Question about PORT & POLISH
10-22-02, 01:18 AM
#1
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Question about PORT & POLISH
Has anyone PORT & POLISH their GS400 throttel body or pistons and if so what was the cost and time to do it? Also what gains are expected?
10-22-02, 01:36 AM
#2
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Pusher, porting generally refers to smoothing the intake and exhaust ports in the heads to allow higher flow, polish generally refers to polishing to a mirror shine after porting of both the ports and combustion chamber. Polishing is not necessary and other than looking pretty does not help power and in fact can reduce it.
You can Port/polish the Tbody but there are vacuum ports and idle speed considerations. Some companies bore the Tbodies out and install a larger throttle plate.
All of these things IF DONE PROPERLY can improve power. Improperly done can cause a LOSS in power and in some cases ruin the parts completely.
Done properly you are looking at $1k-2k for the heads (possibly more) for just labor NOT including removal and replacement of the heads. Power on our engines could potentially go up around 25hp at stock RPMs.... MAYBE 50hp if the work was cutting edge... BIG, HUGE ""IF"". But, without improving the exhaust manifolds and the remainder of the exhaust you would be lucky to see more than 10 of that. So, you guessed it, I would suggest better exhaust FIRST. A FULL cat back from JIC of Greddy could be the answer but I have no first hand experience with either. Good luck.
You can Port/polish the Tbody but there are vacuum ports and idle speed considerations. Some companies bore the Tbodies out and install a larger throttle plate.
All of these things IF DONE PROPERLY can improve power. Improperly done can cause a LOSS in power and in some cases ruin the parts completely.
Done properly you are looking at $1k-2k for the heads (possibly more) for just labor NOT including removal and replacement of the heads. Power on our engines could potentially go up around 25hp at stock RPMs.... MAYBE 50hp if the work was cutting edge... BIG, HUGE ""IF"". But, without improving the exhaust manifolds and the remainder of the exhaust you would be lucky to see more than 10 of that. So, you guessed it, I would suggest better exhaust FIRST. A FULL cat back from JIC of Greddy could be the answer but I have no first hand experience with either. Good luck.
10-22-02, 11:51 AM
#4
Lexus Test Driver
Moderation's the Key!
Pusher - As John said, polishing is generally restricted to high HP engines with alot of cam, gears, etc because the polishing causes the airflow to lose some volumetric efficiency ( U need some turbulence in a street motor to ensure complete combustion ). A simple porting job ( just matching the openings on the heads to the intake runners - also called "gasket matching" and, in some cases, "blueprinting" ) is about all I'd recommend on a mild street motor ( domestic or import ). I keep coming back to the stock GS fuel system as the bottleneck.
Doesn't do ya much good to open up the intake for more airflow IF U can't add additional fuel for a proper air/fuel ratio. Consider dyno'ing your engine to see if ya have the fuel headroom to make the work worthwhile ( unless U're gonna change the injectors and/or add a engine management system like the Apexi or Haltech to go beyond the electronic restrictions of the stock fuel system 
)? SRT still holds the theory ( backed by dyno testing, I recall ) that the stock fuel system will only support 400 flywheel HP so if U've added an intake ( as U have ) & other mods which require additional fuel, U MAY not have room to make the work worth the effort/money. For example, my GS4 dyno'ed at roughly 346.2 flywheel HP ( when it was new ) so I've shyed away from even a nitrous kit ( for now
) because I'm concerned about being able to inject enough additional fuel to keep from leaning things out. Just some heads-up for U to consider but keep us in the loop!
Doesn't do ya much good to open up the intake for more airflow IF U can't add additional fuel for a proper air/fuel ratio. Consider dyno'ing your engine to see if ya have the fuel headroom to make the work worthwhile ( unless U're gonna change the injectors and/or add a engine management system like the Apexi or Haltech to go beyond the electronic restrictions of the stock fuel system )? SRT still holds the theory ( backed by dyno testing, I recall ) that the stock fuel system will only support 400 flywheel HP so if U've added an intake ( as U have ) & other mods which require additional fuel, U MAY not have room to make the work worth the effort/money. For example, my GS4 dyno'ed at roughly 346.2 flywheel HP ( when it was new ) so I've shyed away from even a nitrous kit ( for now ) because I'm concerned about being able to inject enough additional fuel to keep from leaning things out. Just some heads-up for U to consider but keep us in the loop!
Last edited by Mean Gene; 10-22-02 at 11:53 AM.
10-22-02, 03:08 PM
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Re: Moderation's the Key!
Originally posted by Mene Gene
Pusher - As John said, polishing is generally restricted to high HP engines with alot of cam, gears, etc because the polishing causes the airflow to lose some volumetric efficiency ( U need some turbulence in a street motor to ensure complete combustion ). A simple porting job ( just matching the openings on the heads to the intake runners - also called "gasket matching" and, in some cases, "blueprinting" ) is about all I'd recommend on a mild street motor ( domestic or import ). I keep coming back to the stock GS fuel system as the bottleneck. Doesn't do ya much good to open up the intake for more airflow IF U can't add additional fuel for a proper air/fuel ratio. Consider dyno'ing your engine to see if ya have the fuel headroom to make the work worthwhile ( unless U're gonna change the injectors and/or add a engine management system like the Apexi or Haltech to go beyond the electronic restrictions of the stock fuel system )? SRT still holds the theory ( backed by dyno testing, I recall ) that the stock fuel system will only support 400 flywheel HP so if U've added an intake ( as U have ) & other mods which require additional fuel, U MAY not have room to make the work worth the effort/money. For example, my GS4 dyno'ed at roughly 346.2 flywheel HP ( when it was new ) so I've shyed away from even a nitrous kit ( for now ) because I'm concerned about being able to inject enough additional fuel to keep from leaning things out. Just some heads-up for U to consider but keep us in the loop!
Pusher - As John said, polishing is generally restricted to high HP engines with alot of cam, gears, etc because the polishing causes the airflow to lose some volumetric efficiency ( U need some turbulence in a street motor to ensure complete combustion ). A simple porting job ( just matching the openings on the heads to the intake runners - also called "gasket matching" and, in some cases, "blueprinting" ) is about all I'd recommend on a mild street motor ( domestic or import ). I keep coming back to the stock GS fuel system as the bottleneck.
Doesn't do ya much good to open up the intake for more airflow IF U can't add additional fuel for a proper air/fuel ratio. Consider dyno'ing your engine to see if ya have the fuel headroom to make the work worthwhile ( unless U're gonna change the injectors and/or add a engine management system like the Apexi or Haltech to go beyond the electronic restrictions of the stock fuel system )? SRT still holds the theory ( backed by dyno testing, I recall ) that the stock fuel system will only support 400 flywheel HP so if U've added an intake ( as U have ) & other mods which require additional fuel, U MAY not have room to make the work worth the effort/money. For example, my GS4 dyno'ed at roughly 346.2 flywheel HP ( when it was new ) so I've shyed away from even a nitrous kit ( for now ) because I'm concerned about being able to inject enough additional fuel to keep from leaning things out. Just some heads-up for U to consider but keep us in the loop!
10-22-02, 05:10 PM
#6
Lexus Test Driver
Sounds About Right
Pusher - Using an 80% efficiency factor ( the same one I used ), U're making roughly 325 flywheel HP. Given your posted best time of 13.9 @ 100 mph, that seems very reasonable as my best time was a 13.79 @ 103.17 mph ( with too much wheelspin despite the stereo weight in the trunk ) & I'm making right at 21 HP more than U. Rule of thumb in this time slip range is it takes an additional 10 flywheel HP to drop a tenth off your quarter mile time so we're there. Looks like U may have enough fuel headroom to make the port job worth it!
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