Jan 7, 2014

Save The SOHC | A New Lease On Life

Generally speaking, for as long as DOHC engines have been around, they have always taken precedence over their cheaper, less complex single overhead camshaft siblings. On paper, the increased efficiency of DOHC engines are undeniable, proving time and time again to extract more juice from the same sized fruit. With the uprise in popularity of the technologically superior K series and continued prevalence of the well established B series, engines like the D series have become relics in today's world. What is regarded by many as a throwaway motor, is for others like myself, a viable option to modest performance at a low cost while achieving excellent fuel economy and stellar reliability.

The D16Z6 that took residence in my EH3 for many years was no stranger to the daily grind. 5 times a week or more it would start up in sub freezing temps and face the harsh winter roads for 50 miles a day. In the summer heat, idling in traffic was a common occurrence but never a debilitating one. It ran quite well for most of its life under my ownership; all while getting an average 38mpg. Then one day, oddly enough, a pin sized hole in the lower radiator hose caused all of the coolant to drain out in a matter of minutes. Before I knew it there was a trail of steam behind me and I stopped immediately. There I was on the side of the road in the middle of nowhere waiting for the temperature to come back down. Making constant stops and driving for under a minute at a time, I made it back home but not without blowing the headgasket just a tiny amount.

After all that it had been through, was I really going to let it meet its fate over a headgasket? I don't think so, homie don't play that. That same week I placed an order with the guys at AutoFair Honda for a full maintenance refresh. All new radiator hoses, timing covers, water pump, tensioner, timing belt, headgasket, bolts and various other bits. Rather than being ditched for a DOHC swap, the single jingle was back to humming its tune again. Sooner than later unfortunately, the SOHC grim reaper "knocked" on the door again less than a year later. At the EG's first shakedown trackday down at New Jersey Motorsports Park, oil starvation got the best of it after about an hour of track running. It had finally bit the bullet and not on it's own merits either, a pesky CEL indicating a fuel issue was left unresolved as everything indicated that the pressure was normal. Under those circumstances the track day should have been postponed which is something I realized in hindsight. To add, my inaction towards the matter proved to be rather costly.

The real cause behind the CEL is uncertain but during the teardown, a halfcut VTEC solenoid wire was discovered which could have very well been the reason as to why VTEC engagement had been intermittent at times or outright not working weeks prior. It would also explain the fuel related CEL as the ECU would have been expecting a higher level of air intake past the crossover point which it wasn't getting sans VTEC, subsequently affecting the air/fuel mixture. The lack of an oil pan baffle was more than likely the real cause behind the rod bearing failure as the unusually wide 225/45/16 Direzza ZII tires provided an overly abundant amount of grip on the lightweight Civic chassis. With high cornering forces sloshing the oil left and right and questionable engine operation, the outcome is fair to say comprehensible.

At approximately 250,000 miles and 2 decades of use, the D16Z6 had spun its last revolution. Weeks went by attempting to source a replacement to no avail. A few cold leads and a trip later, another potential heart was located. With the help of a friend to evaluate it's condition, we concluded that it was in fact healthy with compression numbers an even 195psi across the board. Here I was again saving the SOHC.

Making room for its new home, the old Z6 saw it's way out in through the bottom and then gently parted of its healthy organs. Since they were almost new, it only made sense to transfer them over to the new motor and start off fresh again. 

It wasn't the cleanest motor, but with a little elbow grease it certainly had the potential to be close to it. I was able to get the block and transmission shinning again using a wire wheel on a drill and some Simple Green. A can of WD-40 and Brakleen also facilitated things.

To reach inside every little nook and cranny possible, a $2 set of Harbor Freight brass/metal/nylon brushes was used and did the trick just as I needed.

The most important parts that had been transferred were the timing belt/tensioner/waterpump but also the oil pan with a new gasket and Hondabond. A full service was in order so it didn't stop there...

...a valve adjustment was done on the tighter end of the spec for decreased wear at .007'' on the intake side and .009'' on the exhaust side.

The fuel injectors had seen cleaner days and so the old injectors were reused with new o-rings following a bath in a 50/50 mixture of injector cleaner and Brakleen; an easy way to bring back some lost performance.

With the IACV and FITV taken apart and cleaned, the days of worrying about an erratic idle are gone. New spark plugs were thrown it too for good measure to make sure it would purr like a kitten when swapped in.

Before finding it's way inside the engine bay, the transmission was pulled and of course the aftermarket Clutch Masters FX100 was worn down to the bone. An Exedy OEM replacement clutch/pressure plate/flywheel setup was then fitted for its low cost and endless life. Though a Stage 1/lightweight flywheel would have been a good upgrade, it simply wasn't in the cards. SHG_Mike helped me get it installed, closed up and the entire longblock bolted up to the mounts sans cherry picker, simply from underneath the same way the old one came out.

It was a hefty amount of work to do in the cold garage but some warm chocolate milk with marshmallows on a few occasions naturally helped ease the pain. Over the course of a couple of weeks the swap was done and with a fresh shot of synthetic 5W-30 oil and Honda fluids, the engine was properly prepped and ready to get fired up. From the get go it turned over without hesitation and ever since that night, it's been running fault free. Now that the clutch has been broken in and the trip odometer marks a little over 1,400 miles, I give the engine a clean bill of health. All that's left to do now is reap the fruits of my labor and rack up the miles.

One day I hope to make the switch to DOHC but until then, I'll save my pennies at the pump and enjoy modest but most definitely pure, Honda Sports. -Claudio