3.4l Modified Throttle Body...Problem with IM?

[60dgrzbelow0]

I recently purchased a modified SFI Throttle Body for the Camaro-Firebird 3.4L L-32 207 CID engine via eBay that has been bored out to 55MMs and had the axial shaft halved to increase the CFM airflow through the TB. Once I got it, I measured it carefully to confirm the larger dimensions and then also measured the TB opening on the stock SFI Intake manifold, which showed as only 52mms wide along its NS/EW plane. With the very real difference of the 3mms, my concern is that installing this new, modded TB will be for naught, unless I have my machinist widen the neck on the Intake Manifold to allow them to blend in better. I would appreciate any insights as to whether my concerns are well founded. The images and measurements I made of this modifed TB and the stock SFI UIM can be seen on my photo bucket site, here:

http://s557.photobucket.com/albums/ss19/60dgrzbelow0/PERFTHROTTLEBODY/?

Thanks in advance for any input and assistance with this...

[IsaacHayes]

Yes you will need to open up the manifold too or you are still limited by whatever size the smallest opening is.

[SappySE107]

Worse than that, it will been seen as even smaller because its not blended/matched at all from the TB to the plenum. You would be better off with a stock TB if you don't match the plenum.

[geoffinbc]

If you have a machinist and there is enough material to remove for matching then do it. But after it is done you need to blend in all the sharp edges and remove any casting flash to make a smooth entrance.

[BillS]

Your concerns are well founded, and the comments are correct.

I have a 62 mm. TB on my 3.4 (probably flows better than the rest of the intake can, but at least it isn't a bottleneck). It was necessary to match the intake throat of the upper plenum by boring it out to TB size and profile.

Unfortunately GM had some wall variation and in order to match the TB with the plenum, it was actually necessary to break through the surface on one side (That is repairable with Devcon applied to the outside and then smoothed - it isn't a structural problem in this case).

The only way they can get the stock TB out that far is to basically bore them out and then sleeve them back to size with custom butterfly and shaft.

What you are saying is that you paid for a stock TB that was supposed to be bored 3 mm but was actually still stock bore? Hmmm.

[sr20hardbody]

its better to have the manifolds inlet bigger then the throttlebody to provide a "step" for anti reversion so your intake pulses get harnessed within the plenum instead of lossed out the intake tract.

[60dgrzbelow0]

3.4l Modified Throttle Body...Problem with IM?

Thanks for all the good advice and information to all who responded.

For BillS:

No. What I am describing is the fact that the STOCK SFI INTAKE MANIFOLD is 3mm smaller (52MM) at the opening of the attaching flat, two bolt flange where the TB mates directly there over a gasket. I'm not familiar with the stock inner dimensions of the SFI VIN "S" TB, but the one I obtained has had the following modifications done:

(1) Bored the TB throat to 55mm.
(2) Removed 1/2 of the axial rod holding the TB plate and replaced it with the larger Aluminum 55mm butterfly to allow for greater, unobstructed CFM air flow.
(3) Installed 2 S/S screws on the flat side of the butterfly to secure it to the modified half/shaft.
(4) Cleaned, Painted and Re-Assembled the TB.

Photos of this TB with measurements and comparisons to the stock SFI UIM from various functional views can be seen here on my photo bucket page, along with complete tear down/re-assembly images of the 3.4l VIN "S" engine at the root of this photo bucket site I am maintaining for the duration of the re-build:

http://s557.photobucket.com/albums/s...THROTTLEBODY/?

For BetterThanYou:

Your observation touches upon my very same concerns over the apparent thin casting tube that flows into the UIM body from the lightly cast flange. I thought it might work to simply uniformly scribe out a larger 3mm circle on the UIM flange and just grind out what was necessary until the two items matched one another. But I thought I might get too enthusiastic and wind up accidentally boring holes where they should not be.

To all who replied:

Thanks, Gentleman. I am taking everyone's collective advice and showing this problem to Ken and Steve at Godwin-Singer in St. Pete, Fla and see what they can make of it. They have an optical bore scope to look at the two mating surfaces inside and see what needs to be done to make a match.

I'm satisfied with your guidance and the thread can be closed as necessary.

--==Bob==--

[kflo 93 gt]

You're a breath of fresh air for being a relative "newbie" to our community. With an attitude like yours I'm sure you'll come to find a great deal of useful information and helpful folks.

[60dgrzbelow0]

"Tusen Takke" KFLO... (A Thousand Thanks... As my Viking Ancestors would say). I do have some technical write-ups, such as my latest on the much needed Oil Pump Primer Tool that I recently designed and built that will make the nightmare of having a "Dry Block" go away for many of us Sixty* fans. I just don't know exactly where to place them and if the Admins/Mods need to review them B4 posting. I write fairly well and the photos I usually take make for easy "Step-By-Steps" to help in understanding. But I get the biggest kick from reading and learning about other V6 Enthusiasts who make problem solving an addictive and helpful habit when they show us better and easier ways on how things can be done...and in my case...keep me out of trouble. The more information I can get on these mysterious F-Body Cars ...the better my Camaros can run.

[bszopi]

Any write-ups that you come up with, send my way via email (bszopi at 60degreev6.com), including all pics and what-not, and I will get them posted up on the site as articles, accessible via the sidebar menus.

Thanks!

[60dgrzbelow0]

Will do. Would you prefer the information/articles as ready text in the body of the email messages to you (with image attachments added) or would you prefer the finished articles in MS-Word format, with the images embedded and ready for your editorial work on them?

[bszopi]

How ever is easiest for you. I can extract it from any source and create a page from it. No matter how you send it, I will have to adjust it some no matter what. But, I will make sure I make you (or whoever sends me stuff) as the article owner, so that you get the credit for producing the content.

[60dgrzbelow0]

Cool Beenz... Thanks Brad.

[BMC]

The casting of the 'L32' 3.4L iron head manifold is anything but exact. I made adapters for these and found that of the half dozen manifolds i have around, they all appear to be drilled and cast a little different. From the one I hogged out, I can say that pushing it to 60mm is literally pushing it to the limits without doing something to close holes up that you may break through as BillS mentions. Naturally, the smallest item is the bottleneck and what will cut down on power, TB, UIM, LIM, valves, ports, whatever!

-BMC.

[60dgrzbelow0]

BMC...

My photos precisely bear out what you describe. When looking directly face on into the maw of the UIM Throttle Body mounting flange, the aluminum casting looks like they took two mismatched halves from two separate casting molds...laid one atop the other and poured their electrically melted aluminum into it without any consideration for alignment and then tipped off for a smoke and coffee break. I can't help but wonder how different the impressions of these sturdy little 60* V6 engines would be, had the damned engineers put just a little more time and effort into how the motor should breathe with decently functional intakes. Jesus Palomino... All that lost, natural HP potential!