Greetings all:
10K miles ago, my 2.5L Spit bodied GT6 suffered a blown head gasket (after
50K miles on full engine rebuild). In looking over the top end while
assessing the burnt thru head gasket, I noticed that the cam (regrind from
BPNW) had several lobes wiped out. Purchased a new GP2 grind cam from
Goodparts, can't remember where the lifters came from. I liberally applied
a cam break-in lube, ran the engine at 2000 rpm for 20 minutes for cam run
in and always used a motor oil with good zinc (14.4%) & phos (10.3%) levels.
So 10K miles later, I am disappointed to find out that one lobe looks like
this:
http://i290.photobucket.com/albums/ll272/aribert/Triumph/IMAG0608_zps77751725.jpg.
The rest of the lobes look like this:
http://i290.photobucket.com/albums/ll272/aribert/Triumph/IMAG0612_zps4320a1b8.jpg
I really thought that I was doing everything needed for cam longevity.
I am going to try to get the mating damaged lifter hardness checked and
compare that to lifters in the engine.
A bit more background info - may not have any effect on the cam lobe wear -
this past Aug I noticed a lack of oil pressure at hot idle - above 1500 rpm
the oil pressure was lower than normal but greater than 10 psi/1000 rpm. I
drove the car an additional 40 miles to get home. The screw securing the
rocker shaft had backed out and the oil destined for the rockers was
pumping out of the screw hole. The forward most rocker wore 0.070 to 0.080
deep groove into the underside of the rocker shaft. I replaced the rocker
asm, flushed the engine and upon restart had minimal oil flow to the rocker
shaft. and less oil pressure than before the fixing screw backing out. I
parked the car for the season.
This past weekend I pulled the engine and began to tear it down. Worn oil
pump (understandable since the metal particles from the rocker shaft wear
that were suspended in the oil circulated thru the pump on the way to the
oil filter. The oil filter appeared to do its job - rod and crank bearings
look good (like a bearing with 60K of use). I was very surprised to find a
wiped cam lobe. In hindsight, there was a bit of engine roughness this
year and even back to fall of 2012 that I attributed to a misbalanced carb
(triple Webers) that I was not able to resolve (and did not try very hard
to do so). BTW, the damaged lobe was the 10th from the front, very close
to where the oil was pumping out of the screw hole - in other words plenty
of splash lubrication down onto the lifter & cam lobe while the far end of
the rocker shaft was running dry.
So now I need to source another cam. I was satisfied with the GoodParts
GP2 cam: 2000 to 5500rpm range, 0.360 valve lift, 278 duration. Now I am
soliciting opinions for other potential cams (and lifters, want to buy them
from the same source). TRF lists a GP2 pattern (I presume they are
reselling Good's cam), TSI has an S2 grind (3500 to 6000 rpm, 0.405 lift,
282 duration). I also looked at offerings from SpitBits and BPNW.
This is a vehicle driven 3 seasons/year and must be tolerant of stop & go
traffic to being happy at freeway speeds. Triple 40DCOEs, 6 into1 headers,
head milled for 9.2 to 1 CR with mild porting & port matching and Crane
ignition. *Other suggestions for a potential cam?*
** triumphs@autox.team.net **
Archive: http://www.team.net/archive
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