MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - TD17744 ENGINE TEARDOWN

Good day to all,
Well, I am waiting for a few parts to finish rolling chassis, so engine teardown begins. This xpag was rebuilt in the late 70s. Machine work was done by a well known local racing shop with no experience with xpag. The crank, rods, pistons were balanced but I really don't know to what extent. The engine is overbored +.080". I measure the head between 2.979-2.986. I can't explain the measurement differences. I'll let the new machine shop verify all measurements. The rebuild has very few miles on it but one thing in particular has always bothered me. The rod caps were ground on extensively to balance. Some of this was done by a PO.
So here is what I know (or think I know)
1) Bore measures 2.698" which should verify the +.080" over
2) New pistons were installed at rebuild. I don't know origin(maybe Moss) (see photos)
3) Old rods and caps were reinstalled. (see cap photos)
4) "New" camshaft installed. If my memory is correct, it was bought from a local enthusiast. Looking at it now, it is clearly a regrind (see photo)
5) rod bearings are marked .010"
6) Crank is still in block, so condition of journals is unknown, however, visually the rod journals look good.
7) Valves in head, somewhat recessed. not sure what is acceptable #4 is worst (see photo)
8) head and piston tops very "sooty".

My next plan is to take Block, head, crank, rods, pistons to machine shop for cleaning, magnafluxing, measurements, general evaluation.

What I am really asking is for your initial thoughts about what you see and what you would do, replace, etc. I don't have enough experience to really evaluate what I am seeing.

Since I have a .080" overbore and a new 4.3 rear end, I am considering a moderately aggressive "fast road" rebuild. But I don't really know which of these moving parts would be considered acceptable strengthwise for such a project.

I hope this isn't way too much information for one post





JV Smith TD17744

PISTONS




JV Smith TD17744

CAMSHAFT




JV Smith TD17744

JV – I hesitate to criticize anyone else's work, but really! Those rods need to go in the garbage ASAP! The work on them is just barbaric, and I would be very frightened to have that much ground off the bottom of a rod cap. And why on earth is ALL that weld on another rod? Is the ground one a heavier TF1500 rod (check the number on the beam)? Or is the heavier one from a Morris 10? There is supposed to be a spine at the base of the rod cap, intended be ground and reduced in size SLIGHTLY for balance.

In any case, my advice would be to start again. You ought NOT buy new rods, unless you plan to drive the car hard, in which case you need to get a set of forged Saenz rods. A set of used, stock rods, close to each other in weight, re-done properly on a Sunnen hone and then balanced, will do you fine.

1) Remember that the bore is not round; measure at 45 degree angles at various places in the bore – a bore mic is needed, NOT a caliper.
2) No photo of pistons included.
3) Get new rod bolts, NOT Nylok nuts
4) No cam photo
5) Crank must be magnafluxed, and mic-ed. If you can feel any ridges with your fingernail, chances are excellent it will need to be re-ground.
6) Otherwise it may polish up fine (mic carefully)
7) No pictures
8) Running rich.
Lots more to tell...

Tom Lange
MGT Repair
t lange

HEAD




JV Smith TD17744

Sorry, I was too fast...

Changes to my message:

JV – I hesitate to criticize anyone else's work, but really! Those rods need to go in the garbage ASAP! The work on them is just barbaric, and I would be very frightened to have that much ground off the bottom of a rod cap. And why on earth is ALL that weld on another rod? Is the ground one a heavier TF1500 rod (check the number on the beam)? Or is the heavier one from a Morris 10? There is supposed to be a spine at the base of the rod cap, intended be ground and reduced in size SLIGHTLY for balance.

In any case, my advice would be to start again. You ought NOT buy new rods, unless you plan to drive the car hard, in which case you need to get a set of forged Saenz rods. A set of used, stock rods, close to each other in weight, re-done properly on a Sunnen hone and then balanced, will do you fine.

1) Remember that the bore is not round; measure at 45 degree angles at various places in the bore – a bore mic is needed, NOT a caliper.
2) Mondial pistons are good, older French pistons - NOT Moss. The tops are less important than the sides - is there any scuffing or wear? The shop will be abl to gauge how well they fit the bores.
3) Get new rod bolts, NOT Nylok nuts
4) Cam has certainly been crudely re-welded. I would get a good core (I have plenty) and have a Delta Cam RV grind applied. Or, if you feel ambitious, Len Fanelli's roller cam.
5) Crank must be magnafluxed, and mic-ed. If you can feel any ridges with your fingernail, chances are excellent it will need to be re-ground.
6) Otherwise it may polish up fine (mic carefully)
7) You will need to pull apart the head to see any valve recession. Many people do it automatically to the exhaust valves, but it is not very often needed.
8) Running rich.
Lots more to tell...

Tom Lange
MGT Repair
t lange

Well, Tom...the term barbaric didn't come to mind, but that was similar to my nagging thoughts. What I really couldn't understand is why the original shop didn't tell me the same thing you just did. More photos are on now. I expect, and welcome more. So, even if I decided to add your supercharger, original rods would be ok?
Jim
JV Smith TD17744

Sorry, I was too fast...

Chanbges to my message:

JV – I hesitate to criticize anyone else's work, but really! Those rods need to go in the garbage ASAP! The work on them is just barbaric, and I would be very frightened to have that much ground off the bottom of a rod cap. And why on earth is ALL that weld on another rod? Is the ground one a heavier TF1500 rod (check the number on the beam)? Or is the heavier one from a Morris 10? There is supposed to be a spine at the base of the rod cap, intended be ground and reduced in size SLIGHTLY for balance.

In any case, my advice would be to start again. You ought NOT buy new rods, unless you plan to drive the car hard, in which case you need to get a set of forged Saenz rods. A set of used, stock rods, close to each other in weight, re-done properly on a Sunnen hone and then balanced, will do you fine.

1) Remember that the bore is not round; measure at 45 degree angles at various places in the bore – a bore mic is needed, NOT a caliper.
2) Mondial pistons are good, older pistons. The tops are less important that the sides - is there any scuffing or wear? The shop will be abl to gauge how well they fit the bores.
Get new rings from Deves.
3) Get new rod bolts, NOT Nylok nuts
4) Cam has certainly been crudely re-welded. I would get a good core (I have plenty) and have a Delta Cam RV grind applied. Or, if you feel ambitious, Len Fanelli's roller cam.
5) Crank must be magnafluxed, and mic-ed. If you can feel any ridges with your fingernail, chances are excellent it will need to be re-ground.
6) Otherwise it may polish up fine (mic carefully)
7) You will need to pull apart the head to see any valve recession. Many people do it automatically to the exhaust valves, but it is not very often needed.
8) Running rich.
Lots more to tell...

Tom Lange
MGT Repair
t lange

Tom,
The "running rich" is what I thought. Score one for my limited experience.
Jim
JV Smith TD17744

It's academic at this point but the 3 of the rods have the same marking, and one has the other. However, the one that is built up is one of the three and so is one of the most ground on.
Jim




JV Smith TD17744

It is also going to depend on if the cylinders are worn. I would go with a sleeve if so.

Also, I fully agree with Tom on no nyloc nuts or used rod bolts. Here is a small reminder of why.

We found the nyloc nut on the bottom of the pan.

Bruce Cunha

Wow, Bruce, what a mess. For what it's worth, all of the rod nyloc nuts were tight, but it was very low mileage.
To me, the cylinders look really good. I will rely on the machine shop to confirm that. I agree that if cylinders are damaged, then sleeves are in order. Back to 1250cc would be a little disappointing, but necessary.
Jim
JV Smith TD17744

Bruce be honest. That was the result of a 10,000rpm downshift

When you take your parts to the machine shop you also want to take your crank pulley, flywheel, along with a new clutch plate and disc to be balanced as a unit.

Although Tom has another train of thought on specific items, I prefer to either use a late TD crankshaft or ultimately a new billet crank. I also prefer to buy new billet rods and forged pistons for piece of mind. Granted I operate my XPAGs from 3500-6500 rpm, but I also am not worried about hurting the engine while keeping up with 70mph traffic on the highways. Roller cams are an excellent choice especially for their longevity and no need for ZDDP. I run VR1 just the same. However, if you go with a roller cam be prepared to possibly needing to fly cut the cylinder bore for valve clearance. That will depend on the size of valves used, how much the head has been decked, the head gasket thickness used, the bore size and the camshaft lift at the valve. I believe all of Len’s roller profiles spec at .430 lift at the valve. This is quite a bit more than any stock/street/ fast road cam flat tappet cam. Roller cams rarely fail.

Bill Chasser
TD-4834
W A Chasser

Thanks Bill,
Right now I am keeping all of my options open.

For example: If my existing crank checks out without cracks, then should I keep it, and if I do, what are my reasonable options? It seems unwise to run a supercharger on an original crank, but what about a roller cam? I am not going to race this car, but keeping up on the interstate and having enough power for fun is on my list.

The rods are toast, so they will definitely be replaced.
The cam is a poor rebuild, so something is required there.

Thanks for the info on balancing. I hadn't considered getting down to the crank pulley, clutch plate and disc. I had considered lightening the flywheel based on the plans previously shown here.

Lastly, can you explain the term "fly cut the cylinder bore"?

Jim
JV Smith TD17744

I suggest that particular emphasis be applied to the magnafluxing of the crankshaft with close attention paid to the Front and rear main bearing journals whre cracking is known to be commonly found. (don't ask why I am highlighting this).
There is a lot of info in the archives with photos of the usual failure points.
T W Moore

Jim 1st determine what the compression ratio will be.
Here is maximum recommended C/R for normally aspirated VS camshaft duration:
Static Compression Ratio
(SCR) Intake Valve Duration
(degrees @ .050" lift) Power Range
(RPM)
8.00:1 185º Idle-4,000
8.25:1 189º Idle-4300
8.50:1 194º 800-4,500
8.75:1 200º 900-4,600
9.00:1 204º 1,000-4,600
9.25:1 208º 1,200-5,200
9.50:1 212º 1,600-5,400
9.75:1 216º 1,800-5,600
10.00:1 221º 2,000-5,800
10.25:1 227º 2,400-6,200
10.50:1 233º 2,800-6,400
10.75:1 236º 3,000-6,800
Len Fanelli
Abingdon Performance Ltd.
laf48@aol.com
914 420 8699





Len Fanelli

Because the clutch pressure plate is a wear item, I am of the school that this should be "neutral balanced" independently of the rotating assembly. The disc itself should also be considered as neutral, as it will never clamp at the same place twice. It is still important to "balance" these two items as I have seen them way off the mark as shipped.
J Stone

I run a XPAG 80thou over, Laystal head, 1 ½" carbs and Len's Fast road roller cam and roller rockers, with a 4.55 rear end. Pulls like a freight train, revs freely and cruse all day at 75mph when no police around. Wolsey 4/44 rods and new crank in 70's.

Bernie
B W Wood

Well, the crank is out and rings like a bell everywhere I tried. That's a good sign. On reading a previous thread, is this a TF crank? And if it is, isn't this a stronger crank than the original TD?

Another new development...notice in photo #2....bore #4 is sleeved at .080". If everything else checks out, do you see this as a problem?

Next step, everything off to the shop for cleaning and magnafluxing.

Jim TD17744




JV Smith TD17744

Related question: Do I need to remove the oil pump driven gear shaft to hot tank the block?

I have removed all studs, oil gallery plugs and screws, and the rear oil thrower. Have I forgotten anything before I have the block hot tanked, measured and magnafluxed?
Jim
JV Smith TD17744

Yes Jim 168557 is the later stronger "100 ton" crankshaft.
Yes remove the complete oil pump assembly.
BEST prices on any advertised Crane Cam!
Abingdon Performance Ltd.
Len Fanelli

Jim - please contact me off-line.

tlange@acadia.net
207-479-3695

Thanks. Tom Lange
MGT Repair
t lange

Thanks Len,
This is the shaft I was referring to. Is the lower left a bushing that needs to be removed for hot tanking?
Jim

JV Smith TD17744

No it is a by pass valve & should be removed and inspected for wear.
The shaft usually wears & should be removed as well.
Very Important contact Doug Pelton @ From the frame Up for oil pump failures after a new rebuild!!
Len
Abingdon Performance Ltd.
914 420 8699
laf48@aol.com
Len Fanelli

I rebuilt my engine using Venolia Pistons, Crower rods and a Moldex crank. rods and pistons new and modern. any weakness in the XPAG will show in about 10 minutes if you supercharge.My pistons were built to take the extra heat from a supercharger. looks to me like the builder who did not know much about these engines did a horsesh*t job.
TRM Maine

Sorry for the premature question about the bypass valve, Len. I'm going to have to be a little more diligent at looking at the WSM before I ask the question.
Is it your suggestion that I let Doug rebuild the oil pump? One of the last things I want is an oil pump failure.
The reason I am asking all of these quasi-unrelated questions is that I want to do this rebuild right the first time. I really don't want to do it more than once. I would much rather drive the car, on the interstate when necessary and in the mountains of Tennessee for fun.
So I am looking for what existing parts I can or should reuse for various engine scenarios.

AS an example, would a supercharger burn up my existing pistons? If so, I need to take that into account in my decision process.

Thanks for everyone's input,

Jim
JV Smith TD17744

TRM,
Yes, the previous builder obviously didn't care about the project. But, fortunately no permanent damage has been done (that I know of yet). When was your rebuild?
Jim
JV Smith TD17744

Jim,

If you don’t have Doug rebuild your oil pump at least order the parts from him...especially the circlip that goes on top of the drive gear.

As for running a supercharger on an original crankshaft...why not? If yours is good then it should be able the extra horsepower...people have been running superchargers on these cars for years without replacing them.

Gene
Gene Gillam

Jim as my friend Tom stated:
Jim - please contact me off-line
laf48@aol.com
abingdonperforma@aol.com
914 420 8699
Thanks
Len Fanelli
Abingdon Performance Ltd.
Len Fanelli

Jim
just looking back through your pics and not sure but it looks like that sleeve is a bit dodgey -?
If it measures up ok, and 'if' it hasn't been pinned it needs doing as it doesn't look as though the block was machined with a step for the sleeve to sit on
Bit hard to see really in the image but I'd ask your machine shop guy to check that out when it's in there being cleaned up etc
willy
William Revit

Thanks Willy,
I'll have him look at it. At this point, everything in the engine is suspect, due to concerns about previous machine work.
Jim
JV Smith TD17744

This thread was discussed between 14/12/2020 and 23/12/2020

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now