From turbo@montana.com Tue Aug 17 04:36:57 1999 X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil] ["14643" "Monday" "16" "August" "1999" "22:38:03" "-0600" "The Diesel Page" "turbo@montana.com" nil "309" "Re: Help! Need R&R guide asap" "^From:" nil nil "8" nil nil nil nil nil] nil) Return-Path: Delivered-To: luchini@scrye.com Received: (qmail 3318 invoked from network); 17 Aug 1999 04:36:53 -0000 Received: from mailb.montana.com (HELO mail.montana.com) (199.2.139.117) by jelerak.scrye.com with SMTP; 17 Aug 1999 04:36:53 -0000 Received: from turbo (mso-usr1-188.montana.com [208.4.227.188]) by mail.montana.com (8.9.3/8.9.3) with SMTP id WAA14141 for ; Mon, 16 Aug 1999 22:39:15 -0600 (MDT) Message-Id: <1.5.4.32.19990817043803.00c4f0c4@mail.montana.com> X-Sender: turbo@mail.montana.com (Unverified) X-Mailer: Windows Eudora Light Version 1.5.4 (32) Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable From: The Diesel Page To: luchini Subject: Re: Help! Need R&R guide asap Date: Mon, 16 Aug 1999 22:38:03 -0600 Hi Chris, Thanks for ordering the R&R Guide. We'll have it tomorrow's mail. In the meantime, I've included the text of that chapter below. Thanks again, and good luck, Jim PS. Your next credit card statement will list Jim's Electronics as the merchant for this $14.95 transaction. Approval code: 050662 The Diesel Page R&R Guide 6.2/6.5 Cylinder Head Gaskets=20 ----------------------------------------------------------------------------= ---- By Jim Bigley ----------------------------------------------------------------------------= ---- Let's begin the discussion on 6.2/6.5 head gasket replacement by talking about why these gaskets fail in the first place. The early 6.2 head gaskets had a couple of design problems that resulted in compression and coolant leaks. GM and the major gasket manufacturers recognized this problem and tried several different approaches in gasket design in an attempt to accomodate all the competing head gasket requirements inherent in a diesel engine. The original gasket design pictured above was made from a heat resistant fibrous material. This gasket didn't do well in sealing the various coolant passages and became brittle with age. The most likely spot for a burn-thru occurs at the leading edge of cylinder #2 and the trailing edge of cylinder #7. Here, the hot exhaust valve lays very near a narrow coolant passage. The head gasket is weakest at this point and is the first spot on the head gasket to begin leaking compression pressure into the coolant system. Hot combustion gases had burned through in this area. All 6.2/6.5 head gaskets (including the new ones) use a metal sealing ring around each cylinder. The sealing ring is actually a metal wire with a rectangular cross section. The thickness of this ring is slightly higher than the rest of the gasket. This design allows for most of the clamping load applied by the head bolts to contain the combustion pressure. Having the entire gasket surface aid in that effort is also important. The above gasket style was introduced in the mid 80's and was designed to help eliminate some of the pesky coolant leaks the earliest gaskets produced. A thin strip of silicone sealer was "silk screened" onto the gasket around all of the coolant and oil gallery passages. The silicone worked well to contain the coolant and oil, but using silicone on a high compression containing head gasket created a couple other problems. Some areas of the head gasket need all the surface area they can get to adequately contain the high combustion pressures. The silicone strips allowed the gasket to move under high pressure and allowed combustion pressure to force it's way under the gasket in some of the narrow areas. As in the original gaskets, cylinder #2 and #7 were the first to fail. The head gasket in the above photo also failed in this area. This is a picture of a freshly pulled 6.2 head showing the narrow cooling passage on the left side. You can see where the combustion pressure had begun leaking into the coolant system about 2/3 of the way up that narrow cooling passage. Pictured above is the new generation 6.5 head gasket from Fel-Pro. This gasket is a metal laminate, having a perforated metal core with a high heat resistant and resiliant coating on both sides. This gasket is also coated with a tacky heat curing bonding agent. This coating is designed to cold seal the coolant passages and oil galleries, and then cure after a couple temperature cycles, permanently bonding the gasket to the head and block. These gaskets do not need re-torquing. The right side of the gasket shows the additional metal re-inforcement Fel-Pro added to strengthen the weakest area of the head gasket. These are the ones you want. Use Fel-Pro part number 9701 PT. Don't touch the new gasket anywhere except on the edges. This block is in a 16 year old truck and needed new gaskets to repair a compression leak into the coolant system (the most common type of failure). With the project this far along the owner recognized the scope of his undertaking. Replacing head gaskets is a big job, but is do-able by most of us. Doing the job yourself saves about $500. In preparation for this chapter I ordered Fel-Pro gaskets sets for both the 6.2 and 6.5 from Northern Auto Parts. Surprisingly, the 6.2 head gaskets didn't have the additional metal re-inforcement the 6.5 gaskets have. Otherwise they used the same construction materials. I also noticed the 6.2 gaskets had irregular shaped cylinder cutouts where the 6.5 cylinder cutouts were nearly perfectly round. I would be inclined to use the 6.5 head gaskets on my next 6.2 project because of the added re-inforcement. If you use the newest head gaskets from Fel-Pro and follow the advice given in this chapter during your head gasket replacement you shouldn't need to replace the head gaskets again on the same engine.=20 ----------------------------------------------------------------------------= ---- Let's begin............ Remove the negative battery terminal from both batteries. Drain the coolant system. The drain plugs on the block are just to the rear of the motor mounts and are somewhat difficult to get to. The =BC" NPT drain plugs in some older engines will probably be frozen in place. If you try to remove the plugs, be sure to use the Snap-On tool number PP408. These plugs have a =BC" square hole that the tool engages. Don't use a =BC" drive= adapter. It would likely twist off.=20 If you can't get the drain plugs out, you'll just have to pull the heads (spilling some coolant in the process) then siphon the remaining coolant out through one of the coolant passages in the block. Remove the power steering pump, alternator, aircleaner assembly and air conditioning compressor. Don't disconnect any hoses, just lay each component against the fender(s) out of the way. Remove the intake manifold, water crossover housing, injector fuel lines, injectors, and exhaust header pipes (exhaust manifolds will remain on the heads). Next remove the valve covers, rocker assemblies and pushrods. GM recommends keeping all of the valve train components organized so they can re-assembled in the same positions. Use clean newspaper to lay all the miscellaneous components on. Using an 18mm 1/2" drive socket and flexhandle, loosen and remove all of the head bolts. Some heads will be stuck on pretty well, but a mallet or a block of wood and a hammer can be used to loosen the grip of the old gaskets. If a prybar must be used keep it away from the head and block mating surfaces. Be sure to check your cylinder heads for warps and cracks. The limits on warpage is .006 lengthwise and .003 across the narrow dimension. You're probably replacing the head gaskets because of a compression leak into the coolant system. If the cause of the problem is due to either a warp or a crack it won't do any good to install new gaskets. If your heads are cracked, be sure to read the related web pages in the Diesel Page before replacing or repairing the ones you have. The high compression of a diesel engine requires a near perfect head gasket seal. Spending a little extra time getting everything possible off the heads and block will help prevent a compression or coolant leak from re-occurring. I used 80 grit wet/dry paper on a sanding block and tried not to take any metal off, just the old gasket material. I removed the head/block alignment dowels before sanding the block. Getting them out can be a chore on some older 6.2s, but they must come out to do a good job prepping the block. The stubborn ones required pliers, Vice-Grips, screwdriver and a hammer to get them out. If your dowel pins aren't re-useable, new replacements can be purchased at most auto parts stores, picked up at a local engine rebuilding center or ordered through your GM= dealer. Before the sanding began I stuffed clean towels into the cylinder bores and into the pushrod gallery. There will be some grit created in the sanding process and you should try to keep as much of it out of the engine as possible. I vacuumed the entire area before pulling the towels out.=20 Run an M12-1.75 tap down into each bolt hole in the block deck, then spray the threads with an oil free solvent or carburetor cleaner. This process doesn't take very long and will ensure a leak free seal and proper bolt torque. While not shown in the photo, I held a vacuum nozzle next to each hole as the tap was run in and out. Once the block surface was sanded and the bolt holes prepped I scrubbed the block with a clean cloth towel and paint thinner. The head and block surfaces must be clean. The new Fel-Pro 6.2/6.5 TTY (Torque-To-Yield) head bolts came with a thread sealer pre-applied to the threads and under the bolt heads. I stripped all that off using a wire brush wheel and re-threaded each bolt (all 34 of them) just to make sure the threads were clean and undamaged. It's important to have all the torque applied to tightening the bolts instead of overcoming a poor thread or hardened sealant. Since both the head bolts and bolt holes were re-threaded, the bolts went in as smooth as silk. In this case I used GM's bolt thread sealer. This is a non-hardening Teflon based sealant. A little goes a long ways. Apply a small amount of sealant on the first 3/8" of threads and a little under each bolt head. Too much sealant on the threads could cause it to flow under the head gasket and weaken the seal. Fel-Pro makes a bolt thread sealant called "Gray Bolt Prep" that also works well. In addition to sealing the threads, a dab of sealant under each bolt head will help produce the proper bolt torque. GM has begun using Loctite 242 sealant on the head bolt threads during assembly at the GM engine plant. This anaerobic sealant will remain liquid until air is removed. Lightly coat the bottom four threads. There has been some concern about too much of the white stuff getting under the head gasket and weakening the seal. When using this sealant, a dab of grease under the bolt heads will help to ensure proper bolt torque. Felpro head bolts are available from Northern Auto Parts and are about $18 per head. Due to the TTY nature of these bolts, you shouldn't re-use your old ones. Using new bolts is cheap insurance against having to do this= again. I used a couple of old rocker shafts I had laying around to use for hand holds while setting the heads onto the block. This worked quite well. When held by the rocker shafts, the heads lay at about the correct angle to mate with the block and I didn't have to touch the head/block surface and contaminate them with fingerprints. You'll need to insert a prepared bolt into the #16 position (see below) in the drivers side head before setting the head on the block. The close firewall clearance won't allow you to put the bolt in later. I used a rubber band to hold the bolt in place while we set the head on. Otherwise the bolt would stick out and might snag the new head gasket. When setting the heads on a block in a truck, have a helper climb into the engine compartment. Between the two of you, carefully setting the heads on the new head gaskets is a relatively painless step in the process. After securing the heads with a couple bolts, stuff clean towels into the intake runners in each head. This'll keep tools and hardware from falling into these areas. Once you're this far along you get energized to complete the project.=20 Bolt torque specs for both the 6.2 and 6.5 are now: tighten in sequence to 20 ft/lbs, tighten to 55 ft/lbs, then go over all the bolts again in sequence at 55 ft/lbs. This completes the initial torque settings. The next step involves tightening each bolt in sequence another 90-100 degrees. This is the TTY specification. These head bolts are somewhat elastic and will stretch to their yield point when rotated another 90-100 degrees. An elastic bolt stretch helps maintain torque over the life of the engine and provides for a more uniform clamping force applied by the bolts. I made a torque angle meter out of cardboard and taped a piece of wire to the flex-handle for use as a pointer. This worked well with the engine on a stand. This cardboard angle meter worked for most bolts in the truck we replaced the head gaskets on, but some were tightened by the "dead reckoning" method. Before beginning the final 90 degree turn, have your flex handle positioned so you have enough room to make the full 90 degrees. The new final torque angle specs say 90-100 degrees, so being exact is less of a concern (according to the AERA). Just try to get at least 90 degrees. After completing this step in the process you'll know why you're not supposed to arm wrestle someone who assembles engines for a living. You'll notice in the photo that I had painted a white dot at 12 o'clock on all the bolt heads in preparation for the final torque angle. When all the bolts had been tightened another 90 degrees, the dots were at 3 o'clock. This way I was sure I hadn't missed any bolts. When re-assembling the valve train, position all the pushrods with their painted ends up toward the rockers. The end of the pushrods that mate with the rockers have a harder temper. The valve rocker assemblies can now be bolted on. Before positioning the rocker assemblies, dab a little chassis grease on the ends of the valve stems and in the pushrod pocket in each rocker. Then squirt a little motor oil on each rocker so they don't start out dry. Get the bolts started then position the pushrods into the rockers. Now, torque the rocker shaft bolts to 50-60 Nm or 37-44 ft/lbs. Take each bolt down a little at a time before tightening to the final torque. Once all of the rocker assemblies have been re-installed, turn the engine over by hand a couple of revolutions and make sure everything operates correctly. The valve covers are re-installed without a gasket. Fel-Pro ships cork gaskets with their upper end gasket kits, but you shouldn't use them. Just clean the valve covers and mating head area then glue the valve covers on with a silicone gasket sealer. Torque the valve cover bolts to 18-25 Nm or 13-25 ft/lbs. Now, re-install the injection system components and other miscellaneous components. Run the engine and check for leaks. Piece of cake!=20 ----------------------------------------------------------------------------= ---- Copyright =A9 1998 by Jim's Electronics www.62-65-dieselpage.com=20 The 6.2L/6.5L Diesel Page Jim Bigley 418 Grandview Dr. Stevensville, MT 59870 406-777-3675 http://www.62-65-dieselpage.com https://www.montana.com/turbo/order.htm turbo@montana.com