A: There are very few street applications we’d recommend running a locked-out distributor on; however, you’re definitely one of them. That is a very nice small-block that you’re calling a street engine. With the amount of overlap area your COMP Cams roller has, you are bleeding off a good deal of cylinder pressure at slow engine speeds. Also, with the very low rearend gearing, and the First gear ratios of your T56 trans, you get the engine up to torque peak very quickly and past the point of detonation that would cause a problem with street driving. Also, since your car is a manual trans vehicle, you have the ability to control the gear to run the engine with very little load on it. One of the major benefits of running that much spark advance at idle is the quality of the idle and throttle response the engine will have. Again, yours is one of few we would recommend running locked out.
As for the bad points, hot starting can be an issue with that much timing. The engine can kick back and damage the starter. Usually when you run locked-out distributors or crank trigger ignitions in a race car, you will get the engine cranking over, then fire off the ignition. This will allow the engine to spin freely without a load. Many ignition systems have built-in start retard options that will do the same thing. One last thing is that you could probably get a little better fuel economy with more cruising advance but with the engine package you’re running, we don’t think you’re particularly looking for mileage!
Q: In the Chevrolet HT 383 EngineThe Twister, Part III you wrote the stock guides must be cut. You said, We also knew that the stock iron Vortec heads would need some work to accommodate the much more aggressive cam. The first order of business was to machine the valvespring seats for the larger 1.43-inch diameter dual springs. This is necessary because the stock spring pads are designed for a 1.25-inch-diameter spring. The stock guides must also be cut down to clear the additional lift. How much must they be cut?
A: The stock Iron Vortecs were set up for mid-0.450-inch lift. This was based on the retainer-to-seal clearance and the coil bind clearance of the stock valvespring. Giving a blanket dimension for cutting down the valveguide is virtually impossible. Not knowing the lift of your performance camshaft or the type of valve seal and retainer you’re going to use, there cannot be a spec given.
Once you have chosen your camshaft and valvetrain hardware, you will want to check the seal-to-retainer clearance with the valve closed. Once you have this clearance, compare it to the max lift of your new camshaft. To be safe, whatever your max lift is on your new camshaft you will want to cut the valveguide an additional 0.050-inch for clearance. This will prevent the retainer from coming in contact with the seal and any chance of the retainer pumping oil down past the seal.
Sorry we can’t give you a number that will work for everything. We could tell you to cut 0.200-inch off the guide and it would be safe for almost any street-performance camshaft, however, you want the valveguide to be as long as possible to control the valve and reduce wear.
Safety Cutoff Switch, Part II
Q: In the Sept. ’10 issue you responded to a question concerning a safety cutoff switch and how to wire a single-wire alternator to it. I have the same concern. In your response, you stated that you use a smaller-gauge wire as a fusible link. Is it OK to use a fuse/fuse holder rated 10 amps above the rated alternator output, and if so is that a better option than a fusible link? Thanks in advance.
John C. Barnhardt