Why not 3,0 lts ?
 

Some questions from an obvious ignorant,

I have seen in the threads about engine upgrading choices, that the most of you start from the 2 – 2,2 – 2,4 – 2,7 – 3,2 or 3,6 lt.

Just a few from 3,0 lt.

Is there any particular reason in preferring others to the 3,0 lts?

I have been asking here in the board

http://forums.pelicanparts.com/porsche-911-technical-forum/66184-74-carrera-s-what.html

about a 74 that (lately discovered by checking the right #´s) it has a 3,0 transplant on it, and I was looking on it as a future project for an Hp upgrading work.

Is there any limitation in Hp developing, retaining the hardness of this particular engine?

Thanks

Early cars can get away without smog regulations in any state. Since the early motors came with carb or mech injection it is a natural to build these motors, especially as a 2.7 RS rep motor.

The 3.0 is legendary as being builet-proof but is limited to HP mods by the CIS. Changing an early car to the 3.0 requires a bit of work for the CDI and fuel system. CIS is a great running system, and has proven itself over and over with great running cars with 25 year old CIS systems. The CIS is not as fuel efficient and upgradeable as the DME system of the 3.2 and 3.6.

When you move up to the 3.2 and 3.6 you have a fuel management system that allows better HP increases and can be transplanted to practicaly any year car and still maintain smog compliance. You still have just about the same amount of changes to make to the ignition, DME and fuel system but you have the option of future upgrading the HP, i.e. wild cams, without restrictions of the CIS. It seems that the 3.2 and particularly the 3.6 are used more for the bolt in upgrade. Since the required changes are about the same, I would guess most people just go with the 3.2 or 3.6.

I would actually think that the 3.0 with carbs or other fuel system and cams would make a great motor. There is just no substitute for CC's in a motor. Its just more of a project to change out the fuel system with the 3.0. BTW, I love my 3.0 and believe it has lots of power.

Very clear Paul,
Thanks

One thing not to be confused with is that some people (Randy Jones, Kurt Starnes, P-Thomas, others I can't remember) have started with a 3.0 and added 98mm pistons and cylinders to get 3.2, 3.4 or 3.5 litres (the latter two requiring a crank change to a 3.2 anyway, and 3.5 requiring 100mm p&c I think).

The reason for the displacement increase (other than obviously it makes more power) is that increasing the performance of a 3.0 substantially usually requires a camshaft change, together with induction change (from CIS) and piston change (to allow greater valve lift). Usually the compression gets increased too. So... if you are replacing pistons (and cylinders), why not biggie size your order to 98mm - makes sense. Hence, there are 3.2 motors which are 3.0 based. Long-winded explanation!

On the flipside, I've got (paid for, installed, not back at my house yet though :() a 3.0 which has higher compression but for whatever reason the original rebuilder elected to stay with 3.0 (I would have prefered 3.2, but this was what was on offer). It is sort of a 3.0RS engine - S cams, 9.5 c/r, MFI/EFI hybrid.

http://forums.pelicanparts.com/uploa..._on_stand1.jpg

Back in the early 80s 3 liter swaps were the in thing, in the late 80s 3.2 swaps were hot, in the early 90s till today 3.6 swaps were derigueur. See a pattern? Whats available is a factor, whats biggest/best is another. Some people like turbos, there the 3.3 is preferred for many reasons to the 3.0, again bigger, newer, faster are all desireable characteristics. The problem with a custom engine is either $ when buying from a reputable shop, or engineering when diy. Personaly I liked the idea of factory reliability, future growth potential, and relatively low $ of the 3.6 transplant. A minute savings might have been achieved with a 3.2 or 3 but the essence and potential are far less.

By the way- for Bill and other 3.6 guys (and notwithstanding Bills' comment on factory reliability), the engine in the background is a 3.8 from a 3.6 with 50mm RSR stacks and MoTeC EFI. I think it is 350ish hp. Oh how I wish it were mine...

CamB, thats my future!