I have a turbo project started with a 4.2L Vortec (GM L6 Atlas motor) so I figured that I would start a build thread. This is my first turbo build so I can't claim to doing everything right but '¦. here it goes.

This is a bone stock internal build, a junkyard motor with 60k miles. The plan as of now is that the motor will be going into a bantam altered (125' WB tube chassis) so it will be in a dedicated drag car.

These motors were rated at 291HP and 277 ft# of torque from the factory (254CI), My goal is 550HP (http://en.wikipedia.org/wiki/GM_Atlas_engine)

 

Where I am now:

I have started on the intake and plenum

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The manifold is somewhat modular so that if I wanted to change the plenum I could. The runners are tapered and a radius was applied at the entry.

I have decided to move forward on making the plenum similar to this (although I increased the volume a bit)
This is one thing that I went back and forth on- what the plenum volume should be. It ended up about 125% the volume of the engine CID

 

Turbo:

BW airwerks s300 is the selection

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Should be interesting. I know the heads on those motors flow really well. 550 HP shouldn't be hard at all.

 

I hope so, I think it should be able to survive pretty well at these HP levels.

I am working on tackling the exhaust header, I have looked around the forum but have not seen too many L6 motors, if anybody has any links to good L6 builds send my way.

I am thinking about 1 5/8 primaries and merging pairs 1-6, 2-5, 3-4 and just using a single 3-1 collector right into the turbine flange.

 

Sounds like a cool build. You should be able to make your goal with less than 15psi of boost. If The engine makes almost 300hp

 

DIgging the intake porn. With the VCT it's plausible you're quite a bit up on HP even with little to no other work. The intake and any exhaust mods should push that up a bit higher still. I don't see 600hp being an issue at all if you have the compressor to support it.

 

This is awesome. I love altereds, and I love inline 6 motors.

That would certainly be unique, but I'd recommend the more typical joining of cylinders 1-2-3 and 4-5-6 and using a twin scroll turbine. You could do either a log type or a true header type, the only difference would be that the header would have slightly better off-boost performance, and would spool the charger a little sooner as well.

 

I can't wait to see some more progress on this. Are you going to be doing any work to the head/cams?

 

Cool build. I thought this engine would suit a ffr/ac cobra well like the original high ace models. Was wondering are you lowering the compression? Using alky injection? Standalone control unit? It's my understanding the factory unit is a bear to deal with away from the original vehicle..

 

I agree, i have reason to believe that there is a setup out there that is pushing 600+ HP based on 1/4 mile times i see and he was at 17# of boost. I think the s300 should be a good turbo for the HP level although there could be some compressor and TH swaps, had to take my best guess. I have learned that nobody will give a solid opinion on the specifics of things like trim and A/R for specific application until AFTER you already have selected and procured a turbo... then everybody has an opinion

 

eventually i would like to, getting cams ground is a a challenge and the price gets high but it certainly opens things up. for now it will be stock. I have a few of these engines so maybe when i build one complete with stout bottom end then i will work the head. Actually in a way i did work the head without taking it off, more on this later

This is a good point , the compression ratio is 10.3:1 stock but as for now i am not. The only reason I am not at this point is because i know what it can do in this bone stock trim and it will be fine, however when i build a non junkyard version it will be lowered for sure. I was always impressed that at this compression regular gasoline was what was recommended by GM, then again maybe I am ignorant to what other motors have for compression and run on pump gas ...

I am running this engine in another drag car in NA trim and i run the MS3X, to my knowlege I am the only one who has taken over the factory crank triggers on this specific engine with an aftermarket ECU. But with a stock ecu recently guys have been doing some amazing things.

Oh and the plan is to run straight methanol... which brings up a good point.... to use an intercooler or not?? remember this is a dedicated drag car. I have an opinion but want to hear others.

 

Nice, the ms3 looks impressive for the money. With meth, you should be good. I know some i5 had liner issues, is this an issue for the 6 too? What kind of head clamp do they have 4 or 5 bolt? Gasket options? Sorry for all the questions, I really like the engine and love to see someone doing something with it. Inliner international had some threads a few years ago, was not a lot of support for it then.

 

the MS3 has been a good unit for me, many options and features. You may also check out the ms3 pro. The questions about the engine are good ones. In fact i have been involved with spreading the word about them for a while, i will send you some info in a PM. I attached a pic of the head gasket, people are using stock gaskets for some pretty hi HP. The 4200 production went away with the trailblazer/envoy and the others are on their way out as i understand, but to summarize there were 5 atlas motors.

LL8 - Vortec 4200 I6
L52 - Vortec 3500 I5
LLR - Vortec 3700 I5
LK5 - Vortec 2800 I4
LLV - Vortec 2900 I4

As far as liners I personally have not heard of many problems but also the 2006 and later version of the motor are a bit different from the earlier ones, 06-09 is what i have. here are the upgrades: (also noteworthy is these engines have what they call a ladder on the maincaps, ie girdle)

VORTEC 4200 4.2L I-6 (LL8)
2006 model year summary
'¢ Increased horsepower and torque outputs
'¢ Higher 10.3:1 compression ratio
'¢ Improved air flow
'¢ Mass air flow sensor
'¢ Improved A.I.R. system
'¢ Improved ignition coils
'¢ Piston rod squirters

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A little progress on the plenum.

Disclaimer: I am not a fabricator or welder. I don't really do things the right way, I just glue pieces together... mainly because i don't know what the right way is.

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I am at the point where I need to start getting the header figured out and fabricated. I think the reason I was thinking of this method I mentioned is packaging, not that it matters as much because there are no fenders to deal with but I seem to always lean toward simple and less tubes etc.

If anybody has any feedback for primary tube diameters, collector diameters etc I would like to hear. Keep in mind I would like to be able to spool as quickly as possible on the starting line. Also how about tube lengths, it doesn't seem to be as big of deal to have equal length and etc with turbo motors..??

here are some pics of how i made the headers on my other car of the same engine, made them out of rusty old headers, think i will go with smaller primaries on the turbo. this car really needs a turbo as well....

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That looks really nice! Post pics of the whole car!

I agree, I see no reason to make the primaries the exact same length. It is more important IMHO to minimize unnecessary turbulence and restriction. If the lengths are close, they are close enough. Although as I alluded to, longer tubes tend to perform better at low rpm.

 

That is a really cool looking engine. You have great details and its super clean. Good job. Can't wait to see the turbo setup.
Do you have any video clips of these beastie 6 cylinder engines running or racing ?
NC

 

Sweet engine

 

So by minimize restriction do you mean avoid tight bends etc? what about turbulence, how do you minimize that?

How do most people size the primary tubes?

I think the engine will operate pretty much at 4000 plus rpm up to say 6300 ish. do you think longer tubes will be a benefit? i was trying to make things as short and compact as possible... although i have decent amount of flexibility.