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Head and Head Gasket refit prep

25K views 208 replies 11 participants last post by  p76rangie 
#1 ·
Getting ready to pot the heads back on and interested in what you do to prep.

I'd like to clean and make things as pristine as possible.

Thanks.


-sobieski
 
#2 ·
Assuming you have had the heads pressure tested, cleaned and resurfaced (skim cut as a minimum) you now need to prepare the block.
Your pictures in your head bolt post show a whole lot of crud and carbon, you want to get as much of that out without damaging the piston domes or cylinder walls?
As for the block deck surfaces, It Should be cleaned with a solid wide flat blade scraper, composite scrapers are becoming more popular, I still use steel never use power tools buffing wheels etc.it may not look "clean as new" but should be carefully scrapped flat without any gouging. Block should be checked with a proper strait edge to verify no excessive war page. If it is warped or there is excessive pitting then there is no sense putting it back together with new gaskets - it will only fail again and until it does will be unreliable. If it's warped or pitted the engine needs to come out and to a machine shop.
Consider asking yourself a couple questions
Do you know why the previous gasket failed?
Did your temperature go above 220 ever in its life?
Do you want to go through all this work again 6 month from now or sooner

I personally would strongly consider continuing deeper into it and pulling the engine right out if any of your answers don't leave you feeling confident that a reliatively quick and easy gasket job is going to do you and your truck justice.
If the heads are warped it will leak again, if the block is warped or damaged it will leak again

I finished my complete rebuild with flanged and ORinged cylinder liners just a week ago and although it was a hard pill to swallow, I know it was done the best it could be done. No corners cut . No iffy should be O.k. / fingers crossed stuff.

Is that what you want or are you o.k. Patching it up and wait and see , take you chances, wish on a lucky star.....
 
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#3 ·
The most important and often overlooked step is to make sure the head bolt holes are clean AND dry.

I use a re-thread tap to clean threads and brake parts cleaner and compressed air to remove remnants.

Whatever you do, don't use a scotch-brite pad on a die grinder on the mating surfaces or I will hunt you down and beat you with a broken halfshaft!
 
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#4 ·
Red,

I'll check for warpage on the block.

What's the best method for carefully getting the carbon out/off the cylinders?

No it's not been overheated - at least not since I've owned it - that was 60k mi ago.
Ever? No way to know.

It had 70k on it then. 130k on it now.

I do not Know know why the hg failed other than it's just plain got 130k miles on it.

In fact the hg's didn't really look all that bad. A little "erosion" or wear on the rear of the passenger side gasket - where my generous coolant leak was coming from - but the gasket was not "blown" or broken.

These aren't the greatest pics, but:
Groupset Metal

Eyewear Glasses Tire Rim Auto part


Of course I do not want to re do this.
But pulling the engine and a full re build is beyond my experience and skill level, at this point.

HOWEVER, I will keep learning and one day....


PTShram,
Thank you. Good reminder on the holes - clean and DRY.

I would never do anything with scotch except drink it.



-sobieski
 

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#6 ·
On this same topic, what's your recommendation for a "thread chaser" to clean out those threads, before blowing out and being sure it's all clean and dry for the new bolts?

Also, as I am going the TTY bolt route are there "better" bolts out there that I should get other than the standard 9224 bolt set from AB?
 
#7 ·
Aerosol cleaner , carb cleaner, combustion chamber cleaner, even brake parts cleaner will work and not hurt anything. That along with a fairly tame scrub brush ( kit hem dish scrub brush from the dollar store for example and shop towels, even a shop vacuum to suck it all up, compressed air to blow crud out may also be useful.

I didn't want to scare you in my earlier post, only you know what the best decision will be in you situation. As always, I hope my comments help.
I does look like a gasket failure at the rear coolant passage in your case from what I can see in you pictures and read in your descriptions.
If you don't have or have access to a thread chaser, you can apeasily make one using one of the old head bolts,
Best of luck with your project
 
#15 ·
.

Picked this up:
View attachment 66178

And will clean clean clean / get some parts ordered for reassembly.

Stay tuned......


-sobieski
You can make that tap work (OK, not that particular one).

If you have a grinder or an abrasive cutoff wheel, shorten it until it looks like the tap on the right.Make sure you cut it squarely.



A taper tap is used for initial threading- it gradually cuts each thread. In softer material such as aluminum, you can tap with a plug tap, but its real intention is for continuing the tapping of the bottom of a blind hole- again, by making gradual cuts. The bottoming tap goes in last to cut the final couple of threads. One of the reasons you want to do this is that if you were to thread a bolt or stud into a blind hole cut with a taper tap, as it ran out of threads, the bolt would be pushing outward at the bottom of the hole where the threads aren't completely cut- which could cause the material being threaded into to fail.
 
#9 ·
The stock style bolts are fine. I've yet to have a bolt-related failure and have only had one came-back on a head job and I still don't know why that one failed.

As for a thread chaser, Snap-On part number TRT4314A is what you'll want. $3.80 from your local Snap-On franchisee.
 
#10 ·
I'm a Rover noob but have been working with aluminum blocks for about 30 years. I've had my share of premature head gasket failures and I've learned a few things from my mistakes.

There's a long version and a short version. I'll do a brief bit on the long version. Head bolts on an engine, and particularly on an aluminum block are considered to be a precision thread. Precision threads are sub-categorized by what's called Class of Fit. The original design of whatever precision thread was specified at a particular fit. Repair work assumes the original class of fit. The higher the class of fit, the more load holding ability the connection. Any alteration will affect the class of fit and subsequently the ability of that connection to last.

Short version- don't F-up the threads. The best way to do that is to clean out a gunked up hole with a brand new HSS tap, with no lube, chucked into a tap wrench.

First off, you need to use a bottoming tap. Sometimes referred to as a one-an-a-half. That means that the whole first thread and half of the second is missing on the tip end. You cannot clean a blind hole with a plug tap. And absolutely not a taper tap as in Post 8. I use a carbon steel tap with a 2B fit (you would have to really go out of your way to find a 3B CS tap). Just touching it you'll notice how much less sharp it is than the HSS piece. I take them and toss them into my blast cabinet and hit the cutting edge with 120 grit AlOx at 50 psi. It knocks the cutting edge down- but don't overdo it. You can do the same with the little harbor freight jewelers file kit. Then I put a piece of fuel line on the shank to make it easier to turn by hand. The hole should be soaked in brake cleaner and blown out- at least a couple times. Then fill the hole with WD-40. It's very important to feel the tap in on the first thread. never go past a half turn without reversing a bit more than a half. Don't go more than 3 or 4 full threads without coming completely out and flushing the hole.

It's impossible to get accurate torque with a dirty or malformed thread. It will always be higher. This is especially true for TTY bolts, since you're not measuring actual torque. I'm in the middle of redoing a head gasket job done by a rover specialist shop less than 20K/MI ago. Two bolts were broken at the deck and three others hard seized. The two came out by simply pulling upward and the other three snapped off. Since it was so recent, all their prep work was still visible- and the did a good job. But I'll bet they failed to properly prep the bolt holes.

The Snap On chaser pointed out is the same one Sears sells in their kit. I have used them before and wasn't thrilled. They're a bit on the loose side, I suppose to compensate for someone not knowing how to properly chase a thread. I tried it back to back and got a bunch of gunk left behind using the dulled tap I described. If you take your time and follow the steps exactly, you won't see a speck of silver.

After you're done, take the time and thread a new bolt gently into your cleaned out holes using light machine oil. Back off a turn from bottom and feel the fit. If you feel motion, you need to fix the worn thread. On assembly I would suggest a good moly lube on the threads and under the bolt head to ensure proper torque.
 
#11 ·
very nicely written, you obviously know what you are talking about.
Thanks for sharing, some very good points to keep in mind
 
#12 ·
Yes, thanks CT. I won't be using that tapered tap.

Here's the head deck after meticulous, baby-gentle, cleaning to get the residual gasket/schmag off.
Auto part

Auto part Audio equipment Rim Metal

Auto part Engine

Auto part Rim Wheel


The discoloration is, as far as I can tell, just that - discoloration.

Otherwise it's smooth with no leftover schtuff on it.

BUT you guys tell me. Ok? Or more cleaning?


-sobieski
 
#16 ·
Well I always appreciate a robust debate among Rover folks.

Back to my head refit prep....?

How's the deck look ? - pics above

Where can I get a re-threader type tap like the the one PTSchram recommended above, if I can get to "my local snap on franchise"?



-sobieski
 
#18 ·
No, you are WRONG!

You suggested a thread-cutting tap, not a rethread tap. They are supposed to be undersized to avoid damaging the parent/native threaded hole.

Stop spreading incorrect information because you are absofuckinglutely wrong in this case.

As for your $28 tap, why buy the wrong tool when the correct tap is less than $5.00, comes with a lifetime warranty and the service that only your local Snap-On franchisee can bring.

"I" am NOT a Land Rover noob-as you said yourself.

W/R/T your fear of TTY bolts, I only use studs on high-performance Rover engines and frequently don't even use them on the supercharged engines I've built if the boost pressures are low.

There are hundreds of thousands of Land Rovers on the road with TTY bolts that have not had a failure. Once again, we only hear about the bad experiences and never hear about the hundreds of thousands who have NOT had a negative experience-and while I'm on the topic, the vast majority of head gasket failures on Land Rovers are due to pilot error. Either not regularly inspecting the engine compartment, or ignoring the idiot light telling the pilot to stop.

When I was a service advisor for Land Rover Portland (Oregon) I had a woman call one afternoon telling me there was an indicator light on her instrument panel that looked like an antique oil can. I told her to pull over immediately and I'd send a tow truck to retrieve her truck. She balked and said her kids were with her. I told her I'd send a porter to take her and her kids back to the store and we'd give her the truck as a loaner. She hung up on me. 30 minutes later, a BRAND NEW LR3 drove into the service entrance in a cloud of smoke and a woman jumped and said "I'm sure glad I have a warranty!". The parts/service ,anger walked up to her and told her "You were told by not one, but two service advisors to park the vehicle. One of the service advisors is a competent, certified engineer who told you to stop and we'd come get you. Your warranty is void due to abuse".

I can think of no better example of a driver refusing to pay attention to what the truck was saying. You however are a close second in refusing to accept or acknowledge when you're been proven you are wrong.
 
#19 ·
Schram,

I think (hope) you're addressing CT90.

I ordered the thread chaser from SOn that you indicated.

Take a look at the pics above/below.
Is this deck-prep acceptable?

I used a scotchbrite pad and a dremel. And it finally came off.

JUST MESSIN' W YOU.

Before:
Auto part Wheel Automotive wheel system Rim Wood



After:
Auto part Rim Tire Wheel Automotive wheel system

Auto part Automotive engine part Engine

Auto part Automotive engine part Engine


I used a LOT of carb cleaner and mostly my finger nail wrapped in a rag and soaked in carb cleaner.

Appreciate you and the rest of the forum so very much.

Hang with me on this one and stay tuned.....





-sobieski
 
#21 ·
Well I guess we're just going to have to leave it at we have different opinions.

But... I am going to have to correct you on some things.

First, when you modify the tap as I suggested, it will no longer cut threads. It is no longer a cutting tool. Your "rethreader" is merely a bolt with a groove cut in it. It's a fairly crude device. You are correct- it won't cut threads. But it also won't clean them as well as I would require for a precision fastener in a critical torque application.

And, while ARP is many things, including often times a profiteer, they are pretty much the gold standard for automotive fasteners. If they sell a thread chaser, I have every confidence it is well-researched. And since I own a couple of them and have used them, I personally know how they perform. I merely suggested an option that costs less. I'm not sure why you consider a tool made for cleaning and chasing threads in the specific and exact application we are discussing, made and sold by a premier supplier in this field is "the wrong tool", but you seem quite adamant about it.

I have no fear of torque angle bolts in any way. In fact, I stated in my last post that I believed them to be perfectly fine and that despite a substantial amount being written about their "issues", that i did not believe that to be the case. The issue I have is that in my particular instance, I believe the threaded holes in my block are less than ideal, yet not so concerning that I'm going to replace them with inserts. I believe the ARP stud to be a better alternative in my instance. Cheap insurance.

Lastly, the aluminum in the block casting in the Discovery in my shop is wholly unaware that it is residing in a Land Rover. A tapped hole in an aluminum block is a tapped hole in an aluminum block. I'm not really interested in comparing Johnsons with you, but suffice to say, I have had both my share of education and hands-on experience as well.
 
#23 ·
Or a simple brass rifle bore brush in the variable speed drill works absolutely fine followed by a solvent bath and vacuum with a normal large drink straw attached to a siphon gun hose. There is absolutely too much missing information for the average guy to know about machine work performed properly leaving the risk large that it will not be performed properly compromising the finished result. I will point this out once again. For the average home repair guy, pass on the TTY bolts and use ARP studs. It's not about the known short comings of TTY bolts in dissimilar metal that experience stretch and shrink at different rates, it's simply easier to torque studs for the novice with out the proper TTY torque wrench than attempting to "eyeball" the final degree twist with the engine in the frame. Most guys don't have a 360 degree gauge much less a $700 digital angle torque wrench. Be safe!

Doug
 
#24 ·
Sobieski
You have asked a number of times and the replies all seem stuck in taps and chasers

You deck prep looks good to me in your pictures.
Are you planning on cleaning the tops of the Pistons? ..... I can se the next debate starting on this topic;)
 
#25 ·
Your block looks fine.

your method is probably better for someone who hasn't done it a hundred times.

W/R/T the TTY bolts, the 90' is very easy to eyeball and it is unlikely that the few degrees you might be off would be an issue.

Doug Myers-the ATECH3FR250B has a list price of only $559.95 and is frequently on a special with a minimum of $50 trade-in, if not $100 trade-in. Not only is the ability to measure the angle valuable, for me, the speed was the final straw that forced me to buy my own. Now that I have both the 3/8 and 1/2", it's time to get a 1/4" for myself :)

CT-you are a hack and spreading disinformation. You may well be able to stand further from the urinal than I can, however that does not negate the fact that you are still wrong.

Bottoming taps are just as sharp and of the same dimension as a taper or plug tap. the only reason they are different is to allow for tapping to the bottom of a blind hole.

Reference attached:
Everything you wanted to know about taps but were afraid to ask, styles of taps, class of thread , gh numbers , basic point in thread measurement , constants for finding pitch diameter and minor diameter of screw threads , thread constants for variou
 
#27 ·
CT-you are a hack and spreading disinformation. You may well be able to stand further from the urinal than I can, however that does not negate the fact that you are still wrong.
With due respect sir, shouting and ranting really doesn't make you any more right or wrong. You may have some time behind the writeup desk at a Rover dealership, but I can assure you that you won't find one of those thread cleaning tools in any journeyman machinists toolbox- ever. Used properly, a tap works just fine. For the less experienced, a slightly dulled CS tap gives a better margin for error. If you don't feel you possess the skill to use the tool, the lesser device is probably a safe bet for you. But you might want to save your Chicken Little act- this ain't brain surgery. If you can get all the way to the bolt holes without a torch or sawzall, you can properly and completely clean the bolt holes without damaging them.

P.S. Go post your tool on one of the machinist's forums. Be prepared to be laughed at soundly.

Bottoming taps are just as sharp and of the same dimension as a taper or plug tap. the only reason they are different is to allow for tapping to the bottom of a blind hole.
Thanks for correcting me. Oh, No, Wait... that IS what I said. It needs to be the same size as the thread. Otherwise it leaves crud in the thread.

You neglected to address the ARP chaser, which differs greatly from your suggested device. Are they wrong too?

And thanks for the link. I'm going to stick with my Machinery's Handbook and American Machinist's. Interestingly enough, neither of these globally-accepted last-word publications addresses the use of your recommended gizmo.
 
#26 ·
The brass brush is a good idea, provided the holes are not full of foreign material like sealers and such. And I definitely agree on the ARP studs, although I was shocked to find they spec 100Ft/Lbs, although by calculation, is dead center between recommended and max torque-

American

Application Data
Major Bolt Diameter: 0.4375 in
Bolt Thread Pitch: 20
Bolt Proof Strength: 200000 psi
Receptacle Length: 1 in
Receptacle Strength: 46000 psi
k Factor: 0.2

Recommended Torque
1031.6 in-lb
(85.96 ft-lb)
(116.57 N-m)
Resultant Tension:11789 lb

Maximum Torque
1375.4 in-lb
(114.62 ft-lb)
(155.42 N-m)
Resultant Tension:15719 lb


With a precompressed gasket, I'd think 80 would be OK, although it would be close to the line on stud elasticity.


For piston cleaning, I have always had good luck using the GUNK carburetor cleaner that comes in the gallon bucket. If you bring the pistons to TDC one at a time, you can lay a dampened rag on each one and it dissolves the goo in minutes. It's important to lube the cylinders well when you're done to prevent dry startup.
 
#28 ·
I had not planned on do much more cleaning to the pistons.

BUT I will defer to the forum wisdom/best practices.

If I do clean up the pistons, it will be in their current positions.

As long as I clean it out good, would Gunk carb cleaner still be ok to use?

Also, now I'm really debating studs vs bolts: I do anticipate it being difficult to fanangle getting my torque wrench and a precise 90 then 90 degree turn on those back bolts in particular.

I am not going to unmount the motor.

I am willing to pick up an angle gauge.
Which one do you all recommend?





-sobieski
 
#29 ·
Spray Carb cleaner and scotchbrite will work, but it's a bunch of elbow grease. It doesn't need to be perfect. Just get off what comes off easily. It's coming back anyway. There's a reason it's not an inch thick. What's there is about all that's going to stick. It's not nearly as critical as the gasket mating surface.

You can get an angle gauge at Advance for $13. But good luck on those rear lower one's. Never tried, but I'd guess you'd have to pull the motor mounts to do it. For about a few bucks more the ARP's are a no-brainer. But only if you have a GOOD torque wrench. If you don't, or cant borrow one, and don't want to drop $200 on one, go TTY and do the extra work. A $40 torque wrench is useless.
 
#31 ·
Since it feels like moderating a Presidential debate (ha!):

PT,
What's your take on, specifically:

Studs vs bolts - just based on ease/accuracy of installation.
And
If bolts, a decent angle gauge to be sure 90 is really 90 ?

PS the carbon still remaining on the pistons is ON there. And I don't want a half-shaft beating, so scotchbrite pads don't come onto my property.





-sobieski
 
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