Bore stock throttle body
01-14-2011, 12:48 PM
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Bore stock throttle body Has anyone ever bored the stock throttle body to 58mm? I know you would have to get the butterfly plates, but if you could get those, is this possible? May be a dumb question, but it just seems like everyone is paying $300+ for aftermarket throttle bodies, so I'm just wondering if there's a reason you can't just get the stock one machined.
01-14-2011, 03:52 PM
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The stock 48mm can be ported to 52mm max there is not enough material to go bigger. FWIW I'm running a Summit Racing 58mm and it was less then $275 and I haven't had any problems with it
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01-14-2011, 08:19 PM
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Haha. Thanks man. I appreciate that, but it's so hard to do. This is much easier, lol.
Thanks guys, I've never seen it brought up on here, but I haven't been on here long. I figured there was a reason why everyone was buying the aftermarket TBs. If you could just machine the factory to 58mm, I guess they wouldn't charge so much for the aftermarket TBs.
So 52mm or 54mm is as big as you can go. Got it!
Thanks guys, I've never seen it brought up on here, but I haven't been on here long. I figured there was a reason why everyone was buying the aftermarket TBs. If you could just machine the factory to 58mm, I guess they wouldn't charge so much for the aftermarket TBs.
So 52mm or 54mm is as big as you can go. Got it!
01-15-2011, 12:42 AM
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there is a a big single blade out there that is soooo sexxxy I wish I had found it before I found my 58mm! May be able to convert stock to a single blade.... just a thought!
01-15-2011, 06:05 AM
#13
The monoblade makes IAC distribution an issue so I would not go blindly suggesting it. It also lacks the emmisions and PCV hookups. For most a 52-54mm rebored stocker or an aftermarket 58mm with the IAC bypass drilled are going to be very good choices.
01-15-2011, 09:49 AM
#14
A 53.5mm bore is about the absolute max you can safely bore a stock OEM casting. To do this you need to bore them off center of their original centerlines and the casting walls are very thin, around .010 to .015 of an inch in some areas. A 52mm bore throttle body has a casting wall thickness of around .040 of an inch (1.01MM). I've bored many stock throttle bodies and have always stuck to 52mm to be on the safe side. The OEM throttle body is cast aluminum, very brittle material compared to a 6061-T6 or 2024-T3 grade aluminum. Get the walls too thin from an oversized bore and they can crack.
01-15-2011, 10:05 AM
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I read something that a guy had one for sale that was bored to big and it cracked and they patched it.... lol! I would probably just save up a couple of bucks and get the aftermarket if you want 58mm. check ebay and cl and if you look hard enough you will find one used eventually. I got mine on ebay for around $150 and it's a BBK!
01-15-2011, 10:50 AM
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I have an ebay stock bored 54mm, or so it says, and I noticed a difference, but it sticks closed when you first start the car, kinda annoying but I got used to it. I was thinknig about getting a better quality one or a stock bored 52mm from a trusted source, but I don't know if it'll be the same story.
01-15-2011, 12:30 PM
#17
The 54mm thing is only specific stock TB castings the guy who does them is clear about that.
Some of the aftermarket TBs like Holley in particular are known for sticking and none that I am aware of have a properly functioning IAC system to them, they need varying degrees of modification to work right.
Most folks do not understand setting the TPS and IAC counts and particularly the TPS they screw up. You should NOT be slotting the screw holes and clocking it, or using the "idle screw" to improve idle. The "idle screw" is a closed stop, shoul;d be set so the blades don't hang up going too vertical in the bore. IAC bypass should be drilled and sealed to the plenum to get IAC counts right.
Some of the aftermarket TBs like Holley in particular are known for sticking and none that I am aware of have a properly functioning IAC system to them, they need varying degrees of modification to work right.
Most folks do not understand setting the TPS and IAC counts and particularly the TPS they screw up. You should NOT be slotting the screw holes and clocking it, or using the "idle screw" to improve idle. The "idle screw" is a closed stop, shoul;d be set so the blades don't hang up going too vertical in the bore. IAC bypass should be drilled and sealed to the plenum to get IAC counts right.
01-15-2011, 01:28 PM
#18
A cretin casting number is better as far as wall thickness goes, but I still wouldn't run a 54mm ported OEM on my car or risk it failing and on someone else’s engine, just my opinion.
-Mark3.4V6, you should not have any of those problems if the machine work and assembly was done correctly and the proper clearances were held in the shaft/bore area. Before buying another throttle body I would pull off the one you have and clean the bores and throttle blades very well with carb/brake cleaner and a rag. Best if you remove the IAC plate and TPS sensor when doing this to keep them from getting wet/dirty from the solvent. Once cleaned rotate the throttle shaft and look at the bores for blade contact. If they are contacting you can try to adjusting the throttle screw to open the blades slightly. Try 1/8 of a turn at a time and don’t open them any more than needed. If that doesn’t work you can try some fine grit sand paper and carefully remove a little material off the edge of the throttle blade to give it clearance and eliminate the rubbing in the bore. None of these should have to be done if the machining is cone correctly but it may allow you to use the throttle body you have without dropping the cash for another one.
-Mark3.4V6, you should not have any of those problems if the machine work and assembly was done correctly and the proper clearances were held in the shaft/bore area. Before buying another throttle body I would pull off the one you have and clean the bores and throttle blades very well with carb/brake cleaner and a rag. Best if you remove the IAC plate and TPS sensor when doing this to keep them from getting wet/dirty from the solvent. Once cleaned rotate the throttle shaft and look at the bores for blade contact. If they are contacting you can try to adjusting the throttle screw to open the blades slightly. Try 1/8 of a turn at a time and don’t open them any more than needed. If that doesn’t work you can try some fine grit sand paper and carefully remove a little material off the edge of the throttle blade to give it clearance and eliminate the rubbing in the bore. None of these should have to be done if the machining is cone correctly but it may allow you to use the throttle body you have without dropping the cash for another one.
01-15-2011, 01:56 PM
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I already tried all that. Thanks for the tips though. It was a while ago but I thought I remembered comparing my stocker to the bored one trying to see what was making it stick closed, and I could see daylight around the blades in the new one when closed, but not in the stock one, I couldn't figure it out so i through it back on.
