well.. my 2 cents.

If you are going to pay to have the engine out of the car and open (which accounts for half of the total cost of a rebuild no?) why not get as much done as possible, upgrade as much as possible and tweak as much as possible to ensure the time before you have to do it again it as long as possible. I mean even if some of the guides are not so bad why not upgrade them all, what are they $60-100 a side?

I am thinking I will get the top end done in the near future (altho I only have minor signs of problems at this point) mainly because I am sure I will never be without this car and that in the future the parts and labour will only be more expensive.

I want the first million kilometer 993!!!

Cheers,
Scott.

 

As an example (all in Canadian Dollars), here in Vancouver Scan will do the top end in 40 hours of shop labour @ $80 = $3200. The parts for the top end (gasket set, guides, outsourcing the head work) is about $3800. This a basic no frills top end and you are right its about half of the cost. Of course you should check the rings ($300 parts). If you open the bottom end count on another 10 hrs labour ($800) and parts. Of course since the labour is practically zero the RS clutch should go in ($1700). Up to now you are basically stock. What I have found is the next step (RS Valves, cams, 3.8 P/C's) is really really expensive that doubling the final bill is likely. In my case I will stick to stock, stock, stock to keep the costs down. This car is plenty fast enough for me...

Cheers,

Mike

 

I agree with you Mike. If one is to go much further, they should really consider the protomotive stage II turbo. This includes a rebuild. Not cheap but neither would adding cams, bigger pistons, valves, etc.

 

I agree I am not suggesting large scale upgrades with the likes of cams and P/C's. I think that things like upgraded guides and even lifters and rings would be a must if you are taking the engine apart. I mean if you fix just what looks like it need fixing and leave the rest then its $3k just to get back in there at a later date.

 

On my pending rebuilt I am planning/budgeting to replace all the exhaust valves, seals, and all guides. The heads will be cleaned and rebuilt. I will also replace all the hydralic valve lifters. The rings will be replaced if needed. If I slot the cams and predate the cam sprockets in order to go the timing the old fashioned way then its likely that I will replace the cam timing chains. Unfortunately I then need to use split chains but that should be OK. Of course it gets new plugs (I already have done the spark plug wires), filters, etc as well. I will also replace the RMS and add a new clutch. The gaskets on the crankcase vent will be replaced and I might replace the oil sender unit (its cheap and easy to get to). Gee it getting expensive again! Since I am currently planning to DYI it then its zero dollars in labour (but it does cost a gasket set and an alignment) to go in again.

Cheers,

Mike

 

Mike,
What warnings were you given about splitting the case and replacing the bearings, using a non-split chain, etc.? I will eventually be in a similar boat to you (possibly this winter but we'll see what the dyno says plus I think I'm a little higher than you with 140k miles) and I figured if I have almost everything taken apart I might as well continue with the bottom end, most of the cost seems to be labor (free in our case and like you I don't plan to spend $3k extra for 15HP so I will stick with pretty much stock parts).

 

Hi Jason,

One of my parts sources were concerned that PET does not list a split chain for the 993 and then inferred since it was not listed its not recommended for the 993. I have been hanging out on the Pelican Parts rebulding forum and there seems to be some discussion about split chains. Of course the only difference is the master link and how likely it is to slip or cause problems. I don't think it will be a problem but you can always find someone with a different point of view.

This is only an issue if the case is not split. If it is then one piece chains are the way to go (of course).

Your mileage is certainly higher but I think with my car the PO never removed the engine cover and drove it in Toronto which can get really hot. This cooking likely caused muy problems ;-)

Cheers,

Mike

 

From what I've been seeing with the 964 heads and again with the 993 heads is that the valve guides are wearing at an excessive rate which creates several problem. First, oil is leaking down through the guide and being burned which is creating carbon deposits in the combustion chamber and in the exhaust port. Second, the valve is loosing its seat concentricity which allows for higher than normal leakdown since it no longer can seal properly. The material that the valve guides are made from is terrible and in my opinion too soft. Furthermore, the valve material is also soft and the valves are beginning to pit on the seat, also creating sealing issues. These are contributing factors to the plugged injection ports that are seen in the 993 as well as higher than normal leakdown on these engines.

With regard to changing the piston rings. It is not the piston rings that wear in these engines. As with most of the Porsche 911 engine versions, and particularly with the 100mm bore pistons, it is the piston that wears out long before the rings. Due to the poor connecting rod to stroke ratio, there is excessive side loading on the piston causing it to contact the cylinder wall. The piston and cylinder will wear out long before the piston ring itself. By simply changing the rings (while you are in there) you are gaining nothing.

There is no way I'd reuse or purchase new Porsche valves and valve guides and have switched to alternatives with great success. I believe that if you mildly port the heads to clean them up, do a proper multi-radius valve job, use alternative valves and guides, and ensure that the camshafts are timed properly (or change the cams all together) you'll see significant gains +20hp over a stock engine. However, you will require a new ECU chip to optimize proper fueling.

The following pictures are from a 20k mile engine I purchased as a core due to excessive leakdown. The exhaust port clearly shows the carbon build up from the leaking valve seal/guide. The valve shows the seat and the pitting that has occured.

 

Alternative valve guide material has been widely discussed but what alternative valves do the RL gurus recommend?

 

Father, that's a Steve Weiner question.

 

Geoffrey,

That's bad build-up I thought mine was bad (see picture) do you think my exhaust valves are off colour?

My engine is still in bits and I am pondering whether the valves them selves might need replacing.

Interestingly the inlet valves are clean as a whistle not even black, quite yellow infact which my mechanic suggests is due to over fueling, which isn't good.

 

I would imagine that your RSR chip from Steve significantly improved upon the fuling of your engine. Where the stock car runs very rich at peak torque I would imagine that it has been leaned out some as is the normal practice, although I can't speak for Steve specifically. I think some of the coloring you see is due to the particular blend of gasoline you use.

In order to determine if the valves or guides need replacing, your best bet is to have it examined by a machine shop.

 

Thanks Geoffrey, It is with the machanic and the heads have gone to the machine shop, I'll wait to hear from them, I know the guides are to be replaced for sure.