F355 Market

Not only that, the sintered steel guides didn’t have a flange. If anything, design-wise, it seems those are more likely to “walk” out of spec than a guide that did have a flange.

 

FWIW, my Rosso 95 B w/ sintered steel valve guides put in at 18k mi (car now has 29k mi.) pulls pretty damn strong. Stock headers, stock Y-pipe, stock intake, straight pipes, X-OST muffler.

If I could find time, I would dyno it just to see what numbers it’s pulling before my other mods are installed.

 

Guides are pressed into a cylinder head casting with a press to a specific depth. It is a very strong interference fit. On many cars you heat the head and cool the guide as well. The only way a guide would work itself out of a head is through egregious installer error. I've never seen it happen (I'm sure it has, just in my 20+ years of wrenching I haven't seen it).

It's an interesting question. Sintered steel tends to be used in higher-performance applications, especially with high-temp combustion chambers (turbocharging, engines that rev to 8500) but I am sure the guide material had absolutely nothing to do with why some 355's needed guides at 15K or 20K miles (unless the guide material, I assume phosphorus-bronze or manganeze-bronze, was defective). Assuming quality material and correctly reamed bores, 355's would not need them replaced at such low mileage. Sure, over the long haul a sintered steel guide will last longer than bronze in an engine like a 355, and that may be why the factory changed materials, but again, we're talking about low-mileage failure here. That is QC at the factory.

 

A data point. My 97 had its guides done under warranty 2 years in at 5500 miles due to oil consumption. In my mind it has to be poor QC that early. Another data point shes now at 54K and strong as ever.

 

So under warranty, did they give you sintered steel?

 

Not to argue the point but again, you are saying that to correct a QC problem Ferrari changed the guide material from what they had used historically in their engines for years without problem to a new material that has poorer heat transfer and lubrication properties but higher surface hardness. Historically, Ferrari use Naval Bronze which is very soft compare manganese bronze. Manganese bronze guides are also a common replacement alternative for factory guides without the problem reoccurring. Also a difference between excessive oil consumption and poor valve sealing. Anyway, it's all history. For what every reason, the original bronze guides need to be replaced typically between 10k and 20k miles.

Found this on the web: Left OE (soft) bronze guide, center OE sintered steel, right Manganese bronze

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I know this isn't a valve guide thread, but I remember a TSB being issued by Chevrolet in the early to mid 90's addressing oil consumption concerns on some of their engines. They targeted the valve guides as their root cause to the problem, and the explanation was that the installation method at the factory was the cause and replacing the guides with new ones was the correction. Is it possible that the same thing occurred at Ferrari? To have engines burning oil at less than 20K miles and the cause being the valve guides, and other engines making it past 30K plus without using oil tells the tale. I would tend to think that if it was the material being used as the root cause, than wouldn't all of their engines burn oil and need new guides?

 

I changed my valve guides at 30k miles and had zero signs of excess oil consumption. Only due to compression and leak down numbers did I pull the heads. Mine were bronze guides on a 95 model, replaced with the factory sintered steel type used in the 360. Perhaps I could have went bronze but it was based on the techs recommendation.

 

Did the car pull harder after the guide job?

 

"Completely false. According to FNA technical director Adam Williams, only about 20% of all 95-model year 355’s experienced excessive valve guide wear and needed them replaced. And in fact, about half way through the 1995 model year the factory changed over to a different type of valve guide (the ones that they replaced the old ones with on the early cars)."


According to this statement, there a 3 valve guides. A bronze guide on early 95 cars. A bronze guide from late 95 to late 97. Sintered steel from late 97-99.

 

https://www.ferrarichat.com/forum/threads/95-f355-valve-guides-fact-vs-fiction.132778/

"Even with the newer valve guides post 95 production 355’s problems arose. A bad batch of valve guides found its way into several 97s and at least two 98 355s. Ferrari of Washington alone had two 97’s and one 98 355 that had valve guide issues discovered when each of those cars had higher than normal oil consumption."

You need to get to 98-99 to avoid them. I have read out here some 97's with guide issues and I recall a later one too out here.

 

Much harder.

 

I haven’t driven my early Nero 95 in awhile but my butt dyno is telling me my Rosso 95 is pulling 10-20 rwhp more. Identical setup on the Nero, except my Nero had a Capristo muffler, which should be making more hp than an X-OST muffler due to flow design differences.

 

I wouldn’t have otherwise known my car was down on power but my friends 98 had his guides done and all of a sudden he was gapping me.

Once I had my car done the last 2000 rpm the car really pulled a lot harder and I would leave his 98 if I kept in it.

 

Air going in is just as important air going out on our 355’s. The benefits of precision tuning will add up and be noticeable.

I have a buddy who also has a 95 B who had throttle tuning done by GTO Engineering in Los Angeles. I haven’t driven his car yet, but he said it made a world of a difference and has been nudging me to give GTO a visit. I probably will. I will probably polish the intake bodies (reported to give a 10 rwhp gain by another member) before I give them a visit.

 

I would need to see proof of that claim, before and after on the same dyno with no other changes. Butt dynos mean nothing. Were not talking about port and polish heads here, just the intakes... same volume of air it just what, moves faster? It may smooth the feel though and give the sense of more power or response. As far as 10 whp I am calling BS.

High flow filter, polish intakes, exhaust, x over pipe, cat deletes, everyone adds 30 hp, hell everyone would have 500 hp cars. But hey I could be wrong.. maybe polishing intakes somehow increases VE in ways I don't get.

 

Check out this thread when you have time. Atul was constantly dynoing his car to put a number on the changes.

https://www.ferrarichat.com/forum/threads/gruppe-m-air-intake-for-a-1995-ferrari-f355-spider-m2-7.317949/page-10

 

Polishing intakes does not make more power, in fact it could reduce power by promoting laminar airflow.

As for valve guides, they would have to be extraordinarily worn to affect horsepower, so worn the valve heads weren't seating correctly. Valve guides give valve stems a bore to move in, and -- this is key -- they carry heat away from valves, which sit in the combustion chamber. They don't contribute to or reduce horsepower.

 

I'm sorry if I sound like a jerk but this guy has no idea what he's talking about.

The velocity stacks on an engine, including a 355, are bolted on top of the throttle bodies and are already smooth plastic. The throttle bodies are bolted onto the intake ports of the cylinder heads. The velocity stacks for each bank are housed in an intake plenum. None of these surfaces should be polished. Yes, Motec will give you the ability to fine-tune AFR and igniting timing and you can get a little more power from that. You get zero power from polishing velocity stacks or the "intake chamber" which isn't even a real part of a car. Dear lord.

 

I've never pulled a F355 engine, but polishing usually occurs at the intake runner where it meets the head port. I agree polishing the throttle bodies wouldn't result in any improved performance, but want to make sure we are all talking about the same parts here. Any time I've hear port/polish used I assumed (maybe incorrectly) the person was referring to ported heads and port/polish of the intake port to align better with that head port to maximize airflow.

 

* Edit - Ultimate *stock* spec

- There, I fixed that for you

Otherwise we all know the "upgraded" '95 manual GTS/B wins

 

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He also made another statement a few posts after:

"The Motec was remapped yet again and the midrange improved significantly. The car was then re-dynoed with the new exhaust (two separate banks : 4-1-1, flatter but still very good sound, almost like two four-cyl engines). Importantly, the intakes of the velocity stacks were polished and smoothened to decrease air turbulence. My Tech said this was critical in improving power.

Result: a proper 370 BHP at the rear wheels measured on the rolling-road (a different dyno than the last time), which mapped to a shown 444 BHP at the crank, but after corrections for ambient temperature and pressure this number was remapped to 420 BHP at the crank. I ran the car again on Feb 24th at Abingdon as part of an all-day training session (Abingdon an airfield near Oxford, UK, where they have trackways and training sessions). The car felt significantly more powerful. I can't wait to try it again at Silverstone."


It's hard to put a number on what mod did what as he did a bunch at the same time. I'm just going off this - "Importantly, the intakes of the velocity stacks were polished and smoothened to decrease air turbulence. My Tech said this was critical in improving power."

I'm not claiming what is factual or not, but I'm not gonna doubt a man and his tech who took the time to dyno on multiple occasions and freely spread what he found (or what he think he found) for other Fchat members to access. Personally, getting the velocity stacks polished is not difficult and I have no problem giving it a go to see for myself. I'll take hp anywhere I can get it if it's not too much of a hassle.

 

Atul (and his tech) also did one pretty unique thing I haven't seen any others here do, so although Atul might not know what he's talking about, the tech or techs he is working with appears to be knowledgeable.

If you read through the thread, you'll find they analyzed the benefits of the GruppeM Intake on a 2.7 and found (through dynoing) power was found low to mid-range, but power was actually lost in the upper ranges. I believe his tech felt this was because there was no bell-shaped piping behind the GruppeM's K&N air filter. Prior to Atul (and his tech) no one had ever done that type of analysis on the GruppeM system. They later installed a bell-shaped pipe, re-dynoed, and recouped that lost power up the top. Might even have some gains, but I'll have to go back and read it all again.

Guess what will be going on my car? A GruppeM system w/ similar mods to the system thanks to Atul (and his tech) .

 

What do I win?


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