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1970 cadillac deville exhaust manifold

Started by Wilregul8, August 19, 2021, 11:31:04 PM

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Wilregul8

Hi all,
I am replacing the exhaust manifold gaskets on a 1970 Cadillac deville 472 due to a clearly visible and audible leak. After doing some research i made sure to take my time and spray the bolts liberally with Pb blaster. My understanding is that they did not come from the factory with a gasket and the ones that are currently on seem to clearly be aftermarket. I consider myself lucky. I managed to loosen all the rusted  bolts and studs without breaking any. I will be replacing them with Victor Renz gaskets that cover each individual port. Obviously new bolts and studs as well. Can anyone advise me on the proper torque for each and what if any is the proper tightening sequence? Thank you all.

TJ Hopland

If you have a machine shop anywhere near you you will likely get better results if you can take it in and have them surface it.  They basically slap it on a belt sander so its not a long or expensive process.    Every one of these I have had with a leaking gasket leaked again fairly soon after replacing them.    Had em surfaced and put it back with no gaskets and no leaks.  If you really want to use gaskets you will have a better chance of them not burning out again with a fresh surfaced manifold but even there these things seem to be hard on gaskets.

Where did you find replacement bolts?   Exhaust manifold bolts can be tricky because they need to have some stretch in em because the manifold heats and cools differently than the block.   I made the mistake of trying grade 8 bolts one time and ended up with a cracked manifold and broken bolts.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

The Tassie Devil(le)

Torque for Exhaust Manifold Bolts is 35 ft lbs.

No real system for tightening up, but I always tighten them up by hand, with a light "feel" before torqueing to the correct figure.   Even have Torqued them in sequences of say, 15 Lbs first, then the final.

BUT, don't forget that this pressure is for factory manifolds, with no gasket, so with a gasket, one doesn't want to run the risk of "bending" the part, so slow and steady.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Highwayman68

Also run a tap into the head for each of the bolts, this will help the new bolts go in easier and you will get truer torqueing results.

I bought all of my head bolts from 500Cad.
1968 Fleetwood Purchased in 1981

76eldo

I need to pull the pass side manifold on my 70 Caribu.
Leaking badly.
I'm going to buy one of those inductive tools that heats up the bolts and supposedly breaks the rust loose and makes them easier to come out.
I'm scared to break off any of the bolts.
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

TJ Hopland

Those inductive tools don't really work for things you can't get the tool fully around.   The studs for the down pipe sure because you can likely get the tool around the nut but the bolts that go to the head there isn't much you can do with those.   

Even a oxy torch doesn't do much there because the manifold is is blocking the area you need to heat.  If you are pretty sure they are going to break the best thing to do is cut or grind the heads off then remove the manifold leaving studs.  You can then heat the head around the studs and clamp a vice grip to the stud and it will just spin out. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Cape Cod Fleetwood

You may find Kroil to be a better choice vs PB Blaster. Don't let the stink and smoke scare you when you
start the engine.

These are the manifold bolts
https://www.mcmaster.com/92316A633/
There are 2 kinds of cars in the world, Cadillac and everything else....

The Present -1970 Fleetwood Brougham

The Past -
1996 Deville Concours
1987 Sedan De Ville "Commonwealth Edition"
1981 Coupe De Ville (8-6-4)
1976 Sedan De Ville
1975 Sedan De Ville

The Daily Driver and work slave -
2008 GMC Acadia SLT *options/all