63mm TB

[LGAFF]

Got my Experimental Rochester TB machined to 63MM.....blades to be made next

http://i134.photobucket.com/albums/q115/lgaff/DSCN5621.jpg (http://s134.photobucket.com/user/lgaff/media/DSCN5621.jpg.html)

[LGAFF]

Should get my TB and extra plates back tomorrow!!!

[Blue Flame Restorations]

Can't wait to see how it turns out, Lee.

[LGAFF]

Pretty good fit: Kinsler did the blades for me and fitted them...

http://i134.photobucket.com/albums/q115/lgaff/DSCN5643.jpg (http://s134.photobucket.com/user/lgaff/media/DSCN5643.jpg.html)

[Jagdpanzer]

Excelent work Lee.
Are the throttle blades off the shelf or custom made?

[Schrade]

Q's:


Is there a flow rating for stock?
How 'bout for 63mm?
And with 63mm, where's the bottleneck inflow THEN, with stock non-ported plenum / IH's?

AND...

how well do they hold vac @ idle?

When I re-assembled my TB after top end housecleaning, I could see no light around the blades, BUT, when I had the 2nd TB butterflies blocked with the restrictor gasket, I saw a BIG difference in steadiness of idle RPM, attributable ONLY to air leaking by sec butterflies that LOOKED sealed...

[LGAFF]

2.501 is the bore and plates are 2.496 with a 10 degree backcut; these are custom

[LGAFF]

I will need to do some testing on this to see how it idles; Kinsler seemed comfortable with the fit

[LGAFF]

Everyone might not know this but throttle plates are not round....the centers diameter is smaller and that is the quoted measurement.....

The center diameter is the 2.496....top to bottom its 2.55 to account for the pitch/slant of the blade

[LGAFF]

the DAG is what seals the plate, I will be coating my TB in a similar product, coating opposing sides so as not to interfere with the blades opening

[XfireZ51]

Lee,

Is this on the 90? I recall u had 63s on the 92.

[LGAFF]

Yes doing it on the 90 and the 91 project 368

[tpepmeie]

Q's:


Is there a flow rating for stock?
How 'bout for 63mm?
And with 63mm, where's the bottleneck inflow THEN, with stock non-ported plenum / IH's?


a 427 at 7000 will pull 1" HG vacuum in the manifold with twin 63.5mm blades, and an oversize primary throttle plate. That'll cost a few hp. Smaller motors will be fine with 63mm. Not sure what vacuum a ported 350 would pull with the stock TB, maybe less than an inch?

[Paul Workman]

Lee, you mentioned using a substitute for the DAG compound. What would that be?

[LGAFF]

A dry moly lube

[Paul Workman]

A dry moly lube

I'm intrigued! I'm quite familiar with molybdenum disulphide as well as tungsten disulphide dry lubricants (we coat bullets with the stuff to reduce fouling). Both will adhere well, tho some peening (or "sand blasting" process) may be necessary to get it applied.

However, unless there is some kind of bonding agent, pure moly or tungsten will be removed in the presence of oil...which is likely to be present (to clean moly OR tungsten from my rifle barrels a combination of penetrating oil among other chemicals makes short work of either).

So! I know you do you homework, and a dry lube like Moly makes a lot of sense, but I'm just curious what exactly is this moly stuff is mixed with that is being applied? Shrade's Parkerizing comes to mind as an agent that can be applied, that has some inherent dry lube abilities, and is impervious to (gun) oils.

Then again, I wonder if Jerry's Gaskets has any of the original DAG stuff?

[LGAFF]

The dry moly is commonly used for this application....all I can do is test it.

[LGAFF]

http://www.amperemetal.com/dryfilmtech.html

[Schrade]

2.501 is the bore and plates are 2.496 with a 10 degree backcut; these are custom10 degrees on vertical axis.

It grades to 0' on the horizontal - a compound bevel, not exactly a simple cut.

And the 10' bevel on vertical implies that actual angle of the blades when 'closed', is 80'???

[LGAFF]

I think you meant open, not closed

I believe they mean the plate is cut to for a setting of 10 degrees from vertical when closed

[Schrade]

I think you meant open, not closed

I believe they mean the plate is cut to for a setting of 10 degrees from vertical when closed

Yeah - same thing here; we're measuring the angle from different planes.

Now - any way of isolating vacuum on the secondaries butterflies to check seal integrity? Like I was sayin' before, mine looked good, but I got a 50 - 75 RPM swing, until I put in that restrictor gasket. THEN it was ROCK STEADY 675 in DataMaster.

So, how to figure out if vacuum is pulling on the butterflies open AGAINST the return spring, or if they were holding closed, and just a tiny leak is in it being out-of-round??? I think I remember trying to push on the TB 2' cam to check this, and it didn't help steady the rev's............... ?

Isn't someone here who is re-working TB's putting in a 'helper' return spring? Marc perhaps???

[Hog]

I wouldnt be worried about them holding vacuum too much(incorrect, t-body blade sealing is VERY imp[ortant in the LT5), many single blade t-bodies that actually use an IAC motor have a hold drilled in them to help the engine idle.

I would be interested in leaving a modified t-body in the freezer for an hour or 2, then checking for binding.

Vacuum is pulling equally on either end of the blade if the pivot point is central to the blade.

[LGAFF]

I could not find the moly dry lube locally, so I tried a dry graphite lube by PB Blaster which has the same properties as other products that call themselves "DAG"

The stuff locks onto the metal, cannot scratch it off with you nail, good to 850 degrees.....warmed the TB up to promote fast drying and...

awesome seal

http://i134.photobucket.com/albums/q115/lgaff/DSCN5663.jpg (http://s134.photobucket.com/user/lgaff/media/DSCN5663.jpg.html)

http://i134.photobucket.com/albums/q115/lgaff/DSCN5664.jpg (http://s134.photobucket.com/user/lgaff/media/DSCN5664.jpg.html)

[LGAFF]

Drove 35 miles today, idle is just as before....so no issues. Initially it took some time for the DAG replacement I used to loosen up.....it was sticking at 2K when I lifted off the throttle....it would then drop to 850-900 at a complete stop. After a few miles no more issues....

[Hog]

DAG?

[LGAFF]

Dag is a general purpose material that is graphite based and is applied like paint. It's used in various industrial applications that need properties like a thick material buildup, low friction and high temperature range. DAG is a trademark of the Verick, Acheson Colloids company.

It seals the gap between the TB and the plates

[Schrade]

That 2' seal HAS TO be perfect BEFORE any tuning is done (or as perfect as can be).

Once I removed the restrictor gasket, I got a swing in idle of about 50 RPM. Not so good...

I read in an old HOTB article (2006?) that Marc addresses this very thing, because you can't tune UNTIL it's right..................

[Hog]

Thanks, for the DAG info.
I would have thought that the IAC motor could have taken care of slight leakage. Most cars have an rpm swing at idle as the sensors give info back to the ECM in a negative feedback fashion.
Perhaps this is because of the Speed Density system and/or the slower talkback rate of the OBD1 system?

[XfireZ51]

The IAC is a controlled leak. If it's completely closed, that leaves whatever air is coming thru the TB and possible other leaks. That's why you can suspect a vacuum leak of some sort if the IAC steps are at 0.
If you've disassembled the TB, you need to re-do the Min Air Adjustment.


"Isn't someone here who is re-working TB's putting in a 'helper' return spring? Marc perhaps???"

Marc does have a helper spring. I'm using it. TB return spring may get a bit weak after 20+ years.

[Hog]

Makes sense. In the early days of OBD2 controllers guys that were installing lumpy cams were drilling extra holes in in t-body plates to allow for improved idle characteristics.

Ability to recalibrate ECM/PCM's eliminated such a need.

It appears that t-body sealing is very important on the LT5, thanks for the feedback.

I looked up the IAC motor 17112350 for the 1990-95 LT5., $27 from Ecklers or $83 for a GM part from Rock Auto.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/lt5iac_zpscf75343f.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/lt5iac_zpscf75343f.jpg.html)

Does this motor act on the smallest of the 3 primary throttles in the t-body?

[Hog]

Info on DAG.
Throttleblade Sealer DAG

$15.00
This is the VERY hard to find sealer that GM used "back in the day." I am told there was a Service Bulletin that addressed complaints about rough idle on the tripower cars. The bulletin described how to apply the sealer and directed the mechanic to the parts counter for a small vile of sealer, a small paint brush, and directions. DAG213 does an excellent job,. but will not help badly pitted throttleblades, or badly pitted bores. I use this product on all the end carb throttlebodies I restore. I have seen some criticize this product. Hmmm. Can't understand that. You want a good idle, you need to have the end carb throttleblades sealed the best you can. I still find it on some of the end carbs I restore. I have heard some criticize this product, saying that comes off with carb cleaner. Might be so. But, why would you spray carb cleaner down an end carb, anyway? So, if you use the sealer, don't use carb cleaner. It is hard to find for several reasons...1) Suppiers sell it in large quantities..like a gallon for over 500. 2) It has a 24 month shelf life from time of manufacture. Here is the deal...if you buy the DVD I sell on the page..it includes instructions for application. Shows a video of me, applying the sealer, in fact. AND if you buy a set of rebuild kits....I will give you the DAG 213 sealer. But, you will need to remind me of this... there is a place for notes to me when you are checking out. If you miss this...send me a short e-mail. Again, to be clear, buy the DVD and the carbs kits and the DAG213 is included at no charge. Otherwise, it is 15.00. There will be enough to seal several sets of throttleblades. Know, though, that the sealer will not last long in the small tube I send you. So, I suggest using it within 30 days. I would recommend keeping it in the freezer for a longer life.


SKU: 57-66TSDAG-146

from this link
http://www.pontiactripower.com/shop/throttleblade-sealer-dag

[XfireZ51]

The LT-5 has a progressive throttle with the small tb being used for idle and quite a bit of cruise. The IAC motor has its own opening to allow more air into the plenum. It does not move any throttle blade. Earlier Computer Controlled Carb setups would manipulate the throttle blades.
For any tuning, its critical to have all sensors properly operating and for mechanical adjustments to be within correct operating range.