Poor compression, high leak rate = bad valve guides?

Sintered steel went into mine. I'll report back on their longevity in 20 years... 😀

 

I believe this is what Dave Helms recommended for street cars in a thread a few years ago. Accordingly, that's what is in my heads too. In that same thread Dave stated all 360's use them as well and in his experience, there have never been any problems with them.

 

Subscribed

 

I understand Dave. For a race car, MB appears to be a better choice for obvious reasons. But a street car driven for pleasure is very different even if it has a race type engine. I think that was Helm's point and why he felt SS was a better choice for a street car. He believed the statistics for SS appeared to support an enhanced longevity and reliability. But he's just one man, albeit an expert one.

I'm the first to admit I have no insight or experience with this one way or the other. But from what I've read, there seems to be divided opinion about this among the experts. I'm also sure who installs them is just as important as what they are made of. In my case, they came with the car. Just before I bought it, it had a complete engine out along with new guides installed and a valve job. The previous owner's choice was OEM SS based partly on Helm's recommendation and his own research. I'm just glad it was all done and I didn't have to worry about it.

 

355 motors run forever when the cars are driven regularly. Its nonsense that these cars fall apart. I agree with dave rocks here, Carbon is the enemy, and people pass up perfectly excellent car because of ignorance thinking the compression numbers are the end all. True italian engineering in that 5VALVE motor. Hand built quality which makes them unique. If the compression goes low, I heard the restore additive (blue oil type) (use the 6 cylinder formula since the motor is only 3.5 L !! will help with any bottom end leakdown problems as well. Not sure if this will work for the valve guides ,maybe lucas stabilizer is better for that and some hot plugs to avoid any miss fires.

 

I spent a couple of years doing research on valve guides after almost 40 years of using manganese and phosphorous bronze guides in our 908/917/935/956/962 Porsche race cars.

The proprietary Hitachi formulated powder mixture valve guides are flat out just unbelievable......I have never seen anything in bronze that even comes close.

These PM guides are used in just about every modern aluminum endurance race engine and other modern race engines including drag race motors. Right up from where I live is the world record holding drag bike team that uses PM valve guides in their engines.

http://www.hitachi-chem.co.jp/english/report/054/54_sou2.pdf

In the early development of PM guides due to different formulations when a valve would bend the guide broke apart unlike bronze which stayed together, but I believe all those issues were resolved over the years with the different formulas. There are a lot of different formulas available today with big price differences between them.

BTW, the correct bronze guide will work on the 355 engine which is great for most owners. Some say the PM guide is overkill which may be so, but it is the superior guide and it will cost you a little more.

 

Bruce,
I couldn't agree with you more. The sintered guides represent amazing advances in metallurgy. The water characteristics are better than virtually every other material out there, with the caveat of perhaps reduced heat transfer characteristics. Costs and often challenges with machining preclude their use.

Unfortunately, some feel that these sintered guides are in the cast iron/generic steel category. That couldn't be further from the truth. Thanks for sharing your actual experiences.

 

Great work and posts Dave!

I did some metallurgy work on a variety of Ferrari valve guides that people sent to me, it's posted somewhere in the general Ferrari tech section I think. If anyone here has extra guides they'd like to donate to the cause, I can check the chemistry, microstructure and hardness and add to the chart. Send me a PM if you can send me one (destructive testing)

 

Metallurgy today is so advanced a pee brain knuckle scraper like myself could only rely on what my peers are using.

 

Nice article.

 

Good info in this thread and as a new 355 owner it seems like I need to drive the piss out of my car