I'm looking to replace the worn out/sloppy 52mm TPI throttle body on my 305. Can anyone recommend a place that sells or rebuilds them? Summit sells these new ones, but I have zero experience in replacement throttle bodies to know if one is better than another. They all seem cheaper than a new one from GM and rebuilds that I've seen seem to go for close to $200. Seems like for a few more bills you can have a brand new one of these ones I listed below.

Professional Products - $231.97
Summit Racing - $219.97
BBK - $319.99
Holley - $370.95

 

There is a guy on EBay called Doctor Injector based in the Seattle, Wash area. Besides selling fuel injectors, he also rebuilds TPI throttle bodies and rebush the throttle shaft. He charges about $170 for his service and includes a used but tested IAC and TPS sensor. I just sent my throttle to him for rebuild. I'm currently running a 52mm BBK and have had problems ever since.

 

What kind of problems is the BBK causing?

When you get your stock one back you'll have to let me know how it turned out.

 

Having unsteady idle. Cannot find any vacuum leaks or air leaks. Adjusted the minimum air too. Not sure if the BBK is the cause, but I'm going to put the stock rebuilt throttle body on and see what happens. My motor is modified but not so much that I need a bigger throttle body. I've heard that the stock throttle body is good up to about 300 HP. You can find Doctor Injector on EBay by typing "TPI throttle body rebuild and rebush" into the search box.

 

Dr. injector rebuilt my throttle body in about 2 days, about $167. I expect to get it early next week. I'll post more details when I get it.

 

I got the throttle body on Saturday, USPS. Doctor Injector did a great job. The throttle shaft has no play, smooth operation, no sticking. I would recommend him for anyone who wants to keep their stock throttle body and have it rebuilt. I'm not going to install it just yet, I have to try a couple more things before I give up on my BBK 52mm throttle body.

 

Let me know how it works out...once installed.

 

The Ramjet 502 big block comes stock with a 49.9mm TPI style throttle body, and it makes over 500hp. I don't think "most" of us really need anything more than stock.

 

Agreed. But you can't get a stock one anymore. Just trying to find out which aftermarket tb works best since the original gm part is discontinued.

 

http://www.gmperformancemotor.com/parts/17113524.html

...not saying I'd pay that for it, but here ya go. .....I don't think you need a new one really though. I mean it's metal parts that can be cleaned easily enough, a gasket kit that's readily available and then sensors. Should be EASY to find one used if you didn't wanna use your current one. I've rebuilt mine a few times over the years,although I don't think it was really needed. Takes about 10 mintues to clean it up.

....I think the issue is most people want a bigger one, and the smallest aftermarket TB is a 52. ....yet a 502 from GM is using a 49.9. .....so my point is rebuild a stock one.

 

I've done the clean and replace gasket route already. The problem with mine is a sloppy shaft and metal pitting. Which is why I'm looking for a replacement.

 

OK, I gotcha! .....but you've got the BBK, right? ...honestly, I'd try and see if I could get a used stock one for $20 or $30 bucks, clean it up and see what happens, before spending a lot of money. I mean mine functions perfectly with no slop at all. ....if it doesn't work, oh well, you're not out much.

 

Check out Cliff's Performance (I think) sell overhaul kits for Rochester and also has bushing kits that includes the tool and new screws for $40.

 

I finally got around to sending my stock TB off to Dr. Injector for rebuild. I'll give my review when my TB is back on the car.

 

I just got my professional products tpi throttle body in the mail and on the car, it immediately cleaned up my idle due to the vac leak the old worn throttle body had. The new throttlebody had zero play in the shaft and was well machined. A few people don't like them since they're a Chinese company but i have zero complaints for the money.

If you do decide to get the one I have don't order it from summit, they're back ordered on it until july 31st. After cancelling my order with them it took them a week to give my money back.

 

Got my TB back from Dr.Injector today. No more sloppy throttle shaft. I'm pretty happy about that. They include a new TB to plenum gasket, which is nice. All is well after a bit of fiddling with the TPS, IAC and idle adjustment screw. Overall I'm happy.

I wish I had another one to play with. After looking at what they did I'd like to take a stab at it myself without the risk of screwing up the only one I have. Other than a real good cleaning, it appears as though they just grind off the bond between the shaft and the TPS lever, then slide out the shaft once the butterflied are removed. Then they just bore out the shaft holes in the body and insert brass bushings. I think with a drill press and the correct size bushings it would be a pretty easy thing to do. I'll have to keep my eyes open in the junkyards for a test subject.

 

Cool that you are happy with their work. I also have a TB rebuilt by Dr. Injector but have not gotten around to installing it. I think the trickiest part of the rebuild is fitting the butterflies back into the bore.

 

I seen lots of BBK TB cause all kinds of problems on TPI cars and older 5.0s .....

 

I've read/heard similar things. Which is why I chose the refurb route over a BBK or similar aftermarket TB.

 

Yep BBK is notorious for the shaft having a good amount of play straight out of the box. I got lucky with my professional products throttle body, shaft was tight with zero play and works great. Replacing it was one of the best things I've ever done for my car, got rid of a huge vacuum leak caused by the worn shafts letting air in behind the return spring which cleaned my idol and got rid of code 44.

 

The Professional Products throttle body I bought for my GTA last year was JUNK. The holes for the throttle shaft were not concentric and the throttle shaft would bind when exposed to manifold vacuum.

I bought a new BBK unit, one of the new ones with the 3 ribs on the top. They have bearings instead of busings. It's been a fantastic piece for me so far.

 

I just smoke tested my TPI and had smoke coming from both sides of the throttle shaft on my TB. After reading this it sounds like it could be a big contributor to my lousy idle.?? That and while re-assembling this thing and learning a lot along the way, I realized the TB I have is from an '85 Corvette. It only had the port that goes to the air-in on the right side valve cover and the water line that comes from the heater core, no vacuum port to the canister? Weird, anyway I drilled it out and installed a port so I could hook it to the canister.


I still have some injector testing and distributor inspecting to do but if I decide to rework this TB I am now wondering if I should go the used route and then have it rebuild by the Dr.? Get the TB intended for this vehicle.. Thoughts?

 

I had smoke coming out of the throttle return spring and when I replaced the tb my car idled like a dream, it was night and day. I've heard great things from people sending their throttle bodies to Dr. I would have done the same if I wasn't in such a rush to get my car running again.

 

I had smoke from the spring AND from behind the TPS! I doused it with carb cleaner while running and had no change at all. It can still make that much of a difference huh? I luckily have nothing but time. My son won't even have his instruction permit for another six months.


Would you suggest I get rid of the Corvette TB and have a used one reworked by the Dr. or send him the one I have?

 

The smoke near the tps sensor could have been from the hole on the idle air control but it very well could have been the shaft portion that rides on the tps sensor, either way it needs a rebuild lol.

Id personally try to get the correct one for your car, I'm sure you did a good job on adding the vac port but it's one less thing you have to worry about and you can get the correct one for fairly cheap that need a rebuild here on thirdgen's classified section. The eBay prices on them when I looked were pretty high at about $80, I'd try to get one for a max of $60.

 

What is the stock TB size for the 305? 48MM??

 

Yea stock is 48mm, anything larger doesn't affect anything it just might make the pedal feel a little snappier. The stock 48mm flows fine for engine builds up to around 450hp if I remember correctly.

 

I recently installed a stock throttle body, rebushed by Dr. Injector. Idles better now than when I had the BBK 52 mm TB. I would definitely recommend him.

 

Hey Fred, Do you happen to know the Dr.'s actual user name on Ebay? I can't find him..

Thanks!

 

Just call them directly. You don't need to go through Ebay.

Dr. Injector
34703 16th Ave. S.
Federal Way, WA 98003
(253) 838-1968

 

Awesome! Thanks...

 

www.docinjector.com

 

Call me kookie, but explain the smoke test? Never done one. Always used carb cleaner.

 

Anyone ever used them for injector service? I can kill two birds with one stone here...

 

I made a smoke machine with a coffee can, air pump, and smoke bombs. Pumped the smoke into the plenum and waited to see where it came out. Pretty cool. I had a little come from the TB shaft on both sides. Stuffed a rag in the tail pipe and blocked the front of the MAS.

 

I was thinking along those lines, only like a bee keepers smoker....same concept I guess

Neat!

Thanks, I learned sumtin today. It's gonna be a good day!

 

I was very satisfied with the end product. Since I did not need a tps nor the iac plate and sensor, the price was reduced.

 

Already boxed up and shipping today.

 

I'm sure he does a good job but I'd go to southbay injectors, Almost everyone on this site buys from them and they have a great track record. he also has an account on here so that's a bonus

 

I'm baffled by the aftermarket TB's sticking open under vacuum. I'm dealing with one now. I will tell you the 52mm TB makes a difference on the 305 motor. Definitely more snap to the throttle.

 

The Doc called yesterday and said my TB turned out great after he re-worked it. It's on it's way back and I'm excited to get the heads back and get her running...