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Start the rebuild by ripping apart your 350LT1. Send the stock
crank with stock flexplate to the balance shop along with your new
Mahle pistons #SBC250030F05 complete with pins, rings, and
wire locks. Also send your SCAT rods #2ICR-6000-7/16 along
with your new Mahle rod and main bearings and flexplate bolts.
1 week later the crank is balanced by McKeown Motorsports.
Expect to pay from $200 to $300. You might opt to have the
crank polished. If you decide to have it turned to .010"
under then indicate that you need .010" under bearings.
One way to check for rod bearing clearance is to install the rod
bearings and torque the caps to spec. I use my rod vice but
you can use a towel in a standard vice.
The bore gauge posing here showed all the rods at 2.1020. The
crank rod journals all measured 2.1000 to 2.0995 which gives .0020
to .0025" rod bearing clearance.
The Mahle piston kit comes with premium file fit rings. I
filed for street/strip performance 150hp nitrous, (.024" top
and .028" 2nd). If you are not good at ring filing ask
the machine shop to do it for you. Make sure they follow the
Mahle instructions. The 2nd ring gap should always be larger
than the 1st ring gap.
The bottom side of the Mahle piston. Here I'm assembling rod
to piston.
And here we have a finished 355LT1 short block bottom end.
All my pistons measured .018" in the hole. With a
.026" Mr. Gasket head gasket, (The VR gaskets are also
.026"), and the pistons .018" in the
hole that will give .044" quench which is pretty good. I
prefer to deck the block as little as possible but try to get
.040" to .050" quench. You can go as tight as
.035" quench but be careful.
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The stock crankshaft gets rebalanced of course because the new rods
and pistons are lighter than the stock rods/pistons. Pull the
old sprocket and hammer on your new Cloyes oversized sprocket while
the crank is out of the motor, (#S505).
You don't have to do this but this is the fun part of engine
building. . . the measuring. I'm using a cheaper set of SCAT
rods with the 3/8" rod bolts. The 7/16" version is cheap
insurance.
The rod at the top is the one you should buy. It cost
$287.95 at Summit. The bolt is much stronger than the
3/8" bolt in the rod I'm using.
Here is my block. I installed the cam bearings but consider
having your machine shop do that along with the freeze plugs and
head deck dowel pins. My machine shop charged $845 for
the following: Remove cam bearings, oil plugs, cook block and check for
cracks, buff machined surfaces, re-clean after final machining
($250). Align hone main saddles ($225), Deck block to 9.010"
($250), Bore/hone cylinders to .030" ($120)
You don't really need to do this either but I measured the main
bearing clearance. Install the Mahle main bearings and main caps and
torque to 77ft-lb.
Then stick your dial-bore gauge in and zero it out.
The mains mic'ed out to 2.4515" and the crank measured 2.449
which gives .0025" main bearings clearance.
I spent $1190 for nice
rods, premium pistons and rings, (and gaskets that we have not used yet),
$845 for machine work, $250 for balance, $25 for cam bearings, $10 for
core plugs. We now have a 355LT1 for $2320. I'll put some
heads on and finish the motor soon.
Below this point I show the
rest of my build-up. I'm a fan of high volume and high pressure oil
pumps, (with proper windage control). You'll hear people warn that
HV pumps suck the stock pan dry so do not copy what I do with this
motor. In other words, build at your own risk. :)
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These are my very well used GM LT4 heads which have been pocket
ported by Terry Samakow of Samakow Racing Engines, Prince Frederick,
Maryland. (Terry is not in business with the public so please do not
call).
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The whole valve train came from my 383LT1. It's a solid roller
set up using the a small Crane street solid roller cam. I love
these T&D shaft rockers. Once you go to shaft rockers you
never return to stud rockers.
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