1968 DeVille Convertible - Restoration

[klinebau]

I should have mentioned that you need to make sure that you are fully on the idle system.  You can check this by making sure that you have full control with the idle adjustment screws.  Turning them both in all the way should lean out the idle enough to make the engine stall or at least run very rough.  Turning them out almost all the way should make the idle extremely rich and you should also get a rough idle.  If you don't have control with the idle screws, then the carburetor is likely pulling in fuel from the boosters or transfer slot.

[DeVille68]

Hi everyone,

Just now I found the time to write up what has happened during the last few months. This post is about the modifications I did to the carburetor.

From the post above I concluded that I need to enlarge the idle restriction. When I removed a vacuum hose the idle speed increased. I then removed the large vacuum hose for the brake booster and the engine nearly stalled. The air fuel ratio also increased to over 17. So that was too much air. I then made small holes into a vacuum plug to create a restriction that I could leave on the vacuum nipple and adjust the throttle blades with the vacuum leak in place. From this I could determine how much additional air was needed.

First, I bought the above referenced book: How to Rebuild & Modify Quadrajet Carburetors https://cliffshighperformance.com/Quadrajet-rebuild-kits-and-quadrajet-parts/how-to-rebuild-and-modify-rochester-quadrajet-carburetors

The emphasis of this book is a bit different than the one I already had. The book Rochester Carburetors from Doug Roe is better at explaining all the circuits and how the Quadrajet works. The book from Cliff however is better at explaining how to modify the Quadrajet. In essence you need both of these books.


After reading the book I measured the restrictions of my (original) 69 Quadrajet: 
Idle down channel restriction = 0.040''
Idle top side bleed = 0.049''
Idle Bypass air = not equipped

The idle top side bleed is often miss identified. I have attached a picture 6216 where you can see the correct bleed identified with a drill bit. I also drilled out the idle channel restriction just above the needle. picture 6217 and 6218. You can see there are casting flashes and the they are not equal from side to side.

Then I went to the tool shop an bought every drill bit in 0.1mm increments they had.
I started with enlarging the idle down channel first to 0.051'' and the top side bleed to 0.055''
The idle quality improved a bit but not enough. After several incremental steps I stopped with the following settings:
Idle down channel restriction = 0.060''
Idle top side bleed = 0.060''

This was done with the old ignition system and vacuum advance on manifold vacuum and about 10° initial. The throttle blades could be closed almost completely.

However, I was not satisfied with the air fuel ratio during other driving conditions. WOT showed on the gauge a 10.5 air fuel ratio. Much too rich. Part throttle was also too rich at 13 to 13.5.

I then changed the primary jets from 70 to 69 (going smaller) and increased the primary rods from 43 to 42 (bigger). This should have leaned out the mixture at part throttle but keeping the mixture at WOT the same.

However, the result was pretty bad. I could barely get the car to idle. It was horrible. So I changed the jets and rods back but noticed that I had some dirt in the fuel bowl. After cleaning everything the idle was smooth again.
My conclusion: There must have been some dirt trapped inside the idle circuit preventing the idle to function correctly. 

So I changed the jets yet again and went on to a test drive. The part throttle was too lean now, at 15.5. WOT was still too rich.

After trying different secondary metering rods with no real difference in air fuel ratio I suspected the hangers to be wrong. After inspecting the hangers, I could not determine what the problem was, so I just bent the hanger slightly according to shop manual description. I bent the hanger down in two steps until I got a WOT of 12.5. Bending the hanger down prevents the rods from lifting too far out of the secondary jet, thus leaning out the mixture.

I then changed the ignition to 8° advance because of pinging and plugged the vacuum advance for now.
The idle quality suffered, so I decided to add the idle bypass channels. I used a gasket from the rebuild kit that I had bought about 4 years ago. I marked the spot for the passage and drilled a vertical hole. I then had to figure out a way how to drill a hole at an angle and to exit below the throttle blades. I asked my boss at my company, because he has a nice milling machine at home. You can see in the attached pictures, how we set up the base plate at an angle to drill the passages.
Picture 6242 shows the location of the bypass channel. Picture 6245 shows how I drilled the vertical passage. Picture 6247 shows the main body with the additional holes I made to connect the bypass passage to the main plate. The air horn (top place) must also be modified to allow filtered air to enter the bypass channel. Unfortunately, I don’t have a picture of that. Picture 6252 shows how we set up the drill and the angle to get the channel correctly aligned. Picture 6254 shows the milling machine. Picture 6261 shows the final product. We drilled the hole to 3.1mm and added a thread, then we used plugs with small holes in it to give a selection of “calibrated” restrictions. We made plugs with 1,5 up to 2,1mm holes in them.


Then I went for a test drive and tested the idle. I was finally able to close the throttle blades even more. But not yet enough. The mixture screw now had a real influence on the idle mixture. After about 5 to 6 times of removing the Quadrajet and switching out the restriction and finally drilling the idle bypass to 3.4mm I ended up with a idle mixture and throttle position with which I was satisfied with.

Now I am pretty happy so far. I have:
- WOT at 12.5 air fuel ratio
- Cruise on highway at 70 mph at about 14.7-15.0 air fuel ratio
- Cruise at 30 mph at about 14.9-15.2 air fuel ratio
- idle at about 13.5-14.0 air fuel ratio
- idle speed of about 450 to 500 rpm
- idle vacuum of about 16''

This is still with the old ignition but now with only 8° initial and no vacuum advance at all.

[DeVille68]

When stepping on the gas pedal I felt that the car would not accelerate as I would have thought it should. So while tuning the idle circuit it occurred to me that the acceleration was getting worse and worse. But this would not make any sense at all because the mixture was always good and never too lean or overly rich. So the engine should have made power. Especially at rpms above 3000 there was no power anymore... very strange.
I already started to wonder if I had installed the cam the wrong way...
Until I noticed that by removing, disassembling and installing the Quadrajet about 20 times I overtightened the mounting screws and bent the air horn! 
Check out picture 6387, where I have marked the contact area.
I then used my dremel tool to remove some of the aluminum casting around the bolt hole.
From then on I used less torque on the screws mounting the Quadrajet onto the manifold.

Then I noticed that the spring of the air valve was too tight, so I lessened the spring tension by turning the screw one half turn.

Those two changes gave a immediately responsive acceleration with power well into 4500rpm!
Before, the air valve was blocked by the bent casting and was not able to go fully open due to the too high spring pressure of the return spring.

In essence, make sure that also these "secondary" mechanisms of the Quadrajet are functioning as intended.

Best regards,
Nicolas

[DeVille68]

Next problem was a slight ticking noise of the valve train especially when gold but could also be heard when warm but to a lesser degree. I complained to my engine builder during the rebuild already because I noticed that the valve stem ends where not on the same level. So that means that something within the valve train must compensate for the difference in distance from the rocker arm tip to the valve stem. See the first picture attached below.

My rebuilder then told me that he had concentrated on machining the valve seat such that a nice combustion chamber resulted. He did not spend any though on valve train geometry.

So there are two solutions: Install caps on the valve stems or installing longer push rods. Because the reason for the ticking noise is that the hydraulic lifter is not in the middle of its stroke anymore and hits the upper end stop. This creates the ticking noise.
After buying and installing +0.030'' longer pushrods from cadcompany the noise is almost completely gone. (picture attached).
I should have bought the +0.035'' or +0.040'' but well..

Another reason why I needed longer pushrods was that I decked the block surface a bit, this also changed the geometry of the hydraulic lifter and rocker arms.

Best regards,
Nicolas

[Roger Zimmermann]

Interesting experimentation; you are now able to remove and install the carb with closed eyes!
Did you the test recently with wet roads?

[Highwayman68]

Why did you go with the +0.030''? Did you discuss this with the people at cadcompany and this is what they recommended or did they suggest going longer?

I have had the same issue for a long time and this would be such a simple fix. I just need to know what size to order.

[DeVille68]

Interesting experimentation; you are now able to remove and install the carb with closed eyes!
Did you the test recently with wet roads?

Yes, indeed!
No, luckily I finally found a garage for storing the car in the winter time. It's not great to work on, but better than to keep the car outside...

[DeVille68]

Why did you go with the +0.030''? Did you discuss this with the people at cadcompany and this is what they recommended or did they suggest going longer?

I have had the same issue for a long time and this would be such a simple fix. I just need to know what size to order.

Hi, yes I discussed this with my engine builder. After I explained it to him he agreed and understood the problem. I also talked to one of the guys at cad company, and they agreed that I could try the longer pushrods.

I did measure the lifter pre-load on the lifters during the build, but the measurement was nearly in spec. I missed the opportunity there to change out the pushrods from the start. If you search for "checking lifter preload" you will find a lot of papers describing this procedure. I have attached a picture showing the lifter preload I measured. This was done during building the engine. The photo shows 0.038'' of preload, however other valves measured just 0.030''. I had to change the head gasket, it is now thicker, which means the preload also decreased. Before going to the longer pushrods I measured on some valves as low as 0.020''. However, the measuring is quite difficult, I did not expect to get exact data.
So I figured that with using +0.030'' longer pushrods the preload should be about 0.050'' to 0.070''.
Total travel of my hydraulic plunger was about 0.150'', so there is still plenty of distance for the hydraulic lifter to work with. Ideally you want the plunger to be close to the middle of the stroke of the hydraulic lifter.

If I were you, I would try to measure the lifter pre-load and also check if the valve stems are at equal height. If not this could indicate that you have the same problem that I had.

Hope this explanation makes sense.
Best regards,
Nicolas


Here is an extract from a comp-cams paper:

Section II. Setting preload with NON-ADJUSTABLE ROCKER ARMS
A different procedure is required to set hydraulic lifter pre-load on engines with nonadjustable
rocker arms. First, install the pushrods and torque all rocker arm bolts down in the proper sequence
and torque specification. Rotate the engine by hand in the normal direction of engine rotation until
both the exhaust and intake valves have opened and closed completely. Allow a couple of minutes
for the lifters to bleed down.
Using the valve cover gasket surface on the head as a reference point, place a mark on the pushrod.
The smaller, more defined the mark, the more accurate the measurement. Be sure the reference
point you choose for the first mark is easily accessible and easy to duplicate. The pushrod will be
marked twice. It must be from the same reference point and angle for the measurement to be
accurate.
Loosen the rocker or rocker shaft bolts. Leave the rockers on the head so that they will support the
pushrods. Be sure the pushrods are standing free in the lifters and do not have any pre-load. Using
the same reference point, place a second mark on the pushrod. Make sure the angle and reference
point are the same as the first mark.
You now have two marks on the pushrod: one with the assembly bolted into place as the engine
will run and the second mark with the lifter unloaded. The distance between these two points will
represent the amount of lifter pre-load. If the pre-load is not within .030” to .040,” adjustment is
necessary. The simplest way to accomplish this is by using different length pushrods. When
measuring to find the correct length needed, be sure to include .030” pre-load that the lifter
requires. If the engine uses pedestal mount rockers, shims can be placed under the pedestal to
reduce the pre-load. The stands on shaft mounted rockers can also be shimmed in this manner.
Longer pushrods will be needed for insufficient pre-load.
In most cases, only one intake and one exhaust pushrod will need to be checked. If the valve stem
heights are not equal, then preload will have to be checked on each valve.

[Roger Zimmermann]

Interesting explanation how to check the pre-load. Obviously, the method to check it cannot be very precise, but sufficient.

[DeVille68]

Yes, probably the main purpose is to check that the preload is somewhere within specs.

Another work I did just recently was fixing the radiator. It leaked a small amount of coolant from around the transmission oil cooler fittings. A friend of mine luckily just recently bought a cooling system pressure tester with all the adapters (similar to this one here: https://www.aliexpress.com/item/32818575941.html). There was even one that fit the Cadillac radiator. Since I removed only the radiator and left the hoses in the car I had to find a way to cap of the hose fittings. I found a piece of scrap wood and attached a piece of self-adhesive insulation on one side. The insulation side towards the fitting and above a clamp to hold the wood with the insulation down. You can see it in the fotos below. It worked quite well, there was no leak trough these fittings.

The three pictures below show how we soldered the fittings. It took three attempts with pressure checks in between. Now it holds about 1.3 bar pressure.

Next up is painting the radiator. I will do this with all the brackets in one go.
Hope to get this done in the next weeks or so...

Best regards,
Nicolas

[DeVille68]

Hello

Last week I had to paint and install the radiator since I knew that I had to be able to drive the car today. So I spent the full weekend sanding, prepping and painting the radiator shields and the radiator itself. I again used POR 15 semi gloss black. I used a paint system called: Preval. It came out pretty nice.
Best part of all: the radiator is now absolutely tight. No water leaks anymore! :-)

[DeVille68]

Hello

Today, I had to take the car out of storage with a day - registration. The goal was to drive to a bodyshop to get my glass fixed the second time. The new glass was ready and I wanted to change the way the trim clips mounted also to give a better fit. The original clips are not available anymore, and if, they are insanely expensive. So I ordered some reproduction clips, which are close but not exact. Make sure you install them right, otherwise the chrome piece will sit too low and does not match the chrome windshield frame. I have included some pictures below showing the dimensions. I had about 5/8'' to 6/8'' of an inch in height from the flat frame where the windshield sits to where the clip ends. The windshield is held in place with strips of butyl. On the top edge we had to use a second butyl strip because the windshield itself and the frame were not perfectly flat. Plus my measurements showed that the glass plus one butyl strip was only just 3/8'' thick. So we added another strip to give a total thickness of about 5/8''. The windshield be high enough so that it pushes up on the chrome trim, this way the trim piece is under tension and is pulled down by the clip. The chrome trim and the windshield frame trim should be level where they meet. My chrome trim then dips a bit down to though the windshield. It looks good in my opinion. A massive improvement from the first attempt!

Also make absolutely sure that you water test your windshield before putting the chrome on! We used a water hose and really spray some water down. It took us three attempts to get the windshield to seal all the way around. We started with a bead so sealer (similar to Permatex) all the way around the side and the top. Just a small amount to seal where the butyl meets the frame and the windshield.

Only after I was really sure that the windshield is water tight I did put the chrome on. I bought new chrome screws for the lower trim piece, although I send 5 mails and called they were not able to send me the correct screw. However, it looks pretty similar and no one will notice but me..

So all in all I am extremely happy again. The windshield and chrome sit nice, I can now drive in rain again without having to fear to get wet!

My glass has a marking from PGW solex laminated.

Best regards,
Nicolas

[DeVille68]

rest of pictures

[DeVille68]

Another work I have done was to rebuild the master vacuum switch. Reason: my system has somehow developed a vacuum leak again, and I noticed that the blower would drop out after getting it turning in fog or ice mode. The vacuum switch indeed lost a bit of vacuum. So it was time to open it up and restore it. There is a spring system inside. It is quite evolved but not too bad to understand. The switch itself was indeed dirty inside. I painted the brackets and resealed the screws. Now it holds vacuum forever (ok, after 5 minutes I let go! :-) ).
See the pictures attached.

Since I had to take the car out in January I wanted the heating / blower to work again. Well, there must be some other vacuum leak still, because the blower would still drop out! 
Driving around in January with no heat at all.... ow well. I got a ton of stuff done today, so despite the cold it was a great day.

Best regards,
Nicolas

[DeVille68]

I bought drive-up ramps to be able to work underneath the car without a lift. Looks pretty funny with the car at an angle! Coming weekend I hope to get started on removing the complete driveshaft, axle, suspension and gas tank!
Stay tuned to more updates.
Best regards,
Nicolas

P.S: Let me know if you know someone that makes the correct cooling system decal. Because the reproduction you can buy is completely off. Check out the picture below. Color is wrong, logo is not sharp, font is sometimes wrong. Position is not correct.

[Highwayman68]

Another work I have done was to rebuild the master vacuum switch. Reason: my system has somehow developed a vacuum leak again, and I noticed that the blower would drop out after getting it turning in fog or ice mode. The vacuum switch indeed lost a bit of vacuum. So it was time to open it up and restore it. There is a spring system inside. It is quite evolved but not too bad to understand. The switch itself was indeed dirty inside. I painted the brackets and resealed the screws. Now it holds vacuum forever (ok, after 5 minutes I let go! :-) ).
See the pictures attached.

Since I had to take the car out in January I wanted the heating / blower to work again. Well, there must be some other vacuum leak still, because the blower would still drop out! 
Driving around in January with no heat at all.... ow well. I got a ton of stuff done today, so despite the cold it was a great day.

Best regards,
Nicolas

Thanks for the pictures, it helps to see what I will be getting into.

[Gene Beaird]

Yes, indeed!
No, luckily I finally found a garage for storing the car in the winter time. It's not great to work on, but better than to keep the car outside...

I’m now very wary of storing our cars under covers with the hood closed. Got rodents in the hood liner of two vehicles. In our Calais, they built a nest and my bait got to momma and daddy rodent. The stench from the dead pups required me to throw out the insulation pad. 

Now, everything is covered, but with hoods up.

[DeVille68]

I’m now very wary of storing our cars under covers with the hood closed. Got rodents in the hood liner of two vehicles. In our Calais, they built a nest and my bait got to momma and daddy rodent. The stench from the dead pups required me to throw out the insulation pad. 

Now, everything is covered, but with hoods up.

ohw, wow. Those animals are no problem here in Switzerland. The cats use my car cover to stretch themself and we have an animal called marten - he likes especially rubber hoses! (like gas or power steering hoses....). I was worried while the car was outside during the summer. 
But in the garage I have my car now, no animals should live inside. I stored my car for about three years out in a barn in a field. There was even no road to barn itself. I had to drive though the grass for about 200 yards. I got lucky, nothing bad happened to the car.

Best regards,
Nicolas

[Gene Beaird]

I’ve heard about martins. They can be bad, too. Good thing the cats can guard things. Hopefully no male cat deems it necessary to ‘make’ the covered car his.

The rodents can’t ’live’ in our shop. There’s nothing to eat, but it’s a relatively warm and dry place to set up house, raise the kids, and bring dinner home to every night. Keeping them out requires a multi-pronged attack, which includes keeping the hoods up to discourage hoodliner living.

[spolij]

I wish i had the time space and money to do this to my 66.
Your doing a great job.