Lextasy89

Anyone thought of getting the intake manifold or throttle body ported and polished?

I know for many cars this is a relatively cheap and beneficial mod.. you guys think any power can be made by doing this with the IS350?

A mod like this maybe be only beneficial to people considering some FI like nitrous.. im not really sure though

lobuxracer

iTrader: (2)

Without doing this to the heads, it's a complete waste of time. The biggest gains are in the last 1/2 inch of the intake ports. Everything up to that is pretty much dependent on that part being done first.

Lextasy89

so we could see good gains if we had the heads ported and polished as well?

lobuxracer

iTrader: (2)

It's the most likely place to fix the power limits we're seeing. Intakes don't get much of anything, throttlebodies for drive by wire are typically already bigger than what you'd have seen in years past because the computer can do what you mean, not what you say. So, the biggest opportunity is in getting the flow through the ports in the head optimized along with ensuring the rest of the engine's critical measurements are exact. When the heads are off, you can zero in on what the factory couldn't afford to do right the first time.

llamaboiz

lol... i remember the days of porting a T3 head/18R-G head then matching the intake for dual 44webber IDA's AND dont forget to match the exhaust port too ... hours n hours with the dremel, those were the days

NovaIS350

Would porting and polishing have an adverse effect on the ECU? More specifically will the ECU adjust airflow etc according to the new profile? Will the car idle differently?

Lextasy89

^^ im not sure.. but if i did it, I would get an SAFC as well..

Lextasy89

anyone else have any opinons on this??

lobuxracer

iTrader: (2)

No, because it would be stupid to alter the ports significantly from stock without some other changes. A good street port just cleans up what the factory can't afford to do to individual heads because it's too labor intensive. Most of the gains are found in smoothing and radiusing the inside turn while blending the seat into the port as smoothly as possible. You'll also remove any coarse surfaces resulting from casting flash.

It should be noted not all heads are created equal at the factory. Lots of things can go wrong in the manufacturing process that cause a perfectly good stock head to be unsuitable for porting or any other high performance work. Core shift in the casting process is one of the most prevalent things you'll see on a stock head that make it mostly useless for modifying unless the shift is slight and you're planning on oversized valves.

Still, a basic street port will signficantly improve low lift flow and broaden the powerband. Just don't expect to put full race heads on a street engine and have it work well. Get the work done that makes the most sense for the use profile you envision. An engine is a symphony of parts and pieces. That's why it takes a TUNER to get the best music from your symphony.

Lextasy89

for the cost to get all the porting and polishing done.. im guessing close to $1000.. are the gains going to be worth it?

nabbun

what would the gains be? like 0.5% ???

lobuxracer

iTrader: (2)

It's not possible to accurately predict without full knowledge of the piece we're working on. Maybe 5% maybe 25%. Depends on a LOT of factors and what other things we address with the heads off.

As I said, if there's core shift and the seats are not even close to concentric with the ports you might be able to make a good fix and get a huge improvement. You might also not be able to do much of anything if it's so severe you'll never be able to get rid of the step between the seat and the port. I've got a couple of Mitsubishi Evo heads I'm working on right now, and they're so poorly cast it's hard to imagine how anyone ever got big power out of them (boost does make up for a lot) with any efficiency. I've seen 2JZ-GTE heads that were nearly perfect from the factory, and others that had a full millimeter step because the seats were installed so off center is was hard to imagine. Each head presents a different potential, so, starting with a good head will allow the most extreme changes for the largest impact, and the worst heads will barely even clean up to perform as well as a good stock head.

jimmyjazz

And with core shift there's always a chance you could cut into a water jacket. My friends that cnc LSx heads talk about some kind of cool things. One is where they port the intake port from the intake side and then the same port has to be done from the valve side. There is a little ridge where the cnc machine doesn't quiet reach each other. If the ridge is not hand finished they get 7cfm more flow at full lift than if it is finished. But if they don't grind it out everyone thinks they were being lax and missed it. So they finish every one and people get a head that flows less but looks prettier!

lobuxracer

iTrader: (2)

This is why I don't waste time with polishing. All it does is hide bad work. Good port work does not need or benefit from polishing, it just makes the customer happy about spending a lot of money getting porting done.

uschardcor

so porting is a per individual car case than a model. maybe one day someone will go for it with an is and see what happens