newbie with mysterious Cadillac 429 crankcase backfire

dave brode

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Ted in Olympia said:
I sure would replace that fuel pump; I'm sure this is what caused your problem.

Do you have the extra parts you need to fix this?

TED


Ditto Ted. I would suspect fuel pump too, unless it was flooded a number of times, and allowed to sit so the gas could run past the ring into the oil.

Afaik, oil fumes would not ignite, but gas fumes would.
 

EZ

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I've used POR15 paints and gas tank sealer, and marine clean, and metal ready. In short I guess I love their products!!! Good stuff. You can't go wrong.
 

Cadillac Kid 1

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I'm going to guess that the backfire went through the carb, into the air cleaner, and back through the "oil separator" on the rocker Arm cover-to air cleaner connection.
Greg
 

cedmac

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As I said guys, yea, I think I flooded it because i didnt know the choke was completely open (out of adjustment, guess choke plate screws loosened after driving it two weeks, then it got colder here) :screwy:

so, gas / fumes, everywhere in-there

I still suspect the pcv didnt do it's 'checkvalve' job, preventing the backfire from getting to the crankcase
(correct ACDelco pcv has not come in yet)
 

cedmac

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There are no breather ports in the valve covers and no hose therefore to the aircleaner

This was only the 715th cadi produced in 66', very early

the crankcase ventilation goes from front of carb spacer immediately into pcv (horizontally) then to 'copper' tube with 180 deg bend to galley pan breather tube to galley pan and thus vents the crankcase.

never had a problem with oil leaks before or after the rebuild so I'm pretty sure the cventing system is doing it's job.

you just can't use the wrong pcv mounted horizontally (i'm guessing )
 

cedmac

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CORRECT ACDELCO PCV CAME IN FRIDAY
IT IS THE CORRECT NUMBER " CV 679 C "
BUT THEY HAVE CHANGED IT TO ONLY A NIPPLE ON THE CARB END
DESIGNED NOW TO FIT INTO A VALVE COVER GROMMET
opps caps on
anyway, my 66 is so early, it's an open breather system with no valve cover ports (attached directly to Rochester carb spacer)
so I have to make that diameter transition in a very short piece of tube somehow
or, I may cut an old pcv base off and use it as a transition fitting - then two pieces of rubber tube
 

Cadillac Kid 1

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Ced,
The valve goes in the line between the valley cover tube and the carburetor /bakelight spacer tube inlet.
You will find that the two sizes are different, and a different size (ID) hose fits on each end, going to the correct location the carb, big end towards the valley cover.
Greg
 

cedmac

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EZ - I'll post some pics of the pcv soon
***

I'm currently painting the intake, valve covers, oil galley cover, and other motor parts with POR15.
***

On another topic:

I'd like to ask a favor of anyone out there who may have a 66' available to look at something for me.

Under the A/C compressor - where Front Mount Bracket attaches to water crossover - there is a bolt hole below and between the bracket attaching bolt bosses
see pics
White arrow is bolt in question




Question is - What is attached here on your cars ?

When I reassembled this engine - I overlooked this bolt
I now notice it has the end of what appears to be a wire connector on it

Is one of the leads from the two wire connector which attaches to the A/C compressor a ground that may go here ?

Thanks to everyone in advance.

Ed
 

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EZ

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I have a '66 Cadillac with the 429 but mine is a CA. car and has A/C. My brackets look nothing like what I see in your pictures. However, your theory sounds like it may be right.
 

cedmac

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Sorry EZ,

Let me clarify
what your looking at is the water crossover (left head to right head & at center connects to water pump)
on my car but the A/C compressor and aluminum bracket have been removed
The water crossover casting that you see in the picture is what the front aluminum A/C bracket mounts to.
(the rear aluminum bracket for the ac mounts to the intake)

As far as I know this crossover casting is the same for all 429's
 

EZ

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Here's all the pics I have of that area. Maybe you can enlarge them. Looks to me like that bolt hole is empty on my engine. Can you tell?
 

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cedmac

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Wow, thanks EZ,
yes, I can see it perfect, hole is empty....
hummmm...

but hey, you didnt have to take the whole front of your car off just to take me a couple pics :D
 

EZ

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It didn't take but a couple hours to get the front clip off so I could snap those pics for you.
I used my air tools so it went really quickly. :devil:

Glad it helped.

"EZ"
 

cedmac

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Just have to figure out where the A/C connector wires to.
I know one lead goes to connector towrds firewall
The other lead I have seen gronded to the breather tube feul bowl nut on some cars ?
 

Cadillac Kid 1

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Ced,
The AC Clutch ground wire can be run to any good ground. What I do is use one of the compressor mounting bolts (to the intake manifold).
Greg
 

EZ

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Yeah, a ground is a ground is a ground. If the surface is painted, make sure to use a "star washer" to get a good "bite" into the metal. Or remove some of the paint so you get a good ground. A poor ground will cause intermittent problems that are hard to track down. :cursing: :banghead: :weeping: :curse2:
 

cedmac

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PCV PICS

Well guys,
heres the pcv pics

The one I got from OPGI who says it's correct for 66-76 is actually number CV 769 C
ACDelco site says this is for like 1999-2004

I located an old "actually correct" CV 679 C (yes the numbers are transposed - confused me at first: 679 vs 769)

Functionally they are probably the same but the newer one doesn't have a nipple at both ends !











Guess I'll try another source ! :banghead:

Ed
 

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