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Rockerbox Other Stuff Gearbox Summary

Mac Rocker Box.

Rocker Box:

The rockerbox looked OK, just very dirty inside, but from the state of the pump I had to assume a lot of metal had been supplied to the rocker shafts. The spring cover bolts[1/4 BSW] had been replaced with 5/16 BSW, this meant there was barely any gasket surface in places and some of the 5/16 threads had gone. The bad threads had been replaced with nuts and bolts. So all the holes were welded up and all threads re-threaded 1/4 BSW, took a while but well worth it. I probably would have had a go sealing it all up with 5/16 bolts but I was going to have to re-machine the top as the rocker bores turned out to be a right state. I re-machined all the faces of the rocker covers.

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Figure 1. Tappet cover threads repaired, they have been welded up and these were Helicoiled.

The threaded holes were all welded up, it may sound a bit excessive but if you have to do a few you might as well do the lot, well the undamaged ones were left alone. There wasn't enough meat to Helicoil the damaged existing holes 5/16 BSW and having nuts and bolts holding the boxes together is very inconvenient . The only problem was I left one enlarged fixing not realising it had been enlarged and it's clear when i look at it it's wrong, annoys me whenever I see it. I surfaced the the faces of the rockerbox and was able to rebore the rocker shaft bores.

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figure 2 & 3. These show the upper rockerbox before and after wet beadblasting. Gasket face was scraped and the rocker bores were re-machined.

The picture above shows the top, before and after it had been 'vapor' blasted; poor mans vapor blasting, I put about 20cc of bead in a body schutz can of water. I was amazed how well it worked, it was quite quick[quicker than changing the media in the cabinet] and looks OK. The method needs a bit of development[large coolant pump and bead slurry?] but water and bead is obviously fairly easy to use together. The thing that was most amazing was how virtually no bead remained on the surface or in threads. As you can see I blasted the oil ways! When I went to re-assemble the head I cleaned the rockers and what do you know they had cracks radiating from the tappet adjusters! So add a pair of rockers to the parts list. The fasteners were all replaced, the bolts that hold the cover to the head all had badly distorted threads, the head threads looked sound though!

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Figure 4. Tappet end of one of the rockers, didn't fancy using the rockers with these cracks, so SH replacements were bought. rockerbox2
Figure 5. Was forced to blast all the rocker cover bit's.