Tech Session: Mantis Autosport

OVER 200 CURRENT UCR CLUB MEMBERS, past members as well as PCA Test Drive members, those who may be “test driving” the club while they look to buy a Porsche, tuned in to Mantis Autosport’s tech social on the evening of Feb. 9. Mantis Autosport was excited to welcome everyone and discuss various technical topics, we look forward to more deeper dives in future sessions. Mantis has an excellent and long relationship with the club, both Jon Dunski and I are not only the owners of the business but we are also proud members, we’ve met many of you in-person, and we look forward to engaging more throughout the year and beyond.

I am often asked what my thoughts are on engine overhauls or rebuilds. Now, the topic of engine repairs can be a contentious one, and it often sits at the top of a slippery slope especially when it comes to Porsches.

Many factors weigh into the equation, with budget usually being at the forefront. There is no doubt that when it comes to engines, Porsche makes some expensive ones. From Fuhrmann four-cam engines selling for a quarter-million dollars to GT3 and turbo engines climbing up to and beyond $65,000. When it comes to engine damage or failures, some important decisions need to be made on replacement or repair. With all of the different variants available from inline four-cylinder to flat-six and V8 versions, clearly this conversation could head in many different directions and we will dig deeper into individual aspects in the future.

For most of us, simply buying a replacement engine is usually not an option, so we look at repair alternatives. Fortunately for many of the engine variants that Porsche offers, repairing them is a very logical and economical possibility, and, except for the a few catastrophic failures, repair is most often the most reasonable choice.

The first thing to take into consideration is the value of the vehicle. It would be slightly irrational to invest more than the value of the vehicle into the engine. But with the rising value of some models, the decision becomes somewhat similar to a home renovation, where the investment might actually increase the overall value. Then, of course, you have sentimental value or simply a passion project, in which case budget is hinged on the intended outcome. So here are some things to consider when thinking about overhauling or rebuilding an engine.

Would you like to repair what is wrong, or completely refresh the engine? It doesn’t make much sense to simply fix one or two oil leaks, if the previous history is older than 10 years. Often you end up repairing one thing only to have to repeat much of the labour the following year as the next seal or gasket fails. Certainly, when there is a simple repair that doesn’t require extensive labour to address, it makes sense to rectify and move on, but for the majority of issues if you are planning to go into the engine beyond the cylinder heads, you might as well go all in.

With the fact that Porsches have now been on the road since the 1950s, many of the air-cooled engines are 30 to 65 years old. That is a lot of time for things to have been previously repaired, altered, modified or plain-old jerry rigged. It’s not uncommon now to disassemble an engine only to find that the parts have been swapped out from what they originally were, or in some cases that only 10 percent is original. Hence the importance of vehicle history or a build sheet when undertaking certain projects. Costs and budgets can change very quickly with unexpected discoveries, and even a seemingly clean garage queen can turn into a nightmare. A great way to know what you are getting into is a preliminary health check. Simple tests such as a compression and leak-down can help prepare for possible bottom- or top-end damage or necessary repairs, helping to set the tone for an upcoming build.

Something we have adopted as a good baseline is performing a pre-project dyno pull. Not only does this help determine the current general state of an engine and its performance, it is also a great way to substantiate the value of a rebuild. Imagine being able to free up 30 percent more power or discover that the underwhelming drive you were experiencing was in fact due to an under-performing engine.

In days past when the cost of labour was less, it may have made sense to roll the dice on internal items such as bearings or chains and guides, unfortunately with the cost of modern operations and parts now it doesn’t seem like a good idea.

All Porsche horizontally opposed engines have a two-piece block design, which means that it requires a fair amount of work to get to the core of the engine such as the crankshaft and main bearings. This is a characteristic that has carried through from the very early engines designed under Ferry Porsche. But even the simpler design of the 944 still requires a substantial amount of work in the form of diligence when it comes to overhauling. So it stands to reason that once the decision has been made to go all the way to the crankshaft, vital components such as the main bearings and hardware should be replaced. Although the cost of replacing all of the bearings can add up quite quickly, it is still cheap insurance against having to go back in there. In days past when the cost of labour was less, it may have made sense to roll the dice on internal items such as bearings or chains and guides, unfortunately with the cost of modern operations and parts now it doesn’t seem like a good idea.

So many times I have been asked what I recommend when it comes to engine builds, but each situation is different. I personally feel that doing the same work twice is never a good idea, of course being respectful of individual budgets will always dictate the scope of work, but the old saying of pay now or pay later still holds true. Too many times when short cuts are taken, we end up having to duplicate labour or repairs a year or two down the road. It is always best to cover all the potential items and issues on the bottom end to minimize the potential for having to go all the way back into the engine later on. I would rather make concessions at the top end of the engine that can always be addressed at a later date with less labour, and ideally with the engine remaining in the vehicle.

A topic that doesn’t come up nearly as much as it should is appearance. As we take on rebuilds on older and older engines, aging becomes an issue. Now a job that 20 years ago might have been a simple clean and reseal, ends up becoming a restoration project. I’ve always had a difficult time performing a large repair on an engine that ends up looking just like it did before the $15,000 bill. Removing the years from parts takes more and more time and sometimes by several different means. Many of the soft materials such as aluminium don’t age well and require some kind of physical cleaning such as vapor honing or ultrasonic cleaning, while some of the fibre materials don’t hold up to cleaning at all and simply deteriorate and require replacement. Cosmetic treatments like painting and powder coating can help keep a fresh build looking better longer and protect against the elements but can also add significantly to the cost of a project. This is when having a clear idea of the intended outcome is important.

Sometimes it is all about function over form, when having a strong track engine capable of maintaining that grin for the entire session time after time is the number-one priority, but on the other hand it is also great to have that perfect colour-matched fan shroud for those car-show Sunday cruises.

Bottom line is, there are numerous options and things to consider when undertaking an engine project. The most important thing to outline in advance is the scope of the project you want to undertake, the three basic criteria for this are repair, rebuild, or restoration. Once you have decided which is best suited for your needs, then discuss in advance with the builder all the potential pitfalls that might come up, it is always best to go into any situation such as this with eyes wide open and with good communication. Then the only thing left is to wait for it to be completed and to be rewarded with the sound of that engine as it roars back to life — whether it be a four-, six- or eight-cylinder; inline flat or V. </>

Story and Photos by Dirk Dünschede, Mantis Autosport

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