Just curious. I have one of these laying around and while surely its possibly to fab a TV cable mount, I want to know who has actually done it. Is it more feasible to have my small bore TBI bored out to near the same size?

take a friction cutoff wheel and use it as a grinder to remove the "weld" on the small block throttle body linkage. do the same for the big block one and have some one weld the SB linkage onto the BB one. i personally have done this 4 times without problems. Tbimax has one ive already done. there are pictures in his thread. you MUST tune for the big block unit. my vortec 357 tbi took about 400 burns to get correct and im still not done. it was also my first time tuning. my big block 496 is at the 150 chip mark and i feel im real close.

I was running a GM 454 TBI unit that I converted to front pull by sacrificing a 4.3 TBI.

I have the 50mm SBC unit on a vortec 350
chip count? O, I'd say a thousand different burns at least lol

it's coming together quite nicely now, though

I had to fab a cutom tv cable bracket anyway, since I am using a vortec gmpp 4bbl manifold. But I used the throttle arm from a sbc unit and welded it on the bbc unit, works fine.

my GM 7.4L TBI unit needed no mods to adapt to my Holley TBI manifold. Just needed the adjustable t cable bracket. rear pull.

If Darkshot wants a photo send me a email address.

i am running a 1995 5.7litre with a 1988 big block throttle body in a 1988 pickup, and, duh, a 1988 7.4litre with a 1995 small block throttle body in a 95 yukon. the only difference i could detect between the two throttle bodies was the tps and plumbing, bores looked same size. honestly havent put any miles on the small block, but the big block has, ahem, "too much" cam and is about to get diddled with an ostrich 2 as soon as it shows up. (so no, it doesnt run quite right).

I know you already have one, but xtremefi has 2" and 2.25" TBIs made from f-body unit, so you don't have to mess with the IAC and throttle.

...sounds like they are different and should have different bores- do you think it would work if i figured out the wiring?

Obviously, the stock 305/350 SBC intake will have to be bored to 50mm to clear the 454 TBI blades. Transdapt does make an adapter that will allow a 454 TBI to be mounted on a stock manifold without boring the stock manifold. It starts at 50mm and transitions down to stock manifold size.

The issue with this is clearance for our F-bodies. This adapter will raise the unit at least 1" if not more.

Also, the older 454 TBI units are a standard base footprint just like our SBC bases. The newer style and some marine 454 units have a large base footprint. The large base foot print has larger ports for the IAC valve to accommodate more airflow to the IAC valve and "stabilize" idle issues. The large base footprint must use an adapter to mount on the SBC intakes otherwise half of the IAC Valve ports will not be sealed, thus vacuum leaks.

Here are some pictures for you to explain what i mean. I will post the pics in a few minutes.

Here are the base foot prints that I mentioned in my previous post.

Here are the same units with their respective gaskets

Here is the typical 454 IAC Valve and it's adapter to the SBC factory harness.

Here is my old 305 TBI unit with the linkage removed and then a picture of my new 454 TBI unit with the linkage welded on.

Here are a few pictures showing the 454 large footprint on a SBC intake

Here is the harness adapter i was telling you about.

This is my actual setup. Edelbrock 3704 bored to 50mm with a new large base footprint 454 TBI unit mounted with an aluminum adapter.

The new Edelbrock 3704 has been powder coated by a local shop. It is called "mirror" finish which is a two-step process.

The middle picture show the adapter plate again

So, a ton of pics for you to see.

It is actually an easy project to do. You will need to be able to tune your own chips and to be honest with you the only reason why you would want to add a 454 TBI or 305/350 TBI bored to 50mm is if you require more airflow and fuel to support more horsepower.

If your setup is a stock 305/350 there is NO need to add anything bigger to the top end.

If you are adding heads and cam then GO FOR IT!!!!

Don't waste your time/money on a modified 350TBI unit bored to 50mm. You can get a nice NEW 454 for the same price OR buy a used 454 base and have the shafts rebushed for less than a modified 305/350TBI.

Been doing this along time. If you're patient you can get what i said for less than $249 new and less than $200 used with shaft re-bushed.

There are guys who will disagree with me, but that is the great thing about this board. There are a lot of threads that you can read and make the best decision for YOU and YOUR application.

Good luck my friend and please keep us informed of your project and TAKE PICS!!!!!

Thanks

Sean

The IAC valve and TPS issues are SIMPLE things to correct. The harness adapters for both are less than $35 for the pair.

The only other thing that might cost more is if you need to buy new sensors obviously.

In my opinion if you're going to the trouble to upgrade your TBI unit it's best to put new sensors on anyway. I am one who doesn't agree with putting old sensors on new or modified products. I realize $$$$ can be a big issue. If it is then take a piece of paper and make a list of the costs for both setups.

If you need some help let me know.

For a couple years I ran with no IAC control. could not master the wiring. RBob and my research allowed the IAC to come alive. Very nice to have in WI. 1995 7.4L GM unit. All I needed to do is adjust the steps in bin maybe pulled 50% of steps? Now idles 1000 rpms cold. Nice.

Great thread here and I have a few questions

Do you have a part number for that IAC adapter?

Where did you purchase a new 454 unit?

Where did you get the adapter plate?

I too have an bored Edlebrock 3704 and will likely need a 454 unit in the near future. Struggling with the IAC differences.

Do you have a complete parts breakdown, including the fuel fittings, for everything we see in those pics?

Thanks in advance. These pics are great.

Yea, if you have that adapter PN available (assuming you didnt make it yourself) it'd be handy. There was a company a while back that used to make them but I cant find the link

Thanks!

The bolt patterns are 100% identical with all GM Rochester TBI's except obviously the crossfire.

The reason for the adapter plate is because the mounting surface on the intake is smaller than the mounting surface of the newer style 454. Thus, the larger base 454 would not seal correctly due to the larger IAC ports.

I carry the IAC adapters and TPS adapters, IAC valves, complete gasket kits etc. A ton of new stuff for TBI, CFI and TPI.

I made the adapter, but Transdapt makes a really nice one as well as a few guys on eBay. Transdapt is a swirl design and is $119.00

Here is a link to one on eBay for $50.00 and includes shipping. I have purchased a number of things from him in the past and he's been great to work with.
http://cgi.ebay.com/ebaymotors/ws/eB...3AIT&viewitem=

This one on eBay is 1" thick and too thick for our f-bodies unless there is a modified hood. Works great on a truck. You could have it machined down to 1/2". The price is perfect.

I am currently working with Ken Gomer to get a spot on here to advertise my products. It's not fair to the others on here who are currently paying for their spot. From what i have seen most don't carry what i do.

You can call me 217-473-4998 if you have questions.

Sean

Here are two threads that has some if not all the info you need for the fuel line fittings. Again, if you have any questions please call me.

http://www.thirdgen.org/techboard/af...com-earls.html (WWW.ANPLUMBING.COM EARL'S)


http://www.thirdgen.org/techboard/te...ml#post3908988 (Fuel feed, return, vapor line sizes + AN)

I custom made the IAC and TPS adapters.

I was fortunate to purchase a number of brand new ACDelco 454 TBI units. I still have several left. I put new TPS and new IAC Valve on the unit as it is just a base unit. The pictures you see are the same unit, but i had mine powder coated!!!

wow, this is great information-

i only had to trim the gasket to prevent the 350 manifold from interfering with the 454 throttlebody's butterflies.

but what i am really to mount the cable tv bracket onto is the yukon with the fresh 454, so i can sell the pickup with whatever parts i dont need.
sounds like i need to bite the bullet and swap throttlebodies. should i expect to have to "tune" the pickup's ecm?
i have two ecms, a 7747 which i took out of the donor 88 pickup, and a 6396 that came in the 95 yukon. the 6396 lights up my dash like a christmas tree, and wont run with the new engine but works fine in the pickup. the 7747 seems to make it into open loop in the yukon (w sb throttlebody) and has some emissions, richness at idle issues, poor high rpm performance, and less-than-expected fuel economy.
my ostrich2 just showed up. before i begin soldering the socket booster onto the board, i need to decide if i want to try to get the 6396 working (disabling pickup), pick up a used 7427, or stay with the 7747.
seems like the the 7747 and 6396 have the same connector, probably different pinout, and the 7427 has a different connector. i know the 7747 has alot of stuff out there, but it has a slow baud rate.

Give Brian Harris a call. He's better equipped to answer the ecm questions than I am. I burn my own chips, etc, but I get my advice from him.

www.tbichips.com His contact number is there. Hurry and call now and you might still get him before the weekend. Tell him Sean Rondeau sent you.

Thanks and good luck

are you saying i should swap in the newer tps and iac on the older throttlebody?

I was saying that if you're going to go to the trouble of modifying your stock TBI unit then it's best to put new sensors on there. Going with the original OEM sensors for that TBI.

If cost is a big issue then you can clean up the IAC valve, but that doesnt take care of the "electrical" part of the component.

If the TBI was running fine prior to it being removed I am sure the sensors will do just fine on your modified.

I just go to the extreme with my projects. When i remove something that hasn't been removed in a long time I replace everything that i can. In the long run it does save time and $$$$.

Where can I purchase the IAC & TPS wiring harness adapters ..... web site or phone number would be greatly appreciated?

I custom made a number of those and do have a few extra in stock. I sell the pair for $30.00 to TGO members. You can call me at 217-473-4998 (monday) or email me at tbiparts@mchsi.com.

Turbo City sells them as well or at least used to.

Just found a web site . http://www.turbocity.com/product_inf...products_id=44 should have done some research before I asked a question & wasted everyones time.

No waste of time at all. That's what we're here for. Not sure what Turbo City prices are. Let me know

$30.00 bucks for the IAC adapter only !!!!!

Total for both is $30 (for both TPS and IAC adapter)

Dctrumpet may have alluded to this but it bears repeating. Make certain you have the "correct" base gasket for your 454 TB unit. Area in question is the seal around the IAC passage.

just pulled apart the pickup. the venturis on the original 454 tbi are much larger than i remembered- they measure about 52mm, so i guess i need to try this one out.
i am reluctant to replace all of the sensors at this point because i am thinking i just want to get it through emissions as stock as possible, then off to the dyno, then some changes. the other thought is i probably wont be putting too many miles on a 7.4 litre truck when gas prices start to jump again.

BUT TILL THEN I'M LIVIN' LARGE AND RUNNIN' RICH!!!!

This is a great thread...I am impressed with what you have there DCTrumpet.

There are so many people that don't think a TBI is worth very much but the people on this website just keep making it evolve more and more...its amazing...I never get bored reading on this forum...I commend so many of you that have the tenacity to keep pushing the envelope. There have been so many great engines on this board that have used this little old Rochester 220...and its great when I read about little bits of information just like this stuff...I knew about the difference in the Throttle Bracket but I never even knew there were updated designed for the big bore 454 TB...and the way you pieced it all together DCTrumpet...just looks really pro quality...especially with the anodized AN fittings and braided line...I respect the effort on that...its visually appealing on top of the Edel-y TBI Intake too. Sure would like to hear it run...

Thanks for asking the question Darkshot.

JBLTZ

Thanks for the compliments! For some reason GM TBI has really grown on me. I have enjoyed this far more than carb and multi-port. I guess its the best of both worlds.

I just got your private message. Ask away.... lol

I owe a lot of my knowledge to Brian Harris from Harris Performance, INC. He has helped me tune my chip and has given many recommendations for my current setup.