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In the quest for more power and quicker times, I bought (in early 2000) a new cam, carb, converter (used), and main studs (to help the motor withstand 6500 rpm shifts).
The Damage:
When I tore my
engine down to install the cam, main studs, etc., I decided as
long as I was that far into it, I should check my main bearings
(since the main bolts were off anyway). The bearings were
horrible. The outer two (#1 and #5) were tolerable, but the
middle three were worn down to the copper layer after only 17,000
miles.
Here's one of the mains:
You can see where it's worn to the copper, right? Two others were just as bad. I had no idea what to do. I figured I needed to replace the bearings, and to do that, the crank needed to come out, and to do that, the rods and pistons needed to come out! What a drag. So I look at the rod bearings and #1-#4 are poor, but not horrible, but #5-#8 are really bad!
The Cause:
Soooo, what could be
the problem? I asked around and got several theories.
Bad main saddle alignment
Detonation
Rotating assembly out of balance
Oil pump sucked the pan dry
Oil film breakdown (either air/fuel ratio bad or poor combustion, causing oil dilution)
Bad crank (bent, warped, etc.)
The Solution:
I had a spare crank,
so I brought that and my block into the machine shop to eliminate
as many of these possiblities as I could.
They turned the crank (eliminating a bent/warped crank as a possible cause of future problems).
They decked the block (giving a higher compression ratio but also better quench, and hopefully better combustion).
They align-honed the mains ensuring the crank would stay put.
I also purchased a 7-quart Moroso oil pan, pump pickup, scraper, windage tray, pan baffle, Melling M55A oil pump, and an oil temp gauge, so that should eliminate any worries about the oiling system.
I installed a bigger Comp XE274 cam, so that should bleed off a little cylinder pressure.
Also, as mentioned earlier, I'm putting oxygen sensors in my headers to monitor the air/fuel ratio as I drive.
The only unaddressed possible cause on my list is the balance of the rotating assembly, but since I only need this motor for 2-3 years and I really don't think that was the cause anyway (and it's expensive), I decided to skip the balancing this time.
Here are pics of the crank in the block and my new oil pan.
More Problems:
I found out my stock replacement harmonic balancer I had purchased 2 years earlier had
cracked, so here's the 6-3/4" StreetDampr I got from Summit.
Beautiful, ain't it? It was a shame to paint it. I wanted the 8" Fluidampr, but that
was twice the price.
Finally:
Here's the motor on the stand:
Installation:
I finally got the motor installed on May 23rd, 2000, all hooked up on the 24th,
and fired it up on the 25th for the cam break-in. We had a few
minor problems, but eventually it all worked out. It ran great
during the break-in, no leaks or anything, just burned lots of
the POR-15 off the headers. No surprise. It's got a nice, lopey idle and
will run at 700 rpm, lower than I thought. I love it!
Results:
The motor gave me 13.3s @ 103.2 mph in the quarter. I
think it's strong enough for very low 13s but I need a looser converter,
the Holeshot 2400 is just too tight to let me get into the powerband.
Go to Bruce's '72 Nova - 2001 for what I did in 2001.
Copyright © 2005 Bruce Johnson and Craig Watson