just curious about the 2.9 twin plug

[RichF]

So what all does it take to make a 2.9 twin plug and about how much if you built it at home, I know some things would have to be done at a machine shop but what parts would you need to stock? case, internals, fuel system...?

thanks, rich

[Steve@Rennsport]

Build a 2.8 for a much more reliable engine,....

[RichF]

is it really? How so cause i know nothing about either except that the 2.9 made alot more power with its radical cam than the 2.7 (I think) is it the same with the 2.8?

[Grady Clay]

listen to steve

Listen to Steve

LISTEN TO STEVE

Seriously, the 93 mm cylinder wall just plain was too thin. The structure of the cylinder under these conditions was not up to the task. The 92 mm cylinders are sufficient.

For enjoyment (even single plug) the 90 mm ’73 911RS (8.5:1 CR) Nicksil are very suitable. For outrageous performance the 92 mm 911RSR (at about 11.5:1 CR with non-RSR heads) work well but it takes a lot of work. These are also currently difficult to source.

Best,
Grady

[Steve@Rennsport]

Originally Posted by RichF

is it really? How so cause i know nothing about either except that the 2.9 made alot more power with its radical cam than the 2.7 (I think) is it the same with the 2.8?

Rich:

2.8 engines have been around since 1973 so this is not a new development. I've been doing those since 1977 and its REALLY a neat combination if everything is properly done.

The 2.9's are relatively new as a way to squeeze the very last out of those small magnesium engine cases and the 93mm cylinders are simply far far too thin for durability. Once heated a time or two, they do not stay round and this shows in the leakdown figures.

There are two ways to make a 2.8; one uses a 92mmx70.4mm package and the other is a 95mmx66mm built on a 3.0 Turbo bottom end.

Currently, I have a supply of new Mahle 92mm P/C's.

[Wayne 962]

Sorry, so not a fan of mag cases - too many issues. A 3.0 with high compression pistions and 'S' cams + Weber 40s will really work well. Single plug too. This is what I have in my black RS clone.

-Wayne

[pu911]

Wayne,
I'll agree a hot rodded 3 L is a great motor, big port heads flow like mad stock. The short stroke 2.8 is built on a AL case but ain't cheap.
Phil

[RichF]

i see thanks for the information guys

[Jeff Alton]

Yes, but if you have a 3.0, why not make a SS 3.2 or get a 74.4 crank and rods and build a 3.4.....

My 3.4, the only one I have experience with mind you, sure likes to rev...

Cheers

[Wayne 962]

Yes, I agree. It costs the same to rebuild / build a 2.0 as it does a 3.4, so why leave HP on the table? Best motor to build is the 3.4 high compression, twin-plugged, with 'S' cams and weber 40s or 46s. It will put out as much power as a stock 3.6, and will be easier to install into an eariler car.

-Wayne

[RichF]

How much does it cost to build a 3.4 high compression twin-plug from the ground?, up no tranny