1969 DeVille Convertible Project

[sturner50502]

Now that you will be having it working again as it was designed, it is most important that you use the correct gaskets, in their correct order, otherwise you will end up with a distorted carby base, and leaking exhaust gas into the engine bay.

Bruce.

Hi Bruce,

You mentioned a heat proof gasket and the order of gaskets. Is the heat proof gasket included in the rebuild kit and is there something that distinguishes the heat proof gasket from others? Also, is the correct order (from manifold); gasket, stainless steel plate, and then carburetor?

[The Tassie Devil(le)]

Steve,

The heat-proof Gasket is virtually the same material as an Exhaust Gasket, as it had to contain the hot, acidic gases that come from burnt fuel.   Plus, is only used for a short number of years.

From recollection, and I haven't purchased a Gasket set for a VERY long time, the special Gasket is a separate item and ere is a pair from Cliffs High Performance  https://cliffshighperformance.com/Quadrajet-rebuild-kits-and-quadrajet-parts/quadrajet-stainless-steel-heat-shield-with-gasket
which has the Stainless steel Shim as well.

From what I remember, the Heat-proof one goes on first, then the Stainless Steel shim, then the normal base gasket.

Without the Stainless steel Shim, the upper sealing gasket will just get burnt away.

Bruce.

[DeVille68]

According to my 68 Shop Manual there is only the gasket and then the metal shim.
But I guess that an additional insulation won't hurt..

Best regards,
Nicolas

(correct, I had to ordering of the gasket wrong)

[MikeLawson]

Steve,

I just completed rebuilding the carburetor on my '67 and it is virtually the same as yours. The base gasket is particular to 1967-1969 Cadillacs only. The high temp.composition gasket you want is FELPRO 60010 which you can get from Rock Auto for a little over $3.00. The stainless steel heat shield/ gasket can be obtained from Ebay: https://www.ebay.com/itm/Stainless-Steel-Metal-Baffle-Plate-Rochester-Quadrajet-Carburetor-67-69-Cadillac/273376531825?hash=item3fa682d571:g:md4AAOSwcxhbhvMD

I purchased the Chevy version of the steel gasket by mistake and boy did I ever have problems, major vacuum leaks. I used a Felpro gasket below and above the steel heat shield and it works just fine.

[sturner50502]

Steve,

I just completed rebuilding the carburetor on my '67 and it is virtually the same as yours. The base gasket is particular to 1967-1969 Cadillacs only. The high temp.composition gasket you want is FELPRO 60010 which you can get from Rock Auto for a little over $3.00. The stainless steel heat shield/ gasket can be obtained from Ebay: https://www.ebay.com/itm/Stainless-Steel-Metal-Baffle-Plate-Rochester-Quadrajet-Carburetor-67-69-Cadillac/273376531825?hash=item3fa682d571:g:md4AAOSwcxhbhvMD

I purchased the Chevy version of the steel gasket by mistake and boy did I ever have problems, major vacuum leaks. I used a Felpro gasket below and above the steel heat shield and it works just fine.

Mike,

Can I reuse the old steel gasket or must I replace it?

[sturner50502]

According to my 68 Shop Manual there is only the metal shim and then the gasket.
But I guess that an additional insulation won't hurt..

Best regards,
Nicolas

Hi Nicolas,

Thanks. When I removed the carburetor, there was the gasket on the manifold, then the steel shield, and then the carburetor. There was no gasket between the carburetor and the steel shield, like your manual indicates. But it seems like there is conflicting information in the forum here.

[DeVille68]

Hi Nicolas,

Thanks. When I removed the carburetor, there was the gasket on the manifold, then the steel shield, and then the carburetor. There was no gasket between the carburetor and the steel shield, like your manual indicates. But it seems like there is conflicting information in the forum here.

Sorry, yes this is correct. First the gasket then the shim. However, I guess another gasket between shim and carburetor does not hurt. I however, removed the second gasket and have yet not discovered any problem.

Best regards,
Nicolas

[MikeLawson]

Steve,

If your steel gasket is in good condition you can probably reuse it. If it is kinked, pitted or otherwise damaged. replace it. The 1967 shop manual does show the composition gasket installed directly on the manifold followed by the steel gasket, no second gasket. I used another composition gasket on top of the steel one because I ended up reusing my original steel gasket. Because there were slight imperfections in both the steel gasket and carburetor base surfaces, I thought it would be wise to use the second gasket to eliminate the possibility of any vacuum leaks.

[The Tassie Devil(le)]

I take back all of what I said, but actually, only a little bit.

Yes, the correct factory method is to not have a paper gasket between the stainless steel shim and the Carby base, but as I have always been working with "old" and used stuff, I make it a point of including the extra gasket for a better seal between the carb and the shim.

A bit like using a Gasket between the Exhaust Manifolds and the Cylinder Heads.   When these engines come from the factory, there is no gasket, BUT, everything is perfectly machined, and the mating is also perfect.   Many miles later, not so perfect and sealing.

Bruce.

PS.  I have always re-used the Shim Gaskets, as if I wanted one, it would have to come from USA.   And more waiting, not to mention the expense.

[sturner50502]

I take back all of what I said, but actually, only a little bit.

Yes, the correct factory method is to not have a paper gasket between the stainless steel shim and the Carby base, but as I have always been working with "old" and used stuff, I make it a point of including the extra gasket for a better seal between the carb and the shim.

A bit like using a Gasket between the Exhaust Manifolds and the Cylinder Heads.   When these engines come from the factory, there is no gasket, BUT, everything is perfectly machined, and the mating is also perfect.   Many miles later, not so perfect and sealing.

Bruce.

PS.  I have always re-used the Shim Gaskets, as if I wanted one, it would have to come from USA.   And more waiting, not to mention the expense.

Bruce,

Thank you for your information. I think its important to follow up (for others who may be paying attention) and share what I learned. As Bruce says, after many miles, the carburetor and intake manifold can warp slightly. Placing a second gasket between the heat shield and carburetor will help to prevent the possibility of leaks, etc. So, I will be using two gaskets on my reinstall.

I also wanted to share a photo of the condition of my carburetor. The float bowl was filled with crud... to the point where I could barely see the primary jets. I was able to clean the carburetor using chem-dip and I blew out all the ports. After finding the carb in this condition, I realized why the engine would not stay running.

[The Tassie Devil(le)]

Steve,

That Carby internals looks like it has similar crud to what was in the carby on my boat engine, and it was rock hard to remove, but eventually got it cleaned out.   The fuel tank was a lot worse.   Had to cut that open and re-galvanise it.

The stuff comes from petrol going bad, as it sits for years without use.

Bruce.

[James Landi]

Steve,
Want to amplify on Bruce's point.  Your idle passages in your carburetor are hidden on the fuel bowls, and as he said, the fuel separation leaves a brown crud that blocks those very necessary passages.  You likely have already done so, but just in case you have not, unscrew the idle jets and shoot compressed air through those holes.   Liquid cleaning and even "GumOut" under pressure is not sufficient to break that crud loose, and if those passage remain closed, you'll experience a world of pain.    Happy day,
James

[sturner50502]

Steve,
Want to amplify on Bruce's point.  Your idle passages in your carburetor are hidden on the fuel bowls, and as he said, the fuel separation leaves a brown crud that blocks those very necessary passages.  You likely have already done so, but just in case you have not, unscrew the idle jets and shoot compressed air through those holes.   Liquid cleaning and even "GumOut" under pressure is not sufficient to break that crud loose, and if those passage remain closed, you'll experience a world of pain.    Happy day,
James

Thank you, James

[sturner50502]

Steve,
Want to amplify on Bruce's point.  Your idle passages in your carburetor are hidden on the fuel bowls, and as he said, the fuel separation leaves a brown crud that blocks those very necessary passages.  You likely have already done so, but just in case you have not, unscrew the idle jets and shoot compressed air through those holes.   Liquid cleaning and even "GumOut" under pressure is not sufficient to break that crud loose, and if those passage remain closed, you'll experience a world of pain.    Happy day,
James

Thank you, Bruce

[sturner50502]

Float Bowl Question

Hello Friends,

Can someone help me with a question about my carburetor rebuild. I want to know if the area that I circled in the photo requires a gasket ? When I disassembled it, I saw remnants of some material but I could not tell if it was debris or a gasket which was disintegrated. This item is located in the float bowl of the carburetor. I apologize that I don't know the proper names of these parts but the photos show the area with the tab inserted and also with the tab removed.

Also, can someone educate me regarding the purpose of the tab? But the main question is whether or not a gasket goes under the tab in the float bowl.

[DeVille68]

Hi,

This is the hot-idle compensator. On the top side of the quadrajet (air horn) you should see a small plunger with a spring. This is how it works: When the engine gets too hot and also the quadrajet gets too hot, too much fuel is pulled and the engine runs badly. To offset this there is a themo-spring with a tip and gasket blocking a air passage. If the temperature rises, then this thermo spring rises and frees up this air passage. The plunger and spring on the top side is just there to be able to manually force this thermo-spring to seat, that is to block the air passage. Because for tuning the idle you don't want to have extra air.

So you definitely need a gasket there otherwise you have additional air that is not properly metered with fuel.

Hope this helps.

Best regards,
Nicolas

[sturner50502]

Carburetor Rebuild Update

Thought I would update you all on the progress of my rebuild. I also learned that my smog pump was frozen so I purchased a new one. And since I removed the alternator (it was easier) to get to the smog pump. And since I was there... etc, etc. I decided to paint some of the brackets, pulleys, all the belts, removed the compressor and so on. Any way, I thought it would be fun to show photos of the  progress to this point.

The photos are 1) the condition of the engine the day I bought the car, 2) the engine today, 3) carburetor before rebuild, 4) carburetor after rebuild. 

[James Landi]

Steve,

You're making great progress, and it all is looking so very positive.  May I suggest that you check out the vacuum advance on your distributor.  This is a relatively simple task-- an 1/8 tube long enough for you to connect to the vacuum advance and reach your mouth.  Simply start the test by blowing through the tube,and if you can, the vacuum advance is ruptured and must be replaced.  If you can't, then suck on the tube, and with the rotor cap off, you should be able to see the stator plate move slightly-- then all is fine.  I have owned many 70's Cadillac, but not a '69, so the following recommendation is subject to all the skepticism it deserves to garner.   As GM was introducing smog controls, on a number of model years, there exists a vacuum check valve that negates the vacuum advance until the car gets to a predetermined speed.  I found that my 70 and two 72 Cadillacs were much more responsive to the accelerator and idled better if i circumvented the vacuum check valve entirely.   Something to consider--  we all look forward to the day that you get your engine running again. Happy day, and be of good cheer, James

[DeVille68]

nice! How did your carb rebuild turn out?

Best regards,
Nicolas

[sturner50502]

Steve,

You're making great progress, and it all is looking so very positive.  May I suggest that you check out the vacuum advance on your distributor.  This is a relatively simple task-- an 1/8 tube long enough for you to connect to the vacuum advance and reach your mouth.  Simply start the test by blowing through the tube,and if you can, the vacuum advance is ruptured and must be replaced.  If you can't, then suck on the tube, and with the rotor cap off, you should be able to see the stator plate move slightly-- then all is fine.  I have owned many 70's Cadillac, but not a '69, so the following recommendation is subject to all the skepticism it deserves to garner.   As GM was introducing smog controls, on a number of model years, there exists a vacuum check valve that negates the vacuum advance until the car gets to a predetermined speed.  I found that my 70 and two 72 Cadillacs were much more responsive to the accelerator and idled better if i circumvented the vacuum check valve entirely.   Something to consider--  we all look forward to the day that you get your engine running again. Happy day, and be of good cheer, James

Hi James,

Thanks for the tip. I will check it out!