Hints and Tips - Rolls Royce 20/25 HP head bolt torque

From: Ed Albert
Sent: 24 August 1999
To: british-cars-pre-war
Subject: 1934 Rolls Royce 20/25 HP head bolt torque specs

I am trying to find documented specifications for the torque to be applied to the head bolts on my 1934 Rolls Royce 20/25 hp. Have head off now to regrind/replace valves, solve lack of compression in three cylinders. Looks like head gasket was improperly installed years ago, or failed because of improper torque on bolts.

Manuals I have on hand do not provide any detailed specifications - say things like, "use 3 foot bar" or "until tight." Bolts had from 20 to 30 pounds when removed. Because prior head gasket shows signs leakage, we suspect parts were too tight, or too loose, so want to replace head with proper torque on nuts and bolts. Have proper Whitworth tools, but sure would like to find source for proper documented torque strength to apply.

I am also looking for USA source (or GB) for full set of valves, as current set may be too burned to properly grind and seat. Can provide engine number if needed. Car was built in late 1934 and driven in GB until late 1960's. Has been in Hawaii and now North Carolina since then.

Would appreciate any help. Have also posted question on RROC site in USA.

Ed Albert
1934 RR GAF70
Charlotte, NC


From: Just Brits
Sent: 25 August 1999
To: Ed Albert
Subject: Re: 1934 Rolls Royce 20/25 HP head bolt torque specs

In a message dated 08/24/1999 Ed Albert writes:

<< I am trying to find documented specifications for the torque to be applied to the head bolts on my 1934 Rolls Royce 20/25 hp. Have head off now to regrind/replace valves, solve lack of compression in three cylinders. Looks like head gasket was improperly installed years ago, or failed because of improper torque on bolts. >>

Ed:

Try here:

http://www.flinthills.com/~ramsdale/EngZone/torque.htm

Cheers...........

Ed

Ed Kaler, Proprietor " Just Brits "


From: Peter Adams
Sent: 25 August 1999
To: british-cars-pre-war
Subject: Re: 1934 Rolls Royce 20/25 HP head bolt torque specs

Ed Albert@aol.com writes
>Manuals I have on hand do not provide any detailed specifications - say
>things like, "use 3 foot bar" or "until tight." Bolts had from 20 to 30
>pounds when removed. Because prior head gasket shows signs leakage, we
>suspect parts were too tight, or too loose, so want to replace head with
>proper torque on nuts and bolts. Have proper Whitworth tools, but sure would
>like to find source for proper documented torque strength to apply.

I asked a Rolls-Royce agency this very question back in the 1950s, when I owned a 20HP. All they would tell me was the size of the box spanner and the length of the tommy bar. So, shrugging my shoulders, I kept tightening the cylinder head nuts a little at a time, using the specified tool, until I could not turn them any more. It wasn't scientific - but it worked.

My newly acquired 1937 25/30 came with the detailed handbook, but that doesn't help either. It just emphasises the need to tighten the nuts progressively. It also says the gasket should be greased before the head is tightened, which surprised me a bit, as that practice is now frowned upon.

At a wild guess, I would say that the nut torque would definitely be no more than 40 psi.

--
Peter Adams,
Lincolnshire, England


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