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MG TD TF 1500 - Dry-deck and 8-port blocks

Hi Guys,
I am intrigued by the special XPAG/XPEG blocks made by the MG Factory. Is there an article or website which explains these? Or, can someone fill me in via this forum?

I have only ever seen one Factory dry-deck block. It was fairly inaccessible and I was dressed for a dinner, so I did not get to inspect it closely. I don't know if it had the extra casting and stud holes to make it usable with 8-port head. I am not sure if it was 1250 or 1466 cc

A friend has an 8-port head and matching XPEG block but that is not dry-decked. It has casting and holes to suit standard head AND 8-port head.

I would like to know which came first, and if the dry-deck blocks also had the extra casting and stud holes. Did any blocks have both features? Were they run in parallel for different purposes? etc. I would be interested in any information.

Cheers, Bob
R L Schapel

Tom,
You infer (in another thread) the dry deck blocks were (all?) 1466 cc. I have always assumed the blocks for 8-port heads were also 1466 because the one I have seen is. Where can I find answers to my questions in the above post?

You mention Don Martine. Are there any YouTube videos of him racing? Or old film of Ken Miles? I would love to see it if it exists.

Cheers from South Australia,
Bob
R L Schapel

Bob -I know a fair bit about EX176 engines (I have 3 of them), and gave a talk about them at the Kimber Fest a few years ago. As with so many things, the details and truth about their history are still a bit shrouded in the mists of time, and we have lost most of the factory workers who might be able to shed some light. There are many mentions of them in contemporary literature and more recent texts, but none really seems to capture the essence of the engines.

The long and short of it is that the EX176 engines (so named because they are listed in the EXperimental ledger as project # 176) have been variously called the prototype XPEG engine, an engine made for the Bonneville Land Speed Record attempt in 1954, a special racing engine, an engine prepared for the first Sebring race in Florida, and various other confusing and contradictory descriptions. So little is known of this engine that in a note to me, Neil Cairns wrote, “I have never heard of what you call the EX176 engine.”

EX176 engines are factory-made 1466cc engines cast without any cooling passages between block and head, for high-performance purposes. The Experimental Ledger entry for EX176 begins, “EX176: 72 mm bore by 90 mm stroke 4 cylinder 1466 cc TD engine for USA ”. These specifications – bore, stroke and engine size - match those of the XPEG, so one possible suggestion is that the EX176 is the XPEG’s prototype. The listing continues with this - “10.7:1 compression ratio... to run on 90 octane USA grade petrol.” The engine's itemized parts list continues with a cylinder head with 1/16" removed, oil cooler, and even fuel injection (but none has ever been seen or noted)!

Even what knowledgeable and involved MG people said IN PRINT in the 1950's about this EX176 engine is inexact and inconsistent. Perhaps most authoritatively, John Thornley in Maintaining The Breed, wrote, “Meantime a few blocks had been made by 'knife and fork' methods with bores of 72mm. These had passed into the hands of drivers who consistently raced sports cars, and for some few seasons the overbored XPAG powered the majority of successful racing sports cars in the UK.”

Ken Miles wrote in Road and Track for December, 1953 about the engine in his R1 Special, “For the benefit of many enquirers, the origin of the various parts... is as follows: Engine, except for the block and detail modifications to the lubrication system and camshaft, the engine is stock Mark II, retaining stock crankshaft, bearings, valves, valve springs, rockers, cam followers, etc.” Despite what he says, his engine WAS an EX176 engine, and he is disingenuously describing the EX176 block.

And Gordon Whitby wrote in his Earning the American Dream, “Because of Ken's connections with Syd Enever, Chief Engineer and Designer for the MG Motor Car Company, we eventually received a spare racing engine with a displacement of 1,466 cc.” This engine is neither “a modified Mark II,” an overbored XPAG", or a “hopped-up TC engine”, as another wrote.

The majority of these engines - clearly destined for the US market, came through Ken Miles, an ex-pat at Gough Industries in Los Angeles, who built what was known as R1 with the help of three Gough mechanics. He began work in late 1952, using an EX176 engine with carbs mounted on a flipped manifold for a lower bonnet profile (I have one of these set-ups on one of my engines). The engine is described in a book about Miles as, “... a special 1500cc supplied to Gough by the factory.” With this remarkable Special Miles won all 10 of the under-1500cc races he entered in 1953, and in the OVER 1500 class he placed first once – against Ferrari, Lincoln, Porsche, Kurtis, etc., and similarly fast cars – second three times, and third and fourth, once each. For an under-1500cc car, that is extraordinary performance! Miles was a superb driver and racer with an EX176 engine! When he sold R1 in 1954, he sold it without this special engine which produced almost 100HP at 6,800 RPM; Cy Yedor, who bought R1 engineless, wrote, “I had Bud Hand [my mentor in Los Angeles in the early 70's] build me an engine; it was good but not as good as the special factory engine that was in it when Ken drove it.” Both of Miles' MG powered cars survive today, owned and occasionally raced by the brothers Hart in the Pacific NW. Right out of the crate these engines produced 81HP at 5800 RPM, using the AEG122 cam, and without further modifications, according to factory information sheets!

The engine is a “dry-deck” engine – that is, there are no water passages between block and head – meaning that no head gasket is necessary. These engines have only holes for the head studs. How, you might ask, was coolant moved through the block and head? A stock water pump circulated water in the normal manner, except that instead of a rear core plug in the right side at the back of the block, a drilled and threaded pad was cast to which an elbow was attached, pointing back and upwards. Another elbow was bolted to the back of the head with an elbow pointing down and forward, and a length of radiator hose connected the two. This dry-deck arrangement offered slow circulation inside the block, and fairly fast circulation in the head, where it will do the most good. Also, there are no water passages for hot gas to blow into, and hence no formation of steam pockets.

On many standard XPAG racing engines the head would actually lift off the block under high compression and deceleration, either blowing head gaskets, or making it possible for coolant to leak out, and possibly enter the engine cylinders – a disastrous combination. The EX engine used NO head gasket at all, heavier cylinder head studs, and closely-lapped head/block mating surfaces, which was a technique that MG had perfected in the 30's with the R-type engine. This would enable the engine to run a much higher CR (the EX register lists 12:1 pistons) without fear of blowing a head gasket. Jimmy Cox, an apprentice in the Competitions Department in the 50's reported that it would usually take him 14 hours to lap an EX176 cylinder head to its block using increasingly-fine grades of valve grinding paste, and that the seal was as close to perfect as humanly possible. I have also seen factory photographs of apprentices diligently doing this lapping work to MGA heads and blocks for their 1959 Bonneville LSR attempt. I have spoken to California racers from the 50's who remember seeing Miles running after dusk, where on deceleration before a sharp corner, the cylinder head would STILL lift a small amount, allowing dramatic combustion flames to shoot out the head-to-block joint on every lap! This could ONLY happen if NO head gasket was being used.

The remainder of EX176 engine internals were largely stock, but with free-floating piston pins. Miles was also on the crew when Capt. Eyston took an EX176-equipped streamliner to over 153 MPH at Bonneville in 1954. It appears that while a few EX engines have been found and used in the UK, the majority of the 12, 16,18 or more engines made (depending on whom you believe), came through Miles - Kvell Qvale reported that Miles had never been paid for his work on the team, so he "liberated" the spare Bonneville EX engines for his own use. This seems unlikely, as that is a LOT of spare engines! Based on engines I have traced, I believe there were somewhere between 30 and 50 blocks cast - one of mine is in a street TD and one is NOS; the third was raced in the 50's in a Lotus. One final sobering point: – presumably after they were no longer really competitive - in the March, 1956 Hot Rod magazine, it was stated that one could buy an EX176 block from Gough Enterprises for $150, and a head for $60. Those were the days.

I am afraid that little is known about 8-port heads, although there are some out there - I have one.

I'm happy to answer any questions about these off engines.

Tom Lange
MGT Repair
t lange

Here's a link to a jolly YouTube bio of Miles; it's not !00%, as, for instance, they show a picture of R2, The Flying Shingle, while describing Miles building R1.

https://www.youtube.com/watch?v=vyRuvpbLIdU

Tom Lange
MGT Repair
t lange

Excellent write up Tom. Thank you.

Tim
Timothy Burchfield

Fabulous Tom. Very much appreciated. I have learnt a lot from your post and the video. I will be printing the post and watching the video again for sure.

So it seems the EX176 blocks were earlier in the mix than the 8 port heads. My knowledge of the 8-port head story is limited to what I heard about 50 years ago. In the mid 1950s a South Australian named Brian Wright converted a standard head to 8-port (still using the standard stud placement). He wrote to the factory (I'm not sure if he knew they were trying it too). The Factory reply said they were experimenting with 8 ports but were canning the idea because they were concentrating on the MGA engine. They sent Brian Wright an 8-port head at no cost as they had no further use for it. Brian then wrote back and bought a block to match. These parts were never put into an engine. In fact Brian Wright, who was building a very innovative TC Special did not ever complete the car. The unfinished car and aforementioned parts sat idle for many years before being bought by a friend of mine who completed the car a few years ago. He fitted a conventional XPAG engine and Brian's "home-made" 8-port head to get the car going, but still has the Factory special parts. His special factory block has extra stud holes (allowed by the extra metal suitably cast) so it can be used with both types of head. It is not dry-decked. There are a few 8-port heads about but we never seem to hear about the matching blocks. I am guessing that there are a few about and owners might not even know. The heads were only usable with modified manifolds etc but the blocks could be used for any 1466 engine. Probably the reason Brian Wright had to buy the block.

I dry-decked my race engine in 1995 because it used to lift the head exactly as you described. I naively thought I had invented the idea because I had never heard of it. However, a second reading of "Maintaining the Breed" a few years later revealed what you said about the factory doing it. I had only read the book once before, when I was about 16. Not much is new in motorsport!

Thanks again for your information. It is great!

Bob
R L Schapel

It seems to me that with the head lifting there would be a chance iof torching either the head or block. Yes/No?
W A Chasser

Gentlemen, about a million years ago when Colin Chapman was developing the Lotus MkVI he had made a small batch of 8 port heads for the XPAG engines he was tuning for his cars. I had the chance to work on one of these heads a few summers ago in the UK, with Steve Baker on one of his Q-Type TA specials that we had fitted a supercharger to. The 8 port head was poorly cast of dead soft aluminum (probably recycled) with the intake ports on the ignition side of the block/head. It used standard size valves with a Weslake inspired combustion chamber shape. It was all we could do to keep it on the block as it leaked coolant everywhere due to the poor casting and suspect machining. It looked very much like a cross-flow Ford Kent head. I seem to remember that it didn’t seem to make any additional power over a massaged iron MG head. It did look VERY racey though. Steve told me a while back he knew someone who was now casting new ones with proper alloy and machine work. You could contact Steve at Steve Baker MG’s if you wanted one. A firm grasp of one’s wallet and respiration when you learn the price though.
T A Peddicord

Bill, I would have thought so too, but the leaking gas only leaves a black carbon witness. I imagine there is not a huge blast across the surface but more of a slow leak, which is not enough to damage the surfaces. I lap the head to the block but I need to run a thin decompression plate of solid aluminium. My engine still lifts the head and leaves the black witness but it doesn't seem to have any effect on anything else as it is dry-decked. When I get time I should take a photo of an old decompression plate. This engine is 25 years old now (although the head has been off four times). It still "goes like hell" and is very reliable.

T A, I didn't know about those heads. Sounds like they were cross-flow. I learn a lot from this forum! The Factory 8-port heads were cast iron. They had the Laystall style combustion chamber shape (radiused out on the intake side of the plug hole etc.). Laystall heads were alloy but had port configuration on the same side as originals. Thanks for that information.

Bob
R L Schapel

Was there a specific casting number for an 8 port head? Any pics? PJ
PJ Jennings

This is an image of my friend's 8-port head. 627/507 is the number


R L Schapel

This number is cast in the centre top. 762 4B4.


R L Schapel

Notice the different combustion chamber shape. It is similar to the Laystall. I reshaped my road TC cast iron head to this shape nearly 50 years ago.


R L Schapel

Sorry, This is the best image of the special block number. Is it the same as an "ordinary" XPEG? I think it is AEF 117. My other images are even worse but show the A better.


R L Schapel

This thread has provided me with some fascinating information. I had heard "things" to the effect that the XPEG was originally a factory race engine that was then put into production when the TF's sales were so poor that the 1500 was needed to move them off the sale floor. It now seems like that was only part of the story and the EX-176 engines were actually a precursor to the XPEG, with the same bore and stroke but with the dry deck feature as well.

I love the Ken Miles angle. He is best known as a driver (especially after the recent movie) but the engineering that he put into R1 and especially R2 was really innovative and very well done.

Thank you all for sharing.
Jack Long

Yes, Tom's detailed post, which mentions EX176 being used in 1952 put it all in perspective for me too. I have printed that post and read it a couple of times. More sinks in each time I read it. I have watched the video a couple of times too. I didn't know much about Ken Miles until the recent Ford v Ferrari film and watching the video. Being so far away, in Australia, was perhaps the original reason, but with modern internet and forums like this, there is no longer any excuse!

Tom mentioned the Hart brothers. Is there any video of them racing?

I was unaware of the factory dry-deck system when I did my race engine. Hence I used my own design. I have coolant exiting the core plug at the very rear of the block, straight up to the rear of the head. Due to the complex water flow of the XPAG, I had to drill large holes behind the two core plugs on the side gallery to let coolant into the area around the bores, so it could get to the rear core plug. I added a threaded brass plug in the middle of the water gallery too, so I could drill behind it. In that way I get coolant flow on to the exhaust side of each bore (although I know it is probably not necessary). I also added a small tube from high at the back of the block to the rear of head to prevent any air pocket high in the block.

Come to think of it, how did the EX176 blocks get water to that region so it could exit at the "pad"?
Bob



R L Schapel

An image of the rear of my block/head, showing main hose and "anti-air-pocket" hose.
Bob


R L Schapel

Bob
Slightly off subject but not--
What sealant are you using with your aluminium headgasket-
I ask because I used an aluminium gasket on my B series powered midget and kept melting the gasket out---"everyone" had said use hylomar on it but it was the hylomar that was the problem
I ,luckily ran into an old motorbike racer mate and got talking about the problem and he laughed and said non of that non metal based sealant will be any good, use silverfrost or some other metal based sealer
The theory behind his thinking was that the sealer was insulating the gasket and not letting the heat sink out of it
So I got on the net and searched around and came accross copperkote- Gave the gasket a light spray on both sides, just enough to colour it, then a really really light mist on the head and block and as soon as it got sticky'half dry' whacked it together and the problem went away-----happy boy

willy
William Revit

Hi Willy,
That is interesting! I use Hylomar but only a narrow strip around the combustion edge. I don't need it out further because it is dry-decked. I have often wondered if I should use nothing at all! I do lap the head to the block. The decompression "gaskets" I use I make myself in batches of about 4 sheets of body alloy glued together with contact adhesive and cover both sides of the "pack" with cornflakes cardboard. (to mark the shape and protect the alloy) Once cut, drilled etc I soak in turps until they fall apart and then de-burr. These "gaskets" measure up as consistant thickness but they still might be a source of slight inaccuracy compared to the lapped surfaces.

Thanks for the tip. I must track down some Coppercote sealant. Maybe I will use that next time.

BTW, Have you seen these films? DIlAm1CQgv4 and DVmvThP4JP4 Just copy and paste to Google or YouTube. Is there any similar film you know of which is not already listed under the "MG Motorsport" subject heading? I look in YouTube but either there isn't much similar about, or YouTube is a big haystack in which to find the needle.

Cheers, Bob
R L Schapel

This thread was discussed between 20/02/2020 and 26/02/2020

MG TD TF 1500 index

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