La400

This is an update on 98 GS400 heads, street port.

factory
169.4 @ 150.0 lift
212.0 @ 200.0
249.5 @ 250.0
195.9 @ 300.0
196.8 @ 350.0

Port results
177.2
226.5
259.8
271.9
281.0

These heads will be applied to a factory set up, 100K auto, before and after numbers will be shared. Only addition to engine is cold air intake.

Updates after dyno before and after installed heads.

Happy Holidays to everyone.

SCV8

Cool, I just got on here to see if you'd done anything with that project, sounds like you've achieved.
Do you have any pictures of the work?
Did you remove the guide/boss from the port area, or was it primarily a cleanup effort?
Can't wait to see the dyno #s...

JBrady

Interesting to see someone doing some testing. Porting is a very complex art/science that can be a hit or miss proposition. Higher flow on a flowbench MAY mean more power but that is not a certainty.

Your "before" flow numbers look scewed. I do not see how it is possible that the head looses flow with more valve lift above .250". If anything the flow would just level off indicating that the valves are no longer the restriction. No big deal it would just be better to have solid before data.

Definitely keep us posted and get some pics if possible.

Hollywood

Ya cant wait to see the numbers too.

Too bad cams are not available for the v8 lexus. But im sure cause the VVT-I its tricky.

La400

Yes,
It is a gamble. The whole concept in this was to be able to take your heads, clean them up, put on and see results, target is 40 - 50 HP. I could lose power or I can gain. This was just a slight clean up to enhance what factory was not able to do in mass production. Always been effective in the past, maybe it will work on these engines. Continue to research, any advice is most appriciated.
Don't want affected:
Idle
Emissions
MPGs
- BUT-
In due consideration, applied since the introduction of the VVT systems in 1991, wild cams or even changing cams seem to be no longer needed to get 75-100kW per litre. The 98 GS400 is a hair over 75kW per litre.
Based upon the cams specs of the 1UZ-FE engines, combined with VVT of the GS400 program and its ability to alter cam timing as much as 60 degrees, heads were slightly street ported to enhance the current operating system of the GS400. Intake and exhaust cams can be retarded by 8 degrees for an improvement, the best improvement seems to be in keeping the stock intake cam and putting in a revised opeing of 18 degrees BBDC and closing of 18 degrees, ATDC exhaust cam, no where to be found by the way. There is additional gains by fitting in new cams all around, kills bottom end up to 4,500 rpms, but sure opens up top.
Factory cams from what I have read, have not taken cams and had checked yet, but will be done.
Intake opens BTDC 6 degrees
Intake closes ABDC 46 degrees
Exhaust opens BBDC 46 degrees
Exhaust closes BTDC 3 degrees
Overlap 9
Intake duration 232
Exhaust duration 229
Centerline 110 @ ATDC
Exhaust centerline 111.50 @ BTDC

In review of the improved flow properties of the ported heads. Very little improved over factory flow up to 250 lift, whereas large improvements in the 300-350 range. Combined this information with cam info. Looks to be a good match based upon power bands of current configurations of stock. I am hoping that the computer will learn to work with the new flow over time. So much is in the programing now days, if need be I may need computer upgrade.

Old saying, It is not how much you got, but how you use what you have.

Have a short block to work with on the side, any suggestions, they a excellent as they are, hard to find any improvements.

Hope this info is helpful to others,
Best for the new year.

DaveGS4

iTrader: (2)

Very good stuff, excellent progress! Thanks for sharing with the rest of us!

Vette Boy

It's not clear to me, are you targeting 40-50HP from cleaning up the heads?

IMHO, until there are long tube headers for this car, I think it will be very difficult to make useful 40-50HP with ported heads and a hotter cam. (useful to me means not just a peak but more HP over wide RPM range that will work on the street)

I'd be surprised if cleaning up the heads added 20HP (esp with the stock manifolds in place). I expect the big bottleneck on LS4/GS4 is like every other modern car, the exhaust manifolds.

La400

Hi Dave,
I would lean more towards your way of thinking, all I am going on is by the bits if information from many different directions. I am certain that the heads will not be fully utilized until intake system, fuel, exhaust manifolds, exhaust, computer management is looked into to. I wanted to get information out there that I had not be able to find, more along the lines of street driving daily, good mps and emissions. It is all about getting it in and out, then effectively to the ground. I have a long way to go.
Interesting head flow for old Ponts I came across.

73-74 455 SD #16 casting
CFMs
Intake Exhaust
.100 52-63 35-40
.200 114-121 79-80
.300 154-160 106-107
.400 172-176 117-122
.500 184-189 122-129

Compare to ported flow
150 177.2
200 226.5
250 259.8
300 271.9
350 281.0

If formulas are correct on flow numbers, these heads can handle upwards to 1,400 hp, who know I have lots of questions to be answered. Looks to me like modern technology has really improved. Just learning.

I am most interested in how the Lexus computer is going to handle the flow improvements. A friend at SuperChips tells me that the Lexus computer for the GS400 is hard to map, whereas GM, Ford, etc is easy compared.

Always open to comments,
Best,
Tim

Hollywood

Headers are definately an upgrade before the head, after intake and exhaust its just the next step in general, then add highflow cats in the mix with the header uprade.

An AFCv2 would be a fine solution to handle the extra fuel. I'm not sure how lexus timing maps are, and if they need to be retarted are not, if they did afc is out. Does the engine have a knock sensor? If so, ith the afcv2 you can use the knock readout to see if your running into timing woes. (sorry new to lexus).

La400

Hi Hollywood,
Headers are out, none to be found that I know of, all wish. Whereas investigation of the intake and exhaust manifolds, GS400 design would be hard to beat, only if were going full out with everything. I went to a number of racers utilizing 1UZFE engines and that is what I was told, for my application. This is why I chose, heads, cats back exhaust, LSD, TQ, Computer mapped for these features. Matching ports intake and exhaust will help a little, but would it be noticed. I am just doing this for play, besides everybody could used a new set of heads at one point in time. Hopefully worst case, new set of heads and no loss, best case p/u hp/tq and mpgs, ha, if only. We have exhaust pipe emissions here, have to be real careful about changes.

Ask yourself, why 290 HP LS400 and 300HP GS400, both the same except what?
Best,
Tim

Hollywood

Like I said I am new to lexus. But I can guess the difference is in either the exhaust, intake manifold, throttle body or heads.

I think your investigation into the heads is a great idea dont get me wrong. And I am very excited to see the dyno numbers. But if you cant expel the exhaust fast enough through the stock exhaust manifolds, you might have to change the cam overlap to avoid possible reversion.

Im sure there are places out there that can make custom headers. It's too bad the person here on the forum does not get the ball rolling faster on the headers he is designing.

La400

Hi Hollywood,
I went through everything starting with air filter as to what could be done. The intake systems are acoustic control induction balanced and are quite effective, exhaust manifolds are almost like headers, have to see them to understand. I looked at injectors, exhaust systems seem to be worked out. Not a whole lot out there on these models, specification wise to work from. Hard to find much. Spent way too much time on this car. Might want to look at the soarer web site in AU. They are really doing some work and lots of information. Those are SCs in AU, not the GSs. Chances are I will be moving the cams back by 8 degrees for street use. I am counting on that 1 billion plus dollars they spent on the GS400 design and work with it a little. Only looking for 375 HP with 3:72 LSD to the pavement. Other than that, you have to go SC full blown.
Tim

SCV8

Yeah, headers are a nice thought, but unless you go with something really exotic, you're not going to gain much over the stock stuff.
I have been using a Unichip piggyback ecu in my old SC that was calibrated on another car with simple mods, from what the tuner told me, the injector duration was maxxed out.
I've done a few things since to try and improve airflow, and have increased the fuel pressure along the way to compensate.
The significant adjustments were done after ;1)sharpening the dividing vane between the individual valves inside the intake port; 2)putting a similar delta-shaped profile on the MAF dividing vane(doesn't apply to late model cars); and 3)swapping the air cleaner for one that has about 90 sq. inches of filter area.
The car passes smog with ease, and scoots pretty good now, gets great mileage as long as I don't get that right leg spasm that happens. Didn't think the car would ever get this good coming from stock.
Can you describe what you did inside the ports?

La400

some pictures if of interest
seems I can only do one at a time

La400

here another