best engine upgrade for a 71

[Imageben]

I have a 71T. Iam going to have to rebuild the engine soon. It runs but needs a lot of TLC. If I wanted to go with abigger engine what would cause the less pain in the long run and give me me my best bang for the buck?

[steve911sc]

Hi, I am now doing the exact same thing you are asking about. I have a tired 71T. The 2.2 case is somewhat limited on what you can do with it. I didn't have unlimited funds so I decided against going to the 2.4-2.7 case or the aluminium (3.0 and above) case. I ended up with an E crank (counterweighted), S pistons and cylinders 84mm leaves it at 2.2l ( my t pistons were worn out), Solex grind on the cams, and staying with the Zeniths for the time being. I also went to the oil pressure chain tensioners. If you have more money than I have I would put an SC (3.0) in with carbs (weber) It would be a real screamer ( I don't know how long the 901 trans would take it though) Hope this helps
Steve

[awis321]

Steve, I'd be interested to hear your impressions on before/after performance.

-Dennis

[steve911sc]

Dennis, Sure..but the engine was so tired that anything is an improvement .. I am looking forward to the comparison with my SC
as it is heavier. A good friend (porsche race car builder) said that it will be more fun (nimble)
Will keep in touch.
Steve

[jcbear]

Imageben - I too was in your situation. When I had the first rebuild done, (by someone else) I put in "S" p/c's and "E" cam's, kept the T crank - MAJOR, BIG TIME improvement. Easy upgrade - NO real alterations, machining needed - just swap out the lower performance parts for the higher ones.

Now that I have it apart and rebuilding it myself, I have looked at numerous options.

3 reference sources are: #1 - Wayne's book, page 112; second Bruce Anderson's book Porsche 911 Performance Handbook, page 135; third you might check out this web site.

While B.Anderson and others may suggest putting in European Carrera 90mm (2.7 Carrera RS) p/c's = 2.5 displacement or 2.8 RSR p/c's = 2.6 displacement, those modifications involve machining the case and heads.

Two of Wayne's suggested mod's for a 2.2 involve replacing the 66mm crank with a 2.4/2.7 70.4mm crank (+ you need to also change the connecting rods to go with a 70.4 crank) --- but you can use your 2.2 p/c's and heads = 2.4.

They say "For more performance, changing pistons and cylinders should be at the top of the list. The adage, "There is no substitute for cubic inches" is a truism. All things being equal, a larger engine will produce more torque and power than a smaller one, For best acceleration, the additional torque afforded by a displacement increase is money well spent. Changing pistons and cylinders is also an opportunity to raise compression ratio. This increases power throughout the whole RPM range."

I've decided to go with Wayne's suggestion to increase displacement (2.4) by picking up a 2.4/2.7 crank (and rods) to use with my "S" p/c's. I am also going to replace my E cam's with "Solex" cam's.

However, I am tempted to go with B. Anderson's suggestion (page 138) of a 2.5 liter racing version of the short-stroke engine, which uses the 2.2 66mm crank and a set of 89mm Mahle's = 2,463cc displacement. (This would involve machining the case and heads plus I would probably find a E or S counter-balanced crank to replace the T crank, though I have heard mixed opinions, that a T crank will work just fine

B. Anderson wrote his 2nd edition back in 1996, and he discourages Wayne's suggestions for replacing the crank and rods as being too expensive.

However, I was able to find a 2.4 crank w/rods for a VERY reasonable price. You may want to check with your local dismantler to see, if in FACT going to 2.4 along with replacing your cam together w/ "S" p/c's may be the best option for the MOST BANG FOR YOUR BUCK!!!

Good luck, let me know what you decide along with your thoughts about your best choice.