Poor compression, high leak rate = bad valve guides?

Cut it out, Beavis. You're gonna hose your shorts.

 

From the recent pics of his culinary handiwork the man is a freakin' genius. I wish I could afford to move down the street from the guy, and magically show up for dinner pretty often. No shortage of Mad SkilZ on this forum!

 

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Forgot to add-- BTF out of it. That's what the cars used to be built for. Italian cars thrive on being run HARD, albeit with caring maintenance. At least that's my experience, after <cough> decades of Italian car ownership.

 

I'm 56 and still love that show LOL

 

I have every episode, including the music videos, and I still watch them on occasion. Gotta admit that the latest (season 9?) was even better than the originals-- what is better than B&B skewering Joisey Shore? "Jesus died for your tan". Bwahahaha!

///Mike
(going straight to hell)

 

No argument there.

 

Well aware of what the N54 is. But the problem dates back to the E30 cars with straight sixes. I can comment on anyone's Ferraris but mine which are kept about 1/2 way between max and min.

 

You're just a effing kid. Was getting laid before you were born. I hate being a senior citizen where ever I go.

 

Going back to a post from Fatbillybobt and hydraulic lifters.

1. When is a hydraulic lifter a bad one ?

2. When checking cam timing and clearance - How do you know it's fully expanded ?

3. Is there such a thing as a way to clean them ?

 

So what fuel additive do you guys recommend to keep the valve seats clean?

When dialing cams it is of no importance that the valve lifter is fully 'expanded'. The lifter is in contact with the cam lobe and that is where the timing is measured. Once the engine is running the oil pressure pumps up the lifter and the valve will follow. If its your 1st time dialing in a cam it can be confusing. Maybe in the case of 355s it should be called lifter lift instead of valve lift.

 

Yeah, I was thinking that earlier when someone suggested that the valve opening later and closing earlier was a change in timing. But its not, it's a change in duration (and lift if not pumped up) but the cam lobe center is still in the same spot so it's not a change in degrees of timing.

 

Great thread.

Here is a picture of rebuilt heads. I just got them back. To the point of the thread, this is my second set of heads that I have had rebuilt. Both of them from cars that were extremely carboned up. Though both actually had the guide failure issue on the exhaust sides one bank 1 #7 cylinder in both cases I believe that driving these cars regularly and occasionally pressing them if not tracking them from time to time, increase their reliability and ensure that they run better.
These two cars I purchased with roughly 40k on the clock. It appeared that the cars had not been driven hard ever. I drive my fcars very hard and they prove ultra reliable. I have bought 2 f cars that had been tracked extensively and they are also very strong and reliable.
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Exactly. In a good state of tune that is not experienced. Poor cam timing, poor injector operation, bad valve seals are all big suspects but significant carbon build up on these is just not seen when everything else is in good order.

 

True, big problem.

Also BMW is famous for running very high vacuum in the crankcase to maintain proper breathing required by their design. The vacuum system is prone to failure by a whole host of reasons and is equally famous for going undiagnosed. With a dry sump, big crankcase vacuum is assured by virtue of the scavenge pump eliminating crankcase pressure problems so much so that even bad valve seals are not as big an issue that they are in many other makes.

 

Neither would anyone else who knows what they are doing.

As far as running from high leak down, that depends. If from #2 or #7 the probability of it being a big future expense goes up substantially. Raw numbers are one thing. The circumstances of the numbers can change the picture a great deal.

 

You have stated this before with regard to oil being sucked down the valve stems and burning oil. But the vacuum in the intake runners would still have to be below (greater) than that in the crankcase otherwise the crankcase ventilation system would not work. What am I missing?

 

The closer the 2 pressures the less oil is moving. I didn't say it eliminated oil passage. You are missing that part where I said "not as big an issue".

 

106 octane race gas

 

Why?

 

Ferrari themselves knew there was an issue with the valve guides. There is no question that it's a big problem with the 355.

When you rebuilt the heads, did you or did you not replace the guides and seals.

 

That's interesting. I thought consensus and I believe what Ferrari recommended was sintered metal.

 

Don't get hung up on what the factory had to do 18-19 years ago to quickly solve an unexpected problem. The factory sintered steel guides are stronger than the factory bronze guides, but steel can have porosity issues and doesn't transfer heat as well as bronze does with aluminum cylinder heads. Not all bronze alloys are as weak as what the factory was doing in the early to mid 90s. Aftermarket manufacturers like SI, CHE and others have come up with bronze manganese alloys that transfer heat well with excellent durability at a reasonable cost. You'll see bronze manganese guides in race and street applications as a result. If you do a search on this subject on FCHAT, you'll find lots has been written. A wise man on here who knows these cars as well as anyone once said to find a good machine shop that knows Ferrari 5 valve heads very well and trust what they tell you and that the factory guides either in bronze or steel should be avoided. When I did mine, my machine shop pretty much said that they refuse to use anything but bronze manganese guides on Ferrari 5 valve heads given their 20 years of experience on this specific job.