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Can't get head on with engine in frame.

Posted: Thu Nov 21, 2019 12:14 pm
by Brian_Walker
Anyone seen this, just finished rebuilding the engine and fitted to my 1951 plunger frame. The bottom end is all bolted in but there is no room to get the head on (any-which way) its about 1/8 -1/4 too high and hits the top tube of the frame. I know I can unbolt the engine and lower it or undo the top engine mount to the frame and lever it up but I always thought it shouldn't need these manipulations. The engine although numbered TR117 (1952 VCH) was actually built in Sept 1951 (it has the twin lobe camshaft and the VHA style head and barrel.
20191121_211013.jpg
Not enough head space

Re: Can't get head on with engine in frame.

Posted: Thu Nov 21, 2019 2:53 pm
by adrie.degraaff
The VHA studs are shorter than 1954-1959, the nuths are differend aswell.
The exhaustpipe is differend also.

Re: Can't get head on with engine in frame.

Posted: Thu Nov 21, 2019 8:04 pm
by will_curry
Just measured an unmolested A7/927 barrel - the top of the studs
is 1 5/8" above the face into which they screw.

These motors are a tight fit at the best of times and not just the head, the
rocker boxes can be fun too.

Will.

Re: Can't get head on with engine in frame.

Posted: Fri Nov 22, 2019 12:52 am
by Brian_Walker
Thanks for the measurement, just checked mine and they are close to 1 3/4' with the studs bottomed out in the barrel. If they were 1 5/8" they would only pick up a few threads, I think these are the original heads and barrels together with studs. Last time I had the head off was in the 1970s when I holed the piston during a race and then I probably had the engine out for a rebuild.
Being an early post round barrel VCH things may not have been standardized at that point prior to the 1952 builds, looks like I will just drop the engine down a tad.

Re: Can't get head on with engine in frame.

Posted: Sat Nov 23, 2019 1:08 am
by nevhunter
If you want to be able to remove the head easily you will probably have to shorten the studs and have different extended nuts made or you could use bolts with special washers. Treat the threads carefully and have as much thread length in the alloy and reduce the stem diameters like the studs are if you do the bolt fix.. I do my rockerbox bolts the same way. My round base doesn't have the same problem as I think the studs are shorter. I may be able to compare the NUTS as I have a 54 head and barrel in a box. Nev

Re: Can't get head on with engine in frame.

Posted: Sat Nov 23, 2019 9:45 am
by Brian_Walker
Thanks Nev,
I hope the head doesn't need to come off again anytime soon although the valve guides are a little free. I may look into getting a set of later model studs and nuts rather than messing around with cutting threads and waisting down home made studs without knowing what tensile strength and metal characteristics are required for the job let alone turning down, drilling and hand tapping 5 head nuts.

Re: Can't get head on with engine in frame.

Posted: Sat Nov 23, 2019 1:48 pm
by will_curry
As far as my parts books are concerned the VHA/VCH, HS and all HT engines all use the same stud - 0302.
There are two types of sleeve nut, one somewhat longer than the other, the longer being just over
an inch overall. I've happily used either on motors with no ill-effects.

I dug out a head and set it on the barrel - the top of the stud comes up to 1/8" under the face on the
head where the flange on the sleeve nut bears.

I've never had any trouble getting heads on and off in road frames - it's a fiddle but not impossible.
W/NG frames on the other hand require another approach.

DSCF0579.JPG

Re: Can't get head on with engine in frame.

Posted: Mon Nov 25, 2019 7:02 am
by Brian_Walker
Thanks All,
I removed the front mounting bolts and dropped the engine down to fit the head, plenty of room to fit tappet covers still. Frame is a SA plunger not OR rigid that it was shipped with, could be slightly different.The 1952 parts list give a length of 2 5/16" but too late to check now.
Brian