I was searching through the wrecking yard, and came across a burned 87 coupe.
The rocker cover had burned away in a spot the size of a nickle.
I saw that it had roller rockers, and talked the proprieter to sell me the burned engine for $300.
It turned out to be a 383 with a scat crank and SRP forged pistons with a 14cc dish for the 58cc heads. 1 piece rear main with roller cam.
.080 wall pushrods, roller timing chain.
I tore it all apart, and it had new bearings and a very recent hone job.
There was no ridge, and the rings looked like they had hardly seated.
The engine had a standard harmonic balancer with the rubber burned, but the ring was still there
I have it all back together now, New bearings, polished crank, new cam, new rings, honed, decked, new brass freeze plugs, etc.,1989 TPI, 113 heads with a pocket port.
EXCEPT the harmonic balancer is haunting me. It was one that looked like it came off a 60's pickup with a 283. Hollow ring with holes drilled all around the circumference.
Here's my question...
How do I find out if the scat crank is internally balanced or externally balanced?
I would hate to rely on the previous owner's harmonic balancer installation if it's wrong, but I don't know it's balance orientation.

Also, if it is externally balanced, can I use a 350 flex plate with the weight welded to it? Or do I need a flex plate without a weight?
Anybody???

 

anybody know?

 

check the flex flate you got with the engine if it has any weights on it the engine is probably external balanced and you need a sbc external balanced harmonic balancer .but if the flexplate has no weights the engine is internal balanced and you need to run a zero balance balancer.either way you can buy a sfi balancer for cheap and remember the stock style sbc 400 balancer used on ext balanced 383 strokers wont fit in your car unless you notch the engine cradle so the best thing to do is buy a aftermarket balancer that are under 7 inch diameter so they don't hit the crossmember.scat used both internal and external balanced 383 cranks and usally the external balanced set up has a flexplate with weights and a balancer that has a section of it cut out to balance the set up .

 

" 383 with a scat crank "

As it is a Scat crank is more than likely neutral balance at front as the only ext balance at front cranks are genuine Chev 400 cranks with the bigger journals that need cutting down to fit.

Non 400 cranks are all neutral balance at front regardless of int / ext balancing.

"can I use a 350 flex plate with the weight welded to it? Or do I need a flex plate without a weight?"

Unless someone has done a custom balance job;
2 pce seal main cranks are int balance and 1 pce seal cranks are ext balance (weight on flexplate )
The flexplates do not interchange between the two. Different bolt pattern to crank hub.
Is the crank flange 3" or 3.58? Smaller is ext balance 1 pce seal

 

maybe that's why they used a small balancer. The frame was in the way.
It is a 1 piece seal crank, factory roller cam.
I did not get a flexplate with the engine. Now that I think of it, the wrecking yard must have kept it, thinking it was a trans part and not an engine part.
The crank has scat cast into the first part of the crank that looks like a counterweight, but it's just like opposite the first crank throw right behind the first main journal....
THe timing gear for the crank was marked wrong, and somebody put swirl port heads on it off a pickup truck to allow the valves to close without hitting the head.

It looks like the 383 short block right out of the jegs catalog except for the srp dished pistons. The description for that short block doesn't include whether it is int. or ext. balanced.
The thing looked as though they couldn't get it running right and torched it. It must have been a stone with dished pistons and 76cc heads and the cam gear off a tooth
. It had a stock looking cam with bad lobes and equally bad rollers on the lifters.
Somebody put the fire out with dirt. There was a decal in the back hatch glass that said "river *****". It had funky aftermarket wheels as well.
The accessories were melted, and I threw away the rocker covers, power steering pump, alternator was a melted lump of aluminum around the armature, and the water pump and brackets were melted as well. The smog pump was a pulley and a shaft coming out of a melted lump.
The distributor cleaned up pretty good, but it is just a case with a shaft.
The throttle body is ok, but the spring is literally "toast"
Funny thing though, the TPI is perfect. I guess it must have been running, and the air in the intake kept it from overheating. All of the dirt was at the back of the engine so I guess the FPR was leaking.... or that's where they poured the gas and threw the match.