G54b head removal

[fullchoke]

I finally started removing the head today, and ran into the problem of keeping the chain tensioner on the timing chain when I remove the chain from the cam gear. The Haynes manual mentions a tool or a block of wood, but this is unclear to me. Can someone detail what needs to be done before I unbolt the gear.
I checked compression before I started and 1&2 had 170 lbs, 3 had 125, & 4 had 50. I'm hoping I only need a head gasket, but from what I see in other posts, a cracked head is likely.

Thanks

[Law Dog]

Can’t you just mark the chain and gears before you loosen the chain.

[FMS88]

Assuming you’re not removing the timing cover, you don’t need or want to separate the gear and chain. Unbolt the gear from the cam and rest the gear/chain combo on a small pad that’s bolted to the block below the gear. The slack in the chain isn’t a problem. Don’t worry about the tensioner. It will return to it’s proper position when you reinstall the gear to the cam.

[fullchoke]

That would make it easier if I don't need to worry about the tensioner. I wonder why the manual is concerned with it? I did watch a video where a guy had the tensioner slip off the chain and he then had to pull the timing cover off. I don't know why that happened to him, and was something I certainly wanted to avoid!
The manual also says to attach a large vice grip to the cam to hold it from turning while unbolting the gear from the cam. That seems kind of sketchy to me, and thought about holding the crank instead. Is there a better way to hold everything from turning? I did notice over cylinder 3 on the cam there is a small block cast on the cam. I think that may have been where the manual was talking about holding the cam, but space is tight in there.

Thanks

[Law Dog]

Good time to change out gaskets, seals and other parts depending on the miles on the engine has on it.

[FMS88]

That would make it easier if I don't need to worry about the tensioner. I wonder why the manual is concerned with it? I did watch a video where a guy had the tensioner slip off the chain and he then had to pull the timing cover off. I don't know why that happened to him, and was something I certainly wanted to avoid!
The manual also says to attach a large vice grip to the cam to hold it from turning while unbolting the gear from the cam. That seems kind of sketchy to me, and thought about holding the crank instead. Is there a better way to hold everything from turning? I did notice over cylinder 3 on the cam there is a small block cast on the cam. I think that may have been where the manual was talking about holding the cam, but space is tight in there.

Here's an illustration of the cam sprocket (gear) and the holder on which it can rest without adding enough slack to the chain to cause the tensioner to expand too far.



The cam bolt torque is only 40ft lb, so use the crank pulley bolt to prevent things from turning. Set the crank at #1 TDC then only loosen the cam bolt. If the crank moved, return it to TDC. Remove the bolt, distributor drive gear and sprocket. A split pin aligns the cam, sprocket and drive gear. Place the sprocket on the holder and zip tie the chain to the sprocket. As long as you don't move the crankshaft while changing the head gasket, reinstallation of the cam timing components should be a simple reversal of removal steps and the tensioner shouldn't be an issue.

Law Dog is right. Now is a good time to inspect the timing components, especially the chain guide and tensioner surfaces. If heavily grooved, consider replacing them. With the head off, R&I of the timing cover is pretty easy.

[fullchoke]

Thanks for the detail, and advice. I hope I have time tomorrow to get the head off. The fuel pump did not want to slide out, and I'm not sure the intake manifold bolts are all reachable. The exhaust manifold is off. Nothing has been too tight or froze up except the 4 carb bolts, I was happy they didn't twist off. I didn't have time to do anything with it Monday.
The truck only has 42k on it, so I think the timing components should be OK, but I'll take a look at the guides.

Thanks again

[FMS88]

Yes, with only 42k, you shouldn’t have to worry about the timing components. Some lower manifold nuts are hard to reach. Ratchet extensions and a universal joint adapter should help get to them. With the manifold removed, that should give more wiggle-room to remove the fuel pump.

[fullchoke]

Thanks FMS88 for that suggestion too. I didn't think about removing the manifold first to make more room below it.

[fullchoke]

Unfortunately after removing the head there is a hairline crack in cylinder 3 between the intake and exhaust valves. That cylinder compression was 125 Unfortunately after removing the head there is a hairline crack in #3 between the intake, and exhaust valves. #3 compression was 125, about 45 to 50 below #1, and 2. #4 had only 50 lbs compression. There was a lot of water in #4, but no crack, so the head gasket must have failed there. When I lifted the head off there was a large flat chunk of scale, or rust blocking the entire water passage in #3. I think water flow had to have been affected, making that cylinder run hotter.
Is the only solution replacing the head, or can the tiny crack be welded successfully?

Thanks

[Law Dog]

The g54b is famous for failed head gaskets I think about every truck I bought that was not running was from head problems. I have a head listed in the selling thread see if it’s what you need or look around for one.

The last one I put together I went with the laminated head gasket and stud kit instead of the stock stretch bolts the studs allows for higher torquing of the studs vs the 1X bolts used. That said the laminate gasket and stud kits are not cheap. If you go with the studs run a thread chaser through the bolt holes to make sure the valve cover sits right and clears the breather baffle so it seals correctly. Fail to do so you have oil everywhere it gets messy.

[FMS88]

Is the only solution replacing the head, or can the tiny crack be welded successfully?

You can get the cracked head welded, but if it's a jet-valve head, it's not worth it. Chances are it will crack again. Best option is to replace the head with a non-jet-valve head. To save time and effort, you can get a complete head with new valve train as xboxrox did. (See his informative and entertaining thread: http://www.mightyram50.net/vbulletin...ght=Clearwater). Or to save $$ buy a bare head and install the valve train of the cracked head onto the bare head. If you have the tools to do it, have a machine shop reface the valves or buy new ones. You'll need to lap in the valves on the newe head, but otherwise the swap is straightforward. ARP head studs are best, but new, replacement head bolts are okay. Get a good quality head gasket kit and don't reuse the old bolts. If you get a bare head, clean the bores of the cam cap bolt holes before installation. There may be metal shavings at the bottom of the bores.
There are many threads about replacing the G54b head as well as opinions of what to do or not. So a little research here can be well worth the effort.

[fullchoke]

I called 2 shops locally to me. One said they would not be comfortable welding the crack, and the other said it can be done, but it isn't cost effective. The most experienced shop said to get a ITM head. He said they are all made in China, but the ITM heads come with higher quality parts. He also said all the head gaskets are made in China, but one one brand was better( will try to remember that brand). I asked about head bolts and he said re-use your bolts, just torque them, that they can be re-used as they are not stretch bolts. Now I don't know what that is(stretch bolts, or a stretch bolt head), but I pushed back against re-using the bolts. I told him that everything I read online, everybody says get new bolts....he said "they don't know what they are talking about".
I think I've read every thread where a G54b head was replaced. What I haven't seen is whether or not all the head castings are all the same, aside from being jet valve, or non-jet valve. Also whether hydraulic, or solid lifter cams are identical, and can be swapped. I did see one post that swapped over to hydraulic lifters, but it wasn't clear to me about the cam. I'm not a gear head so I don't know these things. The shop that quoted me $615, or $735 if they swap over my cam and lifters told me the head, and cams are the same. The only difference involves the jet valve and they recommend the non jet valve. I want to keep my parts as I believe they are low mileage, but I haven't decided whether to do the cam and lifters myself, or pay the shop $120 to do it because I don't have a very good work place. The shop said it's easy work just time consuming, and they charge 1 hour. They thought if I'm willing to pull the head, I can swap over the cam and lifters. I haven't made up my mind yet.
I wanted to pass along what I found out so the next guy with this problem has a few questions answered, I couldn't find. I think I might re-use the head bolts, and if I do and have another failure, I will be back to report on it. So far I haven't found anyone re-using their Mitsubishi head bolts except a video where a guy does a lot of Toyota heads, and he always re-uses the head bolts.
I would say that everyone has to make their own decisions, but it sure is nice to get input here from guys that do their own work. I really appreciate it!

[xboxrox]

I forgot to use compressed air to blow out the block head bolt holes UNTIL the new head & gasket were already in place YIKES any oil water or gunk on a head gasket might soften it and eventually cause a leak..!
Good Luck FMS88 really helped me in fixing my truck with a new head ~ the Chinese head looks thicker & stronger but you tube videos say Chinese camshafts are too soft a material ~ so I began using high mileage full synthetic 10w 30w oil + a bottle of zinc additive

[fullchoke]

Another thing the manual is unclear about is the coolant drain plug on the block. It says there is 1 plug but doesn't say where it is. When I removed the head, water is at the top of the block right at head gasket level in the back at #4. Draining the radiator doesn't drain the block.
There appears to be considerable corrosion in the water passage holes that run from the block into the head. I won't worry about the head since I will get a new one, but I'd like to clean out the passages in the block. What would you guys do?
I tried Googling for the block plug drain without success.

Thanks

[SubGothius]

AFAIK it's always safe to reuse head bolts UNLESS they're a) clearly damaged, or b) torque-to-yield "stretch" bolts (which our engines did not use AFAIK).

Seems some folks may have read advice to "never reuse head bolts" in discussions about engines using stretch bolts and, overlooking that engine-specific context, mistakenly thought that advice applied to all head bolts -- or at least a "better safe than sorry" maxim if you don't know whether your engine uses stretch bolts or not -- then that erroneous "common wisdom" just got passed around unquestioningly until nobody knew where it originated.

Besides, I gather new head bolts for these engines have become difficult to find anyway. Lord only knows how many perfectly-good bolts got tossed by well-meaning but misinformed owners, needlessly contributing to that supply shortage.

[fullchoke]

Thanks for clearing that up on head bolts. Mine look perfect, no corrosion on any of them. The shop did say that replacement parts for these engines come from China, so if that includes head bolts which I see come with some of the Chinese heads they probably aren't of the same quality as the OEM head bolts.
I just need to find the coolant drain plug in the block. I think it is just below the exhaust manifold as it's the only bolt not holding something I can find on either side of the engine. I have tried turning it with a breaker bar with a cheater on the end, and with as much pressure as I dare, it won't break loose. I having it soaking in PB Blaster, just for luck on the next attempt.

Thanks again

[Law Dog]

I use a lot of PB Blaster and let it soak for days adding squirts and a soaked rag on or adobe the threads. Trying to get those air tubes off in one piece is challenging. The last one I did I soaked it for several days then locked a pipe wrench on it and extended a piece of pipe that I kept pressure on it using 2X4s that I wedged between the pipe and engine compartment. It came off in one piece, LOL

[fullchoke]

There is a 12mm bolt, or plug directly below cylinder #4 below the exhaust manifold. Is this the block coolant drain? and is this a bolt used as a plug, or an actual plug. I ask this because I'm afraid I could twist this off easier if it is a bolt. I'm putting a lot of pressure on it without any movement. If it snaps off I could have a bigger problem than I do now. I'm not certain this is even the drain plug. I'm thinking I may try a syringe to lower the coolant level at the rear of the block. What would you guys suggest?

Thanks

[SubGothius]

I think that is the block drain just aft of the exhaust manny below #4 cylinder, but like you I couldn't get mine to budge at all and was wary about breaking it or stripping galled threads, so I just skipped it. Not sure it's even necessary for routine coolant draining, but even if so may not be much point to that if you'll do a coolant flush eventually anyway.

FWIW, I've found Free All (now stocked at O'Reilly's) to be a more effective penetrant than PB'laster for loosening corroded fastener hardware.

[fullchoke]

That is the bolt I'm on and like you concerned with stripping or snapping it off. The only reason I need it out is I have coolant at the #4 piston level, and need it lower to clean the block surface before re-installing the head. I have no flat level area to do this work and the nose of the truck is uphill. If it was flat and level I wouldn't have this issue, more of the coolant would have drained out of the radiator. I may end up trying to lower it an inch or so with a syringe down one of the coolant passages if that plug won't come out. I wish I would have had the truck turned around with the nose downhill, but too late now.

[fullchoke]

One casualty in removing the head was breaking off the vacuum connections on a part that screws onto the water jacket on the intake manifold near the front of the engine. They were 2 plastic connections that the vacuum lines attached too. If I can't find a replacement part, or repair this one, can someone tell me the purpose of it, and whether I should cap off these lines or connect them? I'm thinking this activates something heat related at start up. I will get a couple pictures.

[fullchoke]

[SubGothius]

That vacuum thermovalve would only work with the stock Mikuni carb and its electronic feedback-control box. All it does is block/pass vacuum between the two hose barbs, depending on coolant temperature.

If you've swapped to a Weber carb (or plan to), you can just reinsert that thermovalve to plug its coolant hole in the manifold, leaving it otherwise unconnected to anything.

[fullchoke]

I'm going to keep the Mikuni carb until it gives me problems, but I don't like all those vacuum lines. If I can't get a working valve, I figured I would either connect the lines or plug them depending where the valve is, open or closed, at operating temperature. Do you know whether the valve is closed or open when hot? and what it's controlling?

Thanks