Transam1170
Registered User
if i change the stock 60mm throttle body do i have to change the plenum if i put a 75 mm on it? thanks
and would a 75mm professional products brand is it a good throttle body?
Alright, the first picture is of the late model rectangular inlet. I have several of these left over so it was easy to dig one up. You can see that the throttle body opening is fairly small. It was designed to accomodate the factory 60mm tb.
In the next picture, I have installed a BBK 75mm throttle body that I had lying around. Looking through the throttle body's throat, we can see the "ledge" that would be present if the throttle body was installed on the factory inlet as it is. The result would be a disruption in airflow as the rushing air tried to push its way past the obstruction.
I traced through the throttle body to obtain the last picture but tracing around a gasket will be better as it will making the opening the correct diameter in order to maintain a constant width from the throttle body to the opening in the inlet.
The inlet can be ported while it is installed on the the supercharged while still attached to the motor, but you will not get the best results. For the minor extra effort to remove the supercharger and then the inlet, the job will be completed much better. Inexperienced porters will most likely end up with shavings everywhere including inside the engine. If you do decide to do so, stuff the inlet with clean painters rags. They are cheap and easy to work with. Make sure they are back about 1.5"'s from the opening. If a burr catches one at speed, it could hurt. I would recommend covering the rest of the engine to make sure nothing sneaks itsway inside. Carefully fold up those covers when done and dump them away from the engine bay. Vaccum the shaving from inside the inlet before pulling the rags as suggested.
Working on the inlet while of the car and removed from the supercharger would be the best approach. This not only eliminates the posibility of contamination into the motor, but it allows you to be manipulate the inlet as you work on it. To get the best results, you do not just want to "wedge" the opening sharply, but you should blend into the throat for about an inch or more with a gentle radius. The best approach is to remove material with an aluminum burr until you attain approximately 85% of the final desired shape. Then use a large flapper wheel to smooth everything out.
Don't waste time with stones. Three days with stones or 10 minutes with an aluminum carbide burr. The small ones are $15 to $25 bucks.
A flapper wheel looks like a drum and has small "flaps" of sandpaper epoxied into the center. You can prevent both items from filling up with aluminum by coating them in beeswax occasionally. I can post some pictures if this is still unclear.
I'll agree with Flex on that. (How much aluminum do you think you have turned into shavings by now, buddy? )
Get a good carbide burr. The aluminum is pretty soft, so you have some flexibility with speed. You can use a hand drill if you don't have a proper grinder. A 1/4" burr can take material away faster than a 1/8" burr, but bear in mind that the tips move faster with the bigger diameter burr. To smooth things out and get the final shape, you can use a flap wheel or those mini sanding drums that have sandpaper around a rubber cylinder.
I'd gladly buy a burr, I just not sure where to buy them around here. Something tells me I'm not going to find one at Sears, or auto-zone. I could buy one online, but I'm hoping to tackle it this weekend. Grainger sells them, but they are expensive there.
I know what you're referring to now on the flapper wheel. I was reading where a guy suggested using permatex silver anti seize (I have copper i might try) to prevent clogging as well as beeswax (that I don't have).
I'll be using an air powered die grinder, it has both eighth and quarter inch collets, I'd much prefer to use quarter inch tools. I'll have to do some research to find a place that sells aluminum carbide burrs tomorrow...there's gotta be some place in RI that sells them.
Thanks for the tips!