Cylinder head rebuild and upgrade
| Job # 2287 (SCS) - 1968 Lamborghini Miura P400 Cylinder head rebuild and upgrade |
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I am pleased to report that your Miura P400 cylinder heads have now been repaired, machined and rebuilt. Interestingly we discovered that the cams are a custom Megacycle grind so the lash has been set per Megacycle specs. These heads incorporate our exclusive Team CJ valve and tappet assembly upgrade which saves 2.822 ounces per valve assembly. This upgrade also allows us to set perfect clearances between the lightweight tappets and the custom bronze guides.
We also dealt with a problem caused by the oil pressure relief valve piston being too loose in its bore (.006" clearance), causing it to rock and score the piston and sidewall. The solution was to machine a new piston and fit it to .0015" clearance. The new piston now glides freely within its bore. See last six images below.
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| Machine work has now been completed on both heads |
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| Water jackets have been welded and reshaped |
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| Assembling one of the heads on the bench |
Tappet to guide clearances all precisely
.001" |
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| The finished article |
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| Another set of Miura heads upgraded,
rebuilt and ready for installation |
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| Corey machined a new oil pressure relief
valve piston to replace the scored original |
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| Old piston had been loose in its bore and
did not slide smoothly |
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| Relief valve piston now glides smoothly |
Lots of progress with this Miura cylinder head repair and rebuild.
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| Custom TCJ valve guide (on the right) |
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| Honing new guides for perfect stem to
guide fit |
Machining out old valve seats |
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| Custom valve seats will be made to fit |
TCJ bronze tappet guides installed |
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| To be continued! |
The following sequence of photographs show how we dealt with a problem identified when we pressure tested the forward bank cylinder head. We knew the engine had a reported coolant leak in that cylinder head, and the leak turned out to be a very large hole halfway down one of the rearmost head stud passages.
Unfortunately it would have been impossible to weld the hole shut, so the only solution was to install a sleeve and create a new outer wall to the stud passage. We decided the best material for the sleeve was Manganese Bronze because its thermal expansion properties closely mirror those of aluminum. Corey opened up the damaged stud passage and machined a Manganese Bronze sleeve for a .002" (head heated, sleeve frozen) press fit. Once the sleeve was in place, he simply honed the sleeve to fit the 10mm head stud.
Thankfully the fix worked and the head passed subsequent pressure testing with flying colors!
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| Pressure testing the head revealed a
hole in one of the head stud passages |
This was the offending head stud hole |
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| The hole is clearly visible deep
inside the head stud tunnel |
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| Machining a rod of Manganese Bronze
to the requisite size |
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| Installing the sleeve |
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| All that remains is to hone the ID to
fit the 10mm head stud |
Back under water, this time holding
pressure! |
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| Job done, disaster averted! |
These P400 cylinder heads were removed from an engine that was reportedly recently rebuilt engine but experiencing running issues and leaking head gaskets. Unfortunately, extensive corrosion was found in several places on the deck surfaces of both heads, as well as beneath several valve seats. The heads were disassembled, the valve seats were removed and the deck surfaces were welded up prior to being delivered to us for repairs and full rebuild.
The following photographs show the heads 'as delivered', prior to any work being performed in the Team CJ engine shop.
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