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TOPIC: Head Swap

Head Swap 7 months, 1 week ago #83235

I recently had a head built and will be swapping it into my current car in the coming weeks. Are there any DIY walkthroughs or lessons learned for doing this on an M20 / SpecE30?

I have the Bentley, but sometimes it doesn't capture the shortcuts and gotchas which have become part of the collective wisdom. Looking for any head's up before I dive into it.

Thanks!

Julian

Re: Head Swap 7 months, 1 week ago #83236

  • Patton
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Do a leakdown test before and after to see if you made any advances by changing the head.

Better yet, leakdown and dyno before/after test to see if you accomplished anything.

Drain all coolant from the block port on the passenger side of the block. With help from a friend R&I head with intake and exhaust already installed. Use zip ties to collapse the breather tube spring. More later.

RP

Send injectors out for cleaning.
Last Edit: 7 months, 1 week ago by Patton.

Re: Head Swap 7 months, 1 week ago #83241

Patton wrote:
Do a leakdown test before and after to see if you made any advances by changing the head.

Better yet, leakdown and dyno before/after test to see if you accomplished anything.

Drain all coolant from the block port on the passenger side of the block. With help from a friend R&I head with intake and exhaust already installed. Use zip ties to collapse the breather tube spring. More later.

RP

Send injectors out for cleaning.


Good stuff, thanks!

Re: Head Swap 7 months, 1 week ago #83242

  • Ranger
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Be careful with fasteners going into AL. Each time you're about to put a fastener into AL, pause and look again at the bolt to confirm that it's 6mm or 8mm. Put a dab of blue locktite in each, then torque them in on the light side. Go look up the bolt spec in Bentley and then subtract 10%. Failing that, do 70inlbs for 6mm and 12ftlbs for 8mm. Don't use a torque wrench calibrated in ftlbs for the 6mm fasteners because it won't be accurate enough for such a small torque.

Often the timing belt is tricky to get on, and get it in the right place. The way to get the reluctant belt to work is to cleverly manipulate where the slack is...left side or right side of the cam pully. Put the crank at TDC but the cam at a half tooth after tdc. Then wiggle things to get the belt on. You'll find that once you get the belt on and and move the crank to tug the cam pully a couple degrees, the timing will be right.

I'm trying to figure out how to explain the "why" of the above working. When you're putting the tbelt on, you need a little slack on the drive side of the tbelt. By "drive side" I mean the side of the tbelt that will be under tension because the crank will pull the belt. So when you get the belt on, when you first turn the crank, the cam won't actually move because you're turning of the crank has to first remove the tbelt slack. That means that when the cam pully does start tuning, the crank will be a little after tdc. And that's where you had the cam pully....a little after tdc.

There's an 8mm bolt that fastens the tbelt tension pulley to the block. Be gentle with that bolt. The block is only cast iron so it's not all that hard, and the "tang" that the bolt threads into isn't all that strong.

Here is a pic of putting zip ties on the bitch tube, as Robert mentioned. s465.photobucket.com/user/RangerGress/media/Mechanical/IntakeManfoldBitchTube.jpg.html

Thermostat housing. The tstat and the intake manifold kind of get in each other's way during the install. A solution is to remove the top stud holding the tstat housing and use an 8mm bolt instead. Just be careful to not thread the bolt in too tight. What this gets you is the ability to put the tstat housing on over the bottom stud, and then rotate it away (forward) from the intake manifold. Place the intake manifold on, then rotate the tstat housing back towards the manifold and put in the missing bolt. Additional note: Be careful when turnign that bolt with a socket that the socket doesn't get trapped in place. What will happen is that the socket will turn the bolt but the socket will be trapped so the bolt can't back out. This will strip the soft AL threads in the head. It's just a matter of paying careful attention when removing that bolt.

Before you put the intake manifold on, put the intake gaskets on the head. Then trim those gaskets so they won't restrict air flow into the head.

Gasket kits. Victor-Reinz sells a convenient gasket set that includes everything you need. But their headgasket has a mixed reputation. My suggestion would be to buy a Goetz HG and also buy the V-R kit. Remove the V-R HG and use the rest of the kit. Save the V-R HG for the day when you're doing test fits of heads, like claying valves for clearance, or something.

OEM HG's have a good rep but are overpriced. There's another HG outfit with a good rep but it's name escapes me. Lemforder maybe?

Don't deck the head any more than you need to. Rich Bratton did some experiments in this and found that the compression you gain by decking the head doesn't make up for the power you lose due to the retardation of mechanical timing.

Be advised that this all just reflects my opinions. You will find there's plenty of disagreement on any theory I may hold dear.

If you've not bought a new cam and rockers, I would. You'll get more valve lift. The OEM adjustment protocol does not really compensate for valve train wear all that well. The location on the rocker foot where one puts the feeler gauge is not the same part of the foot that is touching the cam lobe at max lift.

If you have replaced or aggressively cleaned cam or rockers, be sure to slather them with high ZDDP oil before turning the engine over. The cam and rocker surfaces will need the anti-wear coating that high ZDDP provides in the first seconds of start up.

If you don't have a coolant pressure sensor in the port near your starter, now is the time.

If you've not blocked off the coolant passage at the back of the head, now is the time.

Make sure you use the 2 locating "pins" that go between head and block. They are not optional.

Note the holes in the HG that allow coolant to go from block to head. Note how they get bigger for piston 5 and 6. Metric Mechanic likes to make them big at piston 4 also. I may be off by 1 piston, but the idea is the same. The bigger holes encourage more coolant flow at the back of the engine.

If you have a helper, you can put the manifolds on the head, and then put the whole thing on to the block. This is a big time saver because it's so much easier to put the manifolds on with the head sitting on your bench. Don't attempt this with 1 person tho, and your helper needs to be a strapping lad because it has to be done carefully and it's an awkward task.

Writing up these issues is like writing a wiki of my mistakes over the years. Dang, so many painful lessons learned.
"Tower, this is Ranger requesting a flyby.
"Negative Ranger the pattern is full."
Last Edit: 7 months, 1 week ago by Ranger.

Re: Head Swap 7 months, 1 week ago #83243

A ton of great advice. Thanks!
Winding Road Racing - supporting racing with info, products and services from the perspective of the novice, the student and the fan of the underdog.

Re: Head Swap 7 months, 1 week ago #83244

  • Patton
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Ranger wrote:
Be careful with fasteners going into AL. Each time you're about to put a fastener into AL, pause and look again at the bolt to confirm that it's 6mm or 8mm. Put a dab of blue locktite in each, then torque them in on the light side. Go look up the bolt spec in Bentley and then subtract 10%. Failing that, do 70inlbs for 6mm and 12ftlbs for 8mm. Don't use a torque wrench calibrated in ftlbs for the 6mm fasteners because it won't be accurate enough for such a small torque.

Often the timing belt is tricky to get on, and get it in the right place. The way to get the reluctant belt to work is to cleverly manipulate where the slack is...left side or right side of the cam pully. Put the crank at TDC but the cam at a half tooth after tdc. Then wiggle things to get the belt on. You'll find that once you get the belt on and and move the crank to tug the cam pully a couple degrees, the timing will be right.

I'm trying to figure out how to explain the "why" of the above working. When you're putting the tbelt on, you need a little slack on the drive side of the tbelt. By "drive side" I mean the side of the tbelt that will be under tension because the crank will pull the belt. So when you get the belt on, when you first turn the crank, the cam won't actually move because you're turning of the crank has to first remove the tbelt slack. That means that when the cam pully does start tuning, the crank will be a little after tdc. And that's where you had the cam pully....a little after tdc.

There's an 8mm bolt that fastens the tbelt tension pulley to the block. Be gentle with that bolt. The block is only cast iron so it's not all that hard, and the "tang" that the bolt threads into isn't all that strong.

Here is a pic of putting zip ties on the bitch tube, as Robert mentioned. s465.photobucket.com/user/RangerGress/media/Mechanical/IntakeManfoldBitchTube.jpg.html

Thermostat housing. The tstat and the intake manifold kind of get in each other's way during the install. A solution is to remove the top stud holding the tstat housing and use an 8mm bolt instead. Just be careful to not thread the bolt in too tight. What this gets you is the ability to put the tstat housing on over the bottom stud, and then rotate it away (forward) from the intake manifold. Place the intake manifold on, then rotate the tstat housing back towards the manifold and put in the missing bolt. Additional note: Be careful when turnign that bolt with a socket that the socket doesn't get trapped in place. What will happen is that the socket will turn the bolt but the socket will be trapped so the bolt can't back out. This will strip the soft AL threads in the head. It's just a matter of paying careful attention when removing that bolt.

Before you put the intake manifold on, put the intake gaskets on the head. Then trim those gaskets so they won't restrict air flow into the head.

Gasket kits. Victor-Reinz sells a convenient gasket set that includes everything you need. But their headgasket has a mixed reputation. My suggestion would be to buy a Goetz HG and also buy the V-R kit. Remove the V-R HG and use the rest of the kit. Save the V-R HG for the day when you're doing test fits of heads, like claying valves for clearance, or something.

OEM HG's have a good rep but are overpriced. There's another HG outfit with a good rep but it's name escapes me. Lemforder maybe?

Don't deck the head any more than you need to. Rich Bratton did some experiments in this and found that the compression you gain by decking the head doesn't make up for the power you lose due to the retardation of mechanical timing.

Be advised that this all just reflects my opinions. You will find there's plenty of disagreement on any theory I may hold dear.

If you've not bought a new cam and rockers, I would. You'll get more valve lift. The OEM adjustment protocol does not really compensate for valve train wear all that well. The location on the rocker foot where one puts the feeler gauge is not the same part of the foot that is touching the cam lobe at max lift.

If you have replaced or aggressively cleaned cam or rockers, be sure to slather them with high ZDDP oil before turning the engine over. The cam and rocker surfaces will need the anti-wear coating that high ZDDP provides in the first seconds of start up.

If you don't have a coolant pressure sensor in the port near your starter, now is the time.

If you've not blocked off the coolant passage at the back of the head, now is the time.

Make sure you use the 2 locating "pins" that go between head and block. They are not optional.

Note the holes in the HG that allow coolant to go from block to head. Note how they get bigger for piston 5 and 6. Metric Mechanic likes to make them big at piston 4 also. I may be off by 1 piston, but the idea is the same. The bigger holes encourage more coolant flow at the back of the engine.

If you have a helper, you can put the manifolds on the head, and then put the whole thing on to the block. This is a big time saver because it's so much easier to put the manifolds on with the head sitting on your bench. Don't attempt this with 1 person tho, and your helper needs to be a strapping lad because it has to be done carefully and it's an awkward task.

Writing up these issues is like writing a wiki of my mistakes over the years. Dang, so many painful lessons learned.



Ditto. When walking the tbelt onto the cylinder head you'll want to use a pry bar to detent the spring tensioner/pulley. Lock it there with the 13mm bolt. Walk belt on, release tension. Notice that you are off by one tooth, remove, repeat, remove, repeat till everything is in-sync.

RP

Re: Head Swap 5 months, 3 weeks ago #83351

  • jlevie
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Also chase the head bolt threads in the block and clean them throughly.
Jim Levie, #38

Re: Head Swap 5 months, 3 weeks ago #83355

For what it is worth, I only use BMW head gaskets. Had poor luck with aftermarket. The OEM gasket seems to tolerate my mechanical incompetence.

Re: Head Swap 5 months, 3 weeks ago #83356

  • Som
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If I had to do it again, I'd have put in studs. Main reason is I was working on it during late nights where I didn't have someone helping me with head placement.

The two dowels will locate the head appropriately, but if you miss them when you release it, the dowels can end up scratching up the aluminum head. Studs (as far as I can tell) would have made aligning the head on the block much easier as a one man job.

Of course, you could just put some long wooden dowels in the bolt holes to help, too.

Make sure the dimples on the head deck are still present. If they're gone, there's a chance it was over decked and you may need a taller HG to compensate.

I think there are some tricks for block cleaning that I didn't use but could help. Like something about putting shaving cream in the cylinders if you're cleaning the block with abrasives or anything to prevent debris from getting into the cylinders. That said, I did't risk it and just went the razor blade route.

That's about all I got that hasn't been covered.

Good luck!

Som

Re: Head Swap 5 months, 3 weeks ago #83357

One other thing. You might consider pulling the motor to do this. It is a million times easier to build up the motor on an engine stand. The motor and trans come out together in about an hour or so.
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