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Cams for vortec headed 383

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Decided when I'm ready to go with my engine I want to go with a smeding 383 shortblock. I would like to use my vortec heads if possiable. They offer different cam choices for the shortblock. I'm looking at the smaller of the 2 which are speced at 480/480 lift 212/222 @112 LSA 380hp cam with their heads other cam is 495/502 lift 220/224 @112LSA 420hp. Do either of these cams seem like they would be a good choice for vortec heads. Want a good cruiser with some pep and really strong torque. Thanks
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You have the heads from an L31 vortec 5700? Or some other "vortec heads"?

With stock springs and valve train parts, the stock L31 heads are limited to somewhere between 0.460" and 0.480" total lift. It varies with the castings and parts and must be measured. The first cam might work with stock valve springs. The second one will at a minimum require alternate "beehive" valve springs. And if the coils bind on the stock springs with the first cam, it will also need these alternate springs.

If it's mainly a street driven vehicle, the first cam is probably going to be a better choice. If you're going to run it down the drag strip more than a few times, the second will make more power, but may not be as good at lower RPMs. You'll probably want a higher stall speed for the torque converter with the second cam.
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Do you have a listing for the pistons short block or do you have options on what pistons come installed? We can crunch some numbers to find an approximate compression ratio.

Generally speaking the compression ratio is going to dictate the cam choice. What kind of "cruiser" you're putting together will help to narrow things down too.
 

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Cam number one is at the limit of a stock stall converter, not that all GM converters are at the same stall but they are a family that stalls pretty much between 1200 to 1800 RPM.

Cam number two will demand more stall somewhere like 2200 to 2800 RPM.

Usually stall is thought of as a racer thing that allows the engine to be brought up on its torque peak or more when staging for a drag race or coming off turns on a roundly connected track. On the street it is an issue of ‘tug’ that is big cams demand a high idle speed and the bigger the cam the higher the idle speed. This combined with a stock stall converter can become physically exhausting applying enough brake pedal pressure to wait out a traffic light combined with the unpleasant habit of the vehicle leaping from every stop. Imagine this with a cop behind you, smells like a speed exhibition ticket to me.

Cam number one will sound aggressive at idle; cam number two will be choppy or staggered at idle.

Max lift on the L31 Vortec head ranges from .450 to .470 inch. This wanders from head to head and intake to exhaust on any given head. So you will have to address this for either cam and keep in mind SBC cams rate and advertise lift at the valve with a 1.5:1 ratio rocker. Changing the typical 1.5:1 rocker to the common hot rod ratio of 1.6:1 increases the lift by 7 percent so what lift might squeak by with a 1.5 rocker may not with a 1.6. The issue here is clearance between the bottom on the spring retainer and the top of the valve seal as it mounts on the top of the valve guide. There are several things that can be done from remachining the too of the guide to lower it to using beehive springs and either Comp 787-16 retainers or the special retainer from Alex’s Parts for vortec heads. There needs .050 inch clearance measured at peak lift to insure the bottom of the retainer does not collide with the top of the guide or it’s seal, however you decide to get there.

Cam number one can be run with GM production LS engine beehive springs and proper retainers that adapt the locks from production 8MM valves to the classic SBC 11/32’s inch valve stem. Cam number two could, also, be used with beehives but will need a higher pressure that stock GM. These are my go to for high performance street builds Howards Cams Electro Polished Beehive Valve Springs, 1.280" O.D., 115 @ 1.800", 354 @ 1.225" - Competition Products

I‘d say 380 HP with cam number one is conservative representing a pretty conventional build of not ported Vortec heads and a more than less factory style valve train with a moderate intake and 650 carb using 1-5/8ths long tube primary headers and not much if any collector length. For careful builders seeking to max cam one there’s probably another 30 horsepower and torque numbers hiding in there for a carefully built valve train bigger carb, Edelbrock Performer intake and larger primary tube headers with a 20-24 inch collector before the exhaust pipes and some mild porting.

The number two cam will get there with more brut force that results in poor low speed driveability. There are ways to tame this or at least build into it with higher stall converters and stiffer rear gearing so the engine is operating in an RPM range it likes on the street.

Frankly the 383 is such a torque monster that it quickly gets crazy in a light weight vehicle.


Bogie
 

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With that gearing and transmission, I think cam #1 is the one to go with.

I would still recommend putting a "towing" type ~1800-2000 RPM stall speed torque converter in while you're installing the engine. That will help some with your gearing and work better with that engine.

And for the Vortec heads, are you going with junk yard heads? Or buying new ones from somewhere?

If you're buying new, check the cc's on the combustion chambers. They should be 64cc +/-. Use a 0.028"-0.030" compressed thickness gasket with new heads.

If you're buying used heads, this is pretty important. You'll probably want them milled flat. Mill them to 62cc chamber volume, and install them with a 0.040"-0.043" compressed thickness for the head gasket. This keeps the floor of the intake manifold runner flat with the floor of the intake port on the head. If you get any kind of "step" there, you lose HP and Torque in a hurry.

If you want to mill for more compression, you absolutely have to mill the sides of the heads or the side faces of the intake and the bottom of the intake or the walls of the block valley by corresponding amounts (this is complicated because of the angles). If you do it right, you can mill for added compression. If you end up with any kind of "step" in the floor of the runners and ports, even as little as 0.010" at the junction between the head and intake manifold, you'll be losing power and torque.

This is a detail that most folks overlook, but with the Vortec heads, all the magical flow properties at moderate valve lift come from the floor of the ports, and any turbulence there from any kind of mismatch hurts performance and fuel economy.
 

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Discussion Starter · #8 ·
With that gearing and transmission, I think cam #1 is the one to go with.

I would still recommend putting a "towing" type ~1800-2000 RPM stall speed torque converter in while you're installing the engine. That will help some with your gearing and work better with that engine.

And for the Vortec heads, are you going with junk yard heads? Or buying new ones from somewhere?

If you're buying new, check the cc's on the combustion chambers. They should be 64cc +/-. Use a 0.028"-0.030" compressed thickness gasket with new heads.

If you're buying used heads, this is pretty important. You'll probably want them milled flat. Mill them to 62cc chamber volume, and install them with a 0.040"-0.043" compressed thickness for the head gasket. This keeps the floor of the intake manifold runner flat with the floor of the intake port on the head. If you get any kind of "step" there, you lose HP and Torque in a hurry.

If you want to mill for more compression, you absolutely have to mill the sides of the heads or the side faces of the intake and the bottom of the intake or the walls of the block valley by corresponding amounts (this is complicated because of the angles). If you do it right, you can mill for added compression. If you end up with any kind of "step" in the floor of the runners and ports, even as little as 0.010" at the junction between the head and intake manifold, you'll be losing power and torque.

This is a detail that most folks overlook, but with the Vortec heads, all the magical flow properties at moderate valve lift come from the floor of the ports, and any turbulence there from any kind of mismatch hurts performance and fuel economy.
These are factory heads on a 350 I have that needs rebuilding. So they will need to be worked
 

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These are factory heads on a 350 I have that needs rebuilding. So they will need to be worked
Then it's 62cc chambers (typically mill 0.011"-0.012" from the head surface) and use a 0.040" (ish) compressed gasket, which is far and away the most common thickness available for that engine.

Valve job is a good idea, obviously. Unless the machinist is volunteering a week on the flow bench for free, don't let them do anything to the ports past the valve seats. Those head with stock ports will work just fine with cam #1.
 

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Discussion Starter · #11 ·
Something to consider is rebuilding the Vortec’s can start to tease the price of import or even lower performance end of domestic aluminum heads. Not a bad idea to put together some comparative cost estimates.

Bogie
Had looked into the brodix ik180, would like a pair of afrs but they are high. I have to pull my budget in some. Really not sure how much I'm looking at for my vortecs to be rebuilt but if it's close to the iks I would probably opt for those. I see they do perform well when ported so that could be a option down the road. Really leaning on this shortblock feel like it's a fair price. I know it can be done cheaper but it's easier for me to go this route. By the time I get the rotating assembly and machine work to the block I'm not that far from this.
 

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First the Vortec’s need to be cleaned and inspected. Unfortunately modern thin wall castings are very crack prone and Vortec’s are no exception. So disassembly, cleaning and very close inspection which can include did penetrant with black light or Magnaflux to be sure before you pour money into them they are worthy. Cracks mostly were a result of overheating from failed cooling systems using Dexcool. People that didn’t pay attention got into an issue where there was leakage which both lost coolant and introduced air. The latter oxidized the coolant and things got really bad forming a sludge that interfered with cooling so this and the former loss of coolant quickly spiraled out of control overheating the heads in particular.

Once past that point comes the decision to port or not, here again these are thin wall castings and porting, if any, should be minimal clean up and no shape changes. The stock Vortec flows very well especially the 062 casting. The 906 is a bit more robust as it was intended for use on the larger trucks, industrial and marine engines. These heads are a little restrictive on the exhaust side where there is added material for a hard seat insert which may or not be there as many were simply received induction hardened exhaust seats just like the 062 head.

The next standard operation is seats but leading into seats is the condition of the valve guides. If out of spec these need to be renewed. The shop classic is to knurl the guides the ream them to size, this is not a long lasting fix. Another is to ream the seat oversize then use new oversized stem valves. This works well but adds new valves to the budget that might not otherwise be needed. Another that in part is similar in that the guides are reamed oversized but a thin wall metal sleeve is pressed in and honed to finish size and similar to this is to bore the old guide with a larger hole then press in a thick wall guide and finish it.

Following any of these operations, other than oversized valve stems, either the current valves receive new seats or are replaced with new if there isn’t enough seat depth left. The operations of refinishing the head seats and refacing the valves themselves sinks the valves deeper into their pockets. This reduces compression be enlarging the combustion chamber volume and degrades flow past the valve. This raising of the valve relative to the spring and valve train affects spring tension and push rod length which affects the contact angle of the rocker to valve stem. Generally the extent is not to extreme to cause problems with grocery getter engines, but seekers after hot rod power need to fix these things and of course this introduces more cost.

Then you arrive at having to deal with more lift of performance cams. The Vortec head uses a tall guide to improve stem and guide wear but this interferes with lift. So there are fixes to be employed from just taking an angle grinder and whacking some of the top off the guide to buying a tool to do this with more precision at home or have the head rebuilder do it in their shop. Then there is the Alex’s short depth retainer which essentially is a retainer with the bottom edge below the locks taper removed since the locks are loading against the sides of the cup in the retainer so the base of the cup while reinforcing the hoop loads at the bottom of the cup is not directly carrying the load of the locks. Then beehive springs and the Comp retainer buys about .050 inch without doing anything. Then this can also be finessed with offset locks that raise the retainer relative to the spring then chase the added spring to retainer length with spring shims.

I point al of this out so that you can visualize the problems hence cost that modifying Vortec heads can get you into. So it’s easy to put as much wealth into fixing a set of Vortec’s as you would invest in a set of Speedmaster’s stuffed with parts and ready to go, these of course will cost you at least .1 inch longer pushrods. Plus the use of an aluminum head either works better with a decked block or a raised compression height piston. Either of these being a process to get control of the squish/quench clearance without going to super thin shim style head gaskets. The makers of aluminum heads love for you to use composite gaskets that are .040 to .053 inch thick which when combined with a chevy’s nominal piston crown to head deck clearance of .025 inch simply adds too much distance between the top of the piston and the step of the combustion chamber.

So if you’re unfamiliar with building these engines you need to grind through understanding what impacts what in both a technical and cost sense or you can get yourself into a batch of unpleasant and costly surprises.

Bogie
 

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Discussion Starter · #13 ·
Thanks for the input Bogie. I really didn't know it was that involved, this is one of my main issues I had with the last motor that was built. It ran really slick, didn't use any oil or smoke everything sounded good. But the engine simply did not perform. I had a huge investment but absolutely no performance. I was very disappointed. I don't want to do this again. For what I'm wanting out of this engine do you think the ik180 heads would be a good choice for a budget head to be similar to vortec performance?
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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Thanks for the input Bogie. I really didn't know it was that involved, this is one of my main issues I had with the last motor that was built. It ran really slick, didn't use any oil or smoke everything sounded good. But the engine simply did not perform. I had a huge investment but absolutely no performance. I was very disappointed. I don't want to do this again. For what I'm wanting out of this engine do you think the ik180 heads would be a good choice for a budget head to be similar to vortec performance?
Out of curiosity, do you still have this huge investment and performance lacking engine?

If so, do you have any information on what went into the build?

If you still have this engine, you may be able to really save yourself quite a bit here. Post up the combination of parts and information you have. If the performance was that lackluster, one or more contributing factors should reveal themselves. It's just a thought, not trying to hijack the discussion.
 

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Discussion Starter · #15 ·
No the engine was sold some years back. It was a 454 bbc with flat top pistons and oval port heads. Had a lunati flat tappet cam with what I remember was 218 duration @ 50 and 500 lift. What I belive to be the problem was I didn't have the right pistons for compression height. Trans was th400 with 2200 stall. I can't remember all the exact specs. When it was all said and done I had around 5k in the engine and it was a turd
 

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WIthout being able to quote all of the details, I would've just told you that all of the posts I read, and advice I was given (thanks guys!), as I planned my 383 build lead to the conclusion that Vortec heads are not the way to go... unless you're broke and have more time, persistence, and machining skills than cash.
Bogie can tell you every detail of how to do it, but leads to the same conclusion...
It seems like the best "low buck" heads, according to the polls, have been the Skip White 200cc aluminum heads for $820.
They're available now.
SBC CHEVY 327 350 383 NKB-200cc ALUMINUM HEADS 64cc STRAIGHT PLUG NKB-272 | Skip White Performance - We have the best prices you will ever find for aluminum heads, rotating assemblies and strokers

ProMaxx has their ProjectX 215cc heads on sale right now for just under $1300.
They claim really good flow numbers...
Also available now.
Project X SBC 215 (Sold in Pairs) - PROMAXX Performance Products

Profiler heads went WAY up in price during the COVID crap, but it looks like the 2.02 heads are back to normal prices.
The 2.08 heads are still much higher than pre-COVID.
You have to realize that their flow numbers are based on the 2.08 valves, so could be very misleading.
Their lead time is a couple of months... and that tends to change along the way.

I'd suggest the Skip White heads if you're going with your first cam choice.
Check out the ProMaxx Project-X heads if you want to go with a more aggressive cam, and you want to maximize the HP potential of the cam... although I'd expect that the heads from Skip will probably be just fine for anything in the .220's

Anyone feel free to correct me if I'm wrong about any of this... 🙄

Best of Luck!
 

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I have a similar cam to your second cam (498/502 .220/.226), with Profiler 215 2.08 heads, and it's super fun in my Chevelle!
I have a 2300 stall converter on my 4L60e, with 3.73 gears.
Great cruiser that really gets up and goes when you get on it.
The only issue I have is traction... ;)
So as long as you're willing to get a new converter, and 3.55 or higher gears, I'd go with that cam. (y):cool:

3.08 with OD is not the way to go, unless you're planning on very long highway trips, and you're trying to max your MPG.
But the more knowledgeable guys have stated that 3.08 with OD may actually give you worse MPG...
I'd highly recommend 3.55 or 3.73 and the .220 cam.
 
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