To bring the list uptodate, I've milled my head down to 3.4 inches,
giving me a CR of 9.5:1. I've ported the head, did some intake
manifold grinding, and put a mild cam in the car. Fired it up,
just a few nights ago, and it started right off, but there's a
slight miss at idle. The other bizarre thing is oil pressure,
but I'll save that for last.
I think I've located the slight miss at idle problem. Actually,
it may be more than one problem, but this is a problem for sure.
My push rods are too long.
Due to poor running, or actually, lack of consistant running,
I started to question my ability to degree in the cam, and decided
I would check where the #1 intake valve moved since I could use
the degrees marked on the crank pulley. It was right on at 22
degrees BTDC. I measured the exhaust as well, it was right on
closing at 22 ATDC, I checked cyl #6 as well, it too was right on.
I figure the rest of the cam should be ok..
I decided I would measure the lift, just as an exersize of to
see if I could use a dial indicator. Total lift should be
around .420 I thought. Nope, it measured no where close. I got
a measurement of .392. So I figure, OK, I must have a rocker ratio
of 1.42, which many trs have. This would also account for a value
of .392 as .280 (cam lift) times rocker ratio would be .398. The
accuracy of my gauge and using the valve spring *could* account for
the missing .006. Right? Well, I was dubious, and measured another
valve. Its total lift was .375. I measured another, and its total
lift was .382. The problem is that my pushrods are too long, and
when they push the rocker up, the back side of the push rod hits
the inside of the rocker, which is where my inconsistant results
are coming from. I hope. That makes sense to me, as it would lift
the rocker closer to the valve reducing my rocker ratio, giving
less valve lift. It's either that, or I've already trashed
another cam. Guess I'll have to get vanity plates that say:
"CAMEATR"
I'm sure the pushrods are hitting the inside of the rocker,
(away from the ball) because of the nice smiley faces the
pushrods left on the underside of my rockers.
I've got pushrods on the way from TRF, they should have left
Pennsyltucky monday, but didn't get here (Colorado) yet.
Guess I won't have the car at the TR meet on Sunday. *sigh*
There's no sense in taking a chance on smashing metal parts
together that aren't meant to meet though, so I guess I'm done
debugging until my pushrods show up. (Probably monday)
The oil pressure problem is bizzare. In my process of doing all
this head work, I decided to drop the oil pan to ensure my thrust
washers were installed correctly. In fact they were, but I measured
the end float of the crank with my handy dial indicator and got a
measurement of .001. Not good I thought. So I removed the .005 over
thrust washer, and put in a stock one. I crushed the bearing
when I replaced it, as it cocked in the journal. So I order new
bearings for the entire low end, and this time, replaced them all
correctly. I think. (I'm learning to leave well enought alone
though...)
Oil pressure is great on startup. It's between 80-100 lbs. However,
after it warms up, I get a very low reading, below 25 lbs. Could
I have mismeasured the end float? How could this be with all
new bearings? Would too much end-float cause low oil pressure? If
so why don't I see low oil pressure at startup?
Ah... One more thing, I removed the oil pump to get access to a
bearing. I put it back without disassembly. Could I
have put the oil pump in wrong? I'm sure I put it in they way
it came out, and my oil pressure was great before this exersize.
For the record, I used cheap Mobil 10W30 oil, non syn. Could the
oil be so cheap that it would do this under high heat?
Any ideas, comments, suggestions, or sleep technique - welcomed.
-Scotty
'75 TR6
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