May 2012 Chevy High Performance Q&A

Richard’s at it Again

Kevin McClelland Mar 22, 2012 0 Comment(s)

Now that you have a roller camshaft case, let’s pick the right camshaft. With the boat’s outdrive limitations for power potential and the need for good idle quality to be able to shift the outdrive, we’d keep it mild. You mentioned 4,000 rpm as an engine speed your boat sees for periods. Building great torque at this speed should be a focus. The factory Mercury Marine small-block hydraulic roller PN 144097395 is a nice little camshaft, and GM uses this camshaft in its RamJet 350 and the HT383 crate engines. The RamJet 350 produces 350 hp at peak, and more importantly, 400 lb-ft of torque from 3,500 to 4,500 rpm! This will give your boat very nice acceleration and keep it on plane with no drama. The camshaft specs out at 196/206 degrees of duration at 0.050-inch tappet lift, 0.431/0.451-inch max lift with 1.5 ratio rockers, and is ground on a tight 109 separation angle. This gives the engine outstanding throttle response and great midrange torque. To get the full performance from this package make sure that you use 1.6 ratio rockers. This will boost the max lift up to 0.460/0.481 inch. This is right where the stock Vortecs start running out of airflow.

This should give you many years of reliable engine performance in your marine application. With the hydraulic roller camshaft you will never have to worry about our new inferior oils and dry starts. Start with a mild 32 degrees of total spark advance and tune from there. Remember, you always want to get back to the dock!


Tuning In The 21St Century, Part 2

At the ripe old age of 72 and having been involved in this addicting sport of drag racing for nearly 54 years, I must say yours is one of the best tech columns to come my way. Your article in the Jan. ’10 issue on tuning with AFR systems hit home, as I am in the process of setting one up in our ’78 Malibu bracket car. You are absolutely right; trying to get the proper jetting by using the mph on any given day of testing is virtually impossible due to wind and weather changes in our part of the country. I went with the Innovate Motorsports LC-1 Digital Air/Fuel Ratio Sensor Controller and a DB Digital Air/Fuel Gauge setup. The sensor is installed in the left header collector. I also have a Moroso Crankcase Evacuation System installed into both headers. Will this affect the readings, or is it necessary to plug the left side where the sensor is installed? It will be a few more months before we get to try this, but I’m encouraged by your results, and if all goes well, we’ll be doing the same in my other son’s Camaro. Keep the excellent tech articles coming.

Ralph Talbot, Talbot Racing
Windsor, ON, Canada

Very nice combination. The full-frame A- and G-bodies are great building blocks. Between having a solid foundation to build from and the aftermarket making all the components we need, they are great race cars.

Every track we have here on the West Coast has the same conditions you’re dealing with. Wind and atmospheric conditions change so fast that you never get a real handle on tuning. The O2 sensors are a tremendous help in these types of conditions. Also, watching the fuel curve of your carburetor throughout the rpm range can give you clues of consistency issues. Just this last week we installed another sensor in our good friend Greg Ventura’s ’66 Nova Super Street car. The fuel curve was very nice up to 7,000 rpm, but from 7,000 to 8,000 in high gear, the AFR climbed over 1 ratio. This took the engine right up to 14:1, much too lean. We haven’t put our finger on the cause yet, but it could be either the fuel delivery system or the way the carb is sealed to the hoodscoop. At least we have a tool now to know when we’ve touched the right part.


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