383 Needs A New Crankshaft

[mrein3]

Let’s just get this over with – I messed up.
In the fall of 2004 I built an old-school 383. I acquired a used 400 crankshaft, used the piston kit with the higher wrist pins to work with my stock 350 rods, had the machine work done to the block, and thought I was done with engine work on my truck.
About 4 years ago I get this weird clacking noise which I quickly determined was the harmonic balancer that was loose on the snout of the crankshaft.
The keyway in the crankshaft was a mess! And the threads for the bolt that holds the balancer on was stripped.
I bought a bottoming tap, tapped that hole as far as I could, put a stud in there, purchased a new 400 balancer, and was able to get the required torque on that bolt – now nut in my case.
This spring it started ticking. At first I thought it was an exhaust leak but nope, it was the balancer hitting the key for the timing chain gear on the crank (you can see how shiny that is in the picture).
Tick-tick-tick-tick. Not a major problem at the moment but it wasn’t going to get better on its own.
My plan is to buy a replacement 400 crank (about $200 at jegs and summit), measure the bearing surfaces because after 12 years I can’t remember who was 10 grand over and who was 20 grand under, get the proper bearings, and replace the crankshaft.
My question is, can this be done with the engine on a stand, without disassembling the whole engine? In other words, turn it upside down, remove the pan, remove the main caps and the bottom of the rods. Or does it have to come all the way apart? I guess more importantly, has anybody replaced a crank this way?
The 383 is already on the stand. I swapped it out for my Chevelle’s original 307 which now propelling its third vehicle in its lifetime as a temporary replacement while I correct this issue.

[truckdude239]

Flip it over and pull the crank no reason to disassemble the whole engine

[truckster]

I've done it that way. You just need to be careful that the rod bolts don't score your new crank. Plastic protectors or a short piece of fuel hose will do the job. And I would Plastigage all the bearings just to be sure.

[mrein3]

Originally Posted by truckdude239

Flip it over and pull the crank no reason to disassemble the whole engine

Originally Posted by truckster

I've done it that way. You just need to be careful that the rod bolts don't score your new crank. Plastic protectors or a short piece of fuel hose will do the job. And I would Plastigage all the bearings just to be sure.

Thanks for the answers guys. And yes, there is a Plastigage kit in my future.

[A1971Blazer]

Years ago my wife's Cutlass spun a rod bearing and locked up....I pulled the motor on Thursday, put it on a stand and removed the intake and the head only on one side (where the bad rod was) pulled it out, unbolted all the other rod bottoms and pushed them down as far as they would go by hand.
Took the crank out and bought a crank kit and one new rod....put it back together and had it running Saturday afternoon. She drove it for another year, and then we traded it. For several years I saw it around town....still running!

So yes, you can replace the crank without a full tear-down....

[Captainfab]

There is no sense in purchasing a 400 crank and having to machine the mains down to medium journal size. Just purchase an aftermarket Scat 383 crank and a set of new standard bearings. Flip your engine over and install it.

[mrein3]

Originally Posted by Captainfab

There is no sense in purchasing a 400 crank and having to machine the mains down to medium journal size. Just purchase an aftermarket Scat 383 crank and a set of new standard bearings. Flip your engine over and install it.

Yes. That is the plan. I guess in re-reading my original post I did say I would get a replacement 400 crank. When I originally did this there weren't a whole lot of options. If I did this again I would start with a roller 350 and buy a 383 "kit".

This is the crankshaft I'm looking at:
JEGS Part Number: 356-103503750

About $200 which if I remember correctly is about what I paid for the 400 crank I had to have turned down all those years ago.

Do I need to worry about the "1870 Bobweight" on this part?

Or is it really plug and play?

[burnin oil]

Most machine shops will tell you to avoid Eagle cranks. Go with the SCAT 9000 and you wont have any problems with durability. They are pretty tough for a cast crank and cost about the same as the Eagle. Personally I would have the whole rotating assembly rebalanced but you would probably be fine if it is a low rev truck 383. Theoretically the crank doesn't really need balanced but that is a gamble that it is 100% correct out of the box. I have done cranks twice in a 400 without balancing and ran them to 6k RPM but both were factory cranks that were ground. Usually they loafed along at 2k RPMs.

[Tom]

Another vote for SCAT 9000.

[mrein3]

Originally Posted by burnin oil

Most machine shops will tell you to avoid Eagle cranks. Go with the SCAT 9000 and you wont have any problems with durability. They are pretty tough for a cast crank and cost about the same as the Eagle. Personally I would have the whole rotating assembly rebalanced but you would probably be fine if it is a low rev truck 383. Theoretically the crank doesn't really need balanced but that is a gamble that it is 100% correct out of the box. I have done cranks twice in a 400 without balancing and ran them to 6k RPM but both were factory cranks that were ground. Usually they loafed along at 2k RPMs.

Originally Posted by Tom

Another vote for SCAT 9000.

Are you guys talking about this one?
JEGS Part Number: 942-9103750

http://www.jegs.com/i/Scat/942/9103750/10002/-1

[Captainfab]

That is what I was talking about........

Originally Posted by mrein3

Are you guys talking about this one?
JEGS Part Number: 942-9103750

http://www.jegs.com/i/Scat/942/9103750/10002/-1

[mrein3]

Originally Posted by Captainfab

That is what I was talking about........

Perfect. Thanks.

Now I just need the money. It is always one of two ways for me. I either have all the time in the world (like now) and no money. Or some spending money and no time.

The engine is on the stand. Once I procure some funding I will tackle this job.

For now that old 307 is getting the job done. Its a bit smokey and the starter needs a shim or two but what are you going to do in this economy?

[crazy longhorn]

Originally Posted by mrein3

Perfect. Thanks.

Now I just need the money. It is always one of two ways for me. I either have all the time in the world (like now) and no money. Or some spending money and no time.

The engine is on the stand. Once I procure some funding I will tackle this job.

For now that old 307 is getting the job done. Its a bit smokey and the starter needs a shim or two but what are you going to do in this economy?

Same for me brother....either money & no time....more often , its no money, & lots of time? Just take your time & do her right....what it cost you in the end don't really matter Longhorn

[Marv D]

Another vote for scat here too, but be aware, Eagle and Scat are the SAME CRANK, forged in the same foundry. I prefer Scat simply because it is cast/forged then shipped and finished HERE in the US. Where Eagle is final machined in China. The old days of the Eagle cranks being terrible in final size is somewhat history. The QC is greatly improved... actually lets just say they actually HAVE a Q C program now <rolls eyes>. So really no reason to avoid them,, other than the Scat / US workers deal. (which is plenty reason enough for me, but that's me)

You guys that have pulled the crank out of a stroked SBC without pulling the heads... I would really like to see that. Never dreamed of even trying it myself,, there is just WAY too many rod bolts in the way that is seems there is going to be a nicked journal going back together. You google and it's definitely possible,, but I just can't wrap my head around, WHY??

[mrein3]

Originally Posted by crazy longhorn

Same for me brother....either money & no time....more often , its no money, & lots of time? Just take your time & do her right....what it cost you in the end don't really matter Longhorn

Originally Posted by Marv D

Another vote for scat here too, but be aware, Eagle and Scat are the SAME CRANK, forged in the same foundry. I prefer Scat simply because it is cast/forged then shipped and finished HERE in the US. Where Eagle is final machined in China. The old days of the Eagle cranks being terrible in final size is somewhat history. The QC is greatly improved... actually lets just say they actually HAVE a Q C program now <rolls eyes>. So really no reason to avoid them,, other than the Scat / US workers deal. (which is plenty reason enough for me, but that's me)

You guys that have pulled the crank out of a stroked SBC without pulling the heads... I would really like to see that. Never dreamed of even trying it myself,, there is just WAY too many rod bolts in the way that is seems there is going to be a nicked journal going back together. You google and it's definitely possible,, but I just can't wrap my head around, WHY??

So here is where I'm at. I'm trying to avoid the slippery slope. I didn't know how much power I gained going from the tired, cam eating, 2 bbl 350 that was in the truck when I bought it to the 383 I just pulled for that ticky front snout issue. This 307 feels like a 4 cylinder Chevy Cruze before the turbos kick in.

The 383 was built with flat-top pistons. When I first installed it I had 87 octane in the tanks. You should have heard that thing ping! Ever since I've run 91 octane. Which is sort of OK because the only non-ethanol I can buy here in the state where nothing is allowed - Minnesota - is 91 octane. And since the truck can go a month without being used during certain times of the year, I don't want ethanol anyway.

So that is where the slippery slope will start. If I pull the heads to get the pistons out, why not newer vortec style heads? Different heads means new intake necessary (cost of heads plus cost of intake). As long as I got the pistons out, why not different pistons that will run on pump gas ($200 crank becomes a $750 - $1000 rotating assembly)?

THEN, if I'm doing all that work, why not just rebuild the 350 roller I got out of a knocking 1999 Suburban and make that a 383? Then what do I do with Mr. Ticky 383? (get back on the slippery slope, make tick go away, swap it in to the '71 convertible and give it's factory provided 307 a rest).

IF I ever get the money this would be easy. But then I wouldn't have any time to work on all this stuff.

See where I'm at? Ug.

[Marv D]

You want to be careful with the little 64cc vortec heads and any flat top 383 piston. With a standard 0.025" deck and typical 3-5cc flat top valve reliefs, you will be at 10.6:1 compression. If the block has been decked you can top 11.2:1 in a heartbeat.

The vortec craze was the 'camelhumps' of the new millinum and just like the camelhumps they are a dated head that has its problems after 20 years of service. Not saying they are not a OK street head, just that today there is much more cost effective and more powerful choices.

[storm9c1]

If you go with Vortec heads, definitely go with a dish piston.

I know how projects can snowball. I'm guilty of it too. For example, I rewired my Charger. And rebuilt the entire front end from the ground up. Why? Because a freeze plug leaked. Of course!

But if money is tight, sounds like you just need to replace the crank and get it back on the road.

[mrein3]

Originally Posted by Marv D

You want to be careful with the little 64cc vortec heads and any flat top 383 piston. With a standard 0.025" deck and typical 3-5cc flat top valve reliefs, you will be at 10.6:1 compression. If the block has been decked you can top 11.2:1 in a heartbeat.

The vortec craze was the 'camelhumps' of the new millinum and just like the camelhumps they are a dated head that has its problems after 20 years of service. Not saying they are not a OK street head, just that today there is much more cost effective and more powerful choices.

The last time I was in my favorite cylinder head exchange place I asked about factory vortecs. He pretty much agreed with what you said. He said he could get me a lot better head for not much more than it would cost to freshen up the factory set I had. And they won't crack.

Originally Posted by storm9c1

If you go with Vortec heads, definitely go with a dish piston.

I know how projects can snowball. I'm guilty of it too. For example, I rewired my Charger. And rebuilt the entire front end from the ground up. Why? Because a freeze plug leaked. Of course!

But if money is tight, sounds like you just need to replace the crank and get it back on the road.

The longer this thing has been sitting on the stand, the more I'm thinking it is new crankshaft AND THAT IS IT.