Dropped Valve Head Repair
 

4G63 Dropped Valve Head Repair


The Subject head is a 1G 6 bolt head.
This head had extensive work done to it and would cost way more to replace than repair.

The head was loaded with SuperTech +1mm valves, and duel valve springs and Ti retainers.

How the head looked when I received it.

https://www.miataturbo.net/attachmen...ine=1340816317

A closer look at #4 cylinder, the one that dropped the valve.

https://www.miataturbo.net/attachmen...ine=1340816317

Yes it looks pretty beat. But it is fixable.

First thing to do is disassemble the head and get a parts list going.
At first look, I thought the 4 valves in the #4 cylinder would be the only ones needing replaced.
It turned out only 4 valves of the 16 could be used.
https://www.miataturbo.net/attachmen...ine=1340816317

The SuperTech duel springs and Ti retainers tested fine and will be used. About half of the Ti retainers had be rubbed on.
https://www.miataturbo.net/attachmen...ine=1340816317
At this time it was decided to install bronze guides, to replace the stock appearing cast iron guides.
https://www.miataturbo.net/attachmen...ine=1340816317

The bronze guides installed.
https://www.miataturbo.net/attachmen...ine=1340816317

Once the head was cleaned, a couple small cracks were found in #1 cylinder.
https://www.miataturbo.net/attachmen...ine=1340816317

The seats were cut out
https://www.miataturbo.net/attachmen...ine=1340816317

Then the head was pressure tested, using 35psi in the water jacket.
The head did not leak.
So work progressed by removing the 4 seats in #4 cylinder.

https://www.miataturbo.net/attachmen...ine=1340816317

New counter bores were cut, and oversized inserts were installed.
https://www.miataturbo.net/attachmen...ine=1340816317

Some grinding, polishing and blending was done to smooth out some of the damaged area in the combustion chamber.

Next was to mark the spots to be welded.
https://www.miataturbo.net/attachmen...ine=1340816317
What it looked like once back from the welder.
https://www.miataturbo.net/attachmen...ine=1340816317

Also to note is the spark plug inserts were installed in cylinders #1 and #4 before welding.

From this point a bit more blending was done to smooth out the welds and a full valve job was performed.

As the seats were cut,
https://www.miataturbo.net/attachmen...ine=1340816317

Valve tip height was checked and set to the proper specs.
https://www.miataturbo.net/attachmen...ine=1340816317

Spring installed height was measured and set to 1.550 @ 85lbs
https://www.miataturbo.net/attachmen...ine=1340816317

New 3g HLAs were installed, along with the followers and cams.
https://www.miataturbo.net/attachmen...ine=1340816317

Bottom of the head.
https://www.miataturbo.net/attachmen...ine=1340816317

Close up of #4 cylinder after repair.
https://www.miataturbo.net/attachmen...ine=1340816317

Head thickness after repair and rebuild. 5.159
Head build # BBB 744

congrats on slightly better pictures with the new camera!

^ lol

Well some of the pics were taken with the new camera, some with the old one and a few with my cell.

But I am trying and learning.

no, they are MUCH better. and very appreciated.