Rover216

As the title says, why was the position of the spark plug wells on D-Series SOHC Engines reversed over time?

The photo shows what I mean.

This engine is a D16A6 (Also known as D16Z2) Fitted to a British Built Rover 216. Notice the plug wells are at the rear of the head when viewed from the front.

Thanks for any replies.

thisguyaves

It's just a different head. The plug location doesn't really matter on a SOHC, it has to be either in front or behind of the cam, angled inward.

Rover216

Thanks for the reply.

I just wondered if there was any specific known reason why they had changed.

TomCat39

It's head dependant. The D16Z6 the wells are on the exhaust side. The D15B7 (non vtec) they were on the intake side like your D16A6.

I don't remember which side the D16Y8 and D16Y7 were, and then there is the D17's from the 7th gen that had coil on plug design which I think is different again.

This generalized statement for "all" SOHC seems to be inaccurate.

thisguyaves

D17s have plugs on the exhaust side as well (front-facing)
-7th gen civic owner

TomCat39

Come to think of it, they seem to have wanted to put the vtec solenoid on the intake side of the head so they naturally moved the wells to the exhaust side for extra vtec room on the intake side.

Non vtec, probably all wells on Intake, all vtec, probably all the wells on Exhaust.

thisguyaves

Now you're thinking with gas.

GreatWave

iTrader: (5)

96+ are all front-facing, regardless of vtec

TomCat39

That likely could be because they did away with the spit wells they used to use on the non vtec motors.

Prior to 96 only vtec motors had one piece solid spark plug wells/tubes. While the non vtec had a split tube design that you had o-rings in between to keep the oil out of the wells locked in place by the rocker arm assembly.