Assembling & Tuning a Blower Motor Summer 2005

Preface It had been years since I had been fooling around with performance motors after dropping this project some 15-16 years ago. I have to admit much of my confidence in my most basic skills was way down. Even to a point I noticed I feared attempting the firing of this Blown Small Block Chevy. With help and guidance from a couple of friends that soon changed over this past summer (2005). So what I can share with you are some of the simple problems discovered and solved in getting this small mouse to run well. Valves: Our first few attempt at firing the small block ended up in the motor quickly over heating. Some of our problems were running rich, back firing, not capable to maintain a even low speed idle. Although factory specifications are a good guideline to setting an engine up be aware not always does it apply to any motor. We first discovered a few valves were too tight. Not by much perhaps to the average person. Adjusting the valves greatly improved the engines ability to run at a slower idle and smoother. It also helped in the problem area of over heating. The motor was still running rich so finding the setting was a bit more of an on going challenge. It was not until I actually had a chance to get the car out on the open road that this problem became less of a problem. Engine Backfiring: Thru the course of working on the car, starting it for short periods of time to move it only a matter of feet daily, running rich was not a good thing. Many oil changes occurred to keep fresh oil in it due to gas in the oil. Always look for this in the beginning! I addition due to running lean and the valves not set right in the beginning. We had to many back firings of the engine. A vacuum leak was discovered in the pop off valve seal. Fixing this and gaining the proper carburetor adjustments reduced backfires to nothing. Thru the course of the motor running rich and then lean. I did some research and found that Holley 1850 600cfm carburetors tend to run rich at idle and leans out when slight acceleration is applied. Although for the time this next information I am going to provide did not pertain to me. This problem will cause a backfire also. See information at HotRod.com for additional useful information. Follow this Link -> Curing Holley Hiccups Engine Timing: Another culprit is the distributor timing. A blower motor dose not run at normal advanced timing setting to a stock engine. And if you have another cam in other than a stock cam you can be sure the advanced timing setting will be different. We started at 10 deg advanced. The motor would run fine at idle but not much for drivability. It ran rich at this setting also. It took to much fuel at 10 deg to keep the motor running and as a result fowling spark plugs was a major headache. (Keep in mind we are using a stock points distributor just to get this project on the street for some miles.) I know a good electronic ignition will go a long ways here and is hoped to be in the winter up grade budget! Also the motor still had a tendency to run hot. Solution: Advancing the timing to some place between 10-14 deg will help solve some of these problems. When I advanced the timing some the motor rpm's raced up. Then I was able to cut back on the idle air/fuel mixture on the carbs to get the mixture down and also control the idle on the idle setscrew much better. These carb adjustments were a must and would not work without it going from 10 deg. Results: Smoother running, more responsive in acceleration, engine temperature ran much cooler, and gas mileage improved immediately. Related useful links Dyer's Blower Troubleshooting SuperCharger Help - powered by vBulletin Holley Performance Products' Instruction Sheets and Technical Information Engine Miss Firing: A simple problem developed just at the end of this fall but hard to detect until it became obvious. I change wire looms from a simple aluminum plate to a billet assemble. Where the wire exits number 5 cylinder on the loom makes the wire bend very close to the header. This caused the wire to melt and eventually burn thru and short. In the beginning of this problem it was not obvious. But as the problem quickly developed the snapping noise of the short became easy to hear inside the car. Simple solution but a temporary fix was to place a wire tie on the back side of number 5 spark plug wire pulling it back in the loom tight to reduce the wires bend onto the header tube. It also keep the wire from sliding forward in the loom. The full proof fix this winter is to machine back the exit of #5 wire about ¾". That should be the trick! Next Problems to be solved! November 2005 When shifting the transmission from reverse to drive. I must allow the load off of the engine that results in a small increase of rpm's to settle out before shifting into the next gear. I am using a stock stall converter in my TH350 Transmission and that needs changed. One is built for street rods with big motors and light cars. This would help and will see if the winter budget will support the purchase. Another change will be a good electronics ignition I think will help solve and allow me better tuning of the motor in all rpm ranges and assist in a smother shift from reverse to drive.