2.4T Rebuild - Many Questions

[frankc]

I purchased a 2.4T engine (911/57) for my RoW '73 project, and upon arrival I noticed that the left bank was exposed to water at some point causing some damage to the Zenith carburetor. I had the Zenith repaired by Paul Abbott, but water also got into the Cyl #3 intake port, and damaged the valve to the point that the cylinder no longer holds compression.

So I know I need a top end rebuild and I currently have the engine down to a long block, with the plan to pull the heads this weekend. My basic questions are this point are:

1. The steps in Wayne's book has one remove the cam carrier and heads together as an assembly, and then dis-assemble the carrier from the heads on a bench. Is there any benefit to this method rather than simply removing the cam carrier from the engine first, and then the heads individually?

2. Is there anything I can do to determine if I need to split the case and perform a complete rebuild? According to the engine PO, it was running when removed from the car about 5 years ago, and it turns freely without any resistance or noise. Other than that, I don't know the history or mileage. I did notice when cleaning the case that the original cosmoline was still on the case through bolts, so I don't believe it has ever been apart.

3. I discovered considerable sludge on the sump cover and in the bottom of the right cam chain housing (see photo 1 below). The white sludge worries me as this indicates internal moisture (there was still some oil in the engine when I received it). If I am only to perform a top-end rebuild, how do I remove this sludge from the bottom of the case?

4. Moving over to the left chain housing, I noticed what appears to be marks in the case from a loose chain (photo 2, red oval), but oddly the adjacent housing has no marks (could have been replaced). And those marks are quite far from the chain. Also, there is some debris accumulated on the case just above the (apparent) chain marks (green oval). As you can see, collars have be added to the chain tensioners, and both tensioners are collapsed and resting on the collars. Perhaps this is a clue to a previous tensioner issue?

I have many more smaller questions, but I'll stop here to get me through this weekend.

Thanks,
Frank

Photo 1:


Photo 2:

[frankc]

Many thanks to jbunda for coming over this past weekend and helping me get the cam nuts off, and to jpnovak for the use of his tools.

With the cam nuts off I was able to remove the sprockets and the chain housings. Next up was to remove the rockers, but a standard 5mm Allen key was flexing too much to break free the rocker shaft, and a 3/8" drive 5mm Allen bit was too large to fit in the opening. So, I took lobster's advice found on jbunda's thread and purchased a 1/4" drive stubby 5mm Allen bit from Snap-On (only $15 shipped from their website). The bit arrived today and I was immediately able to break loose the rocker shafts on the left bank - that tool rocks. I hit the right bank with more Kroil and will let them sit overnight before attempting those.

I'm very curious to see the condition of the #3 cylinder to check for water ingress - I should know by this weekend. Regardless, I was not planning on re-using the cast iron cylinders anyway, and need to decide whether to go with JE pistons and Nickies, or a complete 84mm Mahle P&C set with E or S pistons. Fortunately I have time to research this more before making a decision.

[tharbert]

If you're going to the trouble to do the top end, you're gonna want to, at a minimum, rebuild those tensioners. You can find plenty of arguments both ways but I'd go ahead and install the Carrera tensioners and upgraded idler arms (wider at the shaft). If you stay with the non-pressure fed tensioners, look up the Jerry Woods mod instead of those stupid blue collars.

Even used Mahle P/C's are very $pendy. A contributor here, Henry/Supertec has alternatives that may fit your goal. Something to consider: I think you can go from 84mm to 86mm P/C's with no other modifications: 2.4 to 2.5 There's no replacement for displacement.

You can find lots of information about diving into the case. Mag cases have some specific needs. If you unbolt them to have a look and find nothing wrong, you will most probably have issues upon reassembly if don't have the machine work done. Then, there's the "while you're in there" stuff like oil bypass mod and 4 rib oil pump upgrade. I guessed my mag case internals were shot and I was right. It's a very expensive repair.

Cams: I had my T cams reground to E specs. Had the planets aligned and a set of E cams fallen into my lap, I would have liked to go with a Mod Solex grind.

There's a lot to consider...including how much you're willing to spend.

[frankc]

tharbert,

Thanks for the information.

The tensioners will for sure either be rebuilt or replaced with 930 tensioners (instead of pressure-fed to retain stock appearance), and the improved idler arms will be installed. The 930 tensioners are bit pricey, so I'll research the success folks have been having with the rebuild kits.

And I definitely need to do a lot more research on the pistons & cylinders. I'm would really like to get rid of the cast iron cylinders for many reasons, the question is do I go with biral, cast AL or CNC AL? And should I try to find a used set (in spec), or not even consider it and just purchase new? I plan to keep the bore the same (or possibly 85mm) as I do not want to bore the case. I would like to bump the CR to 9:1 or 9.5:1 (single plug), so this points me to a set of JE pistons. Once I have some ideas and more knowledge, I'll contact Henry for suggestions.

When my 2.7 was rebuilt (many years ago), I had Competition Engineering do the case work, so I'm familiar with the Mg case mods. I had case savers (timeserts) installed in the 2.7 due to the 90mm case bore, but are they really necessary for an 84mm bore? We know that the 2.7 had a problem with pulled studs, but what about the 2.2s & 2.4s - taking into account cylinder and stud material, thermal expansion rates, etc? This will be a street car, so I'll probably do the oil bypass, but leave the original oil pump.

Regarding cams, I am running Solex profile cams in my 2.7 w/Webers & Mahle RS P&Cs and I'm very happy with that combination. I'd be happy with a similar torque curve in the 2.4 w/Zeniths (but obviously with lower numbers). Again, this will not be a track car, so I would prefer more usable torque in the lower RPM range.

Since I was planning to send the heads off to be reworked first, the most immediate decision I need to make is whether or not to increase the intake port size - but perhaps I should wait on this until the complete configuration is known. Going back to the flat torque curve, I don't want to go too large on the ports, but I don't want the stock 2.4T 32mm port size to be too restrictive either.

Like you said, there is a lot to consider...

[E Sully]

Do the case savers. Magnesium is very soft, the one they speak of by the IS in this thread, Casesaver reinforcement of magnesium case, is shot on my 2.4 case. I will be having them installed this winter when I rebuild my original engine.

[frankc]

I got a little bit of time to work on the engine today and the rockers and cams are now out. Tomorrow I plan to pull the cam housings and heads. I'm very curious to see the condition of the valves and cylinders, especially on the left bank that showed signs of water damage.

[frankc]

Originally Posted by E Sully

Do the case savers.

Agreed. After the comments here and some more research, I'm now convinced that I should install the case savers on all the known failure points. Something more to add the to list (and budget).

[jdbunda]

Hey Frank -
Glad you got your rockers free, and thanks for the info on the Snap-On socket, I will definitely get one for re-assembly of my heads. Seems essential if one wants to torque those rocker bolts properly.

After what I have discovered in my motor, I can't imagine getting as far as you have with disassembly and not opening it up. By the time you have the heads off, you are mostly there. The mag case means some additional work and expense, but for me, the peace of mind would be worth it. Of course, it is always easier to spend someone else's money. But given the known moisture issues and the debris we found, along with your conviction that the case has never been opened, it seems pretty risky to cross your fingers and hope the bottom end is good, let alone the age and unknown mileage. It would really suck to do the upgrades you are contemplating and have it fail! Refreshing the top end is only going to increase the load on the bottom end.

I think the slippery slope to be avoided is the temptation to over-build, not to scrimp on assuring the basic integrity of your motor - obviously just my biased $.02!!!

[frankc]

Thanks for the advice, John - after what I've seen today (see next post), somebody would have to give me reasons NOT to split the case.

Here's a photo of the stubby 5mm Allen bit for reference - again, highly recommended for this job.

[frankc]

I made pretty good progress today and was able to remove the cam housings, heads and cylinders. I am glad I decided to remove the cam housings first, and then the heads and cylinders separately because the heads were fused to the cast iron cylinders. Had I attempted to remove the cam housing and heads as an assembly as recommended in Wayne's book, the cylinders would have come with it, which would have made for one large, heavy and difficult to remove assembly.

I did a search but could not find any mention of the heads sticking to the cylinders so tenaciously - I suspect it is due to galvanic corrosion between the Al heads & Iron cylinders. Once each head and cylinder were removed, I had to tap the cylinder with a rubber mallet to break it free from the head.

As suspected, water did get into cylinder #3 as you can see by the rusty valves (photo 1). I didn't notice any rust on the cylinder walls (photo #2), but they are a bit rough, and not nice and smooth compared to the others. I did not notice any signs of water in the remaining 5 cylinders (whew).

Photo 1: #3 Head


Photo 2: #3 Cylinder



Photos 3 & 4 show the piston tops for the L & R banks - appears to be normal carbon deposits to me.

Photo 3: L Bank


Photo 4: R Bank



And regarding what I said about sludge at the beginning of this thread, I pulled the sump plate to peek inside the bottom of the case, and noticed quite a bit of gunk on the sump screen (photos 5 & 6). All the more reason to break this puppy open to see what's inside.

Photo 5: Bottom of sump screen


Photo 6: Top of sump screen



The result of today's efforts:



This Harbor Freight storage box makes a perfect container for the 12 rockers and shafts. And speaking of rocker shafts, I noticed a bit of wear on mine. At what point should these be replaced?

[jdbunda]

Nice progress, Frank. If your rockers look worn, you can get them reconditioned, which you would want to do anyway, since, if I remember right, you are switching cams. The corrosion is a little scary looking, but not as worrisome as that sump screen. I am with you - gotta get a look at the crank and bearings now.

I had to use a rubber mallet to free my heads from the cylinders, I think you would have been all right either way.


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[SWS911]

Hey Frank, That case looks really nice! The insides of those cam towers look pretty clean too. Can't say much for that sump screen or that rusty old yoke though.

[frankc]

Hey Steve,
Yes, the sealed areas of the cam towers were surprisingly clean, as was the residual oil there. The sludge accumulated at the bottom of the case and right chain housing - I'm not sure if this is due to simply sitting for so long, or previous poor maintenance.

Thanks again for letting me borrow the yoke. And that's not rust, it's patina - people pay extra for that these days . If you need it back while I'm having the machine work done on the case, let me know.

-Frank

[tom1394racing]

You should open up the case and check for internal corrosion. Magnesium cases that have been exposed to water can have significant corrosion where the water settles.

[SWS911]

Frank, You keep the yoke as long as you need to, I don't need it any time soon. Check with Tom ^^^ if you need any P/C replacements. I haven't seen too many mag engines that didn't have chain marks on the case. Those 901 tensioners and idlers SUCKED. I'm going with 930 tensioners and the later wide idlers on my engine, it's a 930/10 so they're already on there, and carrera tensioners with the wide idlers for the 2.4 goin' in the Vanagon.
I'll be watchin' . Steve

[frankc]

It has been several months since I posted an update here, but that's mainly because there simply hasn't been much to report. Dec through Feb I was working in Portland most of the time, and then in March I was getting the '77 ready for the Hill Country Rallye.

So now that I have a little free time again, I've been able to get back in the garage. Today I was finally able to remove the pistons in preparation for splitting the case. Tomorrow the plan is to remove the head studs - I'm hoping all will go well there. My plan is to use the double-nut method with heat to remove the studs, as this is the technique I used when rebuilding my 2.7 and it went well. Or is it strongly suggested that I obtain the Snap-On M10x1.5 Collet stud remover for this job?

Btw, what are the two yellow paint dots on the case below each cylinder? I suspect this is some marking by the factory?







When picking up the bin of all six cast iron cylinders, I was really surprised by how heavy they are. I'll be very happy to replace these with aluminum.

[VFR750]

You asked about the rocker shafts.
If you can see a worn surface, they should be replaced. Simple check would be to polish them with 3000-5000 grit wet sandpaper. If there is any evidence of ridges, steps, cup marks, or other non-smoothness they can't be salvaged.

My personal experience reusing polished pins was they chewed up the rocker journals in 2100 miles because the oil film could not overcome the roughness.

After the teardown, I did the 5000 grit polish and saw how much roughness remained. New pins for me. And refurbished rockers, again.

[gereed75]

The double nutting method works OK. Use plenty of heat. Not familiar with the Snap on tool but beware of the "cam lock" style stud tools - they will destroy the threads.

Buy some case saver type inserts of your choice in the 6 and 8 mm sizes and the tools to install them. Invariably you will strip studs when reassembling the engine in any number of places. If you have the inserts to repair them handy it will save a lot of time and anguish. The mag case threads just get old and tired.

Having a variety of spare 6 & 8 mm studs handy is also nice.

[tharbert]

I had no intention of reusing my head studs. All of mine came out easily with my heavy duty vice grips. Or just weld a nut on the stud. You'll have plenty of other places to spend money on this engine.

[0396]

Maybe I missed it, but with all that metal shaving in the cam box, you better look at a new oil cooler. Im not sure one can wash/ clean all that metal shaving out of the cooler. Good luck with your top in build/ full rebuild.