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MG TD TF 1500 - Anyone bored an XPAG to .120?

I'm thinking of either re-sleeving the engine or going to .120 over (the engine is already at .100) I realize the re-sleeve is the best long term solution but I've heard the block can crack with a re-sleeve. What are your opinions?

Thanks

Tim
TD12524
TW Burchfield

You are far more likely to break into a water passage at +.120 (often +/.100 is too much), so I would recommend sleeving it. I cut the top of the block so the lip of the sleeve cannot move downward. Find a careful machine shop!

Tom Lange
MGT Repair
t lange

I have a .100 o/size block also that I purchased as a project. I'm being quoted $150-250 per bore to sleeve it. Wouldn't it be cheaper to just buy another block? XPAG blocks aren't scarce but I'm not sure of the going price.
Or are you trying to keep the car with matching numbers?
T W Moore

TD's are relatively low value cars. Matching numbers is of little to no significance in the value value. Regards, tom
tm peterson

Tim it is not recommended.
.080" over bore with a stroker crank = 1488.
And add a Roller cam!
Len Fanelli

Tom - I disagree. My opinion is that a NON-matching car is indeed worth less than a matching car, even with a T-series car. I don't think I am alone.

The UK seems less concerned; I tried to get a UK replacement-engined Mark II owner to buy his original engine back on eBay, and he could not have cared less. If I found the original engine for my TB I would pay many thousands for it.

Tom Lange
MGT Repair
t lange

To T Lange
What would you estimate to be the cost of sleeving a .100 osize block? Sleeves are about $50-75 each, how much for machining?
Boring machine or Sunnen hone?
It would be useful to have a ballpark estimate.
To L Fanelli
Where would you get a stroker crank? Phoenix special order?
T W Moore

T W Moore, Yes it is a matching numbers engine. I think matching numbers on a car 64 years old is unusual and worth more money than a non matching numbers car (all other things being equal). Matching numbers is certainly mentioned in ads I've seen. But now we are off topic.

Since Moss sells .120 over pistons I'd imagine someone has bored their engine out to that size. Maybe I should contact Moss and see how many .120s they have sold.

Tim
TD12524
TW Burchfield

I have a .120 over XPAG in my TD. I didn't do the engine build, the previous owner did as part of a frame off restoration. The car has over 17K miles on it since restoration and it is running fine with no issues so far. Unfortunately it is a non-matching engine. I have been told that some blocks can be bored that far and some can't. It the luck of the draw.
A. R. Todd

A.R. Thanks for the info. I've had some people say there is no problem going to .120 over and others saying it would be a mistake. I think I'll take the block to a machine shop that has a good rep around here and let them advise. I appreciate hearing from someone who has a .120 over engine.

Tim
TW Burchfield

I agree - it's the luck of the draw whether you break into a water passage or not. I would also be a bit afraid of weakening the block by going that much over - but it obviously has been done, often to +.100 and clearly by some to +/120!

Sleeving around here (Maine) costs about $100 per hole plus the sleeve - the block has to be bored to fit the sleeve, the sleeve installed, then the block bored again to the proper bore size. I'd go get another block, and save the original one for the next owner.

I am not sure that a matching-engine car is worth more than a noon-matching car; it may be semantics, but i think a non-matching car is worth less than a matching car. I would take away value for a non-match rather than add for a match.

Tom lange
MGT Repair
t lange

Tom, good point about the matching numbers. Are you saying the old sleeves are bored out rather than pressed out. Or are there even sleeves in an original XPAG block? I thought the originals were sleeved and had to be pressed out for the new ones.

Tim
TW Burchfield

OEM blocks were not sleeved.
Stroker cranks from Manley Ford in USA, or Peter Edney in UK.
Roller lifter cams exclusivly from me
Len Fanelli


Tim, when you pulled the pistons and measured things did you find what was causing the noise you heard?

Richard Cameron

Richard, I haven't removed the pistons yet. The rocker are shaft was in terrible condition but I'm not convinced that could cause the noise. Before I tear the engine down I'm trying to decide if I should re-sleeve or go with a .120 over bore. Someone here told me the cylinder measurements I provided indicated the bores were .003 outside the the tolerances for a .100 over cylinder. So, the bottom line is, I'm stalling. :-)

Tim
TW Burchfield


Obviously though, your going to need to disassemble it one way or the other.

Understand your concerns and agree that its best to take it to a competent machine shop for evaluation.

Here's why--- Its very hard for the home mechanic to accurately measure cylinder bores at home, even with a good set of mics. The machine shop will use a bore gage that is more accurate than what most people have at home. Yes, approximately .002" is the normal running clearance for new pistons, so you may be correct in saying they are currently outside normal limits.

Tim, the machine shop will have to be very careful in evaluating whether the cylinders can be bored or power honed to fit new .120" pistons. Since your engine is already at .100" plus, the new bore to fit .120" pistons will only require removal of less than .010" material from the cylinder wall sides. Not much margin for error here. Hold a .010" feeler gage in your hand and realize that removing that amount of metal from a cylinder is negligible. Further, a good machine shop can ultra sonic test the thickness of your engines existing cylinder walls to help determine if they are thick enough for further boring. If for any possible reason, the machine shop tells you the .120" pistons won't work, your only remaining option may be sleeves. If this happens to be the best option, realize that many of us have engines that are already running sleeved bores without any issues at all. Just confirm the machine shop is competent at sleeve replacement and has the equipment to do it right. I wouldn't buy any thing new until the machine shop and you agree on a solution. Hope I don't seem too directive in my input, it's just that I've already been down this road several times in the recent past.
Richard Cameron

Richard, thank you for the excellent advice and information. I was being a little facetious when I said I was stalling. I'm having a heater installed in the garage and I'm waiting for that job to be done before I tackle the engine. The body is off so the removal and disassembly is not a big problem. I do have bore gauges but as you said,they are no substitute for the machine shop equipment. I've heard from several people who have XPAG blocks so I might go that route with a re-bore depending what the current bore is. I'd keep the matching numbers block for the next owner. Thanks again for the response.

Regards

Tim
TW Burchfield

Hi Tim,
going from .100" to .120" is only a 20 thou increase. That is only 10 thou extra off the surface in your engine. I run .120" in my road TC, my s/c race TC and my brother's race TC. The latter is running in the cast iron. The first two are sleeved with Laystall hard chrome liners which were fitted for the benefits of hard chrome, not because the bore size went through into the water jacket. In retrospect I should have visited the machine shop before the sleeves were pressed in to see if the boring broke through into the water jacket. It must have been bored to about .300" to take the OD of the sleeves! 69.5 mm (.120") is allowed in historic racing here in Australia, because it was common in the era, so there are many XPAGs with that bore size.

I guess there is always a chance of .100" being too much but I can't remember hearing of it being so. I guess corrosion might be slowly reducing our bore size limits. I think there are methods of testing blocks to see how thin the walls are, but I have never done it.

One issue with the .120" bore is that standard head gaskets sometimes are not quite big enough. It is not an issue for me as I lap the head to the block and use solid shim.

Good luck with your engine.
Bob Schapel
R L Schapel

Bob, good info. I'm torn between a different (under.060 over) block or going from my existing .100 over block to .120. I've had excellent advice from both camps. I've seen a used block for about $500. I would still have to bore it out (probably). So the cost of the block and a rebore makes the rebore of my existing engine look more attractive. Unlike most of the high rollers here I don't have money to burn (just kidding). Hadn't thought of the head gasket issue. I wonder if anyone makes one for .120 over? Thanks again for the information.

Regards

Tim
TD12524

PS Been to Down Under several times. Loved it. Some of the nicest people I've ever met in my many travels.
TW Burchfield

Hi - I thought I'd mention my experience. Many years ago I obtained some XPAG +0.130" pistons (69.8mm bore), which give 1380cc. I did some measuring and established that my XPAG head gaskets (round and oval water holes) would not project into the bores, so I had my round water hole XPAG block bored and honed to match the pistons by a reputable automotive engineering workshop. I completed the assembly, started the engine, there was a loud crack and water came out of the exhaust pipe. On dismantling I found that the cylinder wall in number 1 bore had split, so I took the block back to the engineering shop and asked their advice. We were able to source some thin wall, less than 1.25mm, liners with a bore slightly smaller than the bore needed for the pistons. So they overbored all four cylinders to give a tight fit for the liners, leaving a step at the bottom to stop any unlikely downward movement of the liners in use. During fitting the block was heated and the liners chilled - after fitting the liners projected up by about 5mm, so this was machined off. They then honed out the bores to match the pistons. I re-assembled the engine, which started and ran without any problems. All this was done in 1972, and there have been no leaks since then, and there is still no step at the top of the bores.
Unfortunately, although I have the receipt for the initial boring work, I cannot find the receipt for fitting the liners, so I do not know the manufacturer. It might have been Laystall, which now seems to make them to order (and size), and the liners now have flanges at the top. However, Laystall is a UK company, but a Google search brings up many liner manufacturers in the USA.

PS, Original TB engines did not have the timing chain tensioner, so the aluminium cover plate did not have the "pocket" that covers the spring/hydraulic piston. Thus the timing chain starts rattling much earlier.
R A WILSON

R.A. Interesting. I've been told that the banana head block can be bored out to a larger diameter than the round hole block. I see that there are .140 over pistons available for the XPAG engine. I'd guess that someone, somewhere has installed the .140 over pistons. I was discouraged form going the liner route by a few people but your positive experience is more info to consider. Thanks very much for the info.

Regards

Tim
TW Burchfield

Hi; I assume you have an oval hole block. I have also read that they had thicker cylinder walls, but it still seems to me that you need to know what solutions are available if problems occur.
I have reread your original comments; +0.100" gives 1350cc, which is a reasonable size. If your bores do not have deep steps at the tops and your pistons are in reasonable condition, why not simply fit new rings, using stepped rings at the top, cast iron rings in the middle and spring loaded oil control rings at the bottom (assuming 3 ring pistons). If there are deep steps at the tops of the bores, but your pistons are OK, then sleeve to use your existing pistons, using new rings - unstepped at the top, cast iron in the middle and spring loaded oil control at the bottom.
PS; +0.140" pistons were available to me in 1972, but all my XPAG head gaskets (round/oval) would have projected into the bores, so I didn't buy them.
R A WILSON

In October 1992 I had my engine rebuilt by Crankshaft Rebuilders in Melbourne and it was bored to 70mm to give just on 1400cc. I have been running the car since then (quite spiritedly)without a problem. I have only travelled 12000 miles or so but using it much more these days in my retirement. I still have the invoice showing all the other tricky bits that were done at the same time
Peter (TC9356)
Peter Malkin

+0.140" pistons need a bore of 70.06mm, giving approx 1388cc.
R A WILSON

Interesting to hear about the differences in the amount round and banana blocks can be bored. It is possible that banana blocks had thicker bores.

However, the difference in ability to bore could be because the early (banana) blocks have an extra horizontal web in the water jacket, about half way down. This gives the bore extra support even if the wall thickness is the same. The bores of round hole blocks are only supported at the bottom (roof of crankcase) and top (head gasket face).

Bob Schapel
R L Schapel

R.A. There was no ridge at the top of the cylinder when I took the engine apart. The pistons were in excellent shape so I fitted new rings and bearings and reinstalled. But I had a pretty bad smoking problem afterwards. After numerous measurements I have found that the bores are out of round. The measurement perpendicular to the axis of the engine is several thousandths greater than the parallel measurement. So I'm pretty well committed to a rebore or sleeving.

Perter, I've heard from several people with good reputations in the MG field that the oblong hole (banana hole) blocks will tolerate a larger bore than the round hole ones.

Bob, thanks for the info.

Tim



TW Burchfield

That was quick work. Did you try Cord rings - I've heard they are good at accommodating slightly oval bores, and I think their oil control rings are the type with a spring ring holding apart and pushing out two thin blades.
However, it is not the time of year for mowing the lawn, and you're probably really looking forward to lying under your car and otherwise getting your hands dirty.
R A WILSON

I've done a couple of .100 over blocks. Before any boring, I had them scanned and magna fluxed. The scanning will tell you the current wall thickness in the water passage area and you can then calculate what the thickness will be when finish machined and not have an ugly surprise. One block finish machined with a .100 thick wall and the other with a .200 thick wall, so it's always $ 175 well spent for the scanning.
Charlie
c mac quarrie

RA, I certainly don't mind getting my hands dirty. I grew up working summers at my dad's garage. What I don't like is doing a job over a second time. My fault, rushed the engine rebuild without being diligent in checking clearances.

Charlie, Thanks for the information. My only problem now is finding a machine shop in central Ohio that can do the job. I took my rocker arm assembly to a shop with a great reputation. But, with a good reputation comes a full shop and very long lead time to get a simple job done.

Tim
TW Burchfield

Yes - doing a job twice is a pain. I hope it goes well this time - you should have your new garage heater to make the working environment better.
R A WILSON

R A, it's in. Not a giant unit but should allow me to work in the garage when it's below freezing here in Ohio. Let's hope twice is all I have to do the job :-)

Regards

Tim
TD12524
TW Burchfield

Finally got the block sonic tested and was told there is plenty of metal left to go .120 over. The shop wants the new .120 pistons before boring. That was reassuring. Looks like I can keep my numbers matching block.

Tim
TD12524
Engine 12942
TW Burchfield

Seems to be various thoughts on matching number cars. My TF has matching numbers and because of that, it's nice to know the engine was in it when it rolled off the assembly line on December, 17, 1954. PJ
Paul161

Tim,

Thanks for the follow-up and good luck.

As for numbers matching adding value - how much value can they add to a car worth $25K? Only the owner knows for sure if they match and I personally don't care as long as it's a correct XPAG or XPEG engine and not a Volvo.

Gene
Gene Gillam

Paul. Gene, If you ever watched What's My Car Worth you know that matching numbers always adds value to the cars at auction, regardless of the cars value. I'm not sure why some people on this site downplay the value of matching numbers. In fact, I think this is the only car site I've seen where matching numbers are discounted by some members. I believe that we would all agree that, all other things being equal, we would prefer a matching numbers car over a non matching numbers car.

Tim
TD12524
TW Burchfield

Tim,

The question was "How much value does matching numbers add to the value"?

Also, most cars aren't sold at auction...and those that are are normally overvalued. Try getting an 'auction price' for your car on eBay.

Gene
Gene Gillam

Finally got the block back from the engine shop. Here's what was done:
Boil the block
Sonic test cylinder wall thickness
Bore cylinders to .120 over
Hone cylinders

Total cost was $330.

I won't have the engine running for a couple of months but if things go well I will consider this a good investment.

Tim
TD12524
TW Burchfield

Hi Tim,
Just curious, what part of Ohio are you at? I'm in Ludlow Falls Ohio about twenty miles north of Dayton. Personally, I'd do every thing in my power to keep numbers matching the way the car was born. Best of luck on your rebuild.

Bill TD24570
Bill Brown

Tim, do you have 120 oversize pistons for your car.
TRM Maine

Tim,
Hopefully the photo attached will be clear enough to show the two pistons from our 1466cc XPAG, yeah, punched out way beyond .120". I measure only about .10" wall thickness, so it is a gamble. The old piston has many years and miles on it, unsupercharged. Years ago, I knurled it and installed new rings and it was good to go. I had the new one knurled to ensure a snug fit and my old school thoughts of oil retention on the skirt.
It is getting an upgrade to S.Co.T. blower, roller lifter cam & Moldex crank. Since there's nothing left to bore, it is getting light honing and new rings again. I'm "upgrading" to, what I refer to is the Mowog style piston because I had an Aerolite split the skirt (motorcycle 45 years ago) right where you see that expansion cut. The old ones may have run another 50,000 miles, but I'll never know now.



JRN JIM

The TF I rescued and restored had an early block .120 over. The pistons I removed were marked Jahns 933. Unfortunately, the block was cracked from a bolt hole to the oval water jacket. I have contemplated stitching the crack, but the kit to do this is a little over $600. Since the original engine had been swapped somewhere along the line, I bought a replacement block and sleeved it back to standard. someday, If I ever have the extra money, I will lock n stitch the crack and replace the threaded hole. The PO used a SAE head stud that caused the crack.

Rick

Bill, I live in Columbus. My whole reason for going .120 over was to keep my numbers matching engine. The shop said that if I ever wanted to install sleeves there was enough material left over to allow for that.

TRM, yes I do have the .120 over pistons. The shop wouldn't do the boreing until they had the pistons in hand. Gave me a little more confidence that they know what they are doing.

Jim, the shop wouldn't do the rebore unless there was at least .10 of wall thickness on the thrust side revealed in the sonic test. I haven't seen knurled pistons since the 60s. Obviously you did a great job. I'd say you got your money's worth. Good luck on the upgrade.

Tim
TD12524

TW Burchfield

Rick,
When I first pulled this 1466cc engine down, there was an SAE bolt in the head and it couldn't torque down. It ran for years with that issue.
I wouldn't bother mending the block (I am a welding engineer, for what that's worth). The easiest remedy would be to run a 7/16" helicoil in that, and all the others if you feel like it. It'll torque down and won't care if a bit of water/antifreeze gets to the threads. I'd dose the threads with blue loctite just to insure it won't weep up past the bolt head (chances really low on that, especially if you run your TF without coolant pressure).

Call it overkill- I drilled & tapped the block for 1/2" socket head bolt (higher strength than Grade 8, like it really matters). I plan to torque them to 90 ft.lbs. whhich is very conservative for that large of a thread.

JRN JIM

pistons were toast! Engine sat from 1965 until 2012. the wrist pins were frozen in place.
Rick

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