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MG TD TF 1500 - Into rebuild of XPAG TD2 15613

Last night, after what seemed like weeks and weeks of waiting (ok, it was exactly two months) the head was done, the block ready and all the other internal engine parts checked, ground, and prefitted. All that remained was to assemble the engine. I had loaned most of my reference books to Mike Segar, of Segar Engine Rebuilding because while he seemed to have a good grasp of what I was looking for, he hadn't really done a whole XPAG, instead he had mostly done 'on the cheap, get it back on the road' style of repairs for owners with head or crankshaft or camshaft problems.

I thought it would be cool to assemble the engine with Mike, both because we could easily correct any problems that we might encounter, and because he has seen so many engines, from small skid loader engines to 800 hp dragster engines.

Mike is a quick study, has the most complete equiped 'one man shop' I think you would find, and respects engines and history. He remembered every conversation we had, reminding me of things that I asked for, or had included in my rebuild. While I would be consulting my list of purchased items to see if I had planned on a new bolt or component, Mike would simply reach into a pile of bagged parts and say, "You sent this along, I think we should use it."

Mike was careful with my block, respecting the age of the cast iron, not overtorquing the studs as he turned them in, unwilling to risk too much in altering rod balance, but desiring to assemble the best engine we could. Although we will never race this engine, he wanted to balance the crank with the flywheel and pressure plate attached, because that's just the way he likes them.

We went from .040 over to .060 on the pistons. We added hardened valve seats, and milled the head to 3.010 from 3.0177 to remove the water damage from the head leak at number one cylinder. We ground the crank to .020 under from .010. We kept the original camshaft which looked great, and crowned the tappets by hand, polishing them until they flowed in the bores. Mike allowed me to do a lot of the work, and promised me pictures from the balancing effort his father helped with, pleased because his dad once owned an AH 3000, and had an early love for English iron.

So, it was a lot of fun, following the requirements and recommendations in the manuals and references, and adding some that Mike likes, and some that I thought would be a good idea as well.

And then there are questions...

to be continued.

warmly,
dave
Dave Braun

Here are the questions... I didn't want them to get lost in my reverie...

What do you think the head volumn is with the head milled to 3.010? We considered measuring, but that seemed so anal!

Mike said that he wouldn't safety or put split pins on the castlelated nuts. The torque is enough to hold them in place. But that I could if I wanted. I know Bruce lost an engine in spetacular fashion when a rod bolt broke. But has anyone lost one because a properly torqued nut came loose? Somehow the extra torquing to get to the next hole, or removeing the nut and shaving it to retorque sounds more dangerous than letting the torque do its job. Fletcher Millmore, Bruce, Dave Dubois, Jesus, any others... help me get my head straight on this one, please.

I know my distributor should be rebushed and checked. Is that a job for me, or should I send it off, and if so, to whom?

Also, feel free to toss any advice my way as my engine is now a short block, but there is a bunch of work to go. Yes, I have new timing gear and chain, and I will check the oil pump as soon as I install the housing again.

Thanks!
dave
Dave Braun

Dave,
I've seen lots of shop manuals for various vehicles published a while after the engines were built that say to omit split pins. I had an XK120 that had a sump full of split pins and ends of same, no longer associated; many of them had been through the oil pump. Apparently the inertia loads from high rpm fatigue the pins until they fall off. I leave them out; if you do fit them, use stainless pins and clip the ends as short as possible.
FRM
FR Millmore

I am also in need of advice on the issue of split pins on castelated nuts. My engine that blew was using the self locking nuts. The current engine (not run, but rebuilt by PO) has castelated and was fit with split pins.

We are going to have the engine gone over this winter to assure all the work done by the PO has been done right.

On the question of distributor. I had mine gone over by John Twist's shop in MI. Did the Dist. and the Oil pump. Not inexpensive, but I am more comfortable it was done correctly.
Bruce Cunha

Dave,

I had my local machine shop do the distributor bushings.

Good luck,
Evan
Evan Ford - TD 27621

Thanks Fletcher, Bruce and Evan

I'm going to see if anyone weighs in on the safety is good side, but right now I'm inclined to not.

Last night I checked the clearances in my oil pump, and installed it, along with the core plugs and timing chain back plate and timing chain and gears. I have the one piece oil seal from Moss for the FRONT of the crank, it appears that it will ride on the crank shaft pulley, so I need to get a new one, mine's cracked on the pulley flange.

Right now, I'm trying to figure out if I can prime the pump prior to start up (which might be some time) by injecting oil either into the cap on the filter housing, or the cap near the side of the pump. Schach says fill the darn thing with vasaline.

Dave
Dave Braun

I would use the proper diameter split pins (cotter pins) for safety. The mains are subject to enormous vibrations when running, and torque alone will not necessarily keep the nuts tight. The nylon insert self locking nuts will tend to fail due to the high temperature of the oil when running hard.
Don Harmer

Hi Don,

Well thanks for weighing in. Fortunately, my new big end bolts have castleated nuts on them, so I won't have to worry about nylon failure. I'm still thinking on the cotters.

Incidently, I decided to fill the pump with vasaline.

dave
Dave Braun

Dave

On the oil pump. I recommend that while you can observe the oil pump SLOWLY turn the crank to check that the pump is not binding. That is how I ruined a cam in my TD. PO did not check it and the pump bound up on the first crank.
Bruce Cunha

Thanks Bruce! I did that on install. Great advice though. Any other thoughts would be quite welcome.

warmly,
dave
Dave Braun

First thing I learned on aircraft engines is to tighten the split-pins so they do not wiggle.If they move they will wear and come out. Have disassembled engines that I rebuilt years ago and have no spli-pins in the pan.
DL Rezin

Dave, archive info on combustion chamber size. NOte that it may not format correctly.

Finished Depth Size 1250 1500

Std. 76.75 mm (3.022 in.) 200 cc 7.25 8.33
1/16 75.16 mm (2.959 in.) 175 cc 8.1 9.0
3/32 74.37 mm (2.928 in.) 165 cc 8.6 9.9
1/8 73.58 mm (2.898 in.) 150 cc 9.3 10.7


Regards,
Dennis
D F Sexton

Thanks for that info Dennis. I know we had to skim a bit off the head and the block, not enough to screw up the valve setting adjusting range, but the bit off the head and the bit off the block probably is the same as approx a 3.000 head. I'll have to think about that compression.

I did install some split pins tonight, and although I tightened them as D.L. Rezin said, and used Stainless as Fletcher suggested, I wasn't very satisfied. No matter how tight I put them in, I could visualize them working loose, and decided to pull them all out. I have some time to re-decide, but I feel better with the pins in a bag rather than in the nuts.

Otherwise the only remaining work to be done before painting is to install the oil sump (something I want to devote an evening to) and then masking the engine.

I do like the single piece seal on the front of the crank shaft.

dave
Dave Braun

Ok, my latest plan is to safety wire the big end bolts and the main bolts. I discovered as I attempted to torque some of my main bolts to the 'next slot' that the stud was turning instead of the bolt. Which made me think, "what's to prevent the stud from loosening on the mains instead of the bolts?"

Any thoughts?

dave
Dave Braun

hi Dave,
the safety wire does protect the studs if you connect them pairwise. So one piece of wire connects both stud/nut combination.
I decided to go for nylon nuts and use loctite for the studs.
Good luck, Huib
Huib Bruijstens

Dave,

Interesting thread!

Also drawing on Aero eng' experience and studs turning - use individual split pins, not paired wiring.
I would not be happy with hidden nyloc nuts or solely loctite in such a hostile environment.
I think most failures of split pins are due to:
bending them incorrectly (never hammer, should be a classic anchor shape) and using the wrong size-this ideally should be an interference fit.

Put them in and relax - all sorts of 'what if' problems arise laying in bed at night!

Regards

Has
HJ Oldham

Has,

Forgive me for not understanding your recommendation. Are you saying 'Do not use safety wire, use properly installed split pins'?

I chuckled at your 'what if' statement.

Thanks

dave
Dave Braun

Dave,

My apologies for a somewhat ambiguous response.

Both can be used, but why I prefer split pins goes back to the 'interference fit'. Thus no wire vibrating and consequent chafing with subsequent failure. One broken wire potentially = two loose nuts.

Having worked on both US and UK aircraft the amount of locking wire used in US aircraft compared to UK aircraft is staggering. Not a bad thing, but akin to a different engineering culture.

I am impressed with your dedication to detail.

Regards

Has

HJ Oldham

Dave - I am with the safety wire proponents for the main bearing studs and nuts. I will dig through my stuff and send you some information on how to do up safety wire correctly (yes, there is a right and a wrong way to do safety wire). I also have an in progress check off sheet (can you tell that I used to work on submarines?) that I will send to you. It is a great comfort after everything is buttoned up and you suddenly think, "did I bend up the tabs on the locking plates for the ...nuts? or did I forget to torque..." Cheers - Dave
David DuBois

One item that has not been discussed. With the exception of a split pin part flying into the gear for the oil pump or the differential, would not the pin part just fall to the bottom of the pan? Once past the pan plate, I can;t see it being a problem.

The filter on the oil pick-up would block the metal from entering the oil system.

I had a brand new 1980 Subaru that someone dropped an extra metal clip into at the factory. When the piece came out during an oil change there were teeth marks on it, indicating it had gone through the timing gears. Drove that car for 250,000 miles without a problem one.

As I have the same dilema as Dave B. I also have to choose one over the other. PO installed split pins, but I will wait and see what the shop that is going to go over it says. Dave B. I am having the shop in Hudson take a look at it.

Bruce Cunha

Thanks Dave!

Up to this time I've been using the University Motor checklist for the XPAG as found in their technical book. I'm leaning more towards safety wiring than cotter pins. Although, it appears that if my engine flies apart sans safetying, absent anecdotal evidence of similar occurances, it will be the first to do so. Flying magazine just had a comprehensive article on safety wiring, I would enjoy seeing what you have.

Incidentally, on the last rebuild by a PO, the safety tabs on the rocker shaft support nuts were not bent up.

Tonight, delaying the entire saga, I cut and trimmed all the gaskets and seals for the oil sump, noting just where I intend to fill a gap or two with judicious amounts of RTV sealant. Can't have any of that stuff floating around inside the engine by mistake. I'm using it only at the front and rear seal joinings, and only sparingly.

dave "will he ever decide and close up the sump" braun
Dave Braun

On the Jaguar I mentioned, There was one pin end INSIDE the oil pickup screen, and another stuck halfway through - it didn't go all the way in because it was curled into a C shape from having already been through the pump once already. There were pin section dents in the pump gears as well. Evidently the bits came back out the pressure relief valve, since I found all 24 pin ends in the sump, maybe half of which were "roll formed". A good thing since it was my only car at the time and there was no way I could afford to take it all apart - as it was I had to do about a 60 hour marathon before a necessary trip!
While I have always been a fan of lockwire/locktabs etc., it can be seen that on machinery that has been in production a long time, there is a tendency for these to be deleted in later versions, as in B series engines. I think that it has been rather conclusively established that:
Correctly torqued fasteners do not come loose.
Incorrectly torqued ones may come loose IF they are left loose to start.
Incorrectly torqued ones are more likely to fail from fatigue than self unscrewing.
Extra and unnecessary bits like split pins cause the problems I've seen AND may force improper torque.
Locktabs can squish out from under highly loaded fasteners, causing (again) failure from insufficient torque loading. BIG problem with incorrectly made locktabs, like some I've had in recent years.
My overall impression, which I have also seen in writing and from talking to aircraft mechanics long ago, is that the primary function of these things is as a check that the actual tightening was done. A secondary consequence of this is that they are enshrined in lore and regulation.
The only truly valid application is where something like gasket compression can allow a correctly tightened fastener to BECOME loose, when it would then unscrew itself. An oil leak is better than the sump falling off!
FRM
FR Millmore

Thanks, FR.

I used some upgraded rod bolts and nuts that I bought from Shadetree, and these did not have provision for cotter pins or safety wire, as the bolts were not drilled, and the nuts were not castellated. I've rebuilt MGB engines several times, and never seen any kind of problem with rod bolts coming undone, but to be fair, the MGB rod bolts seem to be heavier duty and better designed that the XPEG bolts.

It wasn't feasible to use Loctite, since the torque specification called for oiled threads. So I torqued them up, and tried to not worry. So far 750 miles, and it hasn't blown up yet. I've had it up to the redline a couple of times. Except for the clenching, it's been rather painless.

I plan to pull the sump some day and recheck the bolts, but I'm enjoying driving the car too much right now. When I do check, I'll post the results on the board.

Mark B.

This thread was discussed between 15/10/2005 and 21/10/2005

MG TD TF 1500 index

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