Engine Rebuild Dilema

[Fishcop]

Well, not really...

I currently run a fresh 2.7RS spec engine (7R case) with new P&C/cams/heads etc.. that I built for my ST interpretation. Unfortunately I screwed up sealing the case at the #8 (nose) bearing and I have an ongoing leak that gives me the sh!ts.

Sitting under my workbench is the matching number 2.0T engine for my car (3R case). Without a whole lot of work; I could rebuild the correct engine into a 2.5 ST spec engine with the gear off the RS. RS p&c mated to the 66mm crank works out roughly at 2.5 litres. I'd then have the 7R case with fresh machining and time-certing to sell off.

What is the general consensus amongst you my learned friends? Build myself a 2.5 screamer to number match the period correct chassis (Karmann T shell, sunroof delete) ST interpretation? or reseal up the 2.7RS spec donk?

If any of you have built such an engine; what are the pitfalls to watch out for? Would it fit into current CAMS requirements?

Cheers

[OBRUT]

john

what comp ratio are the 2.7 pistons? you will lose maybe 1.0 or 1.5 points from memory when you fit them to the short crank.

[CamBiscuit]

John

What sort of revs do you intend feeding this beast!?

If you are going for a screamer that can handle high revs I'd stick with the 7R case for the extra strength and get it shuffle pinned. You don't want to punch a hole in your original case....not much value in matching numbers then.....

[Fishcop]

Factory 8.5:1 .... yeah, that ain't gunna work is it?

I had a search on Pelican for 2.5 engines and the consensus is that they're really only good for track applications due to the high revs required for power and the lower torque. To make it a truly good engine I'd need to use an expensive lightened valve train and run it to 8K and a bit more machining to the case than I have $ saved

It's clearly not sensible to use the 3R as the base for my RS engine, so I guess I'll just stick with what I've got. I just wanted to somehow get my original engine remarried to my chassis... But I'm not giving up my 200hp

[griffiths_r]

john, as long as you have the original on the shelf, drive it like you stole it!!!!

[Fishcop]

I shall drive as if I have every intention to permanently deprive the owner of their property

[JDCW72]

Hi John,
Do you have a recommendation for a reliable local automotive engineering business familiar with Porsche engines in Brisbane (preferably but not essential) for reconditioning a 2.4 (7R) engine case including align-boring and inserting Case Savers, checking and repolishing the crankshaft and reconditioning the cylinder heads.
I am an absolute novice at this. I bought a 1973 911T engine with CIS, needing a rebuild with the goal of seeing how a Porsche engine comes apart (the easy part) and how it goes back together (the less easy part). Equipped with Wayne Dempsey’s book, I now have a 2.4 engine in pieces. My intention is to rebuild a standard 2.4 911T engine however I am frequently tempted to make some simple modifications like “E” camshafts with 2.2 pistons which I read gives a worthwhile improvement in performance. Feel free to offer advice on that aspect as well.
Thanks,
John

[OBRUT]

john

i would ditch the cis in favour of mfi or carbs (in that order). i would also double check that the E cams will be compatible with the cis as it is a very cam sensitive system. E cams should be ok with mfi or carbs.

[Fishcop]

Hi John

Yes I'd echo Ryan on the valve/piston overlap issues. The nice thing about these engines is that they are physically identical on the outside, so you can change what ever you like inside and keep it visually identical. I personally would be very tempted to source a set of RS P&C and build it to 2.7 keeping the outward appearance - this would require the spigots bored out to take the 90mm cylinders...

Keeping it at 2.4 - you should have nikasil cylinders? If so you really only need some nice pistons (mahle or JP). The CIS pistons have totally different crown shapes and are not worth trying to modify for high lift/duration camshafts. Ivan Tihge at Archerfield welded up and reprofiled my T cams to S spec for $170

There are some good places to have crank and internals machined, I actually used a truck specialist in Toowoomba because he had the latest computer gear and could magnaflux and micropolish. He was facinated by "how cute and little the Porsche crank is". He also said it was the nicest factory crank he'd seen. I'll chase down some names and PM you.

I had my heads done by Charles Apel... There are those who love him and those who hate him. He did great work on my heads converting them from 30mm ports to 36mm for the RS. They looked like new when finished and cost $900. The down side is he takes forever (6 months) and you have to ride him.

It is my humble opinion that there is no-one here in Bris truly capable of fully reconditioning a case. There is a brilliant thread on Pelican highlighting that simply align boring the case is not the best thing... case halves should be machined flat ("clipped") before being bored (as they warp when they are disassembled) - this then creates a deck height issue with all other parts of the cases needing re-facing or fly cutting - but it's good for compression. There may be some good shops in Sydney and Melbourne; but personally with our good dollar, I'd be shipping to the USA (Henry Schmidt or Christian Garibaldi) to have my case fully reconditioned. A search of the Pelican Engine Rebuild Forum will identify several 'dead-set genius' machinists that do nothing else in this life but old 911 engines. We just don't have that here.

My case was done by Phil Sumich who time-certed it and flycut all the faces. I took a gamble based on the fact my engine case came from a sporto in Japan and felt it would not have suffered too many overheating incidents keeping the warping to a minimum. I chose not to have it align bored to minimise the other issues this creates (the Dempsey book highlights these issues). I've lucked out so far with no binding on the rebuild and 3000k on the engine...

[JDCW72]

Thanks, Ryan and John, your responses comprehensively answer my questions. I am sure I shall end up doing something that represents a modest improvement regarding pistons and cams and switch to PMO carburetors. I have lot more reading to do before that decision is made.
Thanks again.
John

[PKAUFMAN]

Hi JohnYes I'd echo Ryan on the valve/piston overlap issues. The nice thing about these engines is that they are physically identical on the outside, so you can change what ever you like inside and keep it visually identical. I personally would be very tempted to source a set of RS P&C and build it to 2.7 keeping the outward appearance - this would require the spigots bored out to take the 90mm cylinders...Keeping it at 2.4 - you should have nikasil cylinders? If so you really only need some nice pistons (mahle or JP). The CIS pistons have totally different crown shapes and are not worth trying to modify for high lift/duration camshafts. Ivan Tihge at Archerfield welded up and reprofiled my T cams to S spec for $170There are some good places to have crank and internals machined, I actually used a truck specialist in Toowoomba because he had the latest computer gear and could magnaflux and micropolish. He was facinated by "how cute and little the Porsche crank is". He also said it was the nicest factory crank he'd seen. I'll chase down some names and PM you. I had my heads done by Charles Apel... There are those who love him and those who hate him. He did great work on my heads converting them from 30mm ports to 36mm for the RS. They looked like new when finished and cost $900. The down side is he takes forever (6 months) and you have to ride him. It is my humble opinion that there is no-one here in Bris truly capable of fully reconditioning a case. There is a brilliant thread on Pelican highlighting that simply align boring the case is not the best thing... case halves should be machined flat ("clipped") before being bored (as they warp when they are disassembled) - this then creates a deck height issue with all other parts of the cases needing re-facing or fly cutting - but it's good for compression. There may be some good shops in Sydney and Melbourne; but personally with our good dollar, I'd be shipping to the USA (Henry Schmidt or Christian Garibaldi) to have my case fully reconditioned. A search of the Pelican Engine Rebuild Forum will identify several 'dead-set genius' machinists that do nothing else in this life but old 911 engines. We just don't have that here.My case was done by Phil Sumich who time-certed it and flycut all the faces. I took a gamble based on the fact my engine case came from a sporto in Japan and felt it would not have suffered too many overheating incidents keeping the warping to a minimum. I chose not to have in align bored to minimise the other issues this creates (the Dempsey book highlights these issues). I've lucked out so far with no binding on the rebuild and 3000k on the engine...

i just thought i would throw my 2 cents worth in as well.
to rebuild an early 911 engine "will cost a lot money" in todays world.i would guestimate about 60 hrs labour and probably $15k min. in parts and machining.
the problem lies partly in the fact that just about all the early 911 engines have already been rebuilt atleast once before and from my experience there a lot of "butchers" out there,even with some of the so called experts.to do it properly requires a lot of machining and just about replacing everything internally with new,and being carefull...?
i would never "reweld" cam lobes again.my first rebuild lasted less than 3000klm with massive amounts of damage to crank and cams etc.if you follow bruce andersons procedure you will have no problems.the second time around i organized all the machining and sourced all the new parts myself so i knew what i had.i also sent the injection pump and throttle bodies to the states for rebuild and recalibration.i would never machine the case halves, but what i did do,was get them lapped instead.don't forget to remove the aluminium plugs at the end of the oil galleries for cleaning purposes.timesert and helicoil all the studs.definetly get the case aligned bored/reamed.after more than 10 years of service i am more than happy with the result of my engine rebuild and have absolutely "no oil leaks" whatsoever.

------------------
peter kaufmann
'73e rebuilt 2.7rs carrera mfi specs

[Fishcop]

Good info Peter

I wasn't totally sure about the cams, but I figured I'd try it - so far, so good. I think I was remarkably lucky to have my crank spin freely - in hindsight I won't do this again. But I felt reeming might create "oblong" journals without refacing the case halves. In hindsight I'll probably stick with aluminium cases rather than magnesium too.

I came in at $9k for everything including rejetting webers... but I did just on everything I could myself.

PS I put some breathing room in my rather lengthy post... I couldn't seem to edit it at the time

[Fishcop]

Good thread here that I started on Pelican http://forums.pelicanparts.com/showt...ight=garibaldi
I went with another case in the end.

[JDCW72]

Peter, Thank you for your good advice and it is in agreement with Bob Whymms' advice received via T&D Automotive this afternoon. The recommendation is to align bore the case and build the engine with 2.4S camshafts and "S" P&C's. Yes it will not be cheap but if I look at it as a combination of education and leisure activity, I may be able to persuade myself that it is fun.
I read your very interesting Pelican thread, John. Opinions on this subject are obviously firmly held and strongly expressed! I also found this thread useful:

http://forums.pelicanparts.com/showthread.php?s=&threadid=227195&highlight=horsepower+911t

Thanks again for this information.
John

[Fishcop]

2.2S Pistons for the higher C/R?