head gasket replacement
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This job is complicated enough that you should have a Service Manual. The procedure and all of the torque specs, valve settings, etc, are in it.
David Teitelbaum
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Per Tim Engel the procedure taught to the LOON's follow is to use both torque specs and degree wheel together as using just a torque wrench alone varies a bit per friction load and bolt stretch conditions. A degree wheel is commonly used on end cap and head bolts in many engine assembly procedures.
As stated by others get the manual.
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The ARP head bolts have a fine pitch thread!
You cannot use the Lotus torque angle spec, since the Lotus bolts were coarse pitch thread!
Check with JAE for the torque spec.
Also the black composite gasket, says something about installing it dry, the old gaskets used some "wellseal" around certain features. I've noticed that the new gasket doesn't do a good job about sealing around the roll pins that go through the block below the exhaust manifold. Mine started leaking right away. I'm actually re-doing mine because of this... Nobody like the smell of hot coolant boiling on the exhaust manifold every time the drive the car. I plan on using some sealant around these features next time!
You can see the small roll pin here below the right head stud.
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You cannot use the Lotus torque angle spec, since the Lotus bolts were coarse pitch thread!
Check with JAE for the torque spec.
Also the black composite gasket, says something about installing it dry, the old gaskets used some "wellseal" around certain features. I've noticed that the new gasket doesn't do a good job about sealing around the roll pins that go through the block below the exhaust manifold. Mine started leaking right away. I'm actually re-doing mine because of this... Nobody like the smell of hot coolant boiling on the exhaust manifold every time the drive the car. I plan on using some sealant around these features next time!
You can see the small roll pin here below the right head stud.
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I had breakfast with Tim Engel yesterday morning discussing my future engine assembly. I brought up degree figures as a discussion subject.
Yes the ARP has a fine pitch and the Lotus spec can not be used for a degree wheel for ARP. ARP has only released torque specs but it must be torqued with bolts clean and dry then lubricated with ARP lubricant only during assembly. That is per the ARP instructions.
So I'm not sure if the ARP torque spec are accurate if reusing ARP bolts. In any case motor oil or any other lubricant should not to be used, only ARP lubricant.
On the other hand LOON or Engel derived degree wheel figures can be used on ARP bolts. We all agree that degree based specs are more accurate than torque figures that can alter based on friction load. At this time the final figures are not ready for release. The numbers derived from my head assembly along with others will form the LOON/Engel numbers that can be used in the future. In any case this spec is not an official ARP number as there is none.
Tim has suggested a number procedures in the interests of advancing Lotus maintenance. After I get my car running I will be taking my old cracked manifold for an experimental fusion weld. Tim has said if the weld holds up it will be a cost effective benefit for many Esprit owners. He has a lot good talking points.
Yes the ARP has a fine pitch and the Lotus spec can not be used for a degree wheel for ARP. ARP has only released torque specs but it must be torqued with bolts clean and dry then lubricated with ARP lubricant only during assembly. That is per the ARP instructions.
So I'm not sure if the ARP torque spec are accurate if reusing ARP bolts. In any case motor oil or any other lubricant should not to be used, only ARP lubricant.
On the other hand LOON or Engel derived degree wheel figures can be used on ARP bolts. We all agree that degree based specs are more accurate than torque figures that can alter based on friction load. At this time the final figures are not ready for release. The numbers derived from my head assembly along with others will form the LOON/Engel numbers that can be used in the future. In any case this spec is not an official ARP number as there is none.
Tim has suggested a number procedures in the interests of advancing Lotus maintenance. After I get my car running I will be taking my old cracked manifold for an experimental fusion weld. Tim has said if the weld holds up it will be a cost effective benefit for many Esprit owners. He has a lot good talking points.
What you really want is clamping pressure. It is indirectly measured by the torque on each fastener or the amount of twist after a certain point (angular measurement). That is what squeezes the parts together. When there are gaskets involved (like a head gasket) it gets a lot more complicated. There is squeeze, compression, sequence, retorque, etc. All ARP can tell you is a torque measurement based on stretch and tensile strength. Using that you may very well rip the fastener right out of the block because it is the maximum torque that fastener can develop. Not the maximum the block can handle. There are ways to calculate the necessary clamping pressure and therefore the torque necessary for each fastener but the final values can only be obtained through operational results (experience). The clamping pressure must exceed the actual forces acting on the joint so the fasteners do not experience cyclic fatigue. This gets into the size of each fastener, the # of fasteners, the type of materiel, etc. Get it wrong and the parts will start flying. This is a whole sub-science to itself and is not something you would want to guess at. Especially on critical fasteners like head bolts/studs, rod bolts, main bearing bolts, and flywheel bolts where they are subject to cyclic loading.
David Teitelbaum
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We are not guessing. we are using torque figures along with a degree wheel which is the more accurate way. Torque will vary with thread stretch and even lubricant used along with friction load from everything like washers and distortion of materials. I'm looking for even clamping at when everything is new and comparing degree wheel readings using torque at the same time as a sampling.
Everyone must do as they see fit with regards to their personal feelings towards their own best interests and projects. I tend to follow people with a strong track record in engine assembly.
I am just trying to show that clamping pressure is not always directly related to the torque of a fastener. What would be a good torque for one kind of a fastener will not provide the same clamping pressure if you change the pitch of the threads, the fastener materiel, etc. Angular displacement is just another indirect method of trying to obtain even clamping pressure and is no more accurate than torque if used properly. Also remember if you are aproaching the yield point of the materiel you cannot reuse the fasteners. Once stretched they are not supposed to be reused. I also agree history is the best indicator of success. Up to a point.
David Teitelbaum
David Teitelbaum
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LOL the only reason many have evolved into successful long time Lotus owners is because most of us are so detail oriented. Sometimes to the point what others consider it an illness.I've said it before and I'll say it again....
Pluralitas non est ponenda sine necessitate (William of Ockham)
Let's not over-complicate the act of putting a head on an engine.
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The proof is in the pudding.
4cyl stock head gasket installs don't seem to blow with any unusual frequency. Factory recommended install methods work.
Agreed that lots of new variables create potential for too tight or too loose a head gasket. So when one starts to do it different like newer gaskets, different bolts or different ways of deciding how to torque, then testing is required. Unfortunately that means us.
So feedback is super helpful. The head gasket that we just replaced was a 910 engine with a 907 gasket(metal on both sides) it didn't survive a significant overheat event. It had been installed aftermarket when pistons were replaced. Jeff at JAE said that the newer asbestos style gaskets were more tolerant of modest overheat events.
Randy
4cyl stock head gasket installs don't seem to blow with any unusual frequency. Factory recommended install methods work.
Agreed that lots of new variables create potential for too tight or too loose a head gasket. So when one starts to do it different like newer gaskets, different bolts or different ways of deciding how to torque, then testing is required. Unfortunately that means us.
So feedback is super helpful. The head gasket that we just replaced was a 910 engine with a 907 gasket(metal on both sides) it didn't survive a significant overheat event. It had been installed aftermarket when pistons were replaced. Jeff at JAE said that the newer asbestos style gaskets were more tolerant of modest overheat events.
Randy
I a little late to the party... sorry, but I don't hang out here a lot.
You got ARP bolts or studs?
There are popular ARP bolts for bolting the two cam carriers to the top of the head. They have nothing to do with the torque spec required for securing the head to the block and sealing the head gasket. When you install them, torque them to 14-16 lbs-ft... working from the center outward.
Then there are long ARP studs that screw into the top of the block. The gasket and head slide on over them, then are secured with washers and nuts. The torque for the head/ gasket applies to those nuts on the studs.
The torque varies according to the stud type, so use the torque that's appropriate for the studs that are currently installed in the block. In all cases, the threads and nut/washer faces are oiled first.
1) The original studs were pretty common stuff, and are identified by a flat upper end. Use a torque wrench and torque them to 75 lbs-ft for the three pairs in the middle, and 70 Lbs-ft for the two end pairs (two front nuts / two rear nuts). Don't tighten them to 70-75 all at once, but use three or four small steps, such as 20 lb-ft, 45 lb-ft, 60 lb-ft, and finally 70 or 75 lb-ft. For each increment, work from the center out to the ends in a criss-cross pattern, as shown in the manual.
2) In Jan 1993, Lotus upgraded the OEM studs to stronger steel, and they are identified by a depressed dimple in the upper end. For them, use a torque wrench to apply an initial, light torque. All that does is take up the slack to provide a solid starting point. Then, use a Torque Angle Meter (glorified protractor) to turn the nuts so many degrees, as follows:
a) 15 lbs-ft, torque wrench, initial setting.
b) +75 Degrees, torque angle meter.
c) +40 Degrees, torque angle meter.
d) Wait 5+ minutes (more is better).
e) +20 Degrees, torque angle meter.
The net result of Lotus’ new torque angle spec is a higher final torque/ clamping force than was produced by Lotus’ original 70-75 lb-ft torque spec. Do NOT consider the old spec and new spec as simply different ways of expressing the same thing. They are different, the produce very different clamp loads, and they are NOT interchangeable.
3) The ARP studs are an further strength upgrade, have fine pitch threads instead of coarse (like the Lotus OEM studs), and require yet another unique torque spec. Each stud/ nut is to be tightened with oiled threads, and ARP specifies that you use their proprietary thread lubricant. The tricky part is that they have revised their lubricant a few times, and their torque spec changed with each new version of the lube.
If you didn't receive a torque spec with your parts, then dig around and find the little squeeze-pouch of ARP lube in order to get the name exactly right. Then call JAE, tell Jay exactly which lube you have, and ask for the appropriate torque spec to use with that lube.
If you didn't receive any ARP lube (oops), then order some and ask for the appropriate torque spec to use with that particular ARP lube. The info I have at my finger tips is:
90 Lb-Ft with "ARP Ultra-Torque Fastener Assembly Lubricant".
If the wording on your ARP lube pouch varies from that description even a little, then inquire about the correct torque spec to use with yours. I wish ARP would settle on one lube & spec in order to reduce confusion, but apparently that's the price of progress.
:-(
Don't use the following, but my faulty memory has an echo of 100 lbs-ft with the previous ARP lube, and 120 lbs-ft with motor oil (mineral or synthetic ?? I dunno). Again, don't use those values, I'm just illustrating the impact that the lube can have on torque.
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Using a torque wrench to apply a specified torque is a method full of opportunity for inaccuracy. It only controls the applied torque, but friction between the threads and hex head/ washer eat up 1/2 to 3/4+ of the applied torque. How much actually goes toward producing a clamping force is a crap shoot.
A Torque Angle Meter measures how many degrees the hex head is rotated. The thread is an inclined ramp of so many degrees wrapped around a cylinder. It's geometry. For so many degrees of rotation, you can trig how far the fastener will advance. You know how much clamp you're putting on the joint. It's far more accurate, and I was pleased when Lotus issued a Torque Angle spec for their new studs and gasket. Why the heck ARP is still stuck in the past with 'torque' specs is beyond me. But they are. Jeff at JAE talked with them about a Torque Angle spec, but got no where.
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What Calvin and I talked about over breakfast was something I've wanted to do for some time... come up with an equivalent Torque Angle spec for ARP's torque spec(s). It would be relatively easy to do, given the opportunity. But fortunately, I've not blown any head gaskets lately, so I've been a little short on opportunity.
The last time Dave C blew a head gasket was a few years ago. When we were re-installing the head, we wrote down a few numbers, but we really hadn't planned ahead for it and didn't have a good set-up. We were intrigued by the correlation, and we agreed that next time we should do a better set-up and take real readings. Well, I guess Calvin is the next time. He has his Esprit's head off at the moment (actually, it's in my garage... I'm replacing cam seals and shimming the valves), so here's the opportunity. Maybe we'll have something to report later.
Regards,
Tim Engel
There's a nice little write up here. The Official ARP Web Site | Technical Information
I have always used the supplied ARP lube, but if I've run out, I've used SAE 30 regular motor oil per ARP instructions torqued 10-15% higher than their standard spec. I've only had one headgasket failure in 15 years making 2-3 the stock horsepower. ARP's do seem like overkill for stockish rebuilds though.
I have always used the supplied ARP lube, but if I've run out, I've used SAE 30 regular motor oil per ARP instructions torqued 10-15% higher than their standard spec. I've only had one headgasket failure in 15 years making 2-3 the stock horsepower. ARP's do seem like overkill for stockish rebuilds though.
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When I met Tim for breakfast on Sat and I gave him my head to have the valves adjusted for my future assembly. We also discussed other problems with the current head gasket replacement. From what I understand when they switched over to the Zeus head they milled the head down a bit so to keep the same compression ratio they increased the thickness of the gasket. Which is good but they discontinued the old gasket for the earlier engines (the one I have) so I have to use the one for the later engines. Well the increase in thickness drops my compression a bit. I'm not sure how much it affects things and torque spec. It would probably affect the N/A car more like a GT3 lucky I don't have one of those. But it was a lively topic for discussion. I look forward to car talk during the Sat morning breakfast club meetings. If its not one thing its another.
The later Goetze composite cylinder head gasket has a compressed thickness that is 0.020" more than that of the old steel-asbestos-steel gasket. All else being equal, the new gasket raises the cylinder head 0.020", and reduces the compression ratio by about half a point. In an HC or HCi 910, 8.0:1 becomes 7.5:1. In a carb turbo 910, 7.5:1 becomes 7.0:1.
In Jan 1993, the newly re-tooled Zeus head and block, the Goetze composite head gasket, and the upgraded head studs were all introduced together (Lotus TSB-19). In order to compensate for the thicker gasket, the new block's deck height was cut 0.020" lower. To keep the cylinder liner's nip the same (exposure above the block deck), the spigot bores in the block were also cut 0.020" deeper. The thicker composite gasket raises the head by 0.020", and the revised block dimensions lower the head by 0.020". In the end, it was all same-same for the new parts used together.
However, when the new composite head gasket was introduced, the old, thinner gasket was discontinued. Now, when you use a new composite gasket in an engine made prior to Jan 1993, the thick gasket raises the head, but the old block hasn't been cut back to compensate, so the compression ratio is reduced by a half point. It is what it is, there's no compensating action. Well, not unless you're motivated enough to have your old cylinder block re-machined to Zeus specs (Jan 1993 onward).
For any owner of a pre-1993 engine who buys replacement pistons, consider raising the compression ratio a half point above whatever CR you wanted.
Owners of carb-turbos... that applies to you. All carb turbos came with cast pistons that are marginal for the task, and they only last so long. Given the car's age now, any 910 with original cast pistons is living on borrowed time. Whenever the engine is apart, you should strongly consider replacing the pistons, no matter how good they 'look'.
Turbo owners have the option of turning up the boost (within reason) to compensate for lost cylinder pressure. Carb-Turbo guys need to be careful playing with the boost, since the cast pistons are the weak-link limiter. Put in a set of forged JE Pistons, then you can also crank the boost up a bit (stay under the dump valve's 10 psi vent pressure).
Owners of naturally aspirated engines don't have that option. For them, it's live with the reduced cylinder pressure, or install new, higher compression pistons.
Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
In Jan 1993, the newly re-tooled Zeus head and block, the Goetze composite head gasket, and the upgraded head studs were all introduced together (Lotus TSB-19). In order to compensate for the thicker gasket, the new block's deck height was cut 0.020" lower. To keep the cylinder liner's nip the same (exposure above the block deck), the spigot bores in the block were also cut 0.020" deeper. The thicker composite gasket raises the head by 0.020", and the revised block dimensions lower the head by 0.020". In the end, it was all same-same for the new parts used together.
However, when the new composite head gasket was introduced, the old, thinner gasket was discontinued. Now, when you use a new composite gasket in an engine made prior to Jan 1993, the thick gasket raises the head, but the old block hasn't been cut back to compensate, so the compression ratio is reduced by a half point. It is what it is, there's no compensating action. Well, not unless you're motivated enough to have your old cylinder block re-machined to Zeus specs (Jan 1993 onward).
For any owner of a pre-1993 engine who buys replacement pistons, consider raising the compression ratio a half point above whatever CR you wanted.
Owners of carb-turbos... that applies to you. All carb turbos came with cast pistons that are marginal for the task, and they only last so long. Given the car's age now, any 910 with original cast pistons is living on borrowed time. Whenever the engine is apart, you should strongly consider replacing the pistons, no matter how good they 'look'.
Turbo owners have the option of turning up the boost (within reason) to compensate for lost cylinder pressure. Carb-Turbo guys need to be careful playing with the boost, since the cast pistons are the weak-link limiter. Put in a set of forged JE Pistons, then you can also crank the boost up a bit (stay under the dump valve's 10 psi vent pressure).
Owners of naturally aspirated engines don't have that option. For them, it's live with the reduced cylinder pressure, or install new, higher compression pistons.
Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
Steve,
The 910 has had it's share of blown head gaskets through the years. Driven normally on the street, there's little problem. But sustained high boost (track days) and/or turning up the boost can result in blown gaskets. In the older engines with the original studs, stud stretch was a problem. Even a naturally aspirated 907/912 running 11:1 compression and sustained full throttle can stretch the original studs. The upgraded, late OEM studs were a great improvement, but better-still ARP studs are a further step toward resolving the problem for anyone with a really heavy foot... as is the later, upgrade composite head gasket.
In the ARP link Steve posted, click on the Installation tab for info about torque methods. The key point to take from that is that no method is simple and one dimensional. Each method has a lot of contributing factors... it's own set of demons. The big problem is that most manuals just give you a number value without clearly stating the conditions.
It's important that you use any given torque spec without changing any of the original conditions. If not stated otherwise, the industry standard (and Lotus) generic/ default torque values presume clean, dry threads. Not usually stated is "corrosion free" and "like new". An old, rusty/ crusty fastener that is clean and dry will not give the same results. A plated fastener will not give the same result as raw steel, and chrome is different than zinc, cadmium... whatever. Every time you make a change to the spec conditions, you throw the results out the window.
Putting anything on the threads, whether oil, Anti-Seize or Threadlocker, will reduce the friction and over-stress the fastener. Depending what you take upon yourself to put on the threads (if not otherwise specified), you many have to reduce the torque spec by 50% or more... and you're shooting craps when you do that. Follow the book.
The other standard default that manuals really should clarify, and often don't (Lotus is very poor about this), is that certain critical fasteners must be torqued with oiled threads. That includes rod bolts, main bearing caps, and cylinder head bolts/ studs & nuts. If Lotus says anything, they usually just specify motor oil, without differentiating between mineral oil, and the more slippery synthetic oil. But given the era when most of Lotus' pre-Elise specs were written, it's probably safe to presume 30 wt mineral oil.
ARP gets way more anal about it, and requires the use of their own thread lubricant along with their torque specs. The problem is that they have revised their thread lube from time to time, and with it, the relevant torque spec. If you have a torque spec for your ARP fasteners, it's not valid unless you also know the ARP lube with which it was to be used.
But then, after getting all up tight about that, ARP's fall back is motor oil (mineral or synthetic isn't stated) and 10-15% higher torque. It's sort of like their super OCD/ anal retentive about it, and then say, "but if you can do all that right, then f_ it, just do this". I don't get that... oh well.
The key to all that blabber is to follow the torque spec and it's conditions. Don't mix-n-match elements of torque specs. The 70-75 lbs-ft head torque specs in your old Lotus manual (era of the original studs and steel-asbestos-steel head gasket) do not work with Lotus' later up-rated studs and composite gasket. And vice-versa, the later Lotus torque angle spec doesn't work with the original stud (will over-stress it). And then ARP is out there in their own space... don't use their specs on any Lotus fastener.
Incorrectly torquing critical fasteners is where you can really mess-up any engine rebuild.
Regards,
Tim Engel
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