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VQ35 Engine Update

VQ 35 Engine Program Update

During the course of racing our 350Z in Redline Time Attack we had a couple of engine failures that had us looking for new solutions.

The first failure was a broken valve spring and damage to valves and combustion chamber as a result.  We reviewed all of our data, took a close look at everything and decided to install double valve springs.  The double valve spring engine actually made a bit more horsepower even though the force needed to turn over the engine was much higher.

At the first event run with the double valve springs we broke a cam.  The exact cause of the broken cam is still unknown.  We were never happy with the pressures for the double springs.  We had never broken a cam with any of our other single spring packages. Having logged over 20,000 road racing miles we again new that a different solution was in order.

Throughout this program we were never totally sold on running this 3.8 liter engine on shorter than stock rods.  From previous experience we felt that the short rods were causing harmonic issues in the engines and the harmonics had been a factor in our spring failures.

We decided to again redesign our racing engine, this time using at least stock length rods while still running the larger stroke 3.8 liter crankshaft.  The redesign project had us using the same stroke Cosworth crankshaft but this time we would use stock length Carrillo rods and custom designed CP pistons.  We also decided to use a custom conically wound single valve spring.

The assembly of this engine really followed the same path as has been chronicled here in the previous Engine Build posts.

The new CP pistons were ceramic coated and the skirts were coated to reduce friction.  The crown of the pistons were designed to optimally fit our much repaired and modified cylinder heads.

The new conical valve spring required machining new bottom retainers and  new very small titanium retainers.

After dynoing this engine we are very happy with the results.  The engine made more power than any of our previous engines and the first event at Auto Club Speedway proved the engine runs better and is smoother than previous engines.