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Blown Legal

Want a Supercharged Engine That Will Pass Smog? Here You Go!

Jun 17, 2003

Smog laws don't have to prevent you from making horsepower, as long as you use the correct parts, build the engine the right way, and tune it until it delivers a clean exhaust.

It is true however, that smog laws and legislation are making it more and more difficult for performance enthusiasts to build their toys beyond what the factory did. Things like restrictions of certain years and elevated testing at smog stations are definitely keeping people from modifying some of the later classics.

It is still possible to build a reliable, "smog-legal" engine that will make more than enough horsepower to get you into trouble, and pass the sniffer--and visual--test when the time comes to renew your registration. To give you some insight into how this is possible, we took this little small-block and created a shining example of what you can build when you do a little homework to discover what is available and make a smart decision on what combination of parts to use.

One thing you must take into account, though, is that not all smog laws are the same and you must be aware of the laws where you live. Some will have it a little easier than others, but for those in California we're still faced with the most stringent regulations in the country.

The short block we chose is a 383 that was built by Golen Engines. An Eagle cast-steel crank and a set of SIR connecting rods make up the stroker's bottom end, while a set of forged slugs from JE Pistons fill the holes. Actuating the valves is an Extreme Energy smog-legal bumpstick from Comp Cams. But the biggest addition, and the one most likely not to be considered "smog legal," is the Weiand 142 street blower.

Since the engine will be supercharged the pistons are of a "dish" design instead of the standard "flat top." These pistons equate to a mild 8.5:1 compression ratio, but this will help keep the engine from hammering itself to death with detonation when it's on boost. The cam also is a special grind for a supercharger, since blown engines require a different lobe spread than those that are naturally aspirated. This smog-legal blower cam has a split duration of 218/224 at .050 inches, which is fairly small, but that's exactly what this motor needs.

A set of World Products Sportsman II cylinder heads sits on top of the Golen short-block. These castings are smog-legal steel units with a large 200cc intake runner. This is an excellent street head for the budget-minded enthusiast and comes fully assembled for a fairly reasonable price.

The coolest part of this motor is the Weiand street blower, though. This aluminum lung is smog-legal in all 50 states and proudly displays its Executive Order, or E.O. number. Out of the box, the roots design cranks out roughly 4 pounds of boost, but that should be more than enough to get any street freak's attention. The blower comes complete with everything you'll need including an intake manifold, water neck, belts, pulleys, and gaskets.

To fire the supercharged mix we chose a Performance Distributor's DUI high-voltage HEI distributor along with a set of their Live Wires. The distributor was custom curved by DUI and will retain the use of the vacuum advance. The Live Wires are pre-assembled and come wrapped with a neat heat sleeve that will withstand very high temperatures.

Every part that was chosen for this engine is smog-legal and comes with a government issued E.O. number. It is good to point out that simply because it is an aftermarket smog-legal part, it will still require some tuning and adjusting to get it to pass the smog test procedure. Do not think that you can simply bolt parts on an engine and it will automatically pass a sniffer test.

So follow along as we show you the best of both worlds. And we'll prove that you really can have your cake and eat it, too.


Here's what jumped started the idea of doing this engine story. The Weiand 142 smog-legal supercharger is the centerpiece of the powerplant and comes with everything needed for a complete install. The Holley 600-cfm carburetor is smog-legal, though it does not come with the supercharger.

Here is the long-block as we received it from Golen Engine Services. It was shipped to us in a crate and had already been run. This is way cool, since we knew we had an engine that was already broken in.

These roller tip rocker arms and high-strength pushrods are both from Comp Cams. ARP head bolts are used to secure the World Products Sportsman II cylinder heads.

We used a little gasket cinch around all the ports and silicon for the corners and rails. A detailed inspection of the valley should also be done at this time. You don't want anything ending up in the engine, no matter how minute it may be.

This very short runner intake manifold is supplied with the blower. On forced-induction engines, the length of the runners is not a factor. Since the air/fuel mix is constantly being forced in, it really doesn't rely on the runner length.

Always start tightening the manifold from the center and work your way out. These six-point ARP fasteners were a nice little touch in dressing up our motor.

With the manifold in place we were able to set the blower on. It is recommended that you install the gasket dry, just make sure you don't drag it around trying to line up the blower.

It is very important that you do not over-torque the bolts for the blower. If they're installed too tight it will warp the rotors and cause the blower to lock up. Ten pounds is all the torque needed for the blower to intake manifold bolts.

With the top of the engine buttoned up we decided to seal up the rest of the assembly. The polished aluminum valve covers were a way of keeping up the shine of the rest of the motor. Also notice the Executive Order (E.O.) number on the side of the blower. Weiand is very proud of this and has made it very visible.

The blower's lower drive pulley was designed to run on the outside of the stock crank pulley already on your motor. We did not have one yet, but it was not a problem when the engine was run on the dyno.

With the lower pulley in place we turned the motor over and put number one cylinder at TDC. When number one cylinder comes around, it's simply a matter of lining up the timing mark with zero on the timing pointer.

Here is the ignition system from DUI ignition. This Performance Distributors Street/Strip H.E.I. is custom curved and sent to you ready to drop in and run. The Live Wires are pre-made and are simple snap on. The MR.AMP 130 amp alternator is an especially nice touch. Even though we were not able to run it on the dyno, it will be awesome on the car. This alternator is perfect for those with older cars or with lots of stereo equipment.

With number one still sitting on TDC the distributor was dropped into place. With the rotor pointing towards number one, work it back and forth until it properly lines up with the gear. You may have to use a long flat-blade screwdriver to rotate the oil pump shaft to get the slot to line up.

George Vrbancic of Vrbancic Brothers Racing was absolutely awesome with helping get this engine done on time. Here George fastens on the distributor cap so we can start running wires.

The Live Wires come pre-assembled and numbered. The nice look of these wires really helped with the appearance.

The pre-made wires fit amazingly well. We also had to install a dipstick and oil filter adapter.

This Holley mechanical fuel pump is what is required for use with this blower system. This pump is rated at 130 gph. It's suggested that you use the Holley "blue" regulator, too.

This extended water neck is required to fit around the blower snout and is supplied. It would be much better to install the water neck before you put the blower on.

This is a smog-legal 600-cfm vacuum secondary carburetor from Holley. This specific carburetor is what is called a reverse idle feed model and works very well for smaller cubic-inch motors.

Here is our engine completely assembled. The electric water pump drive is only for use on the dyno. This ended up being a very nice small-block. But the main part to this story is that it was built using all smog-legal parts.

Here's our stroker smog motor as it sat ready to run on the Vrbancic Brother's DTS dyno. The engine was primed on the dyno.

Here is one of the first of only a few dyno pulls that were made, and we learned a little bit about the 600-cfm carburetor. This 600 is a true smog-legal carb and it was designed to open only with very high amounts of vacuum. Even then the secondary is not supposed to open completely therefore the engine never receives full throttle. Luckily the employees at Vrbancic Brothers Racing were willing to go the extra mile, and open the throttle manually by hand.

Here are the best results that we could get using the 600-cfm carburetor. Let us remind you that this is with the throttle being held open by hand and changing the primary jets a little. This is only the beginning: 404 hp at 5,500 rpm and a max of 463 ft-lbs of torque at 3,500.

Here Bob Vrbancic tunes on a remanufactured 750-cfm Quadrajet. This Q-jet is also smog-legal for cars and trucks through 1978. Depending on what kind of car you have will depend on what smog-legal Q-jet you can run. Being the carb master that he is, Bob installed and quickly tuned this carburetor and we ready to go again.

The first few attempts with the 750 Q-jet were promising. The added amount of air that can travel through this larger carburetor quickly surpassed the capabilities of the mechanical fuel pump. It made 404 hp on the first hit and 465 ft-lbs of torque from 3,300-3,800 rpm. Watching the fuel pressure on the dyno screen, we saw that it was losing fuel pressure and was causing the motor to lean out and not make the power that it should.

Unwilling to give up yet, we decided to go straight to the electric fuel pump that is used for the dyno. Here George is setting the fuel regulator to 6 pounds in hopes of generating some more power.

Here is a quick carb lesson for anyone who doesn't know Q-Jets. These little needle looking things are how jet changes are made on a Q-Jet. If you look closely at the tips you can see that they are different sizes and the tapers are little different. This is how fuel is metered going into the carb and essentially how to change the "jets."

Here is the best that was done with 750 Q-Jet. The motor was now making 410 hp from 5,300-5,500 rpm and 468 ft-lbs of torque from 3,500-3,900 rpm. It seemed that we were taking steps in the right direction so we pushed on and hunted for some more power.

Our next step was to spin the blower faster to make a touch more boost and see what we could do. The pulley on the left is the standard pulley that comes on the blower and it measures 3.05 inches. The one on the right measures 2.86 inches and should add another 2,000 rpm of blower speed. When doing this you want to make sure that keyway is installed in the new pulley before installation on the blower.

With the smaller pulley installed we ran into another problem. The stock belt that is supplied with the blower started to slip causing us to lose boost at high rpm and make the motor do things it isn't supposed to do. The good thing is that we learned that you could get a blower belt from any auto parts chain. With the new belt on, the motor now made 425 hp at 5,300 rpm and 485 ft-lbs of torque at 3,400 rpm.

These next couple things that we tried are outside the realm of being smog-legal. This carburetor that was used was a 750-cfm double-pumper that was outfitted with Carb Shops new Quick Change metering blocks. These metering blocks are designed as a stock replacement-metering block that offers much more adjustability and the ease of changing jets without removing the fuel bowls.

With the new 750 double-pumper the numbers jumped up more than anything else that we did. We were now making 438 hp at 5,500 rpm and 494 ft-lbs of torque at 3,700 rpm. The engine was also much more responsive and the torque curve has gotten a little longer. All the averages are up and 500 ft-lbs is right around the corner.

The last few pulls were nerve wracking to say the least. We never could get 500 ft-lbs; the motor would only produce 499 ft-lbs. It did however carry 490-499 ft-lbs of torque for a span of over 1,000 rpm. Our max horsepower is now 442 at 5,500 rpm. We tried many different things like spinning the motor higher and even added a couple more degrees of timing. In the end neither idea really worked out the numbers you see here are the best that we could do. With this story we feel we have demonstrated a couple of things to those readers who are starting to lose hope in our hobby. You can still make power while following the rules.


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