3.3 stroke of the 1098 limits your redline RPM's... better not see over
7,000 RPM too often.
On the 3.0 stoke of the 948, mine see 8,000 RPM regularly.
Whatever you build, have your crankshaft ground with the correct radius, and
have it nitride. Shot peen the rods... stock work fine. Pinch bolt 948's are
fine, floating 1098 (can be used on the 948) are better.
Usually the only performance pistons that can be found are .040 over for
948's. You'll want either a good Hepolite Powermax or similar for a cast
piston, or have Jahns, JE, or Venolia make a set of forged pistons.
Either motor will benefit from a well reworked head. These motors like a
good snappy cam and a decent compression ratio to go with that good flowing
head. I try to build between 12.5:1 to 13:1 on my race motors. I favor Elgin
75-12 cam for a lower compression motor, or their 77-12 cam for something
with forged pistons that I'll spin higher.
Lighten your flywheel. I favor a lightened steel to an aluminum, not only
for cost, but I think clutches last longer.
Check with your sanctioning body as to their engine requirements. SVRA
allows up to a .047 overbore. VSCDA allows .060. That's for SCCA GCR rules.
FIA rules allow a little more, but you can't mix & match. If you prepare a
948 to 1.0 litre FIA spec, you'll need windshield, top, 2 seats, etc.
Contact me off list for any more particulars.
WST
-----Original Message-----
From: James Sailer [mailto:BJ8Healey@msn.com]
Sent: Saturday, May 05, 2007 10:24 AM
To: Spridget List
Subject: 948 or 1098
Hello again listers,
Some list wisom is needed here.
I am going to build a motor for my Bugeye project but it must be period
capacity. That is no 1275 in store and I must use a 948 or a 1098 cc motor
to
qualify for the class I want to build the car for.
As such, which motor can be built up to be a better race engine (again using
essentially period parts)?
Thanks.
Jim Sailer
61 Bugeye.
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