This special ring compressor tool is used to disassembles the head. Springs, retainers and valves are completely removed.
After inspection, the valves and valve stems were found to be in good shape. We will reuse them.
The completely bare head is thoroughly cleaned in a hot parts washer.
SR20 engines being a finger follower design are hard on valve guides and it is not uncommon for them to exhibit a lot of wear, especially on a racing engine.
The guides on our head were in surprisingly good shape. We simply sent the head out to the machine shop and had a conventional 3 angle valve job done. Nothing trick or special, just a good valve job. Our engine already makes more than enough power for its race class, so we just want to freshen it up and make it last longer.
Once the head came back from the machine shop it was reassembled with new valve seals and new JWT racing valve springs. Once back from the machine shop, the head was reassembled with new valve seals and new JWT racing valve springs. The JWT valve springs were not needed on stock cams, but they do allow an extra 1,000 rpm before the rockers fall off. We used them as some valvetrain headspace in case of missed shifts.
With the head now complete, our engine freshly rebuilt SR20 is almost ready to go back in Project Infiniti G20 Racecar.
The freshened head is mated to the block, but before the front cover is installed a new timing chain, lower sprocket and chain guides are installed. The head bolts are torque to yield and must also be measured for excessive stretch. They are tightened to a low torque, then turned to a final angle much like the main cap bolts to ensure consistent stretch. The small aluminum peg just above the crank bolt is the oil squirter for the timing chain. It goes directly into the main oil galley. It can get knocked out of the block easily and if it does, the engine will lose most of its oil pressure and go boom! When building an SR20 be sure that it is present when assembling the engine.
Our new/used engine is now all fresh and ready to go. With heavy duty internals more appropriate for racing than the stock stuff, we anticipate many years of trouble free performance out of our turbo SR20DE which is unheard of for a race car.
With lower compression, we can use more spark advance which will result in lower combustion temperatures which will be easier on the engine’s internals.
We will also be able to run more boost which will put the turbo in a more efficient operating area. We will still be able to run our low-cost pump gas with a little race fuel mixed in for low operational costs.
Even though we did not build the engine for power, in case we change our mind in the future our engine has enough strength headspace to accommodate a larger turbo, bigger cams, and more power if we wish it.
For now, we will just enjoy the added reliability and lots of extra peace of mind!