Those of you who have worked on a 70s EFI Cad may have had a problem
with getting a replacement intake to throttle body gasket. These appear to be
made from a pretty durable Stainless Steel center, with a fiber gasket of the
same pattern on each side.
The fiber gasket seems to be easily removed, so I looked into getting some
that could be used with your existing SS center. Just got back enough for
3 cars, made in Thailand by Gaskets-To-Go. I think a little gasket spray could
attach them, though just letting the bolts keep them in place might be OK.
These will fit any 500 or 425 engine, and also 76-77 Seville using the same
Throttle Body. I have been asked about these many times in the past.
The 78-79 Seville and Eldo with 350 engine use a gasket which only differs
in smaller dia bore holes. I no doubt could get some of these made as well.
Cost should be under $40 a pair per TB, and postage.
This is not the gasket between halves of the large Throttle Body, smaller TB
is in one piece.
Bruce Roe CLC # 14630
Hi Bruce,
I know this is an old post, but I know you're still an active member on this forum. I have a question on what side the small hole in the TBI gasket should go on.
The mechanic who made my gaskets said that the hole is for the EGR port, but when I removed the old gasket the hole was on the opposite side. I'm thinking now whoever my Dad working on the car before may have installed the gasket upside down. When you have installed these did you install with the small hole over the EGR port?
huh, the only holes in my gaskets are for the 4
bolts and the 2 throttle bores. Check that SS
plate. I do not see how they can be reversed.
Bruce Roe
Here is a picture of the gasket you need . Part # 1619471 . The correct positioning is embossed on the metal section.
My stainless plate doesn't have any extra holes. As well there was no hole in the gasket. This is the best photo I have for now. That 3M Roloc was very helpful removing the old gasket material.
Just in case it maters when the car was built I found the date code on my distributor. My distributor was 8K5 which seems to mean the 5th week in November of 1978.
The second photo shows the pockets under the gasket. The rear, large pocket, was filled with an oil/gasoline mix and it was quite clean. I soaked it up with paper towels but didn't do anything to clean the surface you see. Bruce and I spoke and we thought possibly it was there from fumes condensing after vehicle off and somehow getting under the gasket because that entire area in the rear is sealed with no communication. The original stainless plate does have a slight "oil canning" I noticed.
The front pocket was completely dry any perfectly clean like the day the intake was made. I literally did nothing to that area and it looked as it does in the photo. That "extra" hole makes me wonder if it was there to eventually allow something to evaporate which ended up condensing in an intake pocket. That said I could see where the gasket was sealed and it's still hard to believe anything got in the area where I found the oil/gas mixture.
Scott
2022_08_20 5_09 PM Office Lens.jpgOriginal1979EFI EldoradoAluminumIntake.JPG
Quote from: Phil Weber on August 27, 2022, 07:39:22 AMHere is a picture of the gasket you need . Part # 1619471 . The correct positioning is embossed on the metal section.
. Hi Phil, that's how my gasket/shim looks like. Did yours come out of a 79 Eldorado? if so, any chance it's a Cal? My 79 is a Cal car.
Edit: I think I answered my own question. The part number you referenced, I cross-referenced in my part book and it's the same. It also doesn't mention anything about Cal having a different part number, so I'm assuming the gaskets were all the same.
Also, my shim has TOP RH Side embossed, so I think they helps answer my question about the small hole in the gasket. If I install with that TOP RH SIDE positioning that leaves the small hole over the EGR.
Hi Scott,
Does your stainless steel plate have the correct positioning embossed? Mine says TOP RH Side on one of the corner tab that's larger then then the rest. Now the question is: Does Top RH SIDE mean me looking at the manifold intake from the front of the car? Is the RH SIDE mean sitting in the driver seat like normally referenced when it comes to body part? I may be overthinking this, but I want to make sure I get this positioned the correct way.
Here's how my manifold looked under the gasket. I too had the oil/gas condensation that I had to soak out as well. If you go back up to look at the image of how the underside of the TBI looked when I first pulled it out, the small hole would have been over the large pocket. I thought maybe that's how oil/gas got inside, but that wouldn't help answer how oil/gas got inside yours.
It's strange that you or Bruce have seen gaskets with that small hole. I thought well maybe I had the wrong gasket until I read Phil's post with the correct part number and seen his gasket with the small hole.
Quote from: bcroe on August 26, 2022, 10:40:24 PMhuh, the only holes in my gaskets are for the 4
bolts and the 2 throttle bores. Check that SS
plate. I do not see how they can be reversed.
Bruce Roe
The SS plate says TOP RH SIDE on the larger tab of the 4 corners. I'm assuming that's me standing on the top of the car looking at the TBI. If this is the case, the small hole would be positioned over the EGR hole.
Jack,
My stainless plate has no additional ear and no additional markings. Mine can be correctly assembled upside-down or rotated 180 degrees and there would be zero difference.
It's interesting that both cars had oil/gas in that rear reservoir but I guess if it's fumes condensing it makes sense that it somehow works it's way there on more than one car.
My front, smaller, reservoir looked like it was sealed so perfectly that I likely let out 40+ year old air when I removed it.
The Left/Right in terms of a vehicle is always based on the driver seated position. So right top means that the tab is on the passenger side and up so you can read it.
BTW: I'm using a cast iron intake from an older Seville. Bruce just made me aware that the TB is normally larger. He sent me a sketch of the gasket so I could make thicker replacement plates but neither of us knew about that extra tab and extra hole until now. I wonder if the idea was that, if something gets in that cavity, it can eventually evaporate during subsequent operation. The idea of the thicker plate is because the entire surface of the smaller TB is no longer supported with the larger opening in the intake. There's around a 6mm overhang. It doesn't seem like it would be an issue. I did cut back my lower gasket though. If we had thought about it Bruce could have sent a small TB gasket for the top and a large on for the bottom.
Scott
Edit: I looked back at Jack's photo and realized the hole is in back over the reservoir which is filling and not the front.
Jack,
Is there and feature directly over that extra hole which makes it seem like precision location is required? I just added a diagonal line to your photo because it didn't appear to fall on the line between the corners and it does not seem to. I was thinking I could probably make one plate and simply indicate where the hole should be so people could add it. I wish we knew why it's there. Clearly both our cars were able to capture oil/gas in the cavity regardless of the hole but it seems like it must be related to what we're seeing.
Scott
Jacks TB Plate zDiagonal added.JPG
Jack,
Can you try to provide the location of that hole plus the dimensions indicated in the capture below?
Scott
CAD TB StainlessPlate 27AU2022.JPG
I can get those measurements when I get back to the car tomorrow.
If the TOP RH SIDE tab is positioned on the lower left corner (standing in front of the car looking over the engine) the small hole is over the large pocket of the manifold. I'll have to see how it aligns under the TBI to see if there's any logic there.
The way the old gasket was installed the TOP RH SIDE tan was positioned facing down on the upper right corner aligning the small tab over the small pocket opposite side of the EGR pocket. Again, would have to check how it aligns on the underside of the TBI.
"The way the old gasket was installed the TOP RH SIDE tan was positioned facing down on the upper right corner aligning the small tab over the small pocket opposite side of the EGR pocket. Again, would have to check how it aligns on the underside of the TBI."
Jack are you sure you have that correct? I placed the intake photo next to the plate. Both are oriented as they should be. That should place the extra hole over the large reservoir. Are you saying the gasket was placed differently than pictured below.
I would avoid referring to left/right in any way which contradicts the drivers left/right as that's how the left/right sides are defined on a vehicle. So that Top RH should be vehicle right and "Top" would seem to be so you can see the note.
BTW: It looks like Bruce's sketch does show the corner radius so I just need to know the tab extension and the hole location. Determining if the placement is critical is also important.
Scott
Intake and Plate side-by-side.JPG
My 76-81 Cad parts books only list the 1619471
gasket, used on the 78 and later 5.7L EFI Olds
with aluminum intake and smaller Throttle Body.
I presume it is the entire assembly, lately we
are just cleaning and reusing the SS plate.
There are half a dozen of the gasket assemblies
in my collection, for earlier larger and 78 up
smaller TB. Not one has either the extra hole
or the extra length positioning tab. Looks to
me like that hole just vents an unused cavity,
added at an undefined late time. Looks to me
like the vent is not needed, esp operationally.
Bruce Roe
Bruce,
I could add an etch for people who want to drill that hole. I'd rather not add a tab if it's not needed. I guess a set of instructions could tell where it goes without having a tab. I could add an etched note on the plate "RH Rear Top" near the hole in an area which is not critical. So eliminate the tab and just add a note on the actual part where a person could drill their own hole at their discretion. In addition that "extra" hole doesn't even look like the same diameter as the corner holes..
Doesn't in seem like there would be a technical service bulletin or some sort of history? It's crazy that they would have extended the plate unless they saw some real issue but it seems with or without the hole the same thing happens...rear reservoir traps oil/gas condensate. Cadillac would have needed a die change. I just need to add an extra models for cutting but I wanted to make only 2 blanks... We already have large TB and small TB. So unique PNs would go up to at least 3 assuming the large TB plate didn't as well have an extra hole version.
The only reason for a thicker plate is in the event a small TB user does what I did, use the larger TB intake, but I hate to neglect people with the large TB if they need a part. My plate did "oil can" some off the car and before I realized the Roloc would work so well I spent about 45 minutes trying to scrape gaskets.
Scott
Scott,
I didn't mean to confuse RH and LF. I took some new photos of the SS plate over the actual manifold to help clear up.
If the RH TOP SIDE is placed on the Front RH corner of the manifold, the the small hole goes over the large pocket in the rear. Under the TBI the small hole over a pocket where I circled in green in the image below.
Let's forget about how it was installed though because one would not have been able to read the TOP RH SIDE tab, so I think it's safe to assume that it was installed in correctly.
Now, I want to challenge you on the way left and right should be read because of the way the small hole lines up below the TBI. Look at the new photos I took and if you look closely you can see the words FIRING ORDER and the associated numbers. Given that I can read that standing in front of the engine, I'm going to assume that the TOP RH SIDE tab is placed on the upper rear "right" corner. That places the small hole over the EGR passage on the manifold and in a cavity under the TBI related to the Canister Purge vacuum port. Is there any logic there?
Based on Bruce's responses about never seeing a gasket with a small hole and the number of Cadillacs he's worked on, I feel like there is no logic and doesn't impact the operation of the vehicle and we're over thinking this.
Jack,
That is pretty incredible that it seems to line-up with that casting area you circled in red when the plate is not aligned with typical GM L/R convention.
GM was really regimented on L/R to the point on some parts, which were L/R specific, I recall they even had odd vs even PNs corresponding to the side. I don't recall though which odd/even was associated with which L/R though. Anyway that doesn't apply here. My point is though it would be extremely strange for GM to change L/R convention.
I don't know if it would make sense that they would add a port for EGR bleed to the canister. I mean the solution was to add it to the intake "charge" and CA cars even had a different orifice in the EGR gasket. I guess someone with a fresh set of eyes needs to comment.
Scott
Quote from: 79 EldoradoI wanted to make only 2 blanks...
Scott.
Scott, What are you making? I have never had
an issue re using the Stainless Steel plate, and
I have several if needed. So far there are a
quantity of the fiber gaskets here. Bruce Roe
Scott
There is only two gaskets listed in the parts book . I have both these gaskets brand new in there original GM packaging. # 1608403 which is the large throttle body and #1619471 which is the small throttle body . The large is just a plain gasket and the small has the extra hole . If you were able to buy the small gasket new today it would come with the extra hole. If you are making replacements you should only have to make two types . Just add the extra hole to your small pattern.
Phil
Phil/Bruce,
So first my car is the small TB on an aluminum intake. It has no extra hole. I bought a cast iron intake from Bruce because I've never had the greatest luck with other aluminum intakes and I could tell mine was starting to leak on the 1979 Eldorado. In the end the original aluminum intake is in very good shape but I decided to use the cast iron intake.
Bruce reproduced the gaskets years ago so I bought a set from him when I got the cast iron intake. Neither of us thought about my particular situation at the time and I was not aware that the cast iron intakes, even the ones for 5.7L Olds, were designed to match the larger bore TB's; not the small throttle blades which Cadillac went to with the aluminum version.
In my case the TB overhangs the large bore holes by around 5-6mm on the radius (I'm still using the small TB). I really don't think it is an issue but I'm thinking about making an 1/8" plate version of the stainless plate to have a little more thickness to mount to.
If I do I could make extras. Maybe I shouldn't bother making them thicker in general but there isn't really any reason for me to make a thin replacement for myself. Maybe there's no sense making any replacements because how often will anyone need one at all.
I'm also working on motor mounts for this car because aftermarket parts were incorrectly listed and as such not correct for 1979-80. I plan to use 1/8" for those so I was thinking the place I go to may run the TB plates without charging me their full set-up charge. My motor mounts haven't failed but they appear to have been exposed to a lot of oil/grease over the years so I wanted to have a solution available as I own two 1979 E-Bodies. This seemed like a good time to measure everything.
Phil,
You seem to have an amazing knowledge of some of the old parts. I recall you were able to identify some other PNs as well. Any idea if there's a technical service bulletin on the plates/gaskets? My car's distributor was date coded as 5th week in November 1978 so roughly half way through the model year and it has no "extra" hole.
Scott
Scott
Checked back through some older parts books and have found another gasket was used in 78-79 (# 1612942 ) . I can't find any pictures of it but I'm guessing this gasket didn't have the extra hole . This gasket was superseded to the gasket I have with the hole ( # 1619471 ) which was introduced around 1980 . There is a further supersession to # 3634798 which has been sold on Amazon (https://www.amazon.com/ACDelco-3634798-Gasket/dp/B0016HUQBE) and at Walmart. It still might be available from GM .
So here is where I'm at
76-77 large TB *NLA*
78-79 Small TB ( no hole ) *NLA* Supersedes to hole type
80 Small TB ( with Hole) Late number maybe still available
Phil,
What you wrote seems to make sense. That would explain why my car had no hole and why Bruce was not aware of the hole. His car is also a 1979. Jack's car is as well but his is a CA model and so maybe there's a caveat.
I'm shocked that there was even a listing on Amazon. It seems it's not currently available but still incredible. It also appears it's the entire "sandwich" gasket/plate/gasket.
I'm still curious about the history, the reasoning, and even if GM used the standard convention for TOP RH side. Jack's car had it in a different position and it does seem like a big coincidence that it lines-up with what seems to be specific geometry; but only if the correct position seems to conflict "Top RH Side".
Scott
Hey guys - I re-installed TBI today (along with new fuel injectors, but I'll close out that discussion in another post later) and ended up deciding to install the gasket positioned with the TOP RH SIDE tab on the Rear LH side of the manifold (small hole over the EGR passage). I'm going to take the car for a spin tomorrow to see if I feel or experience any issues.
I have seen ALuminum intake bores enlarged to
match the large Throttle Body on a 403, guess
it worked OK for him. I use the large TB with
large bore iron intake on a 403, no problem.
I guess to put the small TB on an iron intake,
someone like Scott needs to check the mating
components match up at the same positions on
the gasket. Failing that, an extra thick plate
could have the strength to maintain pressure
over a gap.
The extra hole was apparently introduced around
the end of the 70s EFI production, might be more
common on service replacements than on originals.
I would just omit the hole if not already
provided. If it is there, I'd install it as the
mfr recommended, assuming nothing like reversing
the EGR passage happened between small and large
TB. Bruce Roe
Just thought I follow up on my last post on how I ultimately positioned my gasket. I positioned the larger tab on the rear LH side of the manifold, but I realized now that that was wrong.
I came across an CA 80's Eldorado with the 350 EFI engine at a local junk yard was able to pull a few parts from the engine. I went directly to the TBI gasket and first think I noticed was that large tab was positioned in the front RH side of the manifold. That's when I knew I installed mine wrong. Also, noticed that there's no small hole on this one.
I thought this would be useful information for anyone reading this thread in the future. The picture below of the gasket is how it was positioned if I'm looking at the gasket from the front of the car.
Jack,
That's even crazier that they had a tab but no hole. Without the tab there's no error proofing needed. There's no up versus down and there's no left versus right. Since the bolts are a different spacing you cannot turn it 90 degrees (obvious wrong but...). Anyway certainly appreciate the update.
Did you also see my question about the alternator cover? J Ward posted but his is different than mine. If you still have one on your car or if the junkyard car has one, and you make it back, could you take a photo?
Thanks,
Scott
Edit: I forgot to ask but was the oil/gas in that cavity on the junkyard car?
Yes, for gaskets with no hole, then it doesn't matter how that large tab is positioned. Only for the ones that do that small hole like mine and over the EGR port is not the correct position!
I did see your post. Mine doesn't have the alternator cover and I didn't pay attention to the one I saw at the junk yard. I'll see if I can get back there this week.
I pulled the fuel injectors off that car to have them cleaned at some point and I tried to get the fuel rail off. That fuel inlet in the rear you had trouble removing was not budging with the tools that I had. It was so frustrating because it was the last item that I needed to remove to get that thing off.
Jack,
That line goes down to the the transmission area and it just goes to a rubber line. I could access the hose clamp from the rear of the driver side wheel. I removed it without removing or even turning the wheel. So I wouldn't try to take it off the rail itself while it's in the car. Instead just remove the hose clamp.
Another thing is there's something which looks like a carrot top. That's actually factory! It's pictured in the FSM. It's slipped over the fuel line in that lower area because there's are several things which could rub so they likely wanted to make certain nothing would rub through the fuel line. That carrot was so strange I took a photo. At first I thought it was a hack-job but then I realized those "fingers" were cut so perfectly it was likely factory.
Here's the carrot:
2022_09_13 5_50 PM Office Lens.jpg
I cut the original, not knowing it was just going into a rubber line, so when I made a replacement I used a -6AN tube nut and I put a male -6AN to hose barb in the replacement piece of EFI fuel line.
Here's my replacement line. I covered it with some wrap but it's almost too bad because I nailed the bends perfectly:
2022_09_10 12_44 PM Office Lens.jpg
Scott