I'm having my valve guides done on my '95 F355 Berlinetta, 45,000 miles. The shop called me today to go over some parts needed. When I asked him what valve guides he was going to use he said, bronze manganese. I told him I was not comfortable with the bronze manganese & wanted sintered steel. His response was they have had no issues when using the bronze manganese & this was news to him. I've read the recent threads on valve guides: http://www.ferrarichat.com/forum/348-355-sponsored-bradan/438978-valve-guides.html http://www.ferrarichat.com/forum/348-355-sponsored-bradan/473354-bronze-manganese-valve-guides.html I forwarded the 1997 FNA letter from Bill Story to the shop showing the sintered steel valve guides recommended. Am I misinformed & overreacting?
Don't own a 355 but if it were my car and after reading posts about 355 valve guides, I would want steel ones in there and not bronze. If the shop owner doesn't want to use steel and you're not comfortable using the bronze, then it's time to take it to a new shop.
Steel guides are best, but they are pricey for now. I am having them manufactured so they will ultimately cost about the same as others though. Probably won't be for 3-4 months though.
Put me on the list for a couple sets please What is the procedure to fit the valve? I understand you cant use a reamer on the steel.
I think Dave Helms or Brian are more qualified to comment on this, but what little experience I have with sintered steel guides is that they can be honed to fit no different than that of bronze guides, but a higher grit hone is used initially, followed by a finer grade, whereas bronze guides usually just need a single quick pass with a fine grade hone. That all being said, I don't believe sintered guides will get all that internally distorted as bronze guides do during installation anyway.
It has long been a matter of the quality of what is available. There are many bronze guides on the market from unmitigated trash to the best there is. Ferrari guides are famous too. If there becomes a good iron guide available it would be a great choice. Lots of these cars have had more than one set replaced but never in my experience were they quality parts, properly installed. It is not a job for the local machinist that does SBC Chevy's day in and out.
This is my dilemma. Do you trust a shop that has experience doing F355's. Be totally comfortable with the parts they are confident using or do I insist on the sintered steel valves guides mentioned in the 1997 FNA letter? I would not even ask Riflediver or Helms what parts they are using. I would just drop the car off & write the check. I will ask other shops what they are using. I blame Fchat for this train of thought btw. I guess I should stop questioning the experts & let them do what they do best.
Not most of them, no. Ignorance is bliss and I am not ignorant. That's why people like Dave and I (and the other good guys around) get cars shipped here from California, Canada and the East Coast. False economy not to but many never learn that. There are really good shops and then there are the rest. Take it to a really good one and do not micromanage them. I will tell you how important it is to get a great machine shop. My heads go in a big Pelican case and get shipped 1800 miles for the machine work. I have seen to many heads destroyed to do otherwise.
As a side note, you guys won't believe what the tooling cost is for these things. Sintered steel has two processes, basically a powdered cast, then a coining process to get the tolerances I'm after, which is little under half a thou. Waiting for the analysis to come back from IMR then we should be about ready to go. It will be well worth it.
A lot of variable involved in determining the characteristic of the finished part. What alloy, nickel, copper content, sintering temperature and pressure..... It's no different than manganese bronze for which there are, what, at least 1/2 dozen different standard compositions. "Sintered Steel" by itself has little meaning with regard to suitability for the application, and I would bet that Ferrari isn't going to tell us exactly what they are using. Who is going to be the guinea pig for these after market sintered steel guides?
Still pending results of the following tests: Density Chemical analysis Microstructure The early word is that slightly more chromium in the mix being recommended for this batch. I'll have around 150-200 sets made. Hardness for these things is that they're pretty darn hard on the spectrum of sintered steel, and much harder than any manganese bronze. I'll keep everyone posted.
It seems to be near 90% have some type of cluge work done to them! The most common I am seeing now is the guides just driven out, leaving a gauled hole. My experience is that even heated in an oven, removal gauls the hole if the guide is removed in as installed condition. The expansion rates of the bronze and the aluminum are too close to the same, thus leaving them too tight a fit, even hot. Those doing the install of the new guides knew what happened in the removal process.... then using blue loctite on the OD of the new guides being installed in an attempt to make them seal once again. Pride in workmanship, aint it grand! I spent a wheelbarrow full of money making cutters with the pilot being that of the std guide bore, and the cutter leaving a guide with .010" wall thickness. Done this way the old guide collapses in on itself and comes out with hand pressure on a special O/S arbor I made to fit the new enlarged ID, not with a hammer. That works nicely until you come up against one that was 'glued in'. Extra work and extra steps, some call it a waste of time, some dont FP, check your results against what Bruce Wright came up with, He put a lot of time in on this project prior to pulling the plug some years back. Make sure you also look at having some made with an O/S OD to fix the holes that have been gauled in the removal process.
Good meeting you too, sir. Update on the valve guides. Moving forward with the sintered steel guides. The shop said they had to place a few calls to find them. Also had to confirm the original machine shop pricing wasn't going to change do to the sintered steel guides. I'm sure it will be a little higher.
A few questions if you don't mind? 1) who supplied the sintered steel guides? 2) who manufactures the guides? 3) are you replacing valves as well? 4) If the answer to (3) is yes, then (a) would you kindly answer questions 1 and 2 with respect to the valves (b) what material are they?
They are using the parts numbers referenced in the FNA letter. I'll see if they will give up the info on their parts supplier's. He said he contacted Ricambi. Maybe Daniel can chime in. I was told only 1 set of valves needed to be replaced on 1 cylinder. I'll find out if they are using OEM or not.
It did at 1st. But like Rifledriver said you got to trust your machine shop if they have been doing F355's with no issues. What I did like is that the shop found the sintered steel guides I asked for. They probably shrugged it off & said, " Whatever makes the guy happy."
An old friend who was band here has been working on a 95 GTB he bought and is currently tearing down the engine. The car had bad compression and leak down. He and I had been discussing the significance of the bad leak down as an indication of bad guides. Anyway, he decided to check the valve stem/guide clearances and posted a youtube video of what he found. Here is a link. https://www.youtube.com/watch?v=2f77G_iRUjM For those who choose not to take a look the bottom line is that the stem/guide clearance was well with in spec. On his #4 cylinder which had 65% leakage the clearance was 0.0012". He then looked at the valves under a microscope and fond this. So it would certainly appear that this engine had bad leak down because of carbon deposits on the valves and seats while the guides were well below the wear limit. Image Unavailable, Please Login
