Engine rebuild question

Hello, This will be the first time posting/ asking on this forum although I have been reading postings since around 2015 when I got my 2003- 996 C4S. My car now has about 130K miles and at this time the engine is busted. Not the usual IMS issue (changed to the IMS Solution) or the bore scoring as it was check a couple of times and they look fine. It is an issue with the valve seat on the exhaust cylinder 1 (giving engine check light for misfiring on cylinder 1) and checked thoroughly by my Indy shop to find out that it was the valve seat that is coming loose on the exhaust on cylinder 1 (makes ticking sound, that is why the bores were checked for bore scoring). My shop said that they certainly can do the top end rebuild to fix the valve seat, but just doing that and not doing the bottom end rebuild is not a cost effective fix as at 130K the bottom end is getting close for a rebuild. It is certainly nice if I have the money to get the Raby Flat 6 Innovation engine, but it is a lot of money. Any opinion or suggestion of what to do? I really plan to keep the car as long as I am still healthy to drive it (I am in my mid 60s) Is it really after 130K the bottom end is close to a rebuild time? Thanks

You should be able to have the engine dropped, the valve seat replaced, and everything buttoned together for under 5 grand. That's around 20% of the cost of a full rebuild. If your bores are still good and you have an IMSB solution in place, this is what I'd do. You may get another 5 years out of that engine, or even sell the car before a rebuild is due.

I have the same plan for my targa -- drive it until I can't. I have a FSI Stage 2 motor and can't recommend it highly enough; it's not just a rebuild, it's an upgrade that transforms the car. However as you say it is pricey. Porsche still offers short blocks, which would save you a good bit of money vs. FSI and would put you back to zero in terms of the bottom end. There is also Hartech/Slakker which is still kind of a startup here in the US but seems to be heading in a good direction. Also not cheap. Whichever way you go be sure to budget a few $K for "while you're in there".

While I understand the shop's desire to make the job into a full engine rebuild, I certainly would not go down that path just for this repair. It's $5K versus $25K. Fix that one head, move on and save up for the next time you need something.

As a fellow owner of a 2003 C4S, I wouldn�t assume that there�s an urgency to fully rebuild the engine just because it�s at 130K. Save your money. If you have no signs of bore scoring and already have the IMS Solution, then you could still very likely double the current mileage with proper maintenance. Mines still very healthy at 242K+.

It all depends on what they find when they start taking apart the engine. If most everything is in good shape, I agree, fix the head and get on with life. If certain parts look worn, then you might want to make a decision then and there how much to spend and what to address. It�s possible that the bearings and all that are worn out, but it�s also possible they look great.

Thanks for all the advices and opinions

I guess I will be the voice of opposition to above. If you plan on keeping the car, as you have stated, then a rebuild might be a good consideration. The bores will eventually score and / or go out of round. The bottom end will have seen some low oil pressures in turns as all of these engine do. The other bank cylinder head has the same miles as the one with the dropped valve seat so you could surmise a future failure. I rebuilt my engine at 94k based on an increase in glitter seen during oil changes. Bores were not scored however the piston coatings were flaking off which will lead to score. Rod bearings were wearing through the babbit, as suspected. AOS was shot. IMS was fine. my goal was to build an engine that would last a long time, be fun and reliable. I built a 4liter using Nickies, IMS Solution, K1 forged rods, Hoffman rebuilt heads. It was pricey but it runs so well now. And I don�t worry it�s going to have an issue while in the middle of Mojave. Just another viewpoint. Good luck no matter what you decide. These are great cars and glad you want to keep it on the road.

I had my engine rebuilt at 85k miles. It was fine, and could have waited. But it is my forever car and I wanted it fresh for retirement that I had planned for this year. Now I’m pushing retirement since I enjoy my work. As soon as that changes I’ll retire. My rebuild was not cheap, but I’m extremely happy with the results. I would just fix the head, unless you have the funds for a proper full rebuild.

If you read Len Hoffman's blogs/site he describes the problem areas on the 3.6 heads. Valve seats dropping are a problem for many 3.6 heads... Len talks about how he gets heads in that haven't dropped seats (yet) and once in his ultra sonic parts cleaner tank, seats just fall out. A buddy recently got his 3.6 heads back from L Hoffman the m96 head expert. They looked awesome...!!! Got all new valve seats, guides and valve job with mild porting. Cost 5k before shipping. IMHO, thats the way to go for your heads to be reliable, at 130k. Good sealing, worked Heads, are where power and crisp throttle response comes from. Or...Could gamble and just have that 1 valve seat fixed and button it all back up and reinstall the engine. For me Murphy's law always comes back to bite me in the a$$. Hopefully the valve seat hasn't been banging around in there so much the head is not repairable...? Suppose if you're DIY, doing all the labor of removing engine, tearing it down and putting it back together that would mitigate the cost of additional problems down the road from a 1 seat repair... To me the deciding factor for you is if you do it yourself or have to pay a qualified shop. DIY will cost you next to nothing to remove/tear it down and see whats wrong. Combine what you find once heads are off and cylinders are measured for OOR, combined with what your current running and hot idle oil pressure was before it 'got busted'. This would aid my decision on what to do next.... jmo

I will give you my .02 as well. I completely agree with doing the top end only and just inspect while heads are off what is visible. Drive the car. I swapped a 40k mile unit when I blew the motor in mine. With what you have already done just do the top end and run it.

Agree with those in favor of sending BOTH heads to Hoffman for rebuild. Not mentioned above: do not split the case until you really need to, I.e., worn cylinders, pistons, etc. I should have done that but decided to go with full 3.8L rebuild ($21K) five years ago at 95K miles. Would recommend doing some other �while you�re in there� like new chain guides, tensioners, etc.

OP - I concur with sending both heads to Hoffheads for rebuild. Those original heads were built with the same parts using the same technique by the same hands on the same day. Where one valve seat goes, the others will soon follow. All the other stuff depends on when they were last inspected or replaced as part of your maintenance program.

My heads went Hoffman for a full rebuild and stage 1 port/polish.

What does Len Hoffman do to fix and improve the "falling out valve seat" problem? Does he use a different seat or a different installation procedure?

Quotes source post: 19573448

http://newsite.hamheads.com/porsche/

Quotes source post: 19573448

Seems some have a problem opening up this site so here is the gist of it, some stuff did not copy/paste,,, sorry... Exact quote copy paste from Len Hoffman Blog "Valve Seat Issues This problem of intake valve seats dropping has struck quite a few owners over the past few years. We first became aware of it with track cars back around 2014. Shortly after, we started seeing seats actually fall out in our ultrasonic parts washer (heated to just 165*) and our casting oven (heated to 210*) during valve guide installs. Lucky for all involved it happened in the shop and not on the road or track. As you can imagine the results can be catastrophic to the engine and the wallet. As a result of these issues, three years ago we began compulsory replacement of all 3.4l 987 (not to be confused with the 996 3.4) and 3.6l 996/997 intake valve seats when we service these heads. In June of 2018 we expanded that to include exhaust seats after seeing several failures. We will not rebuild these heads without total replacement of all valve guides and valve seats. Here are some pics of exhaust seat failures. It’s worth pointing out that the mechanic working on the car made a bad situation worse by pulling a spark plug to diagnose what caused the engine to lock up. The sparkplug was damaged in the failure and when the mechanic pulled it out it mucked up the plug threads. We recommend not pulling the plugs to scope a cylinder on any locked up engine or engine that has clearly suffered a major failure. We can mill out the offending plug in the shop. These heads do not have a lot of meat between the sparkplug and the intake seats for an insert so we always attempt to save the factory threads. We recently had several intake seats drop in the shop on a pair of 3.4 987 heads. We always take measurements when this happens and this time around we decided to snap some pics and share the results. Here’s what we found: Interference fits of a mere .003″. And the thing is, that .003″ was on the tight side of what we usually see. In the past we have measured interference fits as small as .0015″, making those heads ticking time-bombs. We’re pretty sure these heads did not leave the factory with seats this loose. They wouldn’t have made it this long. It’s my opinion that these seats are loosening over time as a result of a perfect storm of valve-train conditions that lead to major valve bounce. These conditions are: worn guides, weak valve springs and aggressive cam profiles. These conditions lead to tremendous shocks to the heated aluminum seat bores, enlarging them over time. Think of the valves as little hammers pounding the valve seats in a wobbling spiral motion. Keep in mind that aluminum softens with heat, making it even more vulnerable to dimensional instability. The intake guides in these heads are very short. Aside from linear valve movement they must also deal with the valve spring wave actions typically present in parallel non-interference dual springs, as the intakes use. These wave actions move up and down the spring and transfer through the retainer into the valve stem leading to lateral and spiraling valve motion during valve events, causing a wallowing of guide material. The resultant hour glass shape of the guide puts the valve out of square with the seat during the valves critical landing point and allows the valve to transfer that wallowing motion into the seat itself. These seats are so hard that they do not wear like typical seats in early aluminum heads. They take the abuse head on and transfer that motion into the aluminum head. Bounce when worn guides are in play will very often loosen valve seats in aluminum heads, especially when performance cams are used. Weak valve springs and worn guides are a potentially lethal combination in a performance engine and can easily lead to catastrophic failure. We machine new seat counterbores for a more shock proof seat with excellent wear qualities. Here’s a pic of a finished counterbore. "

Thanks for all the replies, informations and suggestions. As I said on my original post, I am planning to keep the car as my forever car (if it is possible) and I will get it fixed properly. I can do some minor wrenching, but opening a head is beyond my capabilities let alone opening the bottom end. So I will defer that job to the “expert”. The trick is to find the “expert” that is excellent, good to work with and doesn’t cost double the current cost of the car. Checking around and reading some articles from UK magazine and talking to some knowledgeable people, I am leaning to get it rebuild using the Hartech way, done by Slakker Racing Development. It is a bit different than FSI, and one can argue which one is better. I will be interested to hear 1st hand experience from the people that has done their rebuilt with either FSI or Hartech So for now it is time for me to start saving my money to get the rebuild. It might take a while, but I want it to get it done correctly