View Full Version : TB revival

04-11-04, 02:41 PM
I have removed the TB off the plenum and I am pulling it apart to clean, I cannot seem to get the bottom off, I have removed all of the screws (except one that broke off in the hole) there is no reason why it should be stuck??

Is there anything besides brute force to remove the bottom?

It may just be the remainder of the broken screw that is holding thing on.

Oh man, is it filthy in there, I will post pics later, but what a mess the TB to plenum gasket was broken at the back and had 2 leaks out the bottom. And the plenum.....
Words cannot describe it.

Should I do some porting while it off, will it help, I now know what ridges people are talking about when they say get rid of the ridges just inside the plenum entrance.


04-11-04, 03:02 PM
You could hone it out but it would be purely for carbon removal.

The only mods you can really make with that TB is having it professionally bored out. But the cost really isn't worth it because a guy can just buy 1000 CFM TB's from BBK or Holley.

You could stick on a airfoil to help direct air they help a little.

Make sure you readjust your TPS to the correct voltage if you have removed it.

04-11-04, 03:18 PM
I htink I may be misunerstood sorry BigRed, I meant anything I could do to the Plenum, It's coming off too.

I am in the process of repairing an intake leak at the back, so I am thinking is there anything I can do while I'm in there.

Has anyone changed thier fuel regulator with a high output one.


04-11-04, 04:38 PM
Mart, you can gently pry at the bottom of the TB to get the IAC housing off - there's a gasket there that sticks, and you'll need to work two sides alternately because of the broken screw. Be absolutely sure, though, that you did get all the screws out... and don't worry about breaking one. I broke two, even being gentle, but they're a size that is easily available at hardware stores.

04-11-04, 08:18 PM
Thanks Rich,

I'm glad to here that, the screws were really dry and rusty inside there, my guess is there is a lot of crud in there to clean up.

I almost died when the screw broke, I had barely turned it.

Anyway thanks alot guys.

04-11-04, 08:32 PM
Pretty sure coolant flows in/around the IAC housing, and leakage is what causes those screws to rust so badly. My gasket was brittle on the outside and almost nonexistant on the inside edges.

04-11-04, 08:35 PM
And, the corrosion is due to the dissimilar metals being used to hold the thing together (the screws being steel, while the body is aluminum). ;)

04-11-04, 10:46 PM
Hey guys, I just got home from Easter dinner at my outlaws, I quickley went to the garage to check and see if the bottom had loosened up, I had been letting it sit after spraying it with TB cleaner and Liquid wrench, I tried prying from both ends as Rich had mentioned, and POP, off she came, woo,hoo.

The gasket is beyond brittle, hell I've seen soda crackers with more flex...

Has you guys changed your fuel regulator with a high output one like the ones in the TPiS fastpack.

Thanks for the prying tip Rich, your right about the gasket Kenlooks like crud.


04-11-04, 11:46 PM
OK here is the grossest pic, hows this for disgusting.


04-12-04, 05:00 AM
I changed the fuel pressure regulator in my LT1 when I owned it. Important step though is to check the existing fuel pressure to use as a baselinefirst which you won't be able to do until you run your car again.

Then I experimented with raising / lowering the presure to see what the car responded to. Can't remember what felt better now but it depends on the car and what other mods you have too so you'd have to try it for yourself. Best way is probably get some drag strip time and vary the pressures slightly to see if you are picking up more hp.

I've just removed my TB too for an intake gasket change (if you have a leak near the back of the manifold check it isn't the oil pressure sender like it was on mine, you can lose a LOT of oil in no time and be in real trouble real quickly if it is, easy to change when the manifold is off though).

Depends on how cold it gets where you are but I bypassed the throttle body coolant lines. Supposedly this helps HP a bit due to cooler intake charge but the real benefit is it makes the area a bit less cluttered and makes future TB removal a LOT easier.


04-20-04, 07:48 AM
Now here it is all cleaned up, the runners and plenum are looking nice too, the shine has got to be worth a few HP.


04-20-04, 07:57 AM
Now I know why I spray out the TB's on all my vehicles twice a year. I would never have thought that they could have gotten that dirty and still functioned.

Looks like you've gotten all the gunge off the butterflies, and as you said the rest of the plenum. That ought to be good for 15 to 20 HP. If it cant get the air in, it can't get the HP out!

04-20-04, 02:45 PM
wow, i thought my old tb was grungy had the same leak problem.
i replaced my throttle body with a 52mm bbk and installed an adj
bbk fuel pressure reg. i set the pressure to 43lbs and i seem to be
getting the best performance at that pressure setting.....

now its time to mess with the timming


04-20-04, 04:41 PM
Mart, glad to be of service. MAN, that was a gummed-up TB! Mine wasn't quite that bad when I pulled it...

I've installed TPIS's AFPR and I *think* it did some good. My pressure was on the low end of normal at the start (~34-35) so I bumped it to ~43, which is what TPIS recommends. There have been so many other variables with my car, though, that it's hard to say just how much good it did.

Have you actually checked your pressure? Mad-mic bought an AFPR and was going to install it, but we found his FP was already 43.

04-20-04, 07:38 PM
Anybody know anything about the IAC valve, mine is out about 1 1/4 it is supposed to be 1 1/8 but I cannot seem to move it, is there a trick to it.

I went to the local speed shop today to check an intake price (I had both thermostat housing bolts break:mad )

OMG what in the world is with the price of an edelbrock intake $750 CA.:duh

Hmmm I guess I'm gonna try like hell to fix this thing.

Hey Rich, you would not believe the shape of the plenum, serious carbon deposits, and varnish. My guess is it has never been cleaned.

Check out the black runners vs the cleaned pass side.


04-21-04, 07:11 PM
My runners looked that bad... New ones are nice and clean, though!

I need to post pix of the new engine as it goes together.

Also bought the prop-rod upgrade from Taber. Hope to install that this weekend. The '86 scissors lock scares me.

04-21-04, 08:35 PM
BTW - if you find a manifold on eBay or something here in the States, I'll be happy to try and get it for you as cheaply as possible.

Actually, this might be the perfect time to upgrade to an LT1 manifold setup...


04-22-04, 01:44 PM
When you say you broke the screw taking the TB off, which screws are you referring to? My '91 has 82000 on the clock and I don't think anyone ever cleaned the TB before. Idle is a little rough, but otherwise it seems to run fine.

04-22-04, 04:19 PM
Here is a shot of the broken bolts. Thermo housing bolts.

I am having B---- of a time getting the drivers runners off, the bottom bolts are a real pain to get at. I am having to remove the valve cover to get at them. Oh well I wanted to refinish them anyway. which leads to another story, removing the drivers valve cover S$#@, with such a nice accessable engine compartment as this why are things so freakin close fitting.


04-22-04, 05:06 PM
Mart, the runners each have a "hidden bolt" that enters from the rear (i.e. from "inside" the plenum area. Once you know where they are you';ll never forget them (I've just done this job twice on my car and I agree it is HORRIFIC - one of the worst jobs I've ever done on a car, nearly made me sell my vette!)

One of these bolts is accessible by using a long extension from the passenger side and sliding it by the fuel pressure regulator while the other side is right near the thermostat housing.

If you're having a hard time getting to the lower bolts it helps greatly to lift the fuel rails a bit to gain access to these bolts. After undoing the 4 10mm bolts that secure the rails and the 2 fuel lines at the front of the manifold, make sure you remove the "bar" that runs between the fuel rails near the front of the rails. Then you can lift the rails, best to remove them by using gentle but firm pressure on both rails at the same time to lift them.

First time I did this job it took me days as I couldn't work out what order to remove parts in, - it truly seemed an impossible job!

Second time (I still had the oil leak I suspected was from the manifold so decided to do the job again!) I had everything removed right down to the intake in less than an hour! Dont you love a job that's fresh in your mind?

One tip that may sound obvious - make absolutely sure you clean the intake and head surfaces of every last trace of old gasket material, follow the gasket maker's directions using a real quality gasket - I would only use FelPro - nothing else, Callaway recommended FelPro too, and make sure you use RTV on the gasket where specified and a GENEROUS bead (at least 3/8") of quality RTV at the front and rear of the manifold where it meets the block. If you but the FelPro kit they supply RTV but there just isn't enough to seal the front and back. I bought a new (larger) tube and used plenty.

Otherwise you'll be doing that again like I did and swearing all the time you're doing it (like I was!)

Good thing is, once the manifold is out those busted bolts should be easy to drill out and re-tap.

Like you I couldn't believe how difficult this job was and how inaccessible the bolts were.

While you're at it check the oil pressure sender and switch at the rer of the block are'nt leaking My MAJOR oil leak was from a leaky sender and these parts are much more accessible when the manifold and distributor are out of the way. For insurance, while you have the chance and access, I'd get a new oil prssure sender (they are known to fail and when they do they can shut you down, after the embarassment of oil leaking onto your exhaust and smoking you out!) and remove the "hexagonal extensions" the sender and oil presure switch bolt onto, cleaning the threads and using teflon tape to seal the threads.

Access to these parts is very difficult with the manifold and distributor in place - there's no room for a spanner and you need a VERY deep and massive socket for removal.

Had to place this large reply to try and help someone - I can't get this horrendous job out of my mind!

And in rip off Britain the FelPro gasket sets were $110 each time (remember I did this twice!) I know in the US they're only 25-30 bux! It's also a good time not to have a Callaway!

All the best, Malc

04-22-04, 05:13 PM
If you follow my previous reply (i.e move the fuel rails for access) you shouldn't have to remove the vavle covers as I didn't have to.

I did however have to remove the valve covers to replace the gasket on the driver's side (didn't bother with the passenger side as it wasn't leaking and didn't want to tempt fate!)

I found the valve cover was restricted by a bolt in the AIR pump at the front and the wiper motor at back!

I'd leave the valve covers alone unless you have a leak - you don't need to remove them to remove the intake manifold.

These engine's can seriously p*ss you off, I get jealous when I see an old V8 engine with a carb!