I'd like to thanky 1niceride and Mean Gene, for addressing my questions.
I apologize for my vagueness, but found it to be the best approach.

I am familiar with head re-working, what I don't know is.... How high performance was this engine built?

i.e., typical American heads have "2 cut valves", bad for engines... .... good for saving money.

Are the valves on these (4.0l) engine 2 or 3 cut, how good are the guides? Can heavier springs be used?
Are the heads themselves tuned and ported? How large can the ports be brought up?


Which leads to the intake man. and exhuast sytems.

If the heads are re-worked, is the factory manifold the most efficient application?

The obvious point is to increase the breathing efficiecy of this engine, and increase the low end torque.

Kinda long winded but this is what I'm looking into.

Thanx

 

Mighty - If U're referring to a 3-angle valve job or any of the valvetrain questions, I'd suggest ya try Muhammad or Marken at Swift Racing Technologies - www.swiftracing.com. Mo told me that he's had the 4.0 heads off their 700 hp motor so he'd be familiar with them & could better answer your questions concerning those. Now for the rest of things, I've been told by SRT & RMM that the factory exhaust system is actually very efficient & that unless U plan on wringing some serious power from the engine ( probably in excess of 500 flywheel hp ), then the factory exhaust manifold/header system is fine but be sure & use a pair of more free-flowing mufflers like Borlas or GReddy. The factory intake is another question mark. I'd venture to say that either the Swift or APEXi intake/ECU setup combined with the stock Lexus plenum ( which I'd use the aforementioned Extrude-honed procedure on ) would handle the induction duties well enough. Just keep in mind ( & I'm sure U already know ) that by opening up the runners/ports, U MAY increase top end power at the expense of bottom end torque - at least that's been my experience on Tuned Port 'Vettes. Let us know what U come up with!!

 

Gene thanx 4 the input. You are right. I'm familiar with these things, however the web page does help and the Intake man. information is what I'm looking for. As far as top end goes, no real interest here. I'm looking to improve, hopefully dramatically) low end torque. There is nothing funner than dusting the boy racers and what's left of the American muscle.

By surfing this board. I'm intrigued by the number of messages I have seen regarding aftermarket performance enhancements. Maybe this is why I've had such a difficult time obtaining core engine info.

Since I have not read any abundance of these kinds mods. to GS cars, I wonder if I'm pioneering? The main reason for the search is $$$$$. Will I be able to get sufficient gain from these simple procedures to warrant the cost? Most head jobs aren't that expensive anyway.

As you can probably can tell, I'm from the old school of performance gains. It's a lot more hands on, but the gains are indisputable.

 

Mighty - I'm right there with ya on being old school ( come join the website RON430 & I R gonna start - oldfarts.com!! ). I, too, have a drag racing background & normally do the standard mods of opening up the intake & exhaust then working on the heads or cam. However, as U've noticed, there doesn't seem to be an overabundance of parts available for the GS. Maybe it's the cost of the car or the fact that Lexus only produces somewhere in the range of 5000 GS4's per year - don't know. It's kinda like Bobcat & I discussed a few weeks back - the GS series is a wonderful 4 door sports sedan but that's EXACTLY what it is. If wanted a pure drag car, I would have purchased an older F-body Camaro for which there are thousands of proven mods & aren't cost-prohibitive. U R correct in that you're pioneering going into the 4.0's internals in the search for more power. Like I said earlier, I THINK only Mo & Mike have disassembled their motors. The main thing that's keeping ME from doing a teardown ( other than all my money's tied up in the stereo!! ) is that darn computer. Just afraid I might do something with the VVTi system that's both expensive & irreversible. My GS is my wife's daily driver so my hands are more tied by that than lack of funds - if she gets left stranded by something I've done, I'm a DEAD man!!:eek: Maybe if I get her an SC430 like she wants I'll get stupid with the V-8 - by then, I'm sure U'll have some additional info on how the car responded to your mods. Just my .02 but I don't feel ( at least at this point ) that we know enough about getting the factory electronics to work with severe mods to make internal changes worth the effort but maybe U'll prove me wrong!! Good luck in whichever route ya go & keep us in the loop.

 

I guess the other old fart is here. Been a long while since I have done serious engine mods. Last engine rebuild in an unheated garage in Chicago in winter taught me all about onset arthritis. Cal is definitely better. Read your thread. Anyone ever flowed the stock heads? Hard to believe they would be the problem for some initial mods. Gene - seems like the old street wisdom (may be too far out of date now) would indicate that if you want bottom end to look at stroking and adding as many cubes as possible. Crank you could probably modify from stock but rods and pistons would be custom and likely cost a ton. Don't know how much room there is in the block anyway. Am I off here. Back to that F body for serious low buck mods.

Way back when I remember a guy asking Bill Jenkins about improving flow in angle plug 202 small block heads. Grump went on for what seemed like twenty or thirty minutes. Then at the end he said that if you did everything exactly as he had said, the heads might flow better than just taking them out of the box and bolting them on. As Gene says, the GS is really a Gentleman's Sport sedan and not a stoplight warrior but I just believe the stock heads would flow decently well right now. At least at the higher revs. Of course, having an automatic doesn't improve the situation to get up where improved flow could be enjoyed either but still seems like the olden rules would opt for a stroker (or SC?) and gears. But the bills would have to be impressive.

 

Man what the heck happened to the other thread about the heads and internals!?! I posted the rod ratios and everything!

Was this information too much for someone to handle?!?!