A little intro on the project

'06 Vortec 4200 inline 6 DOHC 4 valve/cylinder - sleeved, forged bottom end. The end use is a stout street/track motor - planning on 20# boost. 6500 RPM redline. Have a GT40 turbo for the project.

Since there are NO aftermarket cams available for this engine we're starting from raw round bar and CNC cutting cam cores we can basically do pretty much anything. The limiting factor is 0.510 lift. With DOHC the centerline is set while degreeing in the cams. The engine also has a cam phaser on the exhaust camshaft so this is another tuning point.

The questions are:

- how much duration is needed while not killing drivability - one end goal is to be able to cruise at 2500 rpm and not be rude in traffic.
- should the intake and exhaust cam duration be identical ?
- symetrical lobe or assymetrical ?
- anytihing to watch out for with the cam profile?

Been working on NA motors for quite a while - new to the turbo build so looking to the experience here for advice.

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions??

Neat project, got a pic of what's it going in?

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions??

I will pile another Albertan into the mix here...

This is obviously a pretty basic point, but do you have someone with cam grinding experience at your disposal? Just having the ability to CNC something on a mill or lathe isn't going to cut it for a camshaft. To my knowledge (which is VERY limited) cams are still ground. For roller and sliding tappets/buckets/rockers the issues are the same. In the end if you cut them from billet you still have to have someone finish the lobes properly.

This assumes you can get a decent cam lobe profile from somebody in the first place.

If it were me, and I was only looking to turn 6500rpm, and I had the ability to play with the exhaust cam timing, I would run the factory stuff. Having the ability to tune cam timing gives more flexibilty than the average guy realizes.

-Rob

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions??

Once the cam cores are ready we'll get them copper plated then its off to the cam grinders to be finished into camshafts. We have a couple of cam grinders that will do the job (Isky, Comp) , still looking for one more before we settle on it.

The finished engine is going into so older iron.... post war - pre-55. Should come in around 3300# ...

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

I'm biulding a Lexus 1UZ Twin Cam V8 with these turbo cam specs...
264 264 @ .006 224 224@ .050 .. 9.57mm 9.57mm 108 C/L 114 LSA

As with most turbo engines the LSA is around 114

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

What transmission are you planning to use with it ?

Is your rotating assembly aftermarket or stock ?

I've been interested in one of these motors but there seems to be just about zero aftermarket for them.

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

Depending upon the power you are trying to make, why not first explore the tuning limits of the factory cams before getting a custom grind? They may be good for +/- 400hp? Then, again, the engine has a lot more potential than this with with a forged rotating assembly.

Where did you source the forged crank and rods? I considered fooling around with a turbo on my '02 Envoy's 4.2 until I found out about the composition of the engine's internals.

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

The weak spot is the piston, rods and block sleeves for serious power.

The crank is stock <<< with 7 main bearing and only 1 rod between the mains the crank is good for >> 600+ HP - some drag race guys runing comp eliminator spin them > 9500 rpm - mind you with a light piston/rod.

Rods - Crower - custom order

Pistons J&E - custom order

Sleeves - Darton.

I did consider running the stock cams - there are just really tiny and I want to get to 600HP. One other consideration is that I'm piggybacking my cam order on a set of stout race cams going into a B'Ville racer.. so we may get a better price than a single shot.

The intake and exhaust manifold will be purpose built.

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

I too have been thinking about this, but i havent looked into the internals as of yet because its still a new idea. what is the problem with this engine? how much HP can the 4.2 I6 take in stock for with a properly sized turbo?

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

Here is an article about Chevy's turbo TB prototype: http://www.tyguy.net/gmc_2004tb_tt.htm

They deemed it prudent to replace the 10:1 pistons and the powdered steel rods with forged units in preparation to handle an estimated 400 lbs of torque.

 

Re: Vortec 4200 inline 6 - DOHC - custom turbo billet camshaft questions?? Help!

What needed to keep this alive over 7psi...

My build will include:

Darton sleeves with an o-ring groove
J&E pistons and rings << thermal barrier on the piston tops ... 8.25:1CR
Crower rods

2006 head with custom billet cams ( sure wish someone would cough up some spec's).
72# injectors

The head will be getting inconel exhaust valves and better valve springs.

The exhaust manifold is getting done by Leen at steedspeed.com << very cool shit!

The intake is getting done here.

When the the block is apart I'm going to look at adding piston oil squirters.

 

Re: Vortec 4200 inline 6 - DOHC - turbo camshaft questions - specs anyone?

[size=14pt]
What the hell? [/size]

You are asking something that is impossible to answer without any cylinder head flow data!

 

Re: Vortec 4200 inline 6 - DOHC - turbo camshaft questions - specs anyone?

I just got this flow info on the head... its hard to come by...

intake 320 cfm @ 28"
exhaust 230 cfm @ 28"

 

Re: Vortec 4200 inline 6 - DOHC - turbo manifold - ready...

Winter project ....




Waiting for cnc time....