Big Healey (was MGC) Cam Timing
I fingered out where I went wrong. Actually I had multiple errors,
including a severe case of brain fade. I pulled the timing cover off of the
race car Saturday, and indeed the cam gear was WAY off of where it should
have been. I'm darn certain it was put on correctly, so I assume it jumped
when I started the engine initially. I had used the old timing chain (I knew
it was a bad idea at the time, but I was a week away from race day, and had
to get the engine back together). I also retracted the chain tensioner to
get everything together.
The tensioner is extended by hydraulic (oil) pressure, and held extended by
a ratchet mechanism. I assume that as I cranked the engine initially with no
plugs to get oil pumped into the engine, the chain jumped because nothing was
forcing the tensioner to extend. Once it extended, it kept the chain from
jumping further. This is all supported by the fact that the timing seemed to
be way off initially, and I couldn't tell why. I'm suprised the car ran at
all, the cam was off over 100 degrees! In fact it ran up to almost 100 mph,
although acceleration was understandably slow.
I really feel like Homer Simpson though, regarding my valve timing
measurements. I made a degree wheel and taped it to the harmonic balancer so
I could record when the valves were opening and closing, but I made it
backwards! I simply followed the timing marks as they went from Top Dead
Center to 10 degrees BTDC, to 20 etc. This is all fine, except that's the
opposite direction of how the engine actually rotates. No wonder I thought
the valves were opening in the reverse order, and thought I'd gotten a cam
from some other car!.
Okay, I'm a happy guy now. At least I (think) I know what's been going on.
The new timing chain I ordered should arrive in a few days and I'll get
everything together. Heck, if the car ran 100 mph with the cam off over 100
degrees, I should be able to light up the tires in fourth gear if I get it
set right, eh? And, best of all, it's still almost three weeks before the
next race at TX World Speedway. It's not even close to the last minute yet!
Dave Lapham HEALEY@OAKHILL.sps.mot.com Austin, TX
If it weren't for the last minute, nothing would ever get done!
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