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T-Series & Prewar Forum

Connecting rods, TC

Moss Motors
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Mitchman2 Avatar
Mitchman2 Mitchell Andrus
Mills River, North Carolina, USA   USA
I'm getting the TC block bored to +.080. I've got 2 sets of original con rods, but I'd like to explore the option to install something a bit beefier and perhaps side step the whole rod-through-the-block thing if I can.

Street use, no racing. T9 5 speed, stock rear end, stock crank -.010.

Moss offers a set: ($679.00)

"Set of 4 late type XPEG connecting rods, slightly stronger and heavier than XPAG rods, with hardware. Suitable also for XPEG 1500 engines."

Any opinions?



Buy a man a plane ticket and he flies for a day,
push a man out of an airplane and he'll fly for the rest of his life.

'30 Model A Ford
'48 MGTC
'58 MGA
'58 MGA

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TD4834 Avatar
TD4834 Bill Chasser
Sacramento, CA, USA   USA
Mitchell. Do yourself a big favor and spend the money on a quality set of billet H or I beam contods. For a few couple hundred dollars more. I bought mine through B&G. . I believe they are Phoenix, but Crower, Saenz and others also have ready made offerings. Also contact Manley Ford here in the states. JMHO

Bill Chasser
TD-4834

LaVerne Avatar
LaVerne LaVerne Downey
Fruita, Colorado, USA   USA
1954 MG TF "Green Hornet"
1969 MG MGB
I don't race either ,, but I do run the piss out of it. Got the rods, pistons, valve springs and pistons through Manely.

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LaVerne Avatar
LaVerne LaVerne Downey
Fruita, Colorado, USA   USA
1954 MG TF "Green Hornet"
1969 MG MGB
Those numbers are "out of the box" figures

Interceptor Avatar
Interceptor Mike Brand
Shenandoah Valley, Virginia, USA   USA
1955 MG TF 1500 "The TF"
1956 Volvo TP21 "Sugga"
1963 Jaguar E-Type Coupe "401K"
1967 MG MGB GT "The GT"    & more
Nice!...that's like ....a well made Watch. Pretty stuff.

xpag TC Wm. H
Odessa, florida, USA   USA
Re conrods, some time ago during an XPAG rebuild I noticed that the rod cap bolt holes were plus or minus 1mm oversize. i.e. 9mm. Not good! This could only happen if there was insufficient bolt torque to provide sufficient preload "clamp" to keep cap rod interface from moving/separating. This movement meant the cap must be deformation flexing out of shape for bolts to bend. Cyclic bending of hard bolts had eroded softer cap hole oversize worse, leading to eventual fatigue failure of bolt(s).
In retrospect it seems most likely that at some previous time the rod bolts were tightened to an insufficient torque that did not provide enough preload/clamp to exceed the forces trying to separate the cap/rod joint introducing a fatigue inducing cyclic bending moment.

Most likely the problem had it's roots in insufficient bolt torque from inaccurate torque reading, and or lack of proper assembly lube on threads & under nuts introducing excessive friction resulting in wrong, high torque reading.

Lesson learned, always measure bolt stretch to achieve desired preload clamp that exceeds forces trying to separate a joint. See www.arp-bolts.com for further info on bolt stretching vs. torque to tighten critical fasteners.



Edited 1 time(s). Last edit at 2017-09-21 12:58 PM by xpag TC.

Mitchman2 Avatar
Mitchman2 Mitchell Andrus
Mills River, North Carolina, USA   USA
In reply to # 3596022 by xpag TC Re conrods, some time ago during an XPAG rebuild I noticed that the rod cap bolt holes were plus or minus 1mm oversize. i.e. 9mm. Not good! This could only happen if there was insufficient bolt torque to provide sufficient preload "clamp" to keep cap rod interface from moving/separating. This movement meant the cap must be deformation flexing out of shape for bolts to bend. Cyclic bending of hard bolts had eroded softer cap hole oversize worse, leading to eventual fatigue failure of bolt(s).
In retrospect it seems most likely that at some previous time the rod bolts were tightened to an insufficient torque that did not provide enough preload/clamp to exceed the forces trying to separate the cap/rod joint introducing a fatigue inducing cyclic bending moment.

Most likely the problem had it's roots in insufficient bolt torque from inaccurate torque reading, and or lack of proper assembly lube on threads & under nuts introducing excessive friction resulting in wrong, high torque reading.

Lesson learned, always measure bolt stretch to achieve desired preload clamp that exceeds forces trying to separate a joint. See www.arp-bolts.com for further info on bolt stretching vs. torque to tighten critical fasteners.

We went through this kind of analysis in auto shop in '73-74. A failed 350 SBC with a zillion miles on it... everything that could go wrong, was. I've learned to always use new fasteners on a rebuild for the reasons you note above.



Buy a man a plane ticket and he flies for a day,
push a man out of an airplane and he'll fly for the rest of his life.

'30 Model A Ford
'48 MGTC
'58 MGA
'58 MGA

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condor1 Terrance Thames (Disabled)
Disabled Account, Antarctica   ATA
Mitch the whole rod through the block is generally from not using a billet crank or line boring ahead of time.

Mitchman2 Avatar
Mitchman2 Mitchell Andrus
Mills River, North Carolina, USA   USA
In reply to # 3596632 by condor1 Mitch the whole rod through the block is generally from not using a billet crank or line boring ahead of time.

Where are you getting that assertion from?



Buy a man a plane ticket and he flies for a day,
push a man out of an airplane and he'll fly for the rest of his life.

'30 Model A Ford
'48 MGTC
'58 MGA
'58 MGA

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
condor1 Terrance Thames (Disabled)
Disabled Account, Antarctica   ATA
Mitch, it always good to know about general known faults of whatever engine you are building. Even if you are using fancy pistons and fastener's, the one thing you do not upgrade might be the first thing you should have upgraded.

The crankshaft on this engine has a reputation for breaking. When they built these engines they did not line bore. What they did was use bearing shells of various dimensions, if needed, to make up for out of whack main bearing dimensions.

While a broke crank is a pretty obvious fault, and not obvious cause to send a piston through the block, that is what happens. They don't always snap in two, causing the engine to no longer rotate. Hairline cracks in the old cranks have been known to cause pistons through the block. Not a direct cause of the hole in the block, but indirect. How that happens is either the hairline crack or out of whack mains (not line bored even) set up a harmonic in the engine that goes un-noted. The harmonic eventually weakens something like a fastener on the main cap or wrist pin that lets go. So while the hole in the block obviously came from a piston/rod going through it, it was actually caused by the crank being cracked, or the block being out of whack.

xpag TC Wm. H
Odessa, florida, USA   USA
Guys,
I can relate from personal experience that a broken crank will not necessarily throw a rod through block. In fact barring a uber RPM explosion rod/piston is likely to stay attached to journal.
Some decades ago I broke an OEM XPAG crank at maybe 30-35k miles & still was able to get car home with out a tow. Engine was noisy though! Crank broke at the usual place, front journal. Why?, perhaps poor post WW II metal, or more likely a discordant harmonic.

I also know of an engine being destroyed by failed aftermarket big end stud from a well know Euro. supplier. The big end cap stud fractured and the broken stud/nut on being hit by crankshaft ricocheted around the sump destroying the engine.On analysis,It was determined that the stud had been hardened to V grade, made from inferior bar stock with low levels of nickel and chrome needed to reduce brittleness in high carbon steels. It also had high levels of sulphur, inclusions indicating that stud was made of impure steel stock. Obviously there was no, or limited QC ( quality control), inspection from either manufacturer or reseller, other than from end user. QC feedback from end user to Mfgr. or reseller is no service to end user.

BUY YOUR CRITICAL FASTENERS FROM HIGH END SUPPLIERS such as ARP, et al.
Note that ARP has suitable XPAG big end bolts (not studs on last query), also head studs though not bespoke to XPAG.

ALWAYS USE HARDENED WASHERS UNDER NUTS WITH NUTS OF SAME GRADE AS BOLTS/STUDS!



Edited 3 time(s). Last edit at 2017-09-22 08:52 PM by xpag TC.

LaVerne Avatar
LaVerne LaVerne Downey
Fruita, Colorado, USA   USA
1954 MG TF "Green Hornet"
1969 MG MGB
Pretty much agree with Tom. Even though the cranks break with alarming regularity, it rarely results in a destroyed block. That usually happens with rod failure....more the bolts themselves and not the rod. One of the reasons I went with the high dollar rods...I never cared for the "pinch bolt" set up even with better bolts.

Steve S Avatar
On The Road, Lost in So Cal, USA   USA
I agree, a broken crank does not always put a rod through the block. I've seen a lot of broken XPAG cranks and only a couple broken blocks. In fact I have a TC engine with a broken crank in my garage right now. It was still running and driving when the lady shut it down. It sounded like someone breaking through the gates of hell inside her engine bay and the whole car shook like an earthquake, but it ran. Rear counterweight split right in two, very unusual. I also have a TD block where the only damage was to the lower cylinder web, where a sizeable chunk is missing.

plus4moggie Tom Lange
Bar Harbor, Maine, USA   USA
If you go to mgtrepair.net you will see my listing for ARP main studs and nuts, a new product. I won't go into a description here, except to say that they are the best main cap studs available, and are used by racers and street cars alike, with total satisfaction.

Tom Lange
MGT Repair

condor1 Terrance Thames (Disabled)
Disabled Account, Antarctica   ATA
In reply to # 3596747 by condor1 Mitch, it always good to know about general known faults of whatever engine you are building. Even if you are using fancy pistons and fastener's, the one thing you do not upgrade might be the first thing you should have upgraded.

The crankshaft on this engine has a reputation for breaking. When they built these engines they did not line bore. What they did was use bearing shells of various dimensions, if needed, to make up for out of whack main bearing dimensions.

While a broke crank is a pretty obvious fault, and not obvious cause to send a piston through the block, that is what happens. They don't always snap in two, causing the engine to no longer rotate. Hairline cracks in the old cranks have been known to cause pistons through the block. Not a direct cause of the hole in the block, but indirect. How that happens is either the hairline crack or out of whack mains (not line bored even) set up a harmonic in the engine that goes un-noted. The harmonic eventually weakens something like a fastener on the main cap or wrist pin that lets go. So while the hole in the block obviously came from a piston/rod going through it, it was actually caused by the crank being cracked, or the block being out of whack.

Tom, are you saying you think the ARP fasteners will prevent crank failure, or that after a crank failure they can be re-used?

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