89 RCLB K1500 - Quality time with my son building his first truck.

[SNCTMPL]

Walked into Summit to get a crankshaft, everything in the store was 10% off. I just couldn’t help myself.

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[dave s]

Haha, I understand how that happens. Back in 03 I went to a car show in Columbus. Coming back I passed Summit on the way back to PA. Stopped just to look around. Ended up with my bad half full and wallet a good bit lighter. Couple weeks back returning from my daughters in Kansas City, we passed right by Summit. I said "honey can we stop at Summit". I got the evil eyes. Lol. And didn't stop.

 

[Road Trip]

Hey Dad,

Just read through this string w/pleasure. So so cool what you are
doing with your son! And you aren't making the mistake of just
handing it to him on a silver platter:

So my son went out and got himself a job at 15, saved up a few paychecks, and went and bought...

So listen, I've also got a roller-cam 383ci SBC on the engine stand,
and it will also end up with a manual tranny behind it. (Helping an
old friend put together a sleeper to help stave off boredom once
he crosses the finish line into retirement. :0)

Given this, I find the specifics of your build very interesting. And
before I go further, in the past I've found that with a little effort
a mongrel motor that was put together by cleaning off all the
shelves in the shop can be like the perfect stew that was
created by cleaning out the fridge. It can be astounding -- it is
the nature of the universe that sometimes when we try easier
we get the best results of all!

****

Alright. Since only a relative handful of us still put stickshifts
behind fresh motors, a few small details can cause real grief
once we try to stuff the powerplant in the engine bay w/no joy.
Or worse, it goes together, only to vibrate the entire time you
drive it. :0( Without further ado, here goes:

Clear, concise explanation of difference between '55-'85 SBC cranks w/2-piece oil seals vis-a-vis SBC '86+ cranks w/1-piece seals

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(credit: thirdgen.org -- follow this (link) & refer to post #7)

NOTE: I can tell from your approach that this isn't your 1st rodeo,
so when you read the following I'm just trying to be precise about
the parts combo, not infer that you need a refresher on any of this. (!)

In post #25 you make mention of a "tbi roller block". OK, so that's
a 1-piece rear main seal design. So far so good. Now if you were
installing a stock 3.48" stroke 1-piece seal Chevy crank, the $80 flywheel
you mentioned in post #22 gets bolted on, the clutch/pressure
plate installs after that, and away you go. I get that.

But for this motor's recipe you have a 3.75" stroker crank.
(+ 5.7" rods, nice 2-eyebrow pistons to match, etc)

Q1: Is this aftermarket crank balanced the same as the
3.48" stock crank it's replacing? (Ie: The flywheel that works
behind the stock 3.48" crank will also work behind the aftermarket
3.75" crank? If so, cool beans.

IF on the other hand it has the same (lack of total) counterbalance
weight as the old stock 3.75" (400ci) Chevy cranks, then now
do we have to go down the externally-balanced 400ci flywheel path?
Do they even make those to bolt up to the flange on a 1-pc rear
main seal crank?

Q2: Using the casting part number seen in your photo (#93433010N)
I poked around a little, and came up with this amazon listing showing a
near-identical new flywheel for sale. Please go look at the face of
that flywheel closely before looking at the pic below: (Amazon link)

Is this part of a previous motor's balance job? Or is it just factory balancing to bring this casting into spec?

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FWIW, this would make me want to discuss what I have with the machinist, and see if he recommends balancing? Or this is normal & balancing is optional?

Q3: Is your new crank already machined on the flywheel end for
the tranny input shaft pilot bushing? (bearing?) Given that the
vast majority of new engines are connected to slushboxes, not
all cranks are set up for us 5%'ers. :0)

IF it is machined, what is it machined for? Bearing? Bushing? What's the ID
of the hole in the center of the crank? (And at the same time, what's the OD
of the tranny input shaft that's expecting a bushing to support
the crankshaft end? Now that you have both, do you have the
exact right sized part in hand? Trust but verify, and I won't even
start the assembling/stuffing process until I've slid that bushing/bearing
over the tranny input shaft myself & the feel is confidence-inspiring.
And the same part then fits into the end of crank no problemo?

Color me overly cautious, but thanks to my stubborn desire to
keep driving a standard tranny, I *think* I've been burned every
possible way inside the bellhousing while attempting to marry engines
and transmissions from the far reaches of the automotive hobby.

Look forward to your reply. Best of luck with your home-brew
small block hot-rod stew!

 

[Road Trip]

(Optional Reading: Balancing across the Gen 1 SBC)

Note: Experienced mechanics who bleed Chevrolet Orange
should consider the following Very Optional reading. This
is targeted more towards those who grew up in the LS era
and all this ancient SBC stuff is like old flathead Fords to me.

OK, then. At the risk of oversimplification, SBC balancing
falls into the 3 general categories.

* '55-'85 ALL strokes up to & including 3.48" (ie: except 400ci)

All the counterweighting needed is available on the
crankshaft itself. The harmonic balancer in front
and flexplate/flywheel are neutral balanced. (ie:
no counterweights on either.) This is referred
to as 'internally balanced.'

* '70-'80 3.75" stroke 400ci SBC

This longer stroke crank + an 1/8" factory overbore
(necessitating siamesed bores & steam holes)
allowed Chevy to add 50ci worth of additional
low-speed torque during the bad years of
1st-generation emissions controls.

Since there wasn't enough room in the crankcase
to provide the clearance for the additional
required counterweighting, the additional weight
was added to *both* the harmonic balancer in the
front and the flywheel in the back.

(The unique-to-400 harmonic balancer is
how we knew during our misspent youth that the mystery
dude claiming he had a 307 under the hood was approx.
76ci or even 99ci shy of the truth. :0)

NOTE: This is referred to as externally balanced.
Not the preferred method for extended high rpm
operation...but extended high-rpm operation was at
the bottom of the punch list for the original
smog-era designers.

* '86+ 1-piece rear main seal SBCs

NOTE: I've seen some heated arguments and semantic
debate over the following, but in context with the
above this is how I understand these newer 1st-gen
small blocks.

If you go back to that earlier photo showing both cranks,
when Chevy wanted to improve on the customer satisfaction
having to do with labor-intensive replacement of leaky
2-piece rear main seals, they had a problem -- they
couldn't get those seals over the crank flange that
the flywheel is bolted up to.

So, in order to accomodate the 1-piece rear seal, the
back of the crank flange was made into a perfect circle.

The only problem now was that since the original crank flange
had some counterweighting incorporated into it's shape,
with the new setup they had to replace it somewhere. So check out
what a manual transmission flywheel looks like on an
'86-up 1-pc SBC:

Must-have feature for stock crank-equipped '86+ SBCs running a flywheel
(ie: slightly unbalanced flywheel to make up missing counterbalance wt on now-circular crank mounting flange.)

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IMPORTANT NOTE: Since the rest of the crank was left as-is, there was
no need to redesign the harmonic balancer, so it remains neutral-balanced.
(ie: no asymmetric relieving or counterweighting like the 400ci motor)

So, the '86-newer SBCs kind of straddle the 2 other SBC categories,
in that you must have this unbalanced flywheel in the back and a
*balanced* harmonic balancer in the front! (Wow, this is starting to
feel like 'Brand F' territory! :0)

****

As for Dad, my guess is that since his aftermarket crank is a 1-pc
design, it's going to be counterbalanced for *this* flywheel, and
if he has been living clean, will also be machined on the end to accept
the transmission input shaft whatever. (bushing/bearing.)

And again, I'd like to thank Dad for being a little further along than
my project, so that he can figure all this out exactly & share it
with yours truly. :0)

Hope this clears this up. Here's some additional reading for
those who can't get enough of all this:

* Chevrolet 1-piece rear main seals for maintenance: (link)

* Chevrolet 2-piece rear main seals for maintenance: (link)

* Retrofitting desirable 2-pc seal cranks into '86-newer blocks: (link)

And to wrap this up, here's the newer '86+ 1-pc rear main seal that came with your factory SBC V8-powered GMT400 machines:

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[SNCTMPL]

Thanks for reading this, glad you enjoyed it.

As for Q1, the crankshaft is externally balanced both front and rear. It requires the weighted 400 style balancer and externally balanced flywheel. The reason I went with this setup is that some of the other internal/external balanced cranks may require quite a bit of mallory in the front of the crank to balance, and that can drive up the cost pretty quickly.

For Q2, that is factory balancing to bring it in to spec.

Q3 is a good one. I don’t know, I assumed it was, I will check when I get back home, I’m in Denver this week for work. I bought a Centerforce bearing for it, but now I’ll have to check.

 

[Road Trip]

Thanks for reading this, glad you enjoyed it.

As for Q1, the crankshaft is externally balanced both front and rear. It requires the weighted 400 style balancer and externally balanced flywheel. The reason I went with this setup is that some of the other internal/external balanced cranks may require quite a bit of mallory in the front of the crank to balance, and that can drive up the cost pretty quickly.

For Q2, that is factory balancing to bring it in to spec.

Q3 is a good one. I don’t know, I assumed it was, I will check when I get back home, I’m in Denver this week for work. I bought a Centerforce bearing for it, but now I’ll have to check.

Re: Q1 & Q2: Sounds like you are all over this. Good pragmatic
choice avoiding the need for mallory metal! I would have done
the same thing given the goals of this project. (!)

Re: Q3: You are obviously way early in the build, but by checking
this early it won't become (what should be) an easily
avoidable showstopper when it's time to go in. Been there, no fun
to be had when the tranny input shaft bearing I need is temporarily on
the unobtanium list. You know, when my lack of planning ahead
plays into the excuse du jour:

"You can't have part X due to Supply Chain issues." :-(

Safe travels --

 

[fancyTBI]

This thread has been a great read. Can’t wait to see more. There’s nothing like a good father/son project.

By the way, the truck has perfect patina. I sometimes wish my ‘95 looked like that.

 

[Orpedcrow]

the truck has perfect patina

I was thinking that too.
These trucks don’t usually “patina” very well. Makes me want to get a white w/t that’s been road hard and put away wet for 25 years.

 

[SNCTMPL]

Thanks for reading it. My son and I are actually going to finally get started on it this weekend.

Sorry guys, the patina is not staying. It’s going to get fresh paint before it’s done.

Oh, and Summit did it to me again, another 10% off coupon. I might need a program.

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[Orpedcrow]

Summit is bad about enabling addicts, I’m lucky to not have one close so I’m not tempted by their scratch and dent, open box section.