Job # 2287 (SCS) - 1968 Lamborghini Miura P400
Cylinder head rebuild and upgrade
Back to Home

Update report - August 12, 2020

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.

Machine work has now been completed on
both heads

Water jackets have been welded and reshaped

Assembling one of the heads on the bench
Tappet to guide clearances all precisely .001"

The finished article

Another set of Miura heads upgraded, rebuilt and
ready for installation

Corey machined a new oil pressure relief valve piston
to replace the scored original

Old piston had been loose in its bore and did not
slide smoothly

Relief valve piston now glides smoothly

Update report - July 20, 2020

Lots of progress with this Miura cylinder head repair and rebuild.

Custom TCJ valve guide (on the right)

Honing new guides for perfect stem to guide fit
Machining out old valve seats

Custom valve seats will be made to fit
TCJ bronze tappet guides installed

To be continued!

Update report - July 15, 2020

Pressure testing the forward bank cylinder head (bubbles indicate a serious leak)

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!

Pressure testing the head revealed a hole in
one of the head stud passages
This was the offending head stud hole

The hole is clearly visible deep inside the
head stud tunnel

Machining a rod of Manganese Bronze to the
requisite size

Installing the sleeve

All that remains is to hone the ID to fit the 10mm
head stud
Back under water, this time holding pressure!

Job done, disaster averted!

Opening report - July 7, 2020

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.

Go to other CJ engine rebuilds