355 head rebuild pics

In another thread I said I would be posting pics of the step by step head rebuilding process. These heads were sent to me by another F-chatter for rebuild after getting poor leakdown numbers. We will be installing new guides, full set of new valves and seals. Along with complete port work of the heads and throttle bodies. For those interested, here we go........

The first pic is of the heads as I received them.

The next shows a couple of exhaust valves, note the discoloration up the stem, and the black streaks going from the stem area out to the edge of the valve where it wasn't seating properly.
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This pic shows the head with guides removed. Note the wide shiny seat area on the center intake valve seats. These heads had extreme wear on the intake guides as well as the exhaust guides. The wide seat area is from the valves moving around from the loose guides. Also note the intake and exhaust seats on the far left, the seat area is burnt black and brown from not sealing.
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In this instance, the owner wanted new valves.
Other times the wear/scuffing on the stem requires new valves or the seat area of the valve can be burnt enough (and sometimes burnt all the way through) that only excess grinding of the valve would make it possible to re-use. Then you get into having to grind the valve tip excessively to keep the valve height in spec, etc....

 

The 1st pic is the cleaned head, removed valve guides and the roughed-in port work. During this time I also radius and clean up all oil return holes.

The next pic is the final ported intake runners. Note the re-shaped port entrance. Once the bowl area porting is done, the guides are re-installed.
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Here is a look at the old guide vs the new Ricambi manganese bronze guide. The old guide looks copper colored, maybe why they are so soft and fail??

Next is the newly installed guides in the ported heads, guides are then honed to size. HONED to size-- not reamed. Reaming the guides produces a rough finish with lots of torn material which is the polished out by the moving valve resulting in excess clearance right off the bat. The crosshatch pattern of a honed guide does the same thing that crosshatching does in a cylinder- retains a small amount of oil for lubrication.

The seat tooling uses multi-angle cutters to radius the seat angles into the port and chamber increasing flow. (ALOT better than the single seat angle on the stock exhaust seats.

Once all valve depths are measured and set to proper specs and equalized, the valves are numbered and lapped into their respective seats to verify seal.
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Port work is a combination of flow bench testing and experience.
I've been porting heads now for 20 years. The stock Ferrari port shape is pretty good, but can be improved. A previous set I ported increased 14.5 cfm on the intake side. I expect these to improve more over their stock configuration, as these are late '95 heads and are very different than the early '95 heads I ported before. I didn't cc the intake runners, but just from appearance, these heads were much smaller than the others. And upon starting the port work, calipers verified my suspicions. The throttle bodies will also be matched to the heads and new port entrance shape, then flowed once again.

 

One look at the new guide vs the factory guide and you can tell for sure that there is at least SOME difference in composition due to the color difference. Also when the factory guide is machined, the material comes off in a spiral, telling me its soft material, the new guides when machined cut into little chips and you can tell they are definately harder than stock. Put an already soft part into a port with EGT's of 1200 degrees and we can see why the stock ones fail. To me, any steel on steel contact unless fed with a constant supply of fresh oil, is a no-no. Mang-bronze is also somewhat self-lubricating. Put a steel guide and mang-bronze guide under the same stress with no lubrication, the steel will seize, the bronze won't. (or at least will survive longer)
Not to mention every race head I know of comes with mang-bronze guides.

Not sure why someone would think that lapped valves would not seat at temp. I only do it to verify the mating surfaces of the valve and seat. When I leakdown an engine, it is brought up to temp, then leaked down ( the only way to do it in my opinion) and I've never seen a problem. After only a short amount of time running, the lightly etched seat and valve (from lapping) appear shiny anyway, just like an un-lapped valve and seat. I actual cutters I use are more than 3 angles, and the exhaust is a full radius.