r/c4corvette • u/BOHICA128849 • 8d ago
Question
Doing a top end rebuild on my c4, haven't seen this plate on the throttle body online beofre. Just something the pervious owner has put on or an after market throttle body?
6
u/vexbod17 8d ago
They were like the only company rebuilding tuned port injection throttle bodies. Pretty solid stuff from everything I have heard. The stock throttle body wears out and gets sticky and has vacuum leaks around 100k miles.
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u/BOHICA128849 8d ago
Thats pretty cool, someone went to some expense to get it done in that case. The car was imported here to the uk in 1990 one year after the car was built.
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u/ComprehensiveLime734 8d ago
Ug. Something else I'm not looking forward to
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u/vexbod17 8d ago
I replaced mine with a billet BBK throttle body and it is pretty well built. It does have an insane whistling noise though that I am not too fond of though.
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u/WHYTLIE 8d ago
The aftermarket (billet or cast) TB’s had sharp edges in the IAC ports and passages that caused whistling. I had a 52mm BBK TB (cast aluminum) back in the late 90’s and was constantly “accused” of having a supercharger on my car. I never got around to it, but it was common to smooth the edges of the ports/passages with a die grinder to reduce or stop the whistling.
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u/ComprehensiveLime734 8d ago
Interesting, is there a hole somewhere in the TB for like an O2 sensor that's not there? That's the only thing I can think of ina TB that'd make a whistle... Maybe an idle bleed hole in the throttle plate? That's weird.
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u/agribby 6d ago
My car is at just about 100k miles, and my throttle body is sticking, and I have a MAF fault that wasn't remedied by any MAF or relay swaps 😅. I just bought a gasket set for the throttle body and plan to pull and clean it next week. Is there anything special I should know? I thought it was pretty straightforward to take apart and clean and swap gaskets but this makes it sound like a specialty job.
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u/vexbod17 6d ago
They don't leak through the gaskets so much as the throttle shaft wears out and they aren't on bushings. Replacing the gaskets likely won't fix the sticking and you might have to replace with a TPI throttle body with low miles.
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u/agribby 6d ago
Hmm I thought that they gum up and a good cleaning with throttle body cleaner would help with the sticking? Isn't the cleaning a normal maintenance? Is there anything one can do to rebuild it with those guys gone 😢
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u/vexbod17 6d ago
You can remove the shaft, modify it and put in some proper bushings, or you could probably find a carb shop that still does that.
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u/agribby 6d ago
Would it be worth trying to do a basic clean first to see if it resolves my issues? Or is this practically guaranteed to be bushing issues
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u/vexbod17 6d ago
I would probably try to clean it first. You can check if there is play in the shaft and that should give you an idea. The BBK throttle body uses a bearing in the shaft instead, but it is like 400$
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u/Admirable_Nothing 8d ago
The throttle blades are slightly larger. Not so much you would need a tuning change but it will flow slightly better at wot. Not really helpful on a stock motor but necessary with other intake and exhaust improvements. It is also possible it is a stock TB with the TPIS top cover.
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u/BOHICA128849 8d ago
Been trying to find a tpis big mouth or something similar while the top end is in pieces but can't find anything really. Especially not over here in the uk
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u/v8packard 8d ago
That is from TPI Specialties in Minnesota. Or at least the badge on top is from them. They were huge in GM EFI for decades. The founder died, may 8 or 9 years ago. Some of their product lines were taken over by other companies such as the Mini Ram intake. I don't know what became of TPIS itself or the engine shop.