Hi,
In terms of doing a head, keep in mind that everything depends on the future
use of the motor. A regular street motor may actually need very little in
order to keep in functioning in very good shape. A good basic
head-refreshening can be done for as low as $170 at many machine shops. Of
course you can spend $1200 for a full-blown head too. From years of being a
Triumph mechanic here are two quick lists I've composed off the top of my
head (pun intended).
Obviously clean, disassemble and inspect everything. I recommend tanking
the head. Tanking is a bath in heated solvent to thorought clean in every
internal and external crannie. Replace any freeze plug and any oil galley
plugs. Then, here is a basic list.
1. Check valve seats and valves. Recut or regrind and then lap the valves.
Replace any if overly worn. Hardening the valve seat area or installing
hardened valve seats may be unnecessary even with unleaded gas. The old
steel used for heads was of good quality (in contrast to the general steel
used today).
2. Check the valve guides. This is occasionally where some oil can get into
the combustion chamber and some gasses can get out. Replace and hone any
that need it.
3. Check the plane of the head surface and deck if necessary.
4. Replace the valve springs if they have never been replaced or if they
were replaced by standard valve springs more than 7 years or 50,000 mi. ago.
5. Check the rocker shaft, rockers for wear and adjusting studs for wear.
Replace if overly worn.
If you are going to increase the performance or race the motor or make any
mods, the list grows and the price goes up. Here are additional options.
1. Install new valves with any of the following properties (increased
diameter, made of stainless steel or other higher-end material, reduced
diameter shafts). Harden the valve seat material or install hardened valve
seats.
1a. Port the head. Id est- grind the passageways that that more fual-and air
can travel to the head and can do so in a more streamlined way, hopefully
reducing the resistance to the flow. More fuel-air per second, more power
(also more heat).
2. Replace the valve guides with bronze-alloy based guides.
3. Deck the head and reduce it to whatever compression ratio you desire.
4. Replace the valve springs with higher performance springs.
5. Replace the rocker shaft and rockers with a higher ratio rocker shaft.
This will enable the valves to travel farther without having to have such
steep lobes on the camshaft.
Note for 4. and 5. Milling (decking) the head significantly or installing a
higher ratio rocker shaft often results in valve spring binding. There are
three solutions, all of which have slightly different ramifications. First,
shim the rocker shaft pedestals. Second, install shorter pushrods. Third,
cut slightly down into the head where the valves seat, thus seating them
lower.
Have fun. I hope that I haven't forgotten anything, as I'm a little sleepy.
Sincerely,
Dave Herbert
1969 TR6 and nothing else
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