I've done a lot of research, but am getting a lot of conflicting opinions. And a lot of the info that I have found is outdated or based on equipment that isn't really available any more. So here goes..

I am building a new TPI setup for my car. I have a GM Performance Parts 350 HO crate engine (Vortec heads, 0.435/0.460, 212/222 @ 0.050"). It's nothing special - stock internals. The car has 1-3/4" headers and 3" exhaust. So far, I've gotten a Vortec TPI base and AS&M large tube runners. A realistic max HP I am looking at is 400 or so. I am having a lot of trouble finding a throttle body. I *want* a 52mm throttle body, but it seems that very few are available now. The only new one that I have found from a known manufacturer is from BBK. But there are a handful of places that still make a 58mm one. And the secondary market for 58mm ones seems a lot better. My questions are as follows:

1) Are there any new 52mm throttle bodies out there that I may be missing? Even the used ones seem to be few and far between, or they are beat up pretty bad.

2) Will a 58mm throttle body cause any issues with a mild TPI build? I realize I don't need one that large, but it opens up a few more options for me. I have read a million articles online, and can't seem to come to a conclusion on this.

Any suggestions would be great. Thanks.

 

 

I understand that, but I don't know if I want a Summit Racing throttle body.

 

 

As stupid as this sounds, I don't like the look of the BBK. I have had the car for over 20 years, and have always wanted to have a TPI setup. I'm trying to keep the look as factory as possible because I have loved the look of TPI engines since the early 90's. And, to me, one of the signature parts of a TPI engine is the plate on the throttle body. I can't get that with a BBK throttle body. Again...I know that is a stupid reason, but this build is as much about keeping the nostalgic/old school look as it is the performance.

That is good to know about the benefits of the BBK one, so I appreciate it. I'll definitely keep it in the running.

 

 

 

I don't know what that has to do with my question, but thanks for the response.

 

Thanks...good point on the classifieds. The car is a '91, but I'm starting from scratch. So I can get whatever I can make work I guess. I've actually read a lot on Grumpy's page...TON of good info on there.

 

He is trying to help you maximize the return on HP for $$$ spent.
I am with Vincent, you need injectors and a tune. A set of 1.6 Roller Rockers would also be a better place to spend the money.

What he is trying to get you to understand, the throttle body will help very minimally if at all. On a mild 350, it's basically eye candy.

 

I understand that - and I am, of course, planning on injectors and a tune. I never said I wasn't. That's why I didn't know what that response had to do with my question.

As I said in the OP, I'm building a new TPI setup, so I have no throttle body. I have to purchase one no matter what, so I'm looking for suggestions.

 

My advice, save the money and buy a stock unit off the boards or ebay.

 

Thanks. I don't think I disagree with that...but the issue seems to be finding one that isn't chewed up. A lot of them (maybe even all of them) I have seen are pretty oxidized and in rough shape. I've been looking on ebay for months and months. But I'll keep looking. And I'm still open to suggestions.

 

 

Larger than necessary throttle body's will make the vehicle harder to drive. Very minor throttle inputs result in huge amounts of airflow and and it becomes really "touchy" with the gas. You should use the smallest throttle body that will accommodate your planned power as it will be easier to drive.

GD

 

Thanks for the input. I've looked at Professional Products stuff, and I don't know how I feel about them. I would like to get a Holley one, but they are only available in 58mm. They used to be available in 52mm as well, but they don't make them anymore.

I'm looking for a clean OEM one on ebay right now...I'm going to get one to see if I can clean it up, and also so I have a reference point for how the sensors and linkage came from the factory.

Within reason, I don't mind paying some extra money for one. Availability is the issue unfortunately. Which is why I am considering a 58mm even though I know it is too big for my setup...but I can order a nice new one today. Will it hurt to get one that is too big...that's the question..

 

As long as you tune it, it's not going to "hurt" anything. It's just going to be even more touchy, which the TPI's already were. You lightly tap the gas on a stock TPI car that's setup right and they violently lurch forward. It's partially because of the throttle cable on the earlier ones, but it's also the large throttle body. It lets in a lot of air for very little throttle input.

 

Just get a used one, disassemble it, and glass bead blast it. Paint or clear-coat to your liking, etc. It's not difficult to make the aluminium shiny again.

 

 

That's actually great to know that somebody is using it and having good luck with it. I'll definitely look more into it. Thanks.

 

Look into local "swap meets" if you have those in your area. I was at one a few moths back and there was more than one vendor selling tpi stuff. One guy had a complete TPI set up that was in grat shape for only $250,

 

My advice would be to find and clean a stock 48mm.

...that being said, I have a brand new Holley 58mm that I haven't really up of for sale yet, but is available. It's for an early 85-88 style throttle cable. I used it on my 89, and it worked great, BUT.....I didn't care for the throttle linkage. It was a preference issue, not performance issue. Also, Holley throttle bodies do NOT allow the use of factory throttle body plates. You have to use the HOLLEY plate that it come with. Not what I would do in your shoes, but I'd let it go for a VERY good price. Less than 50 miles on it. Hit me up if you're interested.