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Discussion Starter · #1 ·
I have a set of 062 Vortecs. Valve guides have been machined and shaved .10. Exhaust runners and combustion chambers have been polished only. No cutting.
so my question is should I just leave them alone from there or do more?
 

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Discussion Starter · #3 ·
The truck is a 1990 Chevy 1500 2wd. It will have a th400 in the future. The motor is a 383 stroker balanced eagle assembly. Cam is a Lunati bootlegger. The issue with the cam is I don’t know the specs because it was in the motor when I bought the truck. I do know it’s a hydraulic flat tappit cam. I’ll eventually pull it and look up the part number. It’s gonna be a street truck. “Weekend warrior” Not daily driven
 

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Nothing has been harmed by polishing the combustion chamber and the exhaust ports, but leave the intake ports alone. Roughness there will help air flow to pick up stalled wet flow on the port surfaces and stabilize the air/fuel ratio on the way to the chamber.

I would very, let me repeat VERY, VERY strongly recommend replacing the flat tappet camshaft with a hydraulic roller cam that is meant for street use. I looked at three Bootlegger grinds and all of them....12224, 12232 and 35224 were all ground on a Hydraulic Intensity (H.I.) of 45. This means that there is a tremendous amount of work being exerted between the cam lobe / lifter interface between valve closed/valve open as well as valve open/valve closed. The cam is being asked to get the valve open in a big hurry and get it closed in a big hurry. This is wonderful in a RACE cam, where the motor will be torn down frequently to check for wear on components, but not so wonderful in a motor that has to do duty from stoplight to stoplight and maybe take grandma to Bingo at the church on Wednesday nights and is NEVER torn down to check wear on components until it begins to smoke and/or is down on power and needs a complete rebuild. Apparently the "Bootlegger" grind is akin to the CompCams "Extreme Energy" race lobe design that I also rail against for street use. Now, this design is bad enough in a roller tappet design, but in a flat tappet design, in a street motor, it is just asking for trouble.

Hydraulic Intensity is rated from about 35 in a solid lifter race cam up to about 85 in a hydraulic lifter street cam and is found by subtracting the 0.050" INTAKE duration from the Advertised INTAKE duration. For instance, a cam lobe with a 0.050" INTAKE duration of 220 degrees and an Advertised INTAKE duration of 280 degrees would have a Hydraulic Intensity of 60.....(280 degrees less 220 degrees equals 60 degrees). You only compute INTAKE duration, exhaust duration has nothing to do with it. Harvey Crane, famed camshaft grinder from several decades ago, used to grind all his cams on a Hydraulic Intensity of 62. I mention this just so you will have a frame of reference of how to choose a Hydraulic Intensity for your particular type of motor.

If you are building a full effort race motor, then YES, use the smallest numerical H.I. value that you can find...(35 to 45).....a cam that will get the valve open as quickly as possible and close them as quickly as possible. In this type of motor, you will be tearing it down frequently to inspect components for wear or failure, so you would be able to replace components before a catastrophic failure. If you are building a street motor for Grandma to go back and forth to Bingo or to the grocery store, then choose the highest H.I. value that you can find for THAT build, like 75 to 85 or even higher if you can find one. This will give Grandma the smoothest, quietest valve train action that is possible and will be the easiest on the valvetrain, so that the motor can accrue the highest total mileage between rebuilds. These cams are usually found in jobber's catalogs, from Melling, Badger and such manufacturers.

This brings us back to the street motor at hand. In the first place, the world of flat tappet cams in motors has come and gone. We used flat tappets in all kinds of motors for over 100 years. However, we are into roller tappet motors in this day and age, either hydraulic roller tappets for the run of the mill street motor, or solid roller tappets for the dual-purpose street/strip motor or the single purpose strip motor.

Let me touch here on roller rocker arms.......Famed cam grinder from the last century, Racer Brown, spent a considerable amount of time filming (with very high-speed equipment) the action of roller rockers. He concluded that the roller bearing fulcrum was a very good thing indeed, but that the little roller on the tip of the rocker was in fact too small to effect a mechanical couple with the valve stem tip and so the little roller just skidded across the tip of the valve without any rolling effect. I remember doing some math calculations several decades ago and determining that the wheel on the end of the roller rocker would have to be over one inch in diameter in order to couple mechanically with the valve stem tip. Well, that was not possible to do, because it would have been too heavy to rev to the range necessary for good valve action. So, we have plodded along, using the wrong wheel size for decades now, until the engineers at Chevrolet Motor Division came up with the roller bearing trunnion / "walking shoe" or "pallet" type tip rocker arm that we now find on the new LS motors. Somewhere in the middle of all this, the fellows at CompCams (I won't call 'em engineers, I'll just call 'em fellows) came up with what must have been the worst of all possible rocker arm designs, the sliding trunnion/roller tip design. These fellows got the solution exactly 100% backward and have wreaked a lot of havoc in the hot rod industry as a result.......but it's O.K. now, Chevrolet engineers to the rescue, for the time being. I suspect that the next iteration in valve actuation that we will see will be pneumatic pods acting directly on the valve stems with no cam, tappet, pushrod or rocker arm involved.....just a timer and a pod. Then, we may see tubular rotary valves with slots in them for feeding or evacuating the cylinders, featuring no up/down valves, no rocker arms, no pushrods, no lifters and no cam, just a rotating intake tube and a rotating exhaust tube, timed to the crank.

You will need to disassemble the motor down far enough to determine the stack of parts you are using to determine if they will work with the rest of what you have. A motor is a conglomeration of parts that are chosen to operate together toward a final result, so you can't just throw a bunch of stuff together and hope for the best. Building a good motor is far too expensive for that approach. We will need to know the piston number and whose rods were used, so that we can determine the "STACK" of parts that you have and how they are going to play into the deck height of the block to make an acceptible SQUISH/QUENCH. We will want to know how far down in the bore from the block deck the crown of the piston is, with the piston at top dead center. We will want to know the thickness and design of the head gaskets you will use. When you get the motor together and all of us fellows are convinced that you have maximized your design, then we will get into tuning the combo with reading spark plugs......more fun to come.....
 

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As is usual, I had something pushing me to finish a post (yes, I'm married)......I didn't get through with my thoughts, so I'll try to finish it up here..

Back to port flow......If you study Fluid Dynamics, you will learn that the lion's share of flow goes right down the middle of the vessel....or tube, so grinding on the surface of the vessel will do little or no good if you are not increasing the inside diameter of the tube. Smoothing the intake walls will only allow fuel to puddle when flow slows down on a larger diameter section of the tube or if the flow encounters a turn in the tube. Most engineers would probably agree that the surface of a port or tube can be as rough as a woman's fingernail file and not make one iota of difference in the amount of flow that will make it through the port. You can see that most of the flow goes right down the middle by standing on the bank of a stream or small river and looking out at the middle of the stream bed. The fastest flow and the resultant lion's share of the water going downstream is in the middle. Look at the banks of the stream. There is little to no movement where the water meets the land. This is the same way it is in a head and manifold port.

Speaking of manifolds, let's visit the science on them briefly. Realistically, a STREET MOTOR will want good, strong manifold and head flow from about 1,500 to about 5,000 rpm's. If your tach is above 5,000, you need to grab another gear and get back into the power-producing rev range of the cam (you DID install a STREET cam, didn't you?) Just so you and the rest of these fellows and gals reading this post, any cam you slide into the motor will have a power range of about 3,500 rpm's. It will not have a power range of idle to 6,500 rpm's, or even idle to 6,000, like a number of camshaft manufacturers would have you to believe (JUST SO THEY CAN SELL MORE CAMSHAFTS). Depending on the purpose of the cam, it will have a range of 3,500 rpm's, like 600 to 4,100 RPM's or like 1,000 to 4,500 RPM's or like 1,500 to 5,000 RPM's or like 2,000 to 5,500 RPM's or like 2,500 to 6,000 RPM's or like 3,000 to 6,500 RPM's or like 3,500 to 7,000 RPM's......or whatever.
Anyway......the best STREET intake manifold, where you need power from 1,500 to 5,000 RPM's, will be a long-runner, high-rise, dual-plane manifold mounting a single 4-barrel carburetor using vacuum-operated secondaries. Linkage-operated secondaries, also known as Double Pumpers, can be used effectively on the street if you are using an auto trans with a loose torque converter that will allow the motor to rev to at least 3,000 rpm's. This will prevent bogging from allowing the motor to see too much manifold at low rpm's. You can use a Double Pumper with a stick-shift transmission also, if you have a numerically high enough gear. You would not, for instance, use a Double Pumper with a manual box and a 3.08 rear gear and still expect the combination to work well.

Back in 1967, Chevrolet Motor Division had plans for producing a 5-liter V8 that could compete in National racing venues. That year, they introduced a brand new car that would fit the bill perfectly, a Camaro with a 302 cubic inch V8 that would fit nicely into the 5-liter requirement. They also needed a different intake manifold that would flow more air than the manifolds that were currently available off the shelf at Chevrolet, so they contracted with Winters Foundry to cast up some new aluminum intake manifolds that would pass a ton of air at higher rpm's. The manifolds were cast in a high-rise, dual-plane, single 4-barrel design and proved very quickly to be just the ticket that was needed. Well, it didn't take long for hot rodders to figure out that they needed one of these new Winters designs on their trusty street beast small block Chevy. Aftermarket manufacturers jumped on the bandwagon and began casting up the design too. Edelbrock made the Performer RPM 7101, Weiand made the Stealth 8016 and Holley cast up the best of the lot with their Street Dominator 300-36. Dyno tests have proven over and over that any of these manifolds, but particularly the Holley unit, can make more hp and torque on a street motor than any other design. If I were building a street motor today, I would seek out an offering of one of these on ebay or other used parts venue. Do not be fooled into buying one of the new "Air Gap" designs for the street. It is a RACE manifold, not a STREET manifold.

Nearly forgot to mention torque converters. You can buy a torque converter that will stall anywhere in the rpm range that you want it to, but most fellows will coordinate it with the power range of the camshaft, tailoring the low end of converter range with the low end of the cam's range, plus a few hundred rpm's. For instance, if your cam starts making power at 2,000, then you might want your converter to hook up at maybe 2500, about 500 rpm's above the low end of the cam. Don't be afraid to use some gear on the street.....3.73 or numerically higher will work fine.
 

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Discussion Starter · #8 ·
Thanks for your time. I am also married and have kids lol. Speaking of the rpm range I was shooting for 6000rpm. I’m looking at putting a 750 double pumper on top. How about the z06 valve springs will they handle that?
 

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First, lets determine the static compression ratio of the motor, then match a cam to that and then match some springs to the cam. Step by step by step. What's the situation now, short block on an engine stand? Long block of an engine stand? Short block in the truck? Long block in the truck? We have to get to a piston and pour the heads for cc's. Here's a budget kit for determining chamber size. (You have no idea if the heads have been cut or not).
You MUST know the static compression ratio of the motor before you can match a cam to the motor. I fully understand that you already have a cam. Now, you must fully understand that it may be a cam that will work with your other parts and it MAY NOT be a cam that will work with your other parts. When you buy a motor that was engineered by someone else, you are rolling the dice and it doesn't always work out to your advantage......💔
 
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