CIH Flywheel to Crank Bolts - OEM
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Thread: CIH Flywheel to Crank Bolts - OEM

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    CIH Flywheel to Crank Bolts - OEM

    Hi all, could some one tell me the torque settings for the six bolts connecting the flywheel to the engine? Thank you
    Last edited by Al Olmo; 09-12-2005 at 04:13 PM.

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    Al, according to my Clymer's manual the torque for the flywheel to crankshaft bolts is 43 foot lbs of torque. HTH.




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    Thanks Ron, wow that seams like very high torque, I would be afraid of breaking one of those bolts.
    Thank you again.

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    Moderator jordan's Avatar
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    43 ftlb's is nothing, The head bolts on our deisel tractor get torqued to 180 ftlb's.
    1970 Opel GT 1.9
    1980 Moto Guzzi V50
    2000 Saab 9-3 2.0 turbo
    2000 KTM 200 exc STOLEN

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    Ref:
    https://www.opelgt.com/forums/showthr...flywheel+bolts

    "As for the flywheel bolts, Haynes manual says that that you should use the bolt marked with a "P" in the hole marked also with a "P", and it also says that on a new flywheel one of the six holes is a bit narrower, and this is the one that goes to the "P" marks... "

    I looked for this reference in the OPEL FSM and could not find ...
    "One of the six bolts has a longer shoulder; it helps to locate the flywheel to the crank. If you use it, you will be within 3 degrees of being correct. Without it, you maybe 7-8 degrees off on your indicated Vs. actual timing."
    Last edited by Lindsay; 09-12-2005 at 05:45 PM.

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    Lindsay that was very helpfull, I had no idea of the of the different bolts and its relationship to the flywheel. Thank you

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    OpelGT.com Übermoderator kwilford's Avatar
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    Quote Originally Posted by Al Olmo
    Thanks Ron, wow that seems like very high torque, I would be afraid of breaking one of those bolts.
    Thank you again.
    Yes, 43 ft-lbs for the flywheel bolts is correct, as they are a very fine thread and also a high strength bolt (Grade 12.9 as I recall). Also look for one flywheel bolt that has a slightly longer shoulder. I believe it goes in the one flywheel hole that is somewhat off-set in spacing from the others (or is it actually marked?), and ensures that the flywheel is closer to being at the proper "timing" position.

    Now here is the most important tip with regards to a new clutch that you can be given.

    DO NOT TORQUE THE PRESSURE PLATE BOLTS TO 36 FT-LBS AS IT APPEARS TO SAY IN THE FACTORY SERVICE MANUAL!!!!

    TORQUE THE PRESSURE PLATE BOLTS TO 15 FT-LBS ONLY!

    The FSM's ALL provide a table for various clutch-related bolt torques and the table says 36 ft-lbs for the "Clutch Cover to Flywheel bolts", but this is actually referring to the bell-housing to block bolts, NOT the pressure plate bolts. If you do this, you are CERTAIN to stretch, and probably break, the standard Grade 8.8 (about a SAE Grade 5) bolts that attaches the pressure plate to the flywheel. If you read the actual instructions as to how to replace the clutch, it gets it right in the text, and says 15 ft-lbs. Under the FSM General Bolt Torque Guide, it says all 8 mm bolts with 13 mm heads should be torqued to 15 ft-lbs. I am NOT making this up, as I (and many others) have managed to break countless pressure plate bolts before the correct info was published. OGTS sends out an advisory sheet with their clutch kits, and I believe they say the correct torque is something like 18 ft-lbs.

    One of those cases where the FSM can lead you astray if you don't know better.

    HTH
    Last edited by kwilford; 09-13-2005 at 01:10 AM.
    Keith Wilford
    Finishing up a bare-metal, nut & bolt rotisserie restoration of my '71 Opel GT

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    Interesting stuff, there is nothing in my Clymer's about different length bolts on the flywheel, or that there is an offset hole in the flywheel. But it is very specific about the pressure plate bolts. it says to gradually tighten the bolts to 15 ft.lb., which would mean to me, tighten the bolts in 5 ft.lb. increments up to the max of 15. It appears, the more manuals you have, the more info you get, up to a point. But good stuff to know for the uninformed.




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    Well today is the day.....I'll be mounting a freshly surfaced flywheel to the engine after replacing the rear main seal, than clutch and pressure plate comes in, bell housing with all new components all the way, after that I'm installing the gear box (that has been rebuild by HTS in Sacramento) basically I'm getting a brand new system including speedo drive, clutch cable and even the pedal which was so warned out was about to break. Thank you all for your help I'll keep you inform of my progress.

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    Old Opeler GTJIM's Avatar
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    Pilot Bearing

    Make sure you check and renew the tiny bearing in the rear of the crankshaft before putting anything together - a tiny bit of lube in a new bearing will make sure that this wee bearing is up to scratch too.
    GTJim
    Opel Owner since last Century!

    Copyright © 2000-2009
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    Jim are you talking about the "pilot" bearing? If so it is already on, a new one.

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    Old Opeler GTJIM's Avatar
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    Yep!

    Quote Originally Posted by Al Olmo
    Jim are you talking about the "pilot" bearing? If so it is already on, a new one.
    That is what I am talking about - glad to see you are ahead of the Game!
    GTJim
    Opel Owner since last Century!

    Copyright © 2000-2009
    J D Henry
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    Well Jim I wouldn't go that far I just go step by step and hope for the best with all of your help plus the book.

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    Quote Originally Posted by Lindsay View Post
    "As for the flywheel bolts, Haynes manual says that that you should use the bolt marked with a "P" in the hole marked also with a "P", and it also says that on a new flywheel one of the six holes is a bit narrower, and this is the one that goes to the "P" marks... "
    I looked for this reference in the OPEL FSM and could not find ...
    "One of the six bolts has a longer shoulder; it helps to locate the flywheel to the crank. If you use it, you will be within 3 degrees of being correct. Without it, you maybe 7-8 degrees off on your indicated Vs. actual timing."
    Quote Originally Posted by GTJIM View Post
    Vargos, One of the flywheel bolts should have a "P" on the top of it. This one is the guide bolt with a fatter shank under the head that fits tightly into one of the flywheek holes to line it up with the crankshaft.
    This bolt will usually only fit tightly into one hole in the flywheel - the one clockwise next to the widest gap between the bolts. All the other bolts are equally spaced from each other - this is hard to see but the flywheel will only fit on in one position.
    In the attached picture the wider gap is between the bolt marker "P" and thew one below it. Every Manual I have mentions marking it BEFORE removal !!
    HTH
    Quote Originally Posted by kwilford View Post
    Yes, 43 ft-lbs for the flywheel bolts is correct, as they are a very fine thread and also a high strength bolt (Grade 12.9 as I recall). Also look for one flywheel bolt that has a slightly longer shoulder. I believe it goes in the one flywheel hole that is somewhat off-set in spacing from the others (or is it actually marked?), and ensures that the flywheel is closer to being at the proper "timing" position.
    Sometimes, really old threads are golden. I am proceeding with my engine/drivetrain assembly, and just got my rotating assembly back from the balance shop (WHOLE other thread, someday...). I was also helping John Warga (aka ftl) with his stroker CIH 2.4 yesterday, and ran up against the same question: "What flywheel bolts go where".

    I recalled that one bolt (of 6) is different (longer shank) and that there was some discussion a few years ago on the topic. 12 years ago, but who's counting. And I did what all good Moderators do, which is to SEARCH for answers before he or she starts a new thread. And adds to an existing, appropriate thread, to more fully complete the knowledge base.

    So here are the answers:

    1) One OEM flywheel bolt, marked with a "P", has a longer and LARGER shank than the other 5 bolts. See the photos below

    2) One flywheel bolt hole is smaller (almost exactly 10 mm) that the other 5, which are several thou larger. The "P" bolts fits quite snugly in the smaller hole, but wiggles around in the other holes.

    3) That special flywheel hole is the off-set one (different spacing between that one hole than the other 5), and in some universes, it might have been marked with a corresponding "P", to ensure that the "P" bolt is used in that hole. Not in my universe. It can be tricky to see the spacing offset without measuring the inter-bolt spacing, but it is real, and easier if one stamps the "P" (in my case, 3 times) around the marker hole.

    4) I was contemplating buying a set of the ARP Pinto flywheel bolts (ARP 151-2801), which are very sexy looking and not 40 years old. I don't see the same special bolt in that kit, and without knowing the shank diameter, they may not provide the same accuracy of flywheel placement unless the flywheel is properly guide-pinned to the crank IN ADDITION to the guide bolt. See note above about why the timing mark can be off several degrees; not as important if one marks the front pulley at TDC against the timing chain case marks, which I will do, but VERY important for a routine flywheel/clutch job that doesn't include a full engine disassembly and timing mark addition. And if one has spent a chunk of money getting his rotating assembly balanced, it seems silly to allow the flywheel to out of balance by several degrees.

    HTH (and I am now "sticking" this thread to the Forum to make it easier to reference)
    Attached Images Attached Images
    Last edited by kwilford; 07-16-2018 at 08:38 PM.
    First opel 1981 and SpringGT like this.
    Keith Wilford
    Finishing up a bare-metal, nut & bolt rotisserie restoration of my '71 Opel GT

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    When balancing the rotating assy. don't forget to include the pressure plate(not disc) in the mix.
    Also be sure to mark it so that when reinstalled it'll be in the proper orientation.
    guyopel likes this.

    Si vis pacem, para bellum "If you want peace, prepare for war"

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    I learned something today.
    Well, more than one but Opel related was one.

    I've never noticed the P bolt before. I did, however, notice that sometimes one bolt would hang up while putting it in and have to swap bolts around but never known why.

    I've only rebuilt 20 or 30 Opel motors so what would I know.

    I do know it's not possible to have the flywheel (pressure plate) off rotationally by a hole or two. It only goes on ONE way where all six bolt holes line up. But that alignment hole as you showed, will keep the pressure plate from being off the amount of the looseness of the holes. (1-3 degrees).

    Good thing to add to the rebuild knowledge. I have an unmolested engine sitting on the engine stand. I'm going to check it out when I take it apart. I'm the second owner of that engine so I know it's still factory.
    Opel GTs are not GM products
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    Balancing

    Quote Originally Posted by wrench459 View Post
    When balancing the rotating assy. don't forget to include the pressure plate(not disc) in the mix.
    Also be sure to mark it so that when reinstalled it'll be in the proper orientation.
    Good advice, thanks Dan. This was the first Opel engine I have had properly balanced. I had done some reading and YouTube video watching on the process and requirements, so I knew some of the issues.

    I had my work done at Custom Balancing & Blueprinting and there is some good reading there.

    To do a proper job, the balance shop needed almost all the rotating parts, including the crank, flywheel, pressure plate, rods, pistons (separated), all mounting hardware (front bolt, flywheel bolts, pressure plate bolts) and ALL the bits that are on the crank:

    Front pulley
    Distributor gear
    Timing chain gear
    Both keys

    He didn't need the clutch disc, nor the rod bearings or rings, as those are not required for even-count inline engines. Even-count in-line engines (I-4, I-6 and I-8's) are balanced dynamically without the piston/rod assemblies (by definition, they are balanced by match-weighting as they are on opposing throws ).

    Pistons and rods are matched-weighted to 0.1 grams, and the rods are also end-matched to the same specification.

    The crank is dynamically balanced first, by drilling holes in the counter weights.

    Then each rotating piece is added, using the balanced crank as a mandrel, and each piece individually balanced and marked/stamped to ensure that reassembly is the same. I believe the order was flywheel, then pressure plate, then front parts (gears with keys and even the front pulley). Each part is balanced as it is added.

    Vee engines (and I presume I-3 and I-5 engines) require the piston/rod weights determined, including pins, rings & bearings. Then "bob weights" are made up using lead shot to within 0.1 gram of the piston-rod assemblies, and the bob weights attached to the crank to ensure that the full rotating assembly is balanced.

    It wasn't cheap, as the cost was $50 set up, plus $50/cylinder, plus $20 per piston for rod separation/re-attachment, as mine had been pressed on when initial machining was done. All in, $330 CAD. I don't know if I will be able to tell the difference, but my rod/pistons weighed 4 grams different initially, and since I had lightened the flywheel (by 3 lbs, from 22.6 lbs down to 19.6 lbs), it had to be re-balanced in any case.
    Keith Wilford
    Finishing up a bare-metal, nut & bolt rotisserie restoration of my '71 Opel GT

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    Quote Originally Posted by kwilford View Post
    Good advice, thanks Dan. This was the first Opel engine I have had properly balanced. I had done some reading and YouTube video watching on the process and requirements, so I knew some of the issues.

    I had my work done at Custom Balancing & Blueprinting and there is some good reading there.

    To do a proper job, the balance shop needed almost all the rotating parts, including the crank, flywheel, pressure plate, rods, pistons (separated), all mounting hardware (front bolt, flywheel bolts, pressure plate bolts) and ALL the bits that are on the crank:

    Front pulley
    Distributor gear
    Timing chain gear
    Both keys

    He didn't need the clutch disc, nor the rod bearings or rings, as those are not required for even-count inline engines. Even-count in-line engines (I-4, I-6 and I-8's) are balanced dynamically without the piston/rod assemblies (by definition, they are balanced by match-weighting as they are on opposing throws ).

    Pistons and rods are matched-weighted to 0.1 grams, and the rods are also end-matched to the same specification.

    The crank is dynamically balanced first, by drilling holes in the counter weights.

    Then each rotating piece is added, using the balanced crank as a mandrel, and each piece individually balanced and marked/stamped to ensure that reassembly is the same. I believe the order was flywheel, then pressure plate, then front parts (gears with keys and even the front pulley). Each part is balanced as it is added.

    Vee engines (and I presume I-3 and I-5 engines) require the piston/rod weights determined, including pins, rings & bearings. Then "bob weights" are made up using lead shot to within 0.1 gram of the piston-rod assemblies, and the bob weights attached to the crank to ensure that the full rotating assembly is balanced.

    It wasn't cheap, as the cost was $50 set up, plus $50/cylinder, plus $20 per piston for rod separation/re-attachment, as mine had been pressed on when initial machining was done. All in, $330 CAD. I don't know if I will be able to tell the difference, but my rod/pistons weighed 4 grams different initially, and since I had lightened the flywheel (by 3 lbs, from 22.6 lbs down to 19.6 lbs), it had to be re-balanced in any case.
    Hmmm! I was reading about this recently and a point was made that this type of accuracy is not required! As an engineer my first reaction to almost everything is "Show me the numbers!" This article did that so let me share what they said. I'll convert to English units as most of us are more familiar with those. A pound is equivalent to 454 grams so 1 gram is .0022 lbs (.035 oz). A tenth of a gram is therefore .0035 oz (expressing that verbally is 3.5 TEN THOUSANDTH of ONE OZ.). As a comparison, 100 sheets of "standard printer paper" weights about 1 pound which means that 1 page weights about .01 lb or .16 oz. An 8-1/2 x 11 page has about 93.5 sq inches so 1 sq in of paper weights .0017 oz. Therefore, the balancing is being done to 2 sq inches of paper (that is a square of paper about 1-7/16 inches per side). Yeah, the engine is turning high RPM, yadda, yadda, yadda. The point is still the same: just because you can doesn't mean you should! The guy making the statement builds and races motors for himself and others and they win. I can't find the article now but will keep looking! I think it was in the EngineLabs newsletter, but I get quite an assortment so ??

    Doug

    The brain still works (part time): https://www.enginelabs.com/engine-te...t-crankshafts/
    Last edited by slracer; 07-17-2018 at 12:49 PM. Reason: Added link

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    7,000 Post Club wrench459 (R.I.P.)'s Avatar
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    Every Opel crankshaft that I spun-up bare naked has been out of balance by under three grains out.
    Ooophs I mean three grams.

    Si vis pacem, para bellum "If you want peace, prepare for war"

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    I balanced my pistons and rods to less than .1 grams.

    My engine idled like crud.
    Opel GTs are not GM products
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