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Our goals were simple; one, the engine had to be strong enough to easily live under competition conditions with no problem. Two, the engine had to have a useable powerband all the way out to 8000 rpm. Three, the engine had to run cooler. We had days to do this.
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| We used OEM HR head bolts as they are much stronger and are tightened to a higher torque load for better clamping. JWT provided us with this cool chart explaining the difference between VQ bolts. |
Jim Wolf Technology was kind enough to give us a spare VQ35DE Rev Up long block they had lying around. The engine went to Nick Hunter of 5523 Motorsports an engine builder that JWT uses. With speed being of the essence, we figured that having someone intimately familiar with the VQ engine would get the job done faster than us. Nick disassembled and prepped the block and heads while we rounded up the parts. The block’s bores and valve job were in excellent shape so we would keep the engine at standard bore with a clean up honing and the heads only needed a slight touch up.
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| Cosworth HR head gaskets were our gasket of choice. Cosworth gaskets have a folded stopper layer around the cylinder for superior sealing. |
Earlier VQ engines had the cooling flow of water in the engine coming up from the block towards the front of the engine, flowing across the head from the front and out of the head to the block at the rear of the heads. This was done so that the heads could be kept warmer for emissions reasons. Unfortunately the coolant is cool in front of the head but gets progressively hotter as it travels rearward leaving the rear cylinders to get much too hot. This leads to flash boiling in the head and overheating.
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| In development, Cosworth uses this special pressure film to find out how clamping force is distributed. You can see here that the stock Nissan gasket leaves a lot to be desired. Look at the thin red areas showing minimal sealing clamping. |
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| Cosworth also benchmarks other aftermarket head gaskets. This popular brand has better clamping than stock as you can see by the thicker red band. Things could be better, the band is back from the cylinder and is uneven. |
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| The Cosworth gasket has wide even pressure right around the bores. This is the best of the three. Cosworth was out blow out resistant gasket of choice for this project. |
To prevent this, we changed the water flow around to mimic what Nissan has done on the latest variants of the VQ engine, the VQ35HR and the VQ37VHR. In these engines, the water comes up from the block around each individual cylinder by the hotter exhaust valves and then out to the radiator. This is done by using the head gaskets for these engines. The blocks water passages must also be enlarged in the area near the bores so the passages in the new gaskets line up with the ones in the block. The revised water flow significantly improves cooling on older VQ engines, essential for ones seeing higher boost.
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| Here is how Nick enlarged our coolant passage. As you can see you don’t need to remove a lot of material. |
