- Fri Mar 05, 2010 11:44 pm
#179447
http://www.d-series.org/forums/engine-b ... -pics.html
I remember a guy on here ages ago who had put a ZC 1st gen head onto a sohc block.
This inspired me to see what i could do with the 2nd generation head as i was looking for a new motor which I would turbo.
My current ZC and D16a9 dohc were both blowing smoke and I had access to a d16a6 short block brand new from Honda (New Zealand) for $240 kiwi but didn't want to go back to a sohc head after the ZC.
here's what i had to do...
The short block was a 1994 nzdm d16a6 9.3:1 compression motor and I had a spare HM2 jdm ZC head.
Obviously as most of you know the head bolt holes dont line up between the sohc and the dohc but I have found a perfectly easy and legitimate way around it.
Those who have said in the past that it cant be dont are going to have to re-think thier theory.
The Block
The ZC has 11mm head bolts form factory while the d16a6 I had has 10mm, in drilling out the 10mm holes in the block and tapping them for a 12mm you allow your self a bit of leeway +/- 1mm either side of the center of the hole in the head in any direction you need to when you re-drill the head to suit.
This allows (if you want) the studs or bolts to stay central in the new holes you'll be drilling without having oval holes.
It also gives the chance to upgrade from the piddly standard 10mm bolts.
To do this all you need is a mill (or drill press but I wouldn't recommend it, better to have a bit of accuracy and weight to stop vibration etc) set up exactly perpendicular to the surface of the table.
Cut the top off an old 10mm bolt and discard the top and de-burr and shank where you cut it through.
Put the stripped engine block rightway up on the table of the mill ( you may need to wind out the sump pan studs to get it flat on the bottom.
Use whats left of the bolt to centre the block and hole you wish to start on perfectly under the chuck by clamping the bolt shank in the chuck and winding it into the existing thread.
Clamp the block in position.
Unwind the bolt and remove from the chuck.
Fit a 10.2mm drill bit and drill out the exising thread right to the bottom of the hole.
Keeping the block in place to keep the centre now fit a long series 12mm x 1.75 tap and use the chuck once again (unpowered!) to wind the tap in and cut the new thread.
Buy two taps and grind one flat on the end so you can tapp right to the bottom of the hole. Use the standard one first and then the flat bottom one to finish the hole.
Use meths to assist the cutting in the aluminium and take it slowly.
You wil need to use compressed air to continually remove swarf from the bottom of the hole if you are going to tap all the way down.
Repeat the above steps on all 10 holes.
Do not unclamp the engine block until you have finished drilling and tapping the hole. Only unclamp between holes.
Your local engineering supply store will be able to supply 12mm x 1.75 12.9 grade high carbon allen head cap screws with you can use to hold down the head.
They are almost as expensive as ARP so if you want the piece of mind that a bid brand will give you go with ARP.
Or use studs, use what ever you like or what you can afford.
Stock bolts are 10.2 grade so the 12.9 is a step stronger.
Heres a pic of my finished block with the bolts would in to show the size of the new bolts, they are a huge increase on the stock bolts. There is no way in hell you will break one of these, it'll pull out of the thread before it snaps.
The lengths I needed were 185mm for the oil feed bolt as it's longer than the rest.
150mm for all the reast except for one which was 140mm.
I do not suggest buying your bolts first, each block could be different in hole depth depending on what year you use. Fit and measure to suit, all the nessessary lengths are available.
You will also need new washers, you can get what they call "Hard Flats" in a 12mm inner hole which you can use but make sure the external diamenter can still sit in the seat for it ontop of the head. Keep the thicknessass close to original as possible but you have plenty of room under the cams to pack the bolts up if you are worried about the bolts bottoming out in the block.
When the blocks done and cleaned, this is a good time to fit a block gaurd, I am skeptical about peoples claims of them causing hot-spots as they mount so far down the water jacket that they are miles away from the combustion chamber anyway.
The Head
The top left hole is out the most, and is the exception. It requires that the hole be completely redrilled off centre and will mean a slightly eleptical hole even when re-drilled to fit the 12mm bolt.
You will see when looking inside a ZC head that the seats where the bolt washer sits in have been milled vertically from above with what i remember being a 22mm cutter. You will have to re-seat the top left hole on the new centre by cutting vertically with a flat botom milling bit from above.
This will eat away at the edge of the cam seat but that's exactly what honda has done on a few of the other holes from factory. And it does not affect the operation of the oil feed or wet bearing. Just make sure you dont leave burs on the cam seat.
The stock d16a6 head gasket can be used to find the appropriate centres on the head. There are actually 3 holes which dont centre properly but bu the time you have put a 14mm drill bit through them for the 12mm bolts, there seems to be enough clearance and i did not bother to re-centre them. If you wanted to now is the oppurtunity.
I used the gasket to find the centre of the one hole that is majorly missaligned and then drilled a 12.5mm[b/] hole through the head for the bolt to pass through.
What 0.5mm clearance you're saying? No it's actually more than that because the unthreaded part of a 12mm cap screw is smaller than 12mm as the thread is forged and sticks out proud, but also because the hole is eliptical because of the interference with the other existing hole.
I would not suggest using a 14mm bit here as it gets really thin around the water jacket behind the heater flange. You'll see what i mean when you take a look.
Drill all the rest of the holes at 14mm using the original centres and then check everything lines up.
here it is all drilled out, sorry for the shit pic it's off my phone.
I used the ZC dohc gasket because the water feed holes over the wet liner lined up and the sohc gasket doesn't.
All other oil feeds and returns line up ok though.
heres the finished item.
[b]why do it?
A challenge, because so many people either say it cant be done (when it clearly easily can) or really wanted to know if it was possible.
It was cheap.
The ZC head has a 43cc combustion chamber and with the d16a6 -3cc pistons it makes for 8.3:1 compression, perfect for turboing.
If you were going NA use the ZC PM7 or P29 pistons.
For those of you in the US it'll be cheaper to by or import a ZC head than it will be to get a whole motor and you wont be able to prove the k's of the motor.
New ZC's are no longer available but new d16a's are!
Happy hybriding.
1980 volvo 242
2001 crv
not using punctuation or good sentence structure since day 1
2001 crv
not using punctuation or good sentence structure since day 1
