It's also worth noting that the intake port size of heads are rated to flow up to a certain RPM on a certain displacement

383 Stroker FAQ

The 383 Chevy is one of the more powerful engines you can build. It is also the source of many questions and a lot of confusion. This is a basic 383 information page. The info is specifically about the properties and special conditions they may require in there buildups.
What is a 383 and what do I need to build one?
A 383 is a 350 production block with a 400 production stroke crankshaft. A stock 400 crank has to have some special machine work done, namely the main journals originally are 2.65" and the 350's are 2.45" so they must be turned down by .200" to become the STD. 350 main bearing size. Since the 400 was originally externally balanced you will need a balancer and flywheel/flexplate for a 400 CID Chevy motor. There are now affordable aftermarket crankshafts from Eagle Specialties and SCAT to simplify this process.
Do I need special pistons?
Yes and no. The added stroke of the engine would push the piston out of the bore by .125" if you used stock 350 pistons and rods. If you run stock 350 pistons and stock length 400 connecting rods, you can get away without special pistons but the 350 piston skirts may hit the larger 400 counterweights. If you go this route, you need to pay close attention to piston skirt to counterweight clearance.
What's with this rod thing?
The 400 uses a 5.56" long connecting rod. All other small block Chevy's use a 5.7" length rod. The reason for the shorter rod is GM decided not to raise the piston pin higher so they shorted the rod to the appropriate length to prevent the piston from popping out of the deck. A 383 can have many different rod lengths, but the first combinations used stock 400 rods and stock 350 pistons with relieved skirts. This was before custom pistons were available.
Which rod is better and why?
The longer rods are better than shorter ones. For a full explanation see below.
Will longer rods cost more or require special work?
Yes and Yes!! The longer rods themselves may not actually cost more but the pistons you need will raise the price. The pistons will have higher piston wrist pin heights and will have their ring lands higher up on the piston. In cases where non stock rod lengths of 6.00" or longer are used, the wrist pin will actually intersect with the oil ring. These will require support rails for the ring. The longer rods will also cause a camshaft to connecting rod clearance issue. Special grinding or clearancing of the rod bolt shoulder will be required and/or a reduced base circle camshaft may be required. There are now “pre-clearanced” connecting rods available, sometimes called “Stroker-rods”.
What will the block require?
The block will need to be notched in the oil pan rail area. The longer stroke crank will need deeper notches to clear the counter weights and rod throws.
Should I balance the motor?
Yes!!!!! Any time you change geometry from stock, a re-balance is absolutely essential. That is if you want it to live! The aftermarket pistons and rods are generally lighter than stock 400 components thus leaving more counterweight than is necessary. This will make for a lot of vibration and is bad for a motor.
What kind of heads do I need?
Any kind you want. A 383 takes the same cylinder heads as a 350. The 383 does like larger heads and big valves but it is not mandatory to have 2.02/1.60 valves and huge intake runners.
Do I need steam holes in these heads?
No! A 383 uses a 350 block and it has no provisions for steam holes. It also cools like a 350 so only minor cooling system upgrades are necessary.
What is the cost of this kind of buildup?
This is a tricky question and probably the most asked one! A 383 can be very pricey. The crank will cost a pretty penny to find a used one. There are several aftermarket companies selling '383' cranks that don't require any additional work other than balancing. A crank can cost anywhere from $250 to over $1800 depending on the kind and quality of the crank you buy. Pistons also fall into this wildly ranging category. You can spend $150 on cheap cast pistons or over $700 on lightweight forged units. The balance job can cost from $150 to $300 depending on the shop, kind of balance job and the area you live in. The engine block machine work is not too bad. The extra cost will be the notching for the counterweights and that can be from $100-175 for that work. The rods are also another area of wide variety. You may be able to get stock reworked 400 rods with ARP bolts for $250 or so and you can order the $700 sportsman rods and so on. If you order aftermarket rods that are profiled for stroker motors you will save you the grinding of the rods and/or the reduced base circle cam. If you get stock rods or non profiled rods you will either have to grind them yourself or pay your shop $50-$100 for this. You will also need to do this before the motor is balanced!!!
How much power will the stock 400 crank handle?
A properly prepared stock 400 crank may be able to handle up to 700 HP, but considered a gamble at that. Stock cranks are nodular iron and are generally considered by the industry safe for most builds up to 550 HP. Aftermarket purpose built cranks are not only more affordable, but are cast steel making them even stronger.
What is the red line on these motors?
The red line varies from motor to motor depending on the parts installed and work done etc... A basic short rod 383 will live to 5500 and a 5.7" rod motor will go to 6500. Motors with forged internals and special work done can of course go higher. As a basic rule of thumb you can go 1000 RPM per 10PSI of oil pressure. If you have 70 PSI you can make 6000 with a 10 PSI safety margin. This rule will affect every kind of motor. It's kind of an either/or here. You can go as high as your oil pressure permits or the internal parts permit whichever is lower!
What size cam will I need?
Probably the second most asked question is cam sizing. This is another tricky thing to pick. Since every single aspect of the engine and vehicle it's installed in will affect this, we will just give another rule of thumb. 99% of rated ranges on products are based on the 350. If you’ve built a 383 you can add 10 degrees of duration to the motor and get very similar characteristics. For example; A 350 would probably have a moderate to rough idle with a 224 duration cam, measured @ .050 lift. The 383 will take a 234 duration cam to make almost the same idle and vacuum as the 350. These motors also like to breath so longer duration and larger lift cams work well in them. Do not overcam! Just because you have a bigger engine, don't go and stuff the largest cam you can find into it. Most street engines use less than 234 degrees of duration @ .050! The motor is bigger so it will make more power with less cam so a 383 with a 214 cam will make more power than a 220 duration cam 350 if all else was the same.
What intake manifold should I use?
The intake manifold should be a high rise aluminum with a moderate carb and matched with the camshaft power band. The 383 likes to breath so a bigger intake manifold such as the Edelbrock “Performer RPM” or Weiand “Stealth” would be a good choice for a mid range torque application. The Edelbrock “Performer” and Weiand “Action Plus” manifolds will work nicely too if a lower torque band is preferred. Proper carburetor size depends on the application but, on the street under 6000 RPM you should consider a 650 CFM rating for best throttle response and drivability! A 750 CFM rating will make more power with a larger camshaft and cylinder heads but is the largest you should go unless you are all out racing!
Are there any special things I need to pay attention to when assembling the motor?
Yes, you must check camshaft to connecting rod clearance and cylinder block to connecting rod clearance. Both should be .080" minimum! All other specs will be the same as a 350 or follow the manufacturer specifications.
Should I run a high volume oil pump?
High volume oil pumps add additional stress to the distributor drive gear and in most cases are completely unnecessary. When oil is ported outside of the engine block to remote oil filter mounts and or oil coolers hi-volume oil pumps should then be considered but are safest when used with an extra capacity oil pan. Urban legend has it that a stock oil pan will be sucked dry by a high volume pump at 4500 RPM under hard acceleration. Why take the chance, high capacity oil pans are a small investment compared to all you’ve spent thus far!
Rods and Rod to Stroke Ratios
Connecting rods were an overlooked part of buildups not too long ago but with the recent long rod craze you may be asking if you should be running long rods???
First let’s cover the basics. In the image you will see the black lines indicating the center of both the large and small ends of the rod. This is the length of the rod. If you have a 5.7" or 6" rod it is measured at these points as are all other rods.

Rod to stroke ratio is a simple ratio. If the rod is 5.7" and the stroke of the crank is 3.48" you have a 1.6379 rod to stroke ratio. In theory the higher this ratio the more power it makes. The reasoning behind this longer rod is more power comes from a couple of aspects.
1) If you go back to the basics of a simple machine, the pistons, crank and rods are basically a compound lever. The up and down movement of the piston translates into rotational motion of the crank.
In an engine a longer rod can make more rotational torque from the same piston force because it's a longer lever!
2) Due to the angles involved, a longer rod is less angular than a shorter one, thus side wall loading is lessened. What this means is that the piston is pushed more up and down the bore than to the side of the block reducing friction and increasing HP.


As you can see in the below example that raising the piston pin height changes the rod angle noticeably. You will also notice that the piston top doesn't change. Many people believe that longer rods make an engine a stroker but this is simply not so. The only thing that can change displacement in an engine are the bore or the stroke.


3) The pistons speeds change with rod length. The piston has more dwell at TDC and BDC. The slower it gets at TDC the more pressure builds up at the ignition point. The piston also accelerates away from TDC and BDC quicker making the intake compression and exhaust strokes more turbulent thus making more power.
So what will fit and how do I figure it out???
Here is a simple way to find out what you need to know about fitting rods.
The factory deck height of a small block is usually around 9.025" from the deck surface to the crankshaft centerline.
The "Blueprint" figure is 9.000". In order to make this work this you need to know the stroke of the crank and length of desired rod. You will being figuring the compression height you would need to make this work. For example a stock 350 would be 3.48 stroke and 5.7" rod. If you add half the stroke and then the rod length together you get 7.44" If you know it has to fit a 9" space you subtract the 7.44 from 9 and get 1.56" which is the compression height of a stock 305/350/400 piston. This is also the reason why the 400 has a short rod, GM didn't want to raise the pin in the piston so they shortened the rod to 5.56". If you take 1/2 the stroke of 3.75 or 1.875 and add it to 1.56 compression height and 5.56 rod length you get 8.995 or 9". You can also shorten the stroke too. Say you have 1.56 pistons and want a 6.125 rod. You can figure this out by adding them together and subtracting 9" and the result is 1/2 the stroke so double the figure and this is the stroke you can use with stock 350 pistons in a 350 block with 6.125 rods. 1.56+6.215=7.685-9=1.315*2=2.63" stroke.
Of course nobody wants that small of a stroke.
If you go the other way and install 6.125 rods onto a 3.25" stroke crank for a 327 you will need 1.250 compression height pistons to make them fit.