Head work

[MR2Jedi]

I'm gonna pull the head off my '91 turbo soon. I think I need to replace my valve seals. getting a little smoke in the morning after start up and a little oil on the plugs when i change them. I have HKS 264 cams in/ex that I will install while it's out. I'm pretty much stock but have Greddy Profec II EBC, a rebuilt ct 26 , a TrueLeo Intake manifold, and a new block with all new internals from ATK out of japan. it's got 30k miles on it.so my question is-what other work/mods(if any) to the head would you reccomend?

[JekylandHyde]

Headwork, the cams and the trueleo manifold are not a good idea with the CT26.
They are counter productive. All ofthose mods are for mid- to higher-rpm power/boost and the CT26 is a quick spolling low RPM turbo.

[MR2Jedi]

OK, what would you suggest? different turbo? I'm gonna pull the head for sure anyway.

[JekylandHyde]

The first thing you need to do is figure out your goal for the car.
What do you want it to be able to do?
How do you want to drive it? Where do you want your power to be?

There is a think called the volumetric efficiency (VE) of the engine.
The point I was making above is that the CT26 can't keep up with the stock 3SGTE's VE above 5500 rpms. The CT26's exhaust side becomes a restriction and can't flow enough air out of the exhaust side at those high rpms.

Headwork, cams and an intake manifold are all designed to flow even more air in the mid and high ranges which will just compound the issue of the exhaust side of the CT26 being a restriction.

Think of it like a highway exit ramp (exhaust side of the turbo) that always gets backed up.
We all have seen them. Cars go flying down the highway (engine) and want to take the same exit (exhaust side), but some stupid engineeer put a slow red-light (too small of a turbine) at the bottom of the ramp. So, during high flow (big boost/rush hour), traffic backs up into the highway. If traffic gets really bad, the cars could back up all the way into the highway (this is hot dirty exhaust getting backed up into your engine and causing detonation - very bad).

What you are proping to do is with cams and headwork is liken to widening the highway and adding more lanes. The intake manifold is like detouring other highways onto your highway.
.... the result is going to be a massive traffic jam.

I hope that makes sense.

The mods you have already purchased are for making big power.
Is that what you want? If so, you are going to beed a bigger turbo.
At the very least a TD06 or T3T4 to see th benefits of the parts you already have.

[MR2Jedi]

wow, thats a great analogy Jeff. lol even I can understand that. since I already have these parts, i want to use them and i will just accept the power it gives me.-whatever that may be.I think i will go with your turbo reccomendation-prolly T3/T4. and of course I'm sure I'll need fuel upgrade to accomodate the turbo, via larger injectors and fuel pump. and a new IC..looks like i will need more cash......have I missed anything?

[JekylandHyde]

Unfortunately, I suspect putting those parts on now will hurt your bottom end without seeing improvement anywhere else. It's quite possible the whole power band would be weaker.

This is a great resource for doing things in the proper sequence:
http://www.mrcontrols.com/primers/power.htm

The parts you have are for shooting for 300+ rwhp.
For going over 300 rwhp safely, you will need:
* turbo (obviously)
*better intercooler with fans
*at least 550 ccs injectors (they will get you to 350), adjustable FPR, bigger fuel pump (Walbro is a good one).
*something to control the injectors (either SAFC or a full EMS)
* Water injection (optional, but I would strongly suggest it)

Unfortunately, to do it right, it requires a bit of an investment.

I would really figure out exactly what you want,
how much are you willing to invest (time, money, headaches [i.e. tuning, dyno time, etc]).

[MRQtwinturbo]

add some sort of fuel/engine management also...for head work...shimless bucket conversion..arp studs...hks springs...Ti retainers...the list go go on and on..just how much do you really wanna spend....i would simply sell your cams...get a ct-27 or ct-20b if you want well under 300hp....more than that...takes alot of supporting mods...

[MR2Jedi]

OK, you guys got me re-thinking this now. I'll have to think about this. not really sure that i want to go that far. this is a great forum. you guys rock ...Thanks

[JekylandHyde]

Originally Posted by MRQturbo

i would simply sell your cams...get a ct-27 or ct-20b if you want well under 300hp....more than that...takes alot of supporting mods...

... sell the cams and that intake manifold.

That is some serious coin that you could put toward an intercooler and turbo kit.
I assure you, 250-280 rwhp is quite fun.

If I was not racing, I would go back to 250-280 rwhp.
Fun an reliable

[MR2Jedi]

Thats prolly what I'm gonna do. anyone interested? cams are brand new-still in the box in original packing.