390 HP 2.4L flat 4cyl VW turbo engine, email from a 964 site, para 8, Options

[DonTraver]

Recieved this email from a 964 website I subscribe too. It's a recommendation for a guy that over rev'd his turbo downshifting. Saw the note about the 2.4L engine, thought someone might like it here. It would definitly be a hell of a upgrade for a teener. If there's anyone here thinking of a engine upgrade, this is one more option. Enjoy.

Danéel,
By the look of it, the engine was running fine before, so at 50,000 miles
you do not need to replace many of the parts you have been recommended. If
it were mine, I would build it like this:

R&R, oil/filter, gaskets, spark plugs are definites.

1. Big end bearings. Tend to crush on over-rev, so must fit.
2. Rod bolts. Porsche ones are stretch bolts, ARP are re-useable and
stronger. For $300 a set you must fit them as the stock bolt is a definite
weak link.
3. Forget the oil pump and main bearings, you do not need them unless they
are damaged.
4. Forget the head studs, for up to 1.0bar boost they are fine. They do not
stretch in normal use.
We have just launched a new corrosion proof stainless steel studs that is
15% stronger than the Porsche Dilivar stud (Military engine spec material,
used in sea helicopter engines), so if your studs are showing corrosion
issues (unlikely) there is no point in changing them.
5. The standard ports are good for over 400bhp, so do not waste your money
having them opened up and gas flowed. At the very most, if you are going to
tune the engine to more than 400bhp consider boring the injector blocks with
a taper from 36mm to 34mm and open up the intake manifold and head to match.
Do not go any bigger than 34mm at the head face.
6. Timing chains, tensioners and guides will be ok.
7. Are the rings worn at all?? I doubt it so re-use them for another $900
saving.
8. Cams. Forget billet cams, the only cam that will last in a 911 engine is
made from a chilled iron blank, i.e. factory spec. If you want a perfect cam
for the turbo engine just fit the factory 964 cam, throw the air injection
system in the spares bin and modify the end of the left hand cam to drive
the turbo scavenge oil pump. This cam is good for 500bhp, so do not waste
your money on anything else that will not last with stock followers. You
will have to reset all the valve spring heights to the 964 spec and time the
cams at 1.26mm lift at TDC. As an aside, I have been involved with a flat-4
2.4litre turbo beetle engine that uses 964 heads and modified 964 cams (on
my recommendation), it made 395bhp on the dyno last week at 1.3bar - in
other words had it been a 3.6 6 cylinder we would be looking at 590bhp at
the crank.
9. Fit the custom pulley, although I think I may have a used genuine 965
crank pulley somewhere if you need it.

10. Spend the change on a set of headers, a new wastegate and a boost
controller.

Kind Regards,

Colin Belton
9m Parts . 9m Racing . 9m Panelcraft . 9m Technic
www.ninemeister.com
colin@ninemeister.com