Rebuild to 3.8 with ITBs - help pls.

[Porsche964FP]

Hi new to this forum, although have dropped in for a viewing a few times and am a Rennlist member...

I'm searching for advice on a rebuild I'm going to be undertaking here is the UK and have been directed here by a few people...

Here is the spec I'm leaning toward...

ITB
PMO or Jenvey, I like what I've been reading about the Jenvey and they're very well priced in comparison to others.

http://www.jenvey.co.uk/home/throttl...ody-kit-ckpeo1

http://www.jenvey.co.uk/home/throttl...ody-kit-ckpeo3


CAMS
For ITBs it seems RSR cams are the choice. What other choices are there?

3.8 P&C
Mahle & Mahle - Apparently for durability this is the definitive set up. I read that there are two versions - what are they? I understand that one set is thicker and therefore better for durability. I also understand that a well build 3.6 P&C will out perform Mahle 3.8 P&C.

So what is a well built 3.8 P&C combination that will perform better and yet still be durable?

3.8 JE & LN Nickies - What are experiences with this setup? I read JEs are lighter and therefore perform better. In fact I held one recently - very light!

Omega pistons - Any feedback here? I hear these are the dogs/ overkill - but also very expensive. What cylinders would these be coupled with?

Mixing JEs & Mahle seems to be a bad idea - different expansion rates, piston slap...

CON RODS
I've been reading about Corillos but it seems Pauter perform better and are cheaper by a substancial chunk.

VALVES
Schrick valves (993 spec) for better performance. Stiffer valve spring and titanium retainers.

CYLINDER HEADS
Porting, polishing. Changing valve guides - could someone expand here? Seats need modifying.

INJECTORS
Siemens Deka or .....?

ARP
Head studs & rod bolts.

ECU
Motec or MBE.



Thanks in advance.

[Porsche964FP]

No replies?

I'd like some feedback on combining JE pistons with Mahle cylinders? I'm hearing conflicting reports on this combination, some say the different expansion rates are an issue, others say not at all?

Also valves, some say 993 valves are the way to go... Others say the difference is negligible because the exhaust outlet cant be changed or can it? If it can is this a huge expense for very little change? Remember this is in combination with ITBs.

Your collective advices would be very appreciated.

[ALEX P]

Hey Frank, I think you've seen my engine build on Rennlist & possibly also here:

964 Engine rebuild questions

I combined JE piston with my original Mahle Cylinders and haven't had any problems although I have so far only covered around 3500 miles post-build.

I also went for the 993 valves with the 993RS dia inlet valve. The 993 valves have an 8mm dia shaft instead of the 9mm dia shaft that the 964 valves have so have slightly less mass.

With a rebuild like yours you need to consider how much you want to plunge into the thing as it’s very easy to get carried away! I decided that when stripping it down & inspecting/measuring each part if anything was worn then replace and if it made sense, maybe upgrade. There's a good argument that many parts on an engine like yours can be reused such as p&c's, cams & rockers (reground if necessary) & valves (although many replace the exhaust valves as a matter of course).
The other side to the argument is that if you have budgeted for all new parts and want to build an engine to a particular spec then that's fine but you really won't know what state the engine internals are in until you strip the engine down so you may get a pleasant or unpleasant surprise.

I only say this as I know that you've had a few bits of debris floating round your engine and I believe that you've had a single rocker replaced so I would imagine that you will want to replace/resurface your cams and rockers at the very least. I would also imagine that you are going to replace your valve guides so why not replace with 993 valves at the same time. Past that maybe see what state the rest is in and possibly look at Motec or DTA. I also looked at 3.8 when I had to replace my pistons but the price didn’t really seem worth it but that’s just my opinion.

I keep meaning to get along to one of your London meets & happy to take you out in mine when I do – also have the ‘How to rebuild & modify your Porsche 911 engine’ book that you are welcome to borrow.

Cheers.

[nick-moss]

Who is building the engine for you? What is it based on?

Choice of cams has little to do with the induction type, more on what type of power you want and revs you can use.

There is plenty of expertise here in the UK on these motors: Redtek, RSR Engineering etc. etc.

[Porsche964FP]

Originally Posted by ALEX P

I combined JE piston with my original Mahle Cylinders and haven't had any problems although I have so far only covered around 3500 miles post-build.

I also went for the 993 valves with the 993RS dia inlet valve. The 993 valves have an 8mm dia shaft instead of the 9mm dia shaft that the 964 valves have so have slightly less mass.


I keep meaning to get along to one of your London meets & happy to take you out in mine when I do – also have the ‘How to rebuild & modify your Porsche 911 engine’ book that you are welcome to borrow.

Cheers.

Hi Alex, thank you for the reply. As I understand it upgrading valves get negligible results if nothing is done to the exhaust ports? Difficult as they are ceramic lined... what option are there re cylinder heads? I see that cup cylinder heads are extremely expensive...

Do come to one of the meets, it's always great fun.

[Steve@Rennsport]

Originally Posted by Porsche964FP

As I understand it upgrading valves get negligible results if nothing is done to the exhaust ports? Difficult as they are ceramic lined... what option are there re cylinder heads?

There are lots of different opinions about that. Ultimately, we are all the net sum of our experiences and I can tell you without reservations that upgrading valves makes a measurable difference in airflow and power when uprated cams are installed.

The exhaust ports are no liability up until over 340 BHP.

[Porsche964FP]

Originally Posted by Steve@Rennsport

There are lots of different opinions about that. Ultimately, we are all the net sum of our experiences and I can tell you without reservations that upgrading valves makes a measurable difference in airflow and power when uprated cams are installed.

The exhaust ports are no liability up until over 340 BHP.

Thanks Steve.

With my current spec I'm looking at between 350bhp - 370bhp based on proven figures. So should I be looking at upgrading cylinder heads?

[Steve@Rennsport]

Originally Posted by Porsche964FP

Thanks Steve.

With my current spec I'm looking at between 350bhp - 370bhp based on proven figures. So should I be looking at upgrading cylinder heads?

That depends on whether this is to be a full racing engine or not and what you budget is.

If you can swing it, a good set of heads will do wonders provided you have a good intake, cams, and exhaust. Remember, these things really vary and they are NOT all the same.

[Porsche964FP]

Originally Posted by Steve@Rennsport

That depends on whether this is to be a full racing engine or not and what you budget is.

If you can swing it, a good set of heads will do wonders provided you have a good intake, cams, and exhaust. Remember, these things really vary and they are NOT all the same.

Hi Steve,

ITBs, RSR cams, full exhaust with headers. Budget - all depends on the cost of heads... what kind of money are we talking here and what are the options?

[Steve@Rennsport]

Originally Posted by Porsche964FP

Hi Steve,

ITBs, RSR cams, full exhaust with headers. Budget - all depends on the cost of heads... what kind of money are we talking here and what are the options?

I'd be prepared to spend $10K at least for heads that work.

Please e-mail me for details.

[Porsche964FP]

Originally Posted by Steve@Rennsport

I'd be prepared to spend $10K at least for heads that work.

Please e-mail me for details.

You have mail.