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1959 Cadillac - 390 Valve Cover Torque Specs

Started by DeLoreanDMC81, August 07, 2020, 07:05:28 PM

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DeLoreanDMC81

Hey everyone!

I replaced the gaskets to my valve covers, now I’m re-installing them.

What is the proper torque specs for the bolts? Also, is there a proper order to go in when tightening them?

Thank you for the help,

James

35-709

#1
Maybe someone with a '59 manual will chime in, but the '65 shop manual calls for 25 INCH pounds, the '73 manual calls for 30 INCH pounds.  You are basically doing the same thing on these engines with the same type gaskets and 1/4-20 "screws", so those numbers should be good for your 390.  I like to use 40 INCH pounds but I am using the newer neoprene gaskets on my 472s.  I capitalize INCH to make sure the point is made that it is not foot pounds, if you don't have an "educated hand" use a torque wrench.  30 inch pounds isn't much which tells you that it is very easy to overtighten the valve cover screws which is done with great frequency and only serves to ruin the gasket and make any leaks worse.  There is no tightening sequence that I have seen but a normal criss-cross pattern from bottom to top starting in the middle and working your way out should serve you well.  Do this twice. 

After the car has been run and warmed up, re-torque the screws again once it has cooled back off.

Make sure your valve cover flanges are straight and the screw holes are nice and flat before assembling.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

David Greenburg

For ‘59-‘60, the spec is 35-40 INCH lbs. Always check the FSM; the spec changes from year sometimes even with same engine.  For example, in ‘61, it was reduced to 16-36 INCH lbs (although there’s a typo in the ‘61 FSM making it appear to be ft.-lbs.).
David Greenburg
'60 Eldorado Seville
'61 Fleetwood Sixty Special

fishnjim

Make sure the gasket is the proper thickness.   Some of the replacements are too thin.   I think they fixed the issue with the bolster interference in the 390 heads.   
Use the retainers, if equipped.   Easy to distort the sheet metal and over tighten without.   

76eldo

Snug plus a half turn. Too tight and you bend the flanges.
Use a cris cross pattern.
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

The Tassie Devil(le)

Don't forget that any Factory Torque Specs when compressing gaskets as a part of the retention is only when using original gasket material.

A Cork Gasket requires a different torque to that of a Neoprene Gasket, and as there are so many different gasket materials used in Rocker Covers, sometimes going by feel is the best.

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