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Crankshaft Decisions

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Crankshaft Decisions
#1
  This topic is about my 1955 MG TF 1500
ArchieMcAllister Avatar
ArchieMcAllister Silver Member Archie McAllister
CLeveland, TN, USA   USA
I have been worried about this for some time and should have addressed it during my last rebuild. Broke the crank in my TF1500 a few weeks ago on the way back from the Shoals British Car Club gathering in Alabama. As you can see below, the crank actually came out in three pieces! I am pretty sure it broke at the front journal first. It was still running (although a bit on the noisy side), so I drove a bit farther to bind a safe place to pull over. Engine finally gave up when the second break happened. So, now I have some serious decisions to make. The billet crank is available at a relatively reasonable (?) price right now, directly form England, due to the favorable exchange rate. Also available, from Manley, is a billet crank produced here in the United States that can be machined with the stock 90mm stroke or a custom 96mm stroke, giving the XPEG about 1600cc displacement (actually more for my engine as I will probably have to go .060" over this time on the bore) and also is designed to use MGB 5-main bearings. Manley can also supply lightweight forged rods (which accept the MGB main bearings) and pistons. Cost for the custom pieces is about $1800 more that stock, buying directly from Steve Baker in the UK and the current Moss sales prices. So, the question I pose is the extra stroke, forged pistons and lightweight rods worth the extra bucks? $1800 is a lot of money, but I don't want to end up regretting spending the extra cash if it will actually bring me a noticeable performance or reliability improvement. I am running the T9 5spd and a 4.3 differential, so perhaps the extra torque would really help on the mountain roads here in east Tennessee. Anyway, would really appreciate opinions from the experts on this forum.



Archie McAllister
1955 MG TF1500
68 Austin Healey Sprite

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Cambren Avatar
Cambren Cambren Davis
Hernando Beach, FL, USA   USA
Sounds like a fun decision to make. I am not am expert on XPEG by any means, but my one point is that I have not had good experiences with forged pistons in the past. I got some from a very reputable source for another type engine, and they were soft, allowing for rapid wear of the ring grooves. I have never had problems with cast pistons.



The truth is like poetry.........most people hate poetry.

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
Rats!.....I thought the XPEG had a tougher crank then the early XPAGs. I don't remember reading any reports of this happening to the XPEG crank.

Why do you suspect the need for Re-bore? Has it seen a lot of miles since last rebuild?

I like the idea of new Rods...just to get away from the Pinch Bolts. Not certain about the strok'n.......If I knew I had a Good Engine...I think I would Supercharge.

Good Luck Archie!.......At least the Driving Season is winding down. I'm assuming Tennessee uses Calcium on Winter Roads.

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LaVerne Avatar
LaVerne LaVerne Downey
Fruita, Colorado, USA   USA
1954 MG TF "Green Hornet"
1969 MG MGB
Easy decision on the crank... I bought a Moss forged unit 10 years ago for peace of mind. If I had to do it now I would go with the crank and rods that will take the MGB bearings as the new offerings available for the standard crank are not up to the task. MGB bearings should continue to be good as the market is considerably larger. The down side is that you will need to purchase new rods. I was never a fan of the pinch bolt system on the wrist pin so when I rebuilt my 1250 this spring I went with some pricey rods... and some forged pistons. Good decision???? I'll find out in the years to come. I'm not so sure about the longer stroke as these engines are already longer than what would be desireable I'd think. Manley is good to work with and he can give you some valid advice but keep in mind he may be thinking whats good for a track car, which may not be desireable on a street engine. Make sure you get one of his head gaskets...far better than the big boys offerings.

TD4834 Avatar
TD4834 Bill Chasser
Sacramento, CA, USA   USA
Wow that one really came apart. Hopefully it didn't stress the webbing in the block.

Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
Steve Baker may well also sell new conrods, even if not listed on his website, and he would give good advice on bearings. Brown and Gammons definitely sell new conrods (approx £850 per set with ARP bolts, before tax) and similarly would give good advice on bearings, though their crankshafts are a bit more expensive than Steve Baker.
Dave H

TD4834 Avatar
TD4834 Bill Chasser
Sacramento, CA, USA   USA
I have a set of B&G H beam con rods. I believe they are made by Phoenix.

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ArchieMcAllister Avatar
ArchieMcAllister Silver Member Archie McAllister
CLeveland, TN, USA   USA
I am taking the block to the machine shop today for thorough cleaning and crack check. Apparently a small piece of debris got into #1 cylinder during the crank failure event and I have a small scratch in the cylinder wall. The engine was bored to .040 over during the last rebuild. I have my fingers crossed that going to .060 over will take care of the scratch. Lavern, your comment about the availability of good quality rod bearing s for the XPEG/XPAG engines is exactly what Manley said. Looks like the extra cash may well be worth it. Will keep you posted on any other damage found by the machinist.



Archie McAllister
1955 MG TF1500
68 Austin Healey Sprite

damnfingers Avatar
damnfingers Silver Member Gene Gillam
Saucier, Mississippi, USA   USA
I’ve got Manley’s crank, rods and pistons in my XPAG...money well-spent and quickly forgotten...do it.

As for the XPEG crank being stronger than the XPAG...heavier, not stronger. Vintage racers often swap their XPEG cranks for XPAG to reduce rotating weight.

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crankjournal Len Fanelli
Yonkers, NY, USA   USA
Gene what crankshaft ID numbers are cast on the XPAG XPEG cranks you are referring to?
Archie What crankshaft # is cast into your broken crankshaft?
IMO a stroker crank results in more Torque, not high RPM HP.
Len Fanelli
Abingdon Performance LLC.

ArchieMcAllister Avatar
ArchieMcAllister Silver Member Archie McAllister
CLeveland, TN, USA   USA
Len, the casting numbers I found on my broken crank are rather obscured at this point, but here is what I found.
Between rod journals #1 & #2 - ESCM21A
Between rod journals #3 &#4 - 168557

As for performance, I would opt for a bit more torque and not really worried about additional high RPM HP.



Archie McAllister
1955 MG TF1500
68 Austin Healey Sprite

crankjournal Len Fanelli
Yonkers, NY, USA   USA
Thanks Archie, the 168557 crank is the later & stronger one! Often referred to as the 100 ton crank.
I believe it is the strongest T type cam made by MG.
Historically long stroke with a small bore has a lower peak RPM, with more low end torque, than a short stroke, large bore engine of the same displacement.
Len

damnfingers Avatar
damnfingers Silver Member Gene Gillam
Saucier, Mississippi, USA   USA
Len,

My bad...brain fart time. I should have been referring to connecting rods, not crankshafts. The TF connecting rods are heavier than the TC/TD which are preferred by the vintage race crowd..

For the record though, the earlier crankshafts (TB/TC/early TD) are 168628, the later TD/TF crankshafts are 168557.

I apologize for the confusion.

Gene

ragtc Avatar
ragtc Bob Grunau
Mississauga, Ontario, Canada   CAN
TB/Y/TC/early TD connecting rods are numbered 24005.
Late TD and TF rods are numbered the same 24005 in small letters and appear slightly more slender and are a bit lighter.
XPEG TF1500 rods are numbered 168559 and are noticeably heavier and beefier.

I happen to have a set of four matched XPEG 1500 rods for sale as well as several sets of standard 1250 rods.

Nothing wrong with any of these rods for normal use as long as the pinch bolt is properly torqued and new big end bolts are installed. I use grade 12.9 Metric Allen head pinch bolts for ease of installation.
Now racing, and high revs, is a different story. I raced my TC for 10 years using Phoenix rods and crank with MGB sized rod journals. I often hit 7200 RPM and the odd burst to 7500 RPM. Don't do that with standard parts and expect them to survive long.

Using original crank and rods I would recommend not going over 5000 or 5500 RPM with a cruising range of 3800 to 4200 RPM. Remember these engines were designed to rev freely and not slog along at 3000 RPM or below.
Bob Canada

ArchieMcAllister Avatar
ArchieMcAllister Silver Member Archie McAllister
CLeveland, TN, USA   USA
Thanks for the info Bob. I am going with a billet crank and new rods and pistons this time. Probably will go with the crank and rods that are sized for MGB main bearings. Although I don't plan to exceed 60000 revs, I do go past 5000 from time to time and I do drive the car quite a lot. It has been very dependable for over 30 years, but having to come home on a rollback twice in the last two years has convinced me to put all new metal in the lower end this time.



Archie McAllister
1955 MG TF1500
68 Austin Healey Sprite

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