any pressure/altitude and meters the correct amount of fuel no matter what.

[moparzrule]

Doc440 perhaps you should have read the entire thread before responding, he's going with a suck-through style now and has no need for a 4bbl intake manifold.

[doc440]

My mistake, thought he said he decided against suck-thru.

[finnman1]

ha ha.. here comes the carb war. so, both brands have their ups and downs, but which one should i buy as it comes to ease of tuning and simplicity? how big of a plus is having the power valve vacuum source? it's pretty much a necessity isn't it? sounds like this would outweigh ease of tuning.

[finnman1]

And.... the question of the day:
I have the TI garrett and the Gran Nat. garrett. People say that i should be able to run 7-9 lbs. of boost as a figure. now the gran nat garrett (or a holset for example) will put out more air at a given RPM (granted the engine can push it) than the TI garrett. Sooo, if a boost gauge simply works by measuring the pressure from the boost/vacuum source, and the gauge says 8 lbs. w/ either turbo, wouldn't the holset actually be pumping less air and working not as hard at any given RPM than the TI garrett? SO, why would i want to run the holset if i could just run the garrett a little harder to achieve the 8 lbs. of boost? i'm sure there's a simple explanation for this and ive been wondering this for a while. I mean, 8lbs. of boost from either turbo is the same amount of air right? (the holset is just not being pushed as hard)--since the gauge measures from the amount of air going into it. so why not get a less laggy turbo and just run that a little harder if im only going for 7-9 lbs. of boost?
thanks guys

if you cant tell, i'm trying to avoid rebuilding the gran nat garrett since i have the TI garrett anyways

[TRRBOJEEP]

EGT = exhaust gas temp. Air Fuel gages can be a little vague at times and not a good tuning tool to solely rely on. An EGT gage will give an exact reading of how lean or rich the motor is running by monitoring the exhaust temps. At full boost (whatever that ends up being 7-9psi) you should shoot for around 1,200 F. That should equate to a safe rich mixture. The 500cfm sounds about right. I would personally use the GN turbo, not the smaller one. The problem with too small a turbo on a given application, is that over boost is likely. With 225ci of air moving through it, the waste gate may not be able to bleed off the volume of air needed to keep boost at a safe 8psi. As your rpms increase, the volume of air passing through the turbo will increase to the point that the waste gate is fully open. Once that happens, the added air from that point on will spin the turbo faster and faster, which means boost will shoot up accordingly. It also makes for a healthy exhaust restriction, and heat builds up. (cherry red turbo) The larger GN turbo won't have these issues. You can always try the T1 and she how she runs with it. If you have a problem then swap to the GN turbo.

Without getting to technical, a quick and easy way to size a turbo for flow on a given engine is this: cubic inches x rpm = flow amount
For example, when looking for a turbo for my Jeep
Jeep motor 2.5L or 151ci x 5300rpm redline = 800,300
Ford XR4Ti 2.3L or 140ci x 6000rpm redline = 840,000
Even though my motor is a little bigger it turns less rpms, so flow is about the same through the turbo as the Ford 2.3L motor.
You will want to use a turbo from a motor that flows somewhat close to the output of your slant 6. Crunch the numbers and see which one is best.

[finnman1]

so you are telling me that the only reason people upgrade to larger turbos are to avoid heat and to avoid overboosting? huh? anyone else care to elaborate?

[TRRBOJEEP]

Quote:

Originally Posted by finnman1 so you are telling me that the only reason people upgrade to larger turbos are to avoid heat and to avoid overboosting? huh? anyone else care to elaborate?

No, I don't believe I ever mentioned in my post, reasons for going to a bigger turbo? Just how to size them for a given application, and what you will experience if you put too small a turbo on a motor.

[85lebaront2]

Quote:

Originally Posted by moparzrule Vacuum secondaries blow (unless you go double pumper), nothing like the throttle response of mechanical.

If you don't know how to calibrate them, you are correct. I have used both types for years and each have their advantages. I used 2 465cfm Holleys on my 66 GT350. This was a .030" over 289, or 292 CI. I had the Ford trans-am manifold and had linked the vacuum diaphrams, it would go 2 - 4 - 8bbls at around 3500-4000rpm. I could even open them in the shop with just a good hard throttle rap. I personally like Weber carbs for tunability, but the 4 48IDAs were a little pricey, and required a cutout in the hood.