2000 GT - Need guidance in mild 2V build

Trick Flow Twisted Wedge 185's are a must for that goal.

If you change out your heads to the trick flows go with the 38cc's not the 44cc's. The 44'cs decrease the compression giving less horsepower. I have the 44cc's and didnt know this when I ordered them. However having the larger cc heads give more horsepower when boosted due to increased airflow. So if you plan on supercharging it then get the 44cc heads. I currently have 300 hp to the rear wheels on a full bolt on. This includes stage 3 cams and trick flow twisted heads 44cc's. I would suggest stage 2 cams. I have stage 3 cams and due to backwash it idles rough. Backwash is where the duration of the cam stays open so long that the incoming air moves back up to the intake. Makes it tough to tune and get a good solid idle. It can be done but at a huge expense not worth the hassle nor the few hp's you might gain going to a bigger cam.

Onesick99GT said:

If you change out your heads to the trick flows go with the 38cc's not the 44cc's. The 44'cs decrease the compression giving less horsepower. I have the 44cc's and didnt know this when I ordered them. However having the larger cc heads give more horsepower when boosted due to increased airflow. So if you plan on supercharging it then get the 44cc heads. I currently have 300 hp to the rear wheels on a full bolt on. This includes stage 3 cams and trick flow twisted heads 44cc's. I would suggest stage 2 cams. I have stage 3 cams and due to backwash it idles rough. Backwash is where the duration of the cam stays open so long that the incoming air moves back up to the intake. Makes it tough to tune and get a good solid idle. It can be done but at a huge expense not worth the hassle nor the few hp's you might gain going to a bigger cam.

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You should be seeing a bit higher on the horsepower number. It's not so much reversal of the air that's causing that as it is improper lengths of the headers (I'm assuming you have headers), as well as the lower compression you mention. The stage 3's are surprisingly good with preventing reversal of the air charge. Usually this only happens if the duration is high AND you have manifolds where two exhaust valves are open simultaneously causing enough pressure in the cylinder from the exhaust side.

@AutodesignJohn Two different professional tune shops told me the same thing. One of them actually builds racecars from nothing and races them across the world on professional tracks. The other tune shop is known for building motors to race on the track and has a well reputable name. Only repeating what they both told me. Experience and having been there and done that is better than making guesses. I have longtubes btw. Professionally installed. Not sure where your getting your horsepower numbers from. The hp numbers displayed on manufacturer's websites of increases in hp are rough estimates and don't work on everyone's setups.

Onesick99GT said:

@AutodesignJohn Two different professional tune shops told me the same thing. One of them actually builds racecars from nothing and races them across the world on professional tracks. The other tune shop is known for building motors to race on the track and has a well reputable name. Only repeating what they both told me. Experience and having been there and done that is better than making guesses. I have longtubes btw. Professionally installed. Not sure where your getting your horsepower numbers from. The hp numbers displayed on manufacturer's websites of increases in hp are rough estimates and don't work on everyone's setups.

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When I say a guess, I mean an educated guess. I get my numbers from both wave tuning analysis as well as filling and emptying analysis based on valve size, shrouding effect, pressure equalization, etc. I'm not saying that shops aren't reputable or whatnot, but I don't treat air flow like black magic as some people do. If you are to analyze what happens in a cylinder head it is important to know the pressures in the exhaust port, intake port, and chamber as well as the velocity, temperature, momentum, and a few more quantities to really find what's happening. Simply put, air flow in a system with constant opening and closing is difficult to analyze through a forum, so my "guess" is just based on my analysis of the actual products' capabilities under conditions I can analyze myself. If you're getting true reversal through the intake it means that you have higher pressure in the exhaust port than you do momentum of the air during filling while the piston descends. That would indicate either exhausting from a nearby port, or if you have long tube headers you have some kind of issue with design if them. My work in general is in cylinder head, intake, and exhaust design. Most shops work in the area of assembly, they're different. Not worse, just different. I find most shops just assume it's something simple when in fact almost identical symptoms can be completely different problems. A perfect example would be something along the lines of running an engine with no thermostat. I can't tell you how many times I've read people saying that the car will overheat because the rate of heat transfer is too slow, when in reality it is cavitation of the water pump due to a lack of pressure difference upstream and downstream. While it is true a clogged radiator can cause low heat transfer rates per unit area (q" - heat flux) it isn't what causes an engine to overheat with no thermostat. Trust what shops tell you but don't take it as gospel without damn good explanations. It's not magic, there's reasons for things.

I can post graphs of analysis if you'd like as well based on different compression, it's interesting to see how port pressure and velocity affect air flow

alwayshi said:

Hello everyone,
I recently picked up a 2000 GT 5 speed and looking to do a mild build. Shooting for a reliable 320-350 rwhp (I think 100 more than stock should definitely be a fun weekend/street car).

I’ll attach what the cars specs are currently. I’m definitely wanting to add cams to the 2V because honestly, these 2V’s sound amazing! I still need to check which injectors I really have, and plan to ditch the crappy hyper tech for something more substantial. From what I’ve read, the basic bolt ons are there. I just don’t know what else is needed to reach the goal (maybe supercharger?)

I’ve lurked and read that 400rwhp is the max for our stock internal block, yet seen posts of members going well beyond that mark with forced induction. So how true is that 400 on a stock block?

Any guidance and tips are appreciated!

Here are the specs and of course, the pic of the car.

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You can probably get away with about 450 HP on stock rods, they're powdered metal with does well under stress due to the brittle nature of it but doesn't handle fatigue as well. Most life expectancies of parts include a peak power recommendation averaged with a fatigue life of about 10 years normal operation. So for example, you might be able to put the rods up to 500 HP, but they won't last as long, and as you add more and more power the life gets exponentially shorter. It's the same with transmissions, if it's rated at 300 Ft-lbF, that means it will hold up to that rating for a 10 year life before going out of service specs. The stock bottom end of the modular 4.6 is limited by the rods, so if you want to do one build and be done for a long time you'd be wise to keep it under 450 HP, but if you don't mind less service life you can go to 500 HP but expect way shorter life and you'll end up with a thrown rod most likely. To prevent this you'd have to grind down all stress risers on the rods and you'd have to xray test the rods for internal cracks aa well as consistency of the material. All this expense would just warrant forged internals at that point.

@AutodesignJohn Where do you John? You very knowledgeable and know your stuff. I assume you life has been spent working on cars and building them as well. I'm sure the shops knew most of what your saying but didn't make any recommendations and I didn't ask. I just told them to tune it the best they could so that's what they did for the price I paid. However if I had someone like you explaining this info before hand I would have made modifications to increase the hp or in other words fix the areas that's suffocating my horsepower.

@alwayshi John makes some good points. So hopefully from my experiences and his expertise you wont make the same mistake's as I did even though I didn't install the headers or exhaust. My DS exhaust had to be bent to make it work. I remember looking at it when I had it up on the lift. Sounds like new headers might be in the works since there is a crease that is reducing exhaust flow and causing backwash up into my intake. That would probably be my root cause.

Onesick99GT said:

@AutodesignJohn Where do you John? You very knowledgeable and know your stuff. I assume you life has been spent working on cars and building them as well. I'm sure the shops knew most of what your saying but didn't make any recommendations and I didn't ask. I just told them to tune it the best they could so that's what they did for the price I paid. However if I had someone like you explaining this info before hand I would have made modifications to increase the hp or in other words fix the areas that's suffocating my horsepower.

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I'm a private mechanical engineer. I mostly do custom design of parts and compatibility (tech consulting stuff for cars). Most of the time for the sake of brevity tuning shops make assumptions and test them by running a dyno test. It's not 100% accurate but it gets you 95% of the way there quickly. It's like this, if they spend 2 hours tuning the car you pay for 2 hours of labor and get 95%, but it would require them close to 2 hours to get to 96% and so on, which is why OEM manufacturers tend to do thousands of hours of testing to get 100% of what they want (not always pure power sometimes comfort etc.), so it would cost you thousands more to get your car to 100% without realy intricate modeling of the way your engine works.