Michael Benno

Hi Stan, thanks for the very useful advice for myself and anyone else taking on this sort of work.

Piston Coating - you are absolutely correct the solvent can eat away the coating if left in too long. I discovered that with one of the pistons from the S4 motor. For the GTS, I was only soaking the bowls face up and scrubbing with nylon bissle brushes

I will bring the block into the machine shop and have the deck kissed and the cylinders inspected and lapped.

I plan to split the block and have the crank traps cleaned regardless. Should I polish the crank?

THanks again for the input!

Tom. M

If you do, make sure they have experience with the Sonnen Hone machine. Takes a special expert to know how to "freshen" the alusil bores.
Just as a side note, maybe get one of Greg's 5.9 cranks to run in the car and store the 5.4 stock one in the safety deposit box at the bank :-)

jcorenman

[Edit-- what Tom said ^^ ]

Personally, I would avoid the term "lapped" unless you are absolutely sure that the machine shop understands how to polish Alusil bores. But even then, why touch the bores? They look good, they feel good. And polishing generally follows machining to the next oversize because of wear, but that is not the case here. What are you hoping to accomplish?

Same for splitting the girdle, this is not a high-mileage engine and it didn't suffer any sort of major failure that would spread micro-shrapnel around the internals.
Yes, the cams lost some metal, you would have seen that in the filter. (What do the lifters look like? I suspect they show damage as well, but need replacing along with the cams).

But that is a separate issue and has nothing to do with oil consumption. The cam damage is likely due to a poor choice of oils sometime in the past in some foreign land.

And none of that appears to have scored the bores, nor likely got into the bearings. Do the rod bearings look OK? If the rod bearings are good, then the mains are likely also good. And the end-play is within spec, right? So, with a relatively low-miles engine, what does splitting the girdle accomplish?

I may not understand the goals, but my inclination would be to go through this engine with as light a touch as possible- drill pistons, replace cams and lifters, take minimal risk, reassemble and drive. We chose differently for our 240K-mile GT motor but that was a whole different situation.

Michael Benno

The machine shop I am using is Bearing Service Co. in Portland, OR. This is a four-generation-owned shop with two Sunnen machines, one of which is dedicated to aluminum blocks because of the pad-specific setup. @Zirconocene and I interviewed them for about 3 hours last fall, and we both have strong confidence in their capabilies. They are very familiar with Alusil, which is used in Porsche, Audi, Mercedes, and BMW motors. They showed me a few of the 944 motors they were working on. "Lapping" was a term that GB used to provide guidance on what to do with the block. What is done to block will depend on the inspection and measurements.

Good feedback @jcorenman , it aligns with @Kevin in Atlanta . I am getting opposing points of view on splitting the block from other experts so I need to consider this in my next course of action. I will. get some measurements on the main bearings and con rod bearings when I return next week

jcorenman

Michael, I missed Kevin's comments, apologies. My question on rod bearings was whether they looked OK, as an indication of what might have been pumped through the oiling system. Any streaks or unusual wear? Can you post photos?

The rod bearings are going to get replaced and measured in any case, so measurements of the old bearings are interesting but aren't part of that decision process. My thinking is that the condition of those bearings might provide some guidance on whether to split the girdle, but I am certainly no expert.

Cheers!

Michael Benno

The machine shop contacted me today with some bad news on the heads. He ran them through an initial cleaning to review a lot of heavy corrosion.


The shop indicated that welding metal in to repair is not a good option because of the amount of welding required, he is concerned about changing the metallurgy of the heads.

Options
1. The preferred option would be to find a set of 4R heads or cores. Does anyone have a set of heads they would be willing to sell me? I need 2.
2. Machine the heads down and get a set of Cometic gaskets (link) to offset the machining tolerances.
3. Expoxy fill? This seems crazy to me. Is this really a thing?

I need to provide the shop some guidance as soon as possible so it you know of a set of 4R heads let me know ASAP. (FYI, I reached out to Mark A and awaiting response).

Mrmerlin

I would not split the block or do anything with the crank other than,
oil the throws, and install new rod bearings.

NOTE Determine if the bores are round,
if they are,
wipe them with acetone,
then check your ring gaps .
once in spec,
oil the bores and install the pistons with new rings.
Use a straight edge to check the deck for flatness,
dont get carried away ,
just make sure its level.
YES I know minimal stuff here Mike.

For the heads I would contact Lorenzos fast flow machine shop in Langhorn PA.
they did a good bit of welding on my 88 GP white project and the engine runs great.
they would grind out the corrosion ,
put the heads into and oven,
then cook them to the specific temperature,
then weld them,
then cut them.
then clean them ,
and assemble them

NOTE my heads were much worse than yours.

Michael Benno

Any insight on the cost of all that repair work and when it was done so I can adjust for inflation?

FredR

Michael,

The corrosion damage is consistent with the state of the gaskets. I would classify that level of corrosion damage as "light" based on that photo. The attack is clearly of a pitting type and as I have posted many times now is a certain indicator of a crevice corrosion attack when such occurs in a gasketted joint and absolutely nothing to do with the type or make of coolant or whether the coolant was spent- as a matter of fact if the coolant was spent and had acidised this type of attack could not possibly take place irony of ironies!

With respect to recovery going for a replacement pair of heads with its owen set of potential provenance issues is not really the way to go but it is an alternative of course. That your workshop state that welding changes mechanical properties is perfectly correct - that they see this as an issue is "worrisome". Welding these alloys in this day and age is just a matter of quality control and an outfit with a proven track record of such is paramount. Before welding the corrosion damage needs to be ground out and the heads will need to be correctly prepared for welding. The corrosion process that I mapped out will invariably produce hydrogen and that will pass through and saturate aluminium alloy like a knife through butter. Welding in the presence of hydrogen is a big "no no". The folks doing the welding should know how to de-gas the heads and basically that is to stick them in an oven, raise the temperature to over 200C and hold for at least one hour [maybe longer?] if my fading memory is correct.

Welding however is not without its problems and the biggest one that cannot be avoided is "undercut". No idea if you are aware of such but no mattter how good the weld process and welder are as I am aware it cannot be avoided. This is a phenomena where a small depression is caused at the interface between the parent metal and the weld deposition and thus any machine finished surface needs to be decked to eliminate this indentation irrespective of whether the heads are bowed or whatever. Porsche define in the WSM what the minmum residual deck height is- whether there is any notional useable float due to their conservatism I have no idea.

Clearly you have been doing your homework given you talk about Cometic gaskets and use of epoxy based solutions [concepts I raised some time ago]. Cometic can make gaskets to custom thicknesses to replace machined out metal and that introduces the possibility of a recovery avoiding welding. However as with most things in life there are no "free lunches" and use of these gaskets requires [as per Cometic guidance] a finer surface finish [roughness] of the two joint surfaces but I cannot remember the numbers off hand. Then of course there is the question as to whether they "work". All i can say on that one is i have no personal experience of them but Carl used them in his 1000 BHP Bonneville monster motor and a couple of chaps in UK 928 circles have advised "no problems" using them for whatever that is worth. On the other hand one of our prominent former members condemmned them for whatever non specific reasons that came to mind.

With respect to using epoxy I raised that as a possible alternative. Such approach possibility was condemned by "experts" who seemingly had never heard of the product line involved yet alone practical experience of using such products [as I have]. In your case I see no real world purpose using such given you probably have folks capable of effecting the weld repair right on your door step whereas I do not. I suspect that the total repair of cost using the epoxy approach will be no cheaper than welding - the advantage for me would be not having to ship two cylinder heads halfway across the world and back again and more to the point, it is something i could potentially do myself with the assistance of my local mechanical workshop. The surfaces that need repair are not pressure retaining joint surfaces. In reality they only need isolating from the coolant and epoxy will give infinitely better protection against this specific type of corrosion that is likely to take place again sooner or later on the weld repaired surfaces. If you would like to know a bit more about this subject then visit the Belzona website.

Mrmerlin

The beadwork was 1200.00 to weld and cut and do a valve job they replaced a few ex valves and a few intakes
I would guess Fred is correct that you have a capable machine shop near your location that can fix your heads

Jon B.

I don't have firsthand experience, but knowing a few engine builders in the NC motorsports world, welding aluminum cylinder heads/blocks is just a fact of life nowadays. I'm not sure if the machine shop you contacted just isn't confident in their own abilities, or if they're just seeing "Porsche" and thinking massive upcharge. From what I have seen, once all the appropriate measures are taken to ensure weld viability and such, the resulting decked surface is as good as a fresh set of heads. Keeping in mind that you would likely need to send a used set of heads to the machine shop for work anyway, why not find a shop with a proven track record as Stan pointed out?

Michael Benno

Stan thanks for the insight on welding price. Fred, thank you for all the detailed information.

So many variables to consider in making my decision.

• Welding sounds like a very good option, but the concern is about finding someone with specific experience. Pricing seems to be about $750-$1000 for the pair. Kevin, Stand, and GB all have vendors with experience. The issue is the cost of shipping two heads around the county will be about $400 round trip for the closest option which is GB.
• Shaving the heads and using the Cometic gaskets seems like the most invasive option and there is some debate on the gaskets.
• The epoxy option seems very cost-effective. I am assuming the corrosion needs to be ground out beforehand. But again, a controversial solution.
• New heads are available and run $3K each!

Thanks again for all your input. I need to follow up with my machinist today. Still not sure what to say other than I need more time to figure this out. I am leaning towards the ship and weld option since that seems more tried and true.

Kiln_Red

Michael, just my $.02. Take it or leave it. If it were my car, there is no question that I would go the welding route. It's peace of mind for everyone in the community to have at least 3 credible RL'ers (all around the country) to have references for reputable shops that can adequately resurface our heads. From a cost efficiency perspective, sending your heads to SoCal sounds like the way to go in your case.

PorKen

Shiny new heads!

Only way to be sure

FredR

Michael,

The epoxy solution is not really an option at this stage rather it is a workable concept but given it has never been carried out it would require some development to be viable. I think it would be a bit cheaper to implement but we are not talking about a $5 bottle of Gumbo from Walmart.
The kind of procedure I visualize would involve milling out the vulnerable areas to a depth of 1mm or so to create a viable layer.

Another concept I came up with is to machine out the vulnerable areas, blank off the unused transfer ports and put a few holes in the gasket to allow coolant to refresh the newly created volume and the thus do its job.
Remember the gasket real estate outboard of the fire rings and inboard of the secondary sealing surfaces is little more than material that connects the fire rings to the outer part and keeps them aligned during installation.