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Discussion Starter #1
I'm restoring 1973 Nova that currently has a built 350 engine (from 1987), th350 auto trans. headers, msd ignition, 3k stall, Holley 650 double pumper, and a few other upgrades.

I've got a 383 Vortec Jasper engine (from 1996) that started knocking when an oil coolant line broke, causing the engine to run dry. After disassembling the motor I found a seized piston and some signs of wear on the crank. The other parts appear to be fine, but this is my first time completely disassembling a short block so I'm not certain what parts can be reused.

I need assistance figuring out what parts to buy, and estimating a budget. Since this is my first complete engine build I'm also looking for suggestions and potential problems I may encounter.

  • Machine Shop - Polish the crank - $90
  • Machine Shop - Valve Job on Vortec Heads - $325 (How do I determine if a valve job is necessary?)
  • Camshaft - suggestions?
  • Intake Manifold (must fit Vortec Heads) - suggestions?
  • Carb - I have a Holley 750 Demon and a Holley 650 Double pumper that could be used, open to suggestions.
  • Bearings for the crank.
  • I plan on reusing the lifters, rockers, pushrods, connecting rods and pistons (if possible)
  • New hardware or Reuse old hardware?

The engine will be used on the street for fun when the weather is nice. Not exactly a daily driver. 10:1 compression on pump gas with 500hp is the goal...

 

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Have the crank magnafluxed for cracks and then depending on the wear it may need to be cut. If this is the case, it may be cost effective to buy a new Scat 9000 replacement crank. It may be unlikely to save the crank if it got that hot to seize itself with no oil. Hone the block with a torque plate to ensure round cylinders. If it was me, I would go hydraulic roller cam. Replace the rings and bearings. I would have the heads gone through and the right springs in stalled for the cam. 500 hp is a large number for a pump gas engine with factory casting heads. But it is going to at least take exacting tolerances in parts fit.
 

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If the piston seized up due to lack of oil there is likely to be quite a lot of scoring in the cylinder wall and/or the piston. I would honestly take the block to the machine shop and have them check the bore for taper and trueness. It will likely need to be bored more than the .030 over that it already takes to make a 383.

At the very least, you will need new rings as well as rod and main bearings. The machine shop will be able to tell you if you can get away with running standards or if the crank will need to be turned. Since you are planning on replacing the cam, make sure you replace the lifters at the same time. You never want to put old lifters on top of a new cam... Edelbrock makes a good Air Gap intake for the Vortec heads. The carb is really going to depend on what cam you ultimately decide to run.
 

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Discussion Starter #4
Have the crank magnafluxed for cracks and then depending on the wear it may need to be cut. If this is the case, it may be cost effective to buy a new Scat 9000 replacement crank. It may be unlikely to save the crank if it got that hot to seize itself with no oil. Hone the block with a torque plate to ensure round cylinders. If it was me, I would go hydraulic roller cam. Replace the rings and bearings. I would have the heads gone through and the right springs in stalled for the cam. 500 hp is a large number for a pump gas engine with factory casting heads. But it is going to at least take exacting tolerances in parts fit.
Thank you for your insight. I'll look into everything you mentioned.

I know 500hp is a stretch in this situation.

What do you think is possible in terms of max-horsepower with Vortec heads?

Would I be better off ditching the Vortec heads? That would save $325 + the cost of an intake that fits Vortec heads. I have intakes that fit 1986+ heads and pre-86 heads.
 

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Vortecs work very well for a cheap performance build up to about 400hp.
To make 500, you have to spin the engine up to 6000 rpm, or better. That last 100 hp will be exspensive, easy if you have the money. You can look at the GM crate motors for ideas on the components required, and the power levels, for a reasonably priced Vortec build.
 

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Don't fool with the old crank for not much more you can purchase a brand new one, id have it bored out and also get new pistons. I do all my own work and I take care of the machine shops air conditioner so I get free machine work, so it works out for both of us
 

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Unless you are going to buy a set of aftermarket aluminum heads I'd stay with the vortec heads. If you are really wanting to build horsepower I'd also go with a hydraulic roller camshaft. Even with a set of heads and Hyd roller camshaft 500 hp is hard to do if you are planning on also being able to drive the car. It would be fairly easy to build 400 but as already stated that last 100 is hard to come by. With what has happened to your engine everything needs to be checked. Heads, block, crank, pistons and rods. Any time I build a engine I start with making sure the block is cleaned, checked and has new cam bearings and freeze plugs. After that every part that goes in needs to be checked also. There is no way I'd bolt a set of heads on a fresh engine that hadn't been checked especially one that came off a engine that had had problems. Everything needs to be fresh. When building a engine it needs to be clean. Clean shop, clean parts and clean tools. Things cannot be too clean.
 

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Discussion Starter #8
I appreciate everyone's feedback, very helpful information. I assumed 500hp would be easier to attain with a 383 vs 350. The spec sheet from Jasper says the engine is rated for 325hp @ 5000rpm and 415ft lbs @ 3600. So all of this is beginning to make sense.

Looking at factory long blocks as a starting point is a good idea, I hadn't considered that option. Thanks, Midmo Joe

After reading what 63 Bomb said, I checked the block and found some scratches in the cylinders. The wear on the crank is visible but smooth when I drag my fingernail across the surface. I included some pictures that might help to determine if the crank is reusable.

Please excuse my lack of experience on this topic. The pistons have 0.40 engraved at the top. If the bock needs to be bored an additional 0.30 over to fix the scratches, does that mean I have a 350 block that has been bored 0.70 over stock? I know the cranks' stroke length is 3.750. With all that considered, wouldn't the displacement be greater than 383?





 

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Cylinder heads are the key to making HP. They are also where you can spend a lot of money. One of the reasons the LS motors have become so popular is that their factory cast cylinder heads flow MUCH better than old small block Chevy heads. It is very easy to make 500 hp with a 6.0L LS motor with a cam swap, headers, and a tune.
 

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I would guess, the crank needs to be cut .010 on the rods and mains if its not already cut. The backside of the bearings will have a .010 or .020 if its been cut already. The block, I would try to save at .060 over for a common shelf stock piston. And this would make the motor a 388, but it doesn't matter, the motor at .040 over was technically a 385 not a 383.
 

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That's a pretty considerable gouge in the cylinder wall... does your fingernail hang in it? I'd talk to the machine shop to see what it'll take to clean that up. Just from the looks of it, it's going to take quite a bit. Small blocks don't usually like to stay cool when they've been bored .080 over. Only a good mic will tell what the crank is going to take to clean up.

383's are made by lengthening the stroke of the engine (originally by installing a 400 crank in a 4" bore block), then increasing the bore by .030". Without the overbore it's actually a 379. Before companies started making dedicated 383 cranks you had to make sure you used a 400 balancer and flywheel/flexplate because 400's were externally balanced.
 

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What is your budget. There are a lot of different ways you can go at this point. Right now you are looking at machine work and buying new parts. The only way to know about your block and crank is to use a micrometer and measure. You are literally dealing with measurements as small as the width of a hair off your head. You cannot look and tell. If your block needs boring and your crank needs turning you may be better off buying a long or short block depending on what you decide about your heads. They would need to be checked also. I've been building engines for thirty years. I've built stock engine and I've built seven second quarter mile engines. Right now my car has a crate engine simply because I could not build it for what I could buy it shipped. Also came with a two year warranty.
 

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Several mentioned buying a new aftermarket (Scat?) crank instead of regrinding the old one. These Scat cranks are very affordable and are cast steel, far superior to factory cast iron. Your crank throw on the left shows signs of “blueing”, I wouldn’t re-use it.
We installed one of these Scats in a low budget 383” mud-racing truck engine that has been abused pretty hard. Previous factory regrinds would eat the main bearings after a few seasons, probably the cranks were flexing, and of course they would leak oil out the rear main seal. After 4 years, the bottom of this engine is still oil free, this would be a nice extra benefit on a car you park in your garage.
 

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I thought 383s were built by increasing the stroke length OR increasing the bore size. Is that incorrect?
A 383 is a 350 block bored .030 with a crank out of a small block 400 which is a 3.75 stroke.
 

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Discussion Starter #16
That's a pretty considerable gouge in the cylinder wall... does your fingernail hang in it?
Yes. Now I'll definitely be taking the block to a machine shop if I pursue this build. Thanks for the clarification on 383s.


What is your budget.
Hopefully, this thread will help me estimate how much it would cost to rebuild the motor. At this point, an LS swap or new long block seems more cost-effective in terms of horsepower and reliability. I get your point, and a 2-year warranty would be nice.
 

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I appreciate everyone's feedback, very helpful information. I assumed 500hp would be easier to attain with a 383 vs 350. The spec sheet from Jasper says the engine is rated for 325hp @ 5000rpm and 415ft lbs @ 3600. So all of this is beginning to make sense.

Looking at factory long blocks as a starting point is a good idea, I hadn't considered that option. Thanks, Midmo Joe

After reading what 63 Bomb said, I checked the block and found some scratches in the cylinders. The wear on the crank is visible but smooth when I drag my fingernail across the surface. I included some pictures that might help to determine if the crank is reusable.

Please excuse my lack of experience on this topic. The pistons have 0.40 engraved at the top. If the bock needs to be bored an additional 0.30 over to fix the scratches, does that mean I have a 350 block that has been bored 0.70 over stock? I know the cranks' stroke length is 3.750. With all that considered, wouldn't the displacement be greater than 383?





throw the motor away and start over...seriously...something went wrong with the oiling system or poorly built to look that bad...it looks like it got real hot...the rod ends should be blue if it seized at the crank
 

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Cylinder heads are the key to making HP. They are also where you can spend a lot of money. One of the reasons the LS motors have become so popular is that their factory cast cylinder heads flow MUCH better than old small block Chevy heads. It is very easy to make 500 hp with a 6.0L LS motor with a cam swap, headers, and a tune.
don't leave out the ooddles an goobs of wiring harness and hope it starts...efi from back to front big money just for the fuel system starting a the gas tank which is around 1800$ conservatively...in the end you may have a LS but the headaches just aint worth it...
p.s. a zz406 type crate motor from chevy already tuned to run would be more fun
 

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Welll,
It all comes down to money.
Do u want to build your block or buy another one?
Personally, your engine is no good.
1. Oil supply failure
2. Probably been rebuilt 2X.
3. Needs a crank.
4. Needs a cam
5. Needs heads rebuilt.
It’s not worth much.
Nobody is talking about lifter bores.
I would guess they are excessively worn now.
Buy a rebuilt .030 383 from summit or jegs or Speedway, or chevrolet.
Chevy sells rebuilt engines too.
If you get another shortblock, i recommend 88 or newer.
they are roller blocks.
87 was first year for rollers.
Buy up from there
 

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eastwood has a bunch of 383's, look at some of those, gives a great idea of the amount of cam lift and especially duration you are going to need to get 500hp, plus heads, crank, lifters, rockers, etc. You are not going to hit 500hp without getting close to 240 deg duration and everything working to 7000rpm, and then it will hardly run under 3000 rpm. and there is no way your engine will stay together at the rpm's you will need for 500hp using any of the parts from a 325 hp 350 (talking lifters, pushrods, rockers, springs)
 
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