456 valve questions & other known issues

it's a matter of playing the odds; not every 456M had the valve guides problem. Some of the cars got batches of soft guides, but not all. I rolled snake eyes and needed them at around 46,000 miles. Around $10K for new guides and custom ground valves from Manley blanks. Had a major done at the same time. I wouldn't do it preemptively. If you start to smoke, get it done at the next major.

 

IMO The simplest answer to the valve guide question is on what is a low milage car car oil consuptio is a starting point. These engines are like all late cars they should use oil. If you hadn't been adding oil between changes. Then there is a good indication the guides are fine.
From the reports I have read the late Ms dont seem to have an issue it was the 98 to 2000 that I have noted needed guides. My Feb 2000 456M has just had them replaced.

 

IMO The simplest answer to the valve guide question is on what is a low milage car car oil consuptio is a starting point. These engines are like all late cars they should use oil. If you hadn't been adding oil between changes. Then there is a good indication the guides are fine.
From the reports I have read the late Ms dont seem to have an issue it was the 98 to 2000 that I have noted needed guides. My Feb 2000 456M has just had them replaced.

 

Moe- This malady affected F355s until they started using sintered steel guides in 1998. It also affects 456s, 456Ms, and 550s. Like Allan said, only some random sets of the guides had softer than normal bronze alloys. We do not even have a statistical number for how many it affected. Again, like Allan said, no sense preemptively changing them out unless you are bored and have your own machine shop. The symptoms will be easy to recognize, rapidly increased oil consumption and likely fairly heavy smoke, especially on start. When you get those symptoms, a compression and leak-down check can help confirm the problem.

Although Ferrari knew of the issue and changed guides on the high production F355, they never did on the 456-550 V12s, probably because of low production. When the 575M came out, it too had sintered steel valve guides. Here is the bulletin from Ferrari telling shops to use sintered steel guides when they replace the guides on the 456M and 550.
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In my opinion it is a bit oversold. No question many, if not most will eventually need it but like so many things the stories of cars needing it creates a market that many aggressive selling shops are perfectly willing to take advantage of.

In the case of the 12's, since they are very understressed compared to the V8's with the same guides I'd wait until symptomatic and not do it preemptively. The data base is small enough and the range of usage types prevent a good guess on average mileage. I have seen a few with a lot of miles that were just fine.

 

^^^ Speaking as a new owner of a 456M, this would be useful to me.


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Moe- If it ever comes to changing the valve guides, so not hesitate to use good manganese bronze valve guides, much cheaper than factory sintered steel and at least as good.

Most of the 456/456M foibles are pretty well documented if you do a search.

 

Every time we go through the list, it's like reciting "The Twelve Days of Christmas:"

Valve guides a-smoking, HVAC a-bubbling, headliner a-sagging, alarm light a-shining, dash leather a-shrinking......

 

Windows not a-moving, accumulators not accumulating, shocks not absorbing. I think we could do 12 things. Headliners a-sagging, motor mounts a-bouncing, radiator not a-cooling.

Missed it by one. Actuators not actuating.

 

Don't worry too much and just drive those damned things.

 

Radiator,,,

 

Wiring harness

 

Wiper arms a' clunking

 

Oil chain a-ratling.and Fuel pumps a- buzzing how we doing Taz