Jump to content

993 3.6 Rebuild


BlitzKonig

Recommended Posts

So as the title says, we're about to start a rebuild on my 1995 993 3.6 motor and I figured that it would be interesting for anyone in a similar situation to provide some costs and as many details as I can regarding it. I wont be doing this one, but rather Don at DHM. Give me a simple BMW 4 cylinder and Ill rebuild that, but I dont trust myself with the cost of these motors, its just not something Im willing to try and then be in a situation where Im worse off than when I started.

A bit of the back story, my car is a 1975 Carrera with a 200k km '95 993 swap, still running the 915 gearbox, Ive owned the car for about 20 months now and aside from the caliper flying off TWICE while driving, its had no major issues. However, and it was indicated to me during the PPI, that the motor is old and tired (previously saw a lot of track work, based on the rest of the cars setup) and would probably be due for a rebuild, sooner rather than later. Initially, it was only the occasional puff of blue smoke and the idle was smooth, compression test was spot on. This has been progressively getting worse with external leaks also occurring around the crankcase bolts and occasional unstable idle. Recently the car has also been hunting more than usual, with continued excessive oil being burnt and smoke from the rear. Yep, it is finally time.
Normally, I would not simply give in and say, yep, the motor is a wreck we need to rebuild and Id try diagnosing each point after point, but with the 993 history for soft valve guides failing after 60k miles, I think its a fair point to at least strip the motor and see what we're dealing with.

This will be a fairly standard rebuild with only the addition of a Cup cam and Steve Wong chip to match, (reprogram the current one for the lightened flywheel). The car really doesnt need much more go, the low-mid torque addition of the Cup cam should be more than enough for my desires. It also means that I dont need to worry about sourcing a G50 because of the increased power and torque.

The stripping purpose will begin next week, so hopefully Ill have some updates soon :)

Link to comment
Share on other sites

....but with the 993 history for soft valve guides failing after 60k miles.....

Blitz,

Looking forward to seeing lots of photos and words about your rebuild. 

I hope it goes well and nothing REALLY expensive needs replacing.  Given it only has 200,000km I can't imagine it will need much more than rings (while you're in there!) valve stem seals and the valve seats touched up.  But it will be interesting to see how much wear there really is.

There is frequent reference to prematurely worn value guides in the G series and 993's on US forums but I'm not sure the reality matches the hysteria.

BTW, how much oil is it actually consuming?

Regards

Peter

Link to comment
Share on other sites

 

BTW, how much oil is it actually consuming?

Earlier this year, when I topped it up, I measured it at ~1L per 1500km, whereby the maximum limit Ive read for this engine is specified at 1 quart (~1L) per 1500 miles (2400km).

I should also add, that the oil currently being used is Penrite 10 Tenths Racing15-50w, to try and reduce the impact of worn rings/valve seals, some may argue that this may have also accelerated the wear, but Id rather have a bit more high temperature viscosity, knowing our climate.

I dug through some of the old receipts regarding the previous owner's install of the motor, while I couldnt find any kms recorded for the motor imported (very strange I thought), it was noted on a service about 3 months later there was smoke coming from the
left exhaust and was suspected to be the valve seals. I should add this was back in 2009 and 20k km ago.

The engine is in more than capable hands, but he is also aware of my situation and desires from the motor, this is not going to be a race motor, but rebuilt as per oem specs (with the addition of the cup cams). Hes informed me that when everything is apart, itll be measured and accessed and machining carried out where required.

Yes, looking forward to following this build.

Interesting point Peter M makes about the hysteria of worn guides in the U.S. How many km on your engine?

 

202xxxkm. While I dont have an exact record of the motor kms, reading through the receipts I saw the odometer was adjusted to reflect the motor.
 

Even after almost 2 years, and doing a lot of work on the car myself; examining suspension components and brake assembly, I still feel like the car is quite mysterious to me and also makes me wonder what else Ill discover. Thats also how I see this motor rebuild, it gives me a clean slate to move forward from and a car I can keep in the family, and hopefully pass on.

Link to comment
Share on other sites

Whats everyones opinion on Ceramic coating on pistons? Pros, cons?

Ive read a bit into it and I believe I understand the benefits to be gained, however as this car will be driven mainly on the street and therefore I am trying to extend the time before the next rebuild, I am concerned about coating flaking off, I guess I would like to know the longer term results of such a process. 

 

Link to comment
Share on other sites

Whats everyones opinion on Ceramic coating on pistons? Pros, cons?

Ive read a bit into it and I believe I understand the benefits to be gained, however as this car will be driven mainly on the street and therefore I am trying to extend the time before the next rebuild, I am concerned about coating flaking off, I guess I would like to know the longer term results of such a process. 

 

did it on a set of Pistons on my race bike and saw zero benefits or negatives,not saying none existed, just not obvious to me,on the Dyno, temperature guage , etc, etc, etc, like magic oil additives, probably a waste of money on an air cooled engine designed and built to carpenters tolerances, compared to super modern high temp and high hp turbo motors 

 

Link to comment
Share on other sites

Carpenters tolerances lol.

 

my old man had a joke - engineers work to the nearest thousandth, but carpenters work exact.

Can't wait to see some pictures of the inside guts and find out how really bulletproof these ac engines are.

most of the rebuilds I have seen have had very little wear or damage, except where bodges had previously been applied.

Link to comment
Share on other sites

Whats everyones opinion on Ceramic coating on pistons? Pros, cons?

Ive read a bit into it and I believe I understand the benefits to be gained, however as this car will be driven mainly on the street and therefore I am trying to extend the time before the next rebuild, I am concerned about coating flaking off, I guess I would like to know the longer term results of such a process. 

 

consus seems to be the money is better spent elsewhere- however that was talking about triumph motors which aren't exactly performance units 

Carpenters tolerances lol.

 

my old man had a joke - engineers work to the nearest thousandth, but carpenters work exact.

Can't wait to see some pictures of the inside guts and find out how really bulletproof these ac engines are.

most of the rebuilds I have seen have had very little wear or damage, except where bodges had previously been applied.

I did one on a 3.0L under supervision and the Pistons were fine, got cleaned up and re-ringed and good to go. 3.6's are higher comp though.

Link to comment
Share on other sites

  • 2 weeks later...

So the motor has now been removed and stripped. Parts are yet to all be cleaned, but all in all, were looking quite good, nothing catastrophic. Regular wear and tear on all bearings. Rings are intact (yet to be examined closer) and Pistons and Bores look great (also yet to be measured).

The chain runners/guides however were cracked in multiple places, so it was well worth taking the motor apart to find this prior to it failures.

There were also points on the cam where the hardening had been removed, I asked from what this could have been caused by and it may have been due to Porsche's long service intervals (24k km between oil services or each year, for low km cars). Therefore the cams will need to be refinished, adding on a cost of $300 per cam.
As mentioned earlier, I was considering the cup cam, which were $1000 a pair, however this leads onto the next decision, the 993 motor has hydraulic lifters, which are not compatible with the cam and would require the swap to solid lifters.
I havent looked too much into it... but to me, hydraulic lifters seems like the better of the two due to the self alignment. Would love some feedback/thoughts on this.

To run the cam Ill also need a separate tune, at this stage unichip is being suggested, of which I need to do some more research and whether this system would be compatible with an ITB setup later on down the track.

I did take several photos, so Ill post them up when Ive taken them off the camera.

If there is anything anyone would like to know or have a look at a certain part of the motor, please let me know and Ill try and get some photos/answers :)

 

Link to comment
Share on other sites

Yeah, normal practice is to always use new or refaced followers with new or reground cams so it's a bit of an all or nothing approach.  (It's OK to use new followers on an old cam but not the other way.)

 

Could you post some photos of your worn cam lobes and follower faces please?

Link to comment
Share on other sites

Peter M, yup will post those up tonight.

Yep, I need to do it either way, just depends which route I go.

I just got some pricing for both options:

1) Cup Cam ~$1000
    Hydraulic to Solid Lifter Conversion (Genuine Porsche Item)  ~$3100
    Unichip tune - $1700

2) Refinish Cam ~$600 total, $300 per Cam
    Replace current Hydraulic Lifters ~$900

Im going to see in what condition the heads are in, if they need new valves this will add considerable cost that I would prefer to focus on and would make the decision a lot harder.
If they are good and only wearable items require placement, I will strongly consider the Cam install.
 

Link to comment
Share on other sites

Blitz,

Just to clarify, on 993's the hydraulic lifter and the cam follower are different parts so if you regrind your standard cams, you'll also need to either replace or reface the followers as a minimum PLUS consider strongly replacing the lifters while you're there.

 

Sorry, but a bit more money to spend on this option!:)

 

Link to comment
Share on other sites

  • 4 weeks later...

Parts have been ordered, and were looking to complete in about 2-3 weeks.

Pistons and Cylinder heads have been sent away to be ceramic coated and the cam is off to get machined and re-hardened due to the slight wear noted in the image below:
21648424699_e8ec323567_k.jpgPPRS-3986 by Ferdinand Reisch, on Flickr

I havent been in the shop since my return from OS, but there isnt much left of the motor currently in the shop.

Luckily all my valves were in good condition, but as suspected, Valve guides were out of spec and required replacement.

Currently everything is being rebuilt with OEM components, some may argue that while in there, some things "should" be improved, but my mentality has changed over the years, and Im finally understanding that the team out of Stuttgart probably knows best :)

At this stage, we're looking at about 15k for the rebuild, this is including motor removal and re-installation.
All bearings internal to the motor are being replaced, including main and rod ends.
Rod bolts are being replaced, however the head bolts are being reused, initially I thought this was unusual, but has been advised to me, they are acceptable.
New chains and timing guides are being installed, sprockets being reused.
Crank Sensors are also being replaced.
New Piston rings and as previously discussed valve guides are being swapped for new ones. ?
Crank and Pistons have been measured and well within spec.
Air stacks are being replaced as the plastic base has cracks and excessive warping.

Ill try and get in to get some more photos when the rebuild is going ahead and Im happy enough to post up a final invoice for reference purposes.

Link to comment
Share on other sites

  • 2 weeks later...

Good stuff Ferdinand!

Thanks for sharing this info with us.

Is only one cam lobe pitted or are there many that require grinding and rehardening?

 

Both had small amounts from what I remembered seeing, not on all lobes only on differing areas, unfortunately I didnt pay too close attention to which valves they were related to.

I havent spoken to Don over the past week, but we should be getting close to getting it finished. Unfortunately I couldnt cover the rebuild of the head as it was sent away.

What else would you like to know Mike? 

Link to comment
Share on other sites

  • 1 month later...

And the saga continues...

Drove the car home yesterday, unfortunately its not a truly "happily ever after" kind of story.

Turns out that the previous workshop that installed the engine and with it the Steve Wong chip have set this car up something funny. 

Since the day Ive owned it till now, its apparently been running MAF-less and without the O2 sensor, could explain why Ive had such poor fuel economy in the past...
The wiring was not completed correctly in that while the MAF is plugged in, it is not being supplied with 12V that it needs. Don tried to correct this, only to find it dumps even more fuel in (apparently my injector's duty cycle werent running 100% :P ), so it was disconnected and run home without it.

Next step is to first locate a factory 993 non-varioram chip, install the DME relay for the fuel pump, verify the pump (currently an earlier mechanical injection type, electrically driven) is sucifient for the job of running the 3.6 with enough flow and pressure and then sort the MAF and O2 wiring.

Im going to be honest, it might not seem like a lot of work, but its quite a bit of a downer. I feel in some part like Im going backward to go forwards, but its one of those short term pains, long term gains situations. If everything pans out well, the motor rebuild will be verified when in factory trim and it can then go onto the dyno and tuned. 

Of course with many project, we blow out of budget with this build, so Im going to under take all these task by myself and have Don verify the build when completed. 

Well its not all bad... Ive been itching to tinker on something again :D 

12308385_10156282621385076_8302144929976

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...