Has anyone seen on eBay a seller named "extreme-fi" selling 2" TBI's? They start with a stock 1-11/16" (model 220) and bore them to 2", replace the stock throttle plates with thinner 2" plates, thinner throttle shaft w/ new bearings, perform the ultimate TBI mods, include an injector spacer, all for $179 (TBI core exchange required). Supposedly they flow up to 750 CFM. I'd post a link but looks like that's a no-no here. If you search for seller "extreme-fi" on eBay, you'll find this and a bunch of other TBI related stuff they're selling.

Curious if anyone on this board has bought one or is familiar with the TBI's these guys are selling. Seems like a good deal, almost too good. I read somewhere that the stock 1-11/16" body could only be bored to 1-13/16" (like what TurboCity sells) without breaking through the casting. I was planning on buying a Holley 670 or finding a used GM 454 TBI, but this looks like a cheaper and cleaner alternative if it does what they say.

 

it was discussed a couple of years ago i believe??? that you could not bore the stock unit to 2" only to 1 and 13/16 and that one is like the turbo city one.

 

Actually - the bores measure in a 1.965" which is exactly 50mm if you do the metric conversion.

 

Okay, 50mm is 1.9865", not quite 2.000". I don't care about the .0314" differnece. The question asked is if anyone knows about these TBI's being sold on ebay and if it's possible to bore them out this big.

 

Yes - ebay user ID "xtreme-fi" has them - I have one and they do measure out as claimed. Can post a link if you need it

 

Are you happy with the 50mm TBI? Does it perform as they claim?

 

I am in the middle of tuning so can't say HP for sure, but it is much stronger than before

 

Try doing the ultimate mods before you buy one. It does make a difference. Plus it's fun I'm a big supporter of it.

 

I had my TBI bored out so I could run the TPI plates in it. It's still a pile of pieces right now. I'm building anoter motor, so I wont know how it works until it's all said and done. But, just boring it to the size of those plates, I went through into some of the galleys for vaccum. Between that and the Ultimate TBI mods, I have a pretty clean looking unit now.

 

i have purchased a few things from that ebay seller and had good experience. I recently just bought a set of 55# injectors from them for pretty cheap and they flow just as they claimed. They were also fast at shipping.

They are somewhat helpful if you email the guy with questions. I emailed him asking about a package with a 2" intake with a vortec pattern and he simply replied "just as we state, it only fits stock heads" Thus i probably wont buy the full TBI kit (intake, TB, AFPR) for $270. its still an awesome deal if you have stock heads. they claim it to flow 750cfm and support up to 400hp, but if you read elsewhere they restate that it really only supports up to about 350hp if your lucky. which makes sense since 2 TBI injectors can't really flow good enough to support much more than 370-380hp.

 

Link to website please? I'd like to take a look.

"TBI kit (intake, TB, AFPR) for $270"

Intake manifold? What one?

 

Last I saw, it's a stock manifold bored to 2".

 

Link: http://users3.ev1.net/~thor10/HP-FAQ.htm

Regarding the TBI kit for $270, BronYrAur is right about the intake manifold, it's a stock 305/350 bored from 46 mm to 50 mm. Anyone reasonably talented with dremel or die grinder could do the same for free. If you just by the manifold, it's $79. Not a bad deal if you're on a budget, but not a very good manifold compared to aftermarket manifolds.

I'm pretty tempted to buy the TBI from this guy. Unless I'm missing something, seems to be the cleanest & cheapest option I've seen to get 750 cmf airflow through a TBI.

 

Direct link to the 50mm TBI auction is here: http://cgi.ebay.com/ebaymotors/ws/eB...tem=7948155327

I agree that the stock intake bored to 2" is probably not as good as an aftermarket, but if you are not shooting for over 400hp - the bored stocker is probably better than a carb intake/TBI adapter for tuning purposes. Have gone this route and fuel "puddling" is a real problem on an open plenum type carb intake

 

how is 50 mm going to flow 750 cfm? i measured my holley 670 yesterday and the bores are 55mm thats 10 more mm to flow air and it only flows 670? i would be interested to hear why. also i am using a 1/4" spacer under my fuel pod.

 

Holley is 2" bores (50.8mm) which you can verify with holley. Also, the xtreme-fi throttle body has a halved & thinned throttle shaft which they claim accounts for much of the flow increase over holley

 

at the base underneath they measure just over 50mm as i stated i measured mine yesterday at the top the throttle bores are huge at 55 mm and they slowly taper down to 50 were the plates are at which will increase air speed as in a venturi which will flow more air. also the holley blades are not that thick and i don't see how flatening them more will increase it almost 100 cfm. when you do the ultimate tbi mods which i did 3 years ago it only gives you maybe a 30-50 cfm boost. and i grinded my shafts flat as well as the screws and i knife edged the incoming part of the tb's i noticed a little diffrence. but it was insignificant compared to the 600 cfm carb that i tried next and then i put on the holley unit in june and it really woke the motor up!

 

I just got a note back for Xtreme FI. I asked about the 50mm 750cfm thing. Claim it was tested at 1.5" Sounds pretty good to me, but so does 670 @ 1.5"

 

a local machine shop is going to bore my tbi out to 52mm for 40 bucks. anyone know where i can get the butterflies for it?

 

i have their vavle springs and spacers and they work great im getting soon the 2" tbi from them

 

Which galley's, and did this cause a problem? If so, what was the solution? I'm not running TBI, yet, and am very curious about 'working' the stock unit.

 

Ahh... if only most of you guys were air flow limited, lol... unless you're in the 13's yet with your thirdgen I'd look at spending the money on something that'll make a measurable difference.

 

sorry, but i disagree. i put my car on a dyno before and after doing the ultimate tbi mods. no difference in hp and torque. no difference in 1/4 mile times, either.

i think they're worth doing; anything that increases airflow can't be bad, but the ultimate tbi mods aren't the be-all/end-all they're purported to be on this site.

gunnyhighway bought one of the 50mm tbis from the ebay guy and, i believe, has had a good experience with it. he has a 350 in his car, however. i think a 50mm tbi is overkill for a stock or near-stock 305.

 

i'm a fan of the extreme-efi guy, but i think he may be stretching the truth a bit here. i had a long talk with him last summer about his 50mm tbi. when i asked him whether it was flowed at 1.5" or 3" hg, he said his flow bench wasn't calibrated that way and what they'd done was take a 750 holley 4bbl carb, put it on the bench, adjust the bench till they got 750 cfm, then put their tbi units on the bench and flowed them. the 2" holley 670 tbi unit flows 670 cfm at 3"hg, and that's without the injector pod on it (got that from holley tech last summer). using holley's formula for converting cfm at 3" to cfm at 1.5" (CFM @ 3”HG X 70.7% = CFM @ 1.5” HG), a holley 670 flows 474 cfm at 1.5". there's no way the 50mm tbi flows 750.

i think he's a good guy and sells good products (i have one of his 50mm tbis on the shelf, along with a badass set of ported zz4 heads and a weiand 7525 intake and plan on putting them in this summer), but i also think he's gotten tired of people asking him the same questions over and over and has decided to quit debating with them and just tell them what they want to hear.