Ferrari makes engine head with non-aligned bore holes

First I have heard of this. I do not claim to know how the factory would fix something like this but to me i would think its cheaper to cast a new head then to do all this. I know nowdays it would be. They even show factories throwing out heads that look ok but are not.

Again I am no expert but the sceptic in me would like to see others saythe same thing. What I have seen is after leaving the factory and still undr warranty fixes such as this.

 

Such a head would have gone straight in the scrap bin to be melted back down again.

It would cost more time and effort to set up the machinery to install blank guides and then machine them off centre to compensate than just pick up another set of bare heads and use them. Plus the oils seal on top of the guide would be off centre and not seal properly anyway.

Either its been machined in the past and they messed up and then had to make some off centre guides to compensate (unlikely) or the current people have messed up with their machinists when sorting the latest rebuild and hoping you pick up the tab.

Second hand engine or heads if your ones are now shot as a result, dont go ploughing that kind of money into the existing engine.

If you want to keep the engine number then use the second hand engine to rebuild your block.

 

The 355 is a more modern head than the 348. The 348 head is more like older over head valve heads. The valve alignment issue has nothing to do with how the factory did it. They did it right and now it needs to be done in a way that allows it to be straight again. It's not just Ferrari, so I guess this is the first F Chat guy to post it.

I am sure he will find the right solution and his engine will be great again.

 

Thanks for commenting. I've never heard of or come across the problem in my 50+ years of dicking with cars of all type. Guess I just associated with people who did it right. Not knowing the issue it is hard for me to visualize how this would happen if the seats are installed and ground correctly with the proper tools. No disrespect was intended, but if you don't question, you don't learn.

 

Wade, ethier I don't understand you or I don't understand the OP. The OP has stated the guides were original. You stated it was a common guide installation error but say above the factory did it correct.

I'm confused - perhaps you can elaborate?

 

If the guides weren't replaced and the old valves seated this is impossible.
Guides WERE done, incorrectly, get your car to someone who knows WTF they are doing.
Perhaps guides were reamed for "aftermarket" valves belonging to a different application??

 

Reaching back in my mind I recall that in older engines there used to be problems with pressed in valves seats becoming dislodged from the heads. This could misalign the seat/valve interface resulting in poor sealing if the seat didn't come lose completely. I recall FAF used a process they called Lock Relief where after the seat was pressed into the head, the head material was sort of rolled over the edge of the seat to keep in "locked" into the head correctly.

 

The guides were replaced. The guide installation is the issue here.

 

No disrespect was interpreted here. Just swapping information.

 

Thanks. Guide installation or post install machining? Seems like it would be very hard to press these in off center as the guide bores are fairly long.

 

Installation. Took me three sets of the exact same guide to figure out what was going wrong. I have it now and no more issues.

 

So Wade - you are fixing these exact heads for the OP?

So what was going on? Was the guide bore in the head scored causing some sort of off center condition?

 

Dave,

If Wade wants to keep it a secret.....it's his choice. Based on what he has written and that he "went through three sets of identical guides" logic would suggest that the bore is not the issue but perhaps the guides are indexed to the bore. That would explain the original poster issue and why it remains a "closely guarded secret".

 

I'm not asking for Wade to provide any secrets on fixing the issue - I'm asking about the root cause. I'm a mechanical engineer and own a contract engineering and manufacturing company and have lots of automotive experience as I worked for GM. Machining heads is pretty well understood.

 

Dave,

I'm simply suggesting that in the lack of a clear confirmation the possibility exists that the replacement guides are indexed. As to the why.....I doubt Wade would have gone through three sets of guides before he figured it out if he knew in advance. After all.....he does work at Ferrari of Atlanta.

I appreciate your knowledge and what you have accomplished but there are a lot of people on this forum who have similar backgrounds and accomplishments. We would all like to understand root causes regardless what our backgrounds and accomplishments are.

At the heart of this question is a head which was cast years ago which may have had and a geometry issue. GM would scrape those things. I'm not sure Ferrari would if they had a fix for the problem that would not stop/slow down production.

Hopefully, Wade or someone else who has successfully installed the guides provides the installation answer.

 

JD, I posted my credentials so you knew my background, not to boast about them. This is a discussion board and Wade decided to participate in the thread. I'm interested in what's going on as that is how I (we) learn.

But threads like this (and often with the written word) get very confusing with limited information. You yourself are curious too.

In my refinishing business, we keep some process and materials close to the vest - so I respect that. I am not asking Wade to share any trade secrets that he does not wish to share - I respect that.

I've also done plenty of business with FoA although I've not met Wade.

Regarding your post - I'm not sure if you know this (apologies if you do) but the guide bores are machined - they are not as cast. I posted this in the other thread (there is one in the 355 section too), guide bores and seat bores are typically done inline, with a combination tool - see attached image.

I highly doubt the guide bore and the seat bore are not concentric.

So, Wade says it was an installation problem. All I can speculate from that comment is that somehow the guides were pressed in the head crooked and I'm having trouble understanding how that can happen.
Image Unavailable, Please Login

 

I had a few more minutes to do some research and the following shed some light on the problem:

Ferrari 348 engine ? Speed Talk

Arguably, it makes sense that they originally machined the seat and the final pass at the guide at the same time which may have resulted in creating an off-center valve guide. It certainly would have been an easier fix than indexing guides or recasting the heads.

 

Dave,

While I don't own a 348 .....I am curious about this. Manufacturing tolerances used to be crap for a lot of the automotive industry which led to fixes like this.

So what if Ferrari final machined an off-center guide......if it didn't create a production problem....why worry?

Well, the answer is that when you have to repair it you better hope the new guides have more metal on them or you are using oversize stems. I'm not even sure how you would line it up on a repair since you would have to use the existing valve seat as the reference.

I agree that this is not about pressing the guides into place (its hard to screw that up).....it may be more about the final machine process.

 

Well, it's all speculation without having the heads in hand to inspect. If it was me, I'd remove all the guides and then use an indicator to check the concentricity of the guide bore to the seats (the inner diameter, not the seat area, as it's been cut). That would be my starting point.

I can also say when I worked at GM in the early 90's, the quality was amazing. The equipment was amazing.

 

Interesting info. Thanks.

 

My old timer machinist has run into this on the 12 cylinder Ferrari's from the 70's and early 80's a couple times and once on a set of 308 heads I brought him. All the guides were canted off angle by arc seconds, enough to cause seating issues with the seats. Figured the seats and guides were not machined at the same time or the fixturing was out when they did them. Who knows. Instead of trying to fix the guide bore he re-cut new seats to match.

I've been told more than a couple times by people that I consider to be reliable for information on the factory that stuff sent to the USA was less then optimal at times, in other words the good stuff stayed there.

 

Like the speed talk thread mentions its' a problem with finished concentric guides, my head guy will not install those. Since he's been 'round the block a few times he wants guides that he then has to bore align to the seat, you never know with Italian parts he says.

 

In many ways, it's more difficult to do it wrong than do it right......