Thread: 2.7 MFI rebuild
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Baurice Baurice is offline
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Join Date: Dec 2003
Location: New Zealand
Posts: 47
Garage
Hi guys
Sorry about not getting back to you sooner, but things became interesting (and in many ways clearer) when we took the engine apart.

I had intended to go down the route suggested and use Mahle RSR Pistons to increase CR to 10.5:1 - but not go the twin spark route as this would have been too complex and costly.

I thought that this mild increase in torque and power would be enough for my use of the car (daily driver / very occasional track day).

However!

The previous rebuild (carried out in 1995) was an absolute shambles! And the bottom line is that I’m very pleased to have had the engine rebuild so expertly by Jon Warring at Rennsport here in Christchurch.

We found such things as.......
• The case had been machined and the original crank and pistons kept, but unusual (certainly not Porsche OE) spacers had been used to lengthen the barrels to stop the pistons hitting the valves.
• The engine case and pistons etc were original but the cylinder heads were from 1969! At some point there must have been a big bang and all new head replacements had been needed. When we read the previous owner’s garage bills from 1995, it turned out that he had paid for an additional 81 hours labour after the garage's “misassembly” had damaged the engine after its rebuild. We can’t be sure but we think that this is where the new heads came from as they don’t look that old. I’m tempted to give the previous owner a ring (he had the car for 22 years) to find out exactly what happened. What do you think?!
• The “carrera” tensioners and chain guides were installed wrongly and not working.

All in all John had his work cut out to get the engine back to spec – which it now is apart from an mild increase in compression. This came about because, after looking at Bruce Anderson’s Porsche 911 Performance Handbook, we decided to machine out the ports rather than replace the heads. After machining, John painstakingly buretted each head and found that they were 64 mls - slightly less than spec 66-70mls. This reduction increases the CR to 9.4:1!

The engine is just being re installed so I’ll give you another mail when we have had it running.

Cheers

Andrew
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ROW 1974 Carrera 2.7
Old 10-20-2005, 06:42 PM
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