Since I failed emissions, and the leak down test showed bad intake
valves, I'm now in the middle of a complete top end rebuild. The car
had a noisy valve train, and I was aware of lower than normal
compression, so I figured it was time for this anyway. Anyone got a
good used AIR Injection Manifold for this car?
Once I removed the head and valves from the head, I could look deep
into the ports and see lots of carbon. Carbon on the piston tops,
carbon on the valve seats. Another symptom was mushroomed valve
stems. This was bad news and lead me to believe that I had weak valve
springs. In fact, the old springs are .1 (thats 1/10th of an inch)
short when compared to the uncompressed spec. My theory is that the
poor valve seat pressure allowed the valves to float, and share
exhaust/intake fumes. Thus I got poor mixture, carbon buildup, and
worse, the bouncy valves trashed the valve stems, cam followers AND
the cam which led to even more carbon buildup as now things are way
out of spec.. *sigh*
Several of the tappets were pitted and one in particular was bashed
into something that was no longer a cam follower. So I pulled the cam
and to my dismay, it's no good. Some pitting, and in fact, the lift
varied over .010 between the lobes. I was able to get a good core
out of a local salvage yard, but now I'm faced with which cam profile
to put back into the engine. Denver emissions are about as strict as
California these days, so I need a smooth idle. Here are a few cam
profiles I know about (taken from Bentley's workshop manual):
PRE '72 TR6(carb) PRE '73 TR6(PI) POST '72 TR6(carb)
IO 10 BTDC 35 BTDC 18 BTDC
IC 50 ABDC 65 ABDC 58 ABDC
EO 50 BBDC 65 BBDC 58 BBDC
EC 10 ATDC 35 ATDC 18 ATDC
What's missing here is the LIFT, the height at which the above specs
are measured at (usually .050) and the lobe centers. Does anyone have
these specs? I believe the PRE '72 Cam was .220 and the later cam was
.240. (That does not include the rocker ratio) I have no idea what
the life is on the S2 cam. Please let me know if you do...
The middle cam above is usually called the S2 cam. It was stock in
Europe, and considered a mild street cam here in the US. I know an S2
cam *can* pass Colorado emissions with a bit of effort, so I'm
inclined to find a cam profile that's just a bit milder.
Can someone give me some cam advice here?
What's funny is that the most difficult part of this emissions
exercise is getting the air injection put back on the car. Colorado
won't let me pass without it. Stock air pumps are around $200, the
air manifold is $200, the stock air valves are $100+. (Due to the
cost, I won't be using 100% stock parts for the air injection stuff
and should be able to cut my costs down to about $100-$150 total.)
To top that, The DPO put an early model radiator into the car and
means I have to braze on a different upper hose fitting to provide
clearance for the air pump belt. When I took my radiator into the
shop, they found a few small leaks so I guess I should consider myself
lucky and not stranded.
Thanks,
-Scotty
'75TR6
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