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MG TD TF 1500 - Supercharger slowly degrades a Laystall head

I have heard that a modern supercharger installed on a xpag engine with a new Laystall head will over time totally degraded the head until it falls apart. Anyone have any info on this? And if true how many miles before this happens? THANKS. MICHAEL.
Michael O'Halloran

That's a pretty generalized statement

" totally degraded the head until it falls apart"

So in return a generalized reply would be "popycock".


Will the normal service parts (valves, rocker train, guides, seats) wear faster than a normally aspirated head with high compression? I would think not.

A super charger regardless of modern or vintage design is basically raising the compression of the engine but on more of a sliding scale. So if you don't have the engine under boost( foot to the floor) then the engine (if built correctly) would have a lower compression ratio in normal driving than a comparable performance built normally aspirated engine. Even if you run the engine hard all the time it would be no different than running a performance built normally aspirated engine.

I think who ever told you that statement should elaborate to exactly what they are referring to and back it up with some data.
L E D LaVerne

I agree with LaVerne,
I have a standard XPAG head and I have had a supercharger on it for the 10 years I have owned it. Since it was previously a vintage racer I am sure it had the old supercharger on it for many years. I converted to a modern supercharger six or seven years ago.
I have put over 25,000 miles on the engine and it has no "head" aches.
Mort
Mort Resnicoff

The question is specifically about the aluminum Laystall-Lucas head, and the effect supercharging will have on it. I would want chapter and verse, but can't see that the addition of a supercharger would have "over time totally degraded the head until it falls apart." Due to what force?

I would be more concerned with the excessively-high compression ratio when pairing a supercharger with a Laystall-Lucas head on a street engine. The primary stress on a supercharged engine is directly linked to the compression ratio.

With the Mirage Garages supercharger I sell we do not recommend a compression ratio much over 8.3:1, with a 6# boost.

But a stock L-L head on a STD-bore 1250 already gives a 9.3:1 CR, and an overbored engine (like to 1,466cc) will yield an even higher CR, no doubt in the 10's.

To my way of thinking it's just a matter of time until an engine with such hyper-stressed parts fails. It's all a matter of balance - CR against bore size, cam against piston, carbs against supercharger. But I suppose that for 22,500 GBP...

Tom Lange
MGT Repair
t lange

I have to agree with LaVerne as well. What specifically is meant by degrading the head?

Any performance modification will put stressors on any given engine that wasn’t engineered into the original design. Whether the increased stressors relate to a specific part or the overall package would be subject to great debate. But the debate would be folly unless empirical evidence were to proof otherwise. One such incidence doesn’t make for such a blanket statement.

The fuel load and the ability of the ignition system to burn a proper air fuel mixture would have a greater impact on overall longevity of individual components. The ability of the cooling system and the means of controlling combustion temperatures through correct fuel metering during all operating conditions would be the larger factor in sustained service life. If the fuel load is too fat it will cause carbon deposits to form which eventually will cause galling of parts with tight tolerance. Sticking valves, Black Death on piston skirts as rings wash out, high carbon particulates in the oil causing premature wear to bearing surfaces, etc. Lean mixtures causing increased combustion temps when left unmonitored or uncorrected leading to detonation and an eventual meltdown at sustained exhaust temps exceeding 1500° F. This is evidenced when monitoring exhaust temps by use of pyrometers introduced into the exhaust system near to the exhaust ports.

But to say simply that the use of a SC is the sole cause of degradation of any one component won’t make the case in any debate. There are multiple factors involved that will cause problems that are beyond the addition of a SC. Specifics as to any claim would be required before further comment.
W A Chasser

The only time I can see an issue is that if the comp. is as stated in the 10s on a 1500 and someone poked a supercharger on that like that then yes detonation would damage the surface of the combustion chamber but I would imagine the pistons would give up way earlier than the head
William Revit

Here is some evidence which suggests that there is no problem combining a supercharger with a Laystall head. Note that the heads mentioned below are original 1950s heads which had already had a hard life before I got them. New Laystall heads should be even better because they are made of better material.

My race TC has had a supercharger and Laystall head for 44 years. I have only had two engines in it during that time. The first of those two engines is still in reasonable condition, sitting in my shed, although I removed the head to prevent corrosion. The second of the two engines (fitted in 1995) is still in the car and still going well. The two engines now have 251 competition meetings between them! They include Historic race meetings (2 or 3 days with 3 or 4 races), Sprint meetings, Hillclimbs and, rarely, a "Motorkhana". I know that the engines have not done a typical highway type mileage, but the miles they have done have been VERY hard! 6500 rpm is my usual change point and I occasionally use 7000.

If you would like to hear an XPAG with Laystall head and supercharger, during that engine's 90th competition meeting (in 2014), copy and paste this code into YouTube or Google. DIlAm1CQgv4

Bob
R L Schapel

The only difference between a supercharged engine and a normally aspirated one is cylinder pressure. You could also say more heat due to more fuel exploding, but I've found that my supercharged engines run cooler than they did before supercharging, likely due to increased efficiency. So by "degrade" I have to assume someone possibly meant damage rather than corrosion.
Steve Simmons

Nice video Bob. Very impressive to say the lease. I get nervous in my TD at 5,000rpm's

Bill TD24570
Bill Brown

I've set up 3 XPAGs with blowers and my only concern is how well that extra mass is supported on the aluminum head.

My experience has been the dogs needed retightening frequently and I blame the heavy supercharged cantilevered out on the four studs. The intake/exhaust gaskets have failed a number of times. This has been simply an inconvenience with the iron heads, but I would worry about pulling aluminum threads out of the Laystall head. Running in some helicoils would be a smart move. Adding a support bracket wouldn't hurt. A lot of engines today have heavy duty support brackets for light weight aluminum & plastic intake manifolds with just a throttle body.

One of the first things I did to insure better clamping of the intake was cut some thinner 3/8" steel dogs with a robot so there were enough stud threads to add a locknut.

On the last engine, though, I cut some extra long studs for three reasons:
they could be bottomed out in the head using every thread available;
plenty of rod for double nutting the clamps;
enough stud to add an exhaust cover.

One of the shortcomings to supercharging an XPAG is the blower is located a fraction of an inch above the exhaust manifold, heating the blower as well as breathing in the scorching hot air.

I'm jealous of anyone with the Laystall crossflow ports where the exhaust is on the other side of the engine compartment.

I'm posting a photo of the S.Co.T. blower installation featuring a cover on the exhaust manifold. The cover is meant to provide a touch of insulation between the exhaust manifold and blower casing, but there's barely 1/4" of separation. It is also intended cut the temperature down under the bonnet. I've used thermocouples in the engine compartment and measured temps upwards of 250F at the fuel lines located to the rear of the exhaust manifold. I even covered the exhaust pipe with flexible stainless tubing, but it isn't very effective. My feet used to get burned in the passenger footwell until I finally insulated that inside and out. One last benefit to the cover is eventually, I intend to run the exhaust directly from the manifold into a catalytic convert and then a couple of flash boilers for a prototype steam-hybrid package.

My followup post will display the support bracket for the Italian huffer.



JIM N

I fabbed up a belt tensioner with an extension for a blower support. To each, his own.

JIM N

Hi Jim,
I have been running a supercharger on a Laystall head for about 45 years with no mounting troubles. However, I designed and fabricated my own manifolds and included lugs for support stays. One stay runs from under the rear of the pressurised manifold down to one of the starter mount bolts. Another runs from under the front of the manifold down to a bracket on top of the front engine mount. Stays for the drive pulley run to the same engine mount bracket and to a lug welded on to the fabricated water outlet. I used to drive the car on a very rough dirt sprint circuit named "Lanac Park" in South Australia. If it stood up to that it would stand up to anything! You can see how rough the track was by copying and pasting JOtAKn9Ri4U into Google or YouTube. It is very old copied film.

Bob
R L Schapel

Awesome video, Bob!

Not T-Type, but just to throw some ideas out there, here is how the Moss blower support arm works on a B-Series. I've modified things a little bit and I'm not quite done putting it all together, but you get the idea.

Steve Simmons

Looks great Steve. I see you tension the belt via the alternator .. very clever! The blower and pulley sizes look as if you will get a lot of boost. Good luck with the project.

Thanks for the comment. If you enjoyed that old dirt track video, you might enjoy a couple of more recent ones in the same car. I have put them in the "MG Motorsport" threads but here is a taste. DIlAm1CQgv4 is a fast track with a 3.7 diff and DVmvThP4JP4 is a tighter track with a 4.2 diff. To make it appropriate for this thread .. the car has a Laystall head and supercharger.

Cheers from South Australia,
Bob
R L Schapel

The tensioner is a Cadillac part that I adapted to the engine, because my other one is putting out so much power that there was nothing else I could do to prevent the belt from slipping. The tensioner worked so well that I'm putting one on this engine as well. I'm expecting about 9PSI max boost on the engine in the photo. Also, that's a generator not an alternator. I've converted the rear from bushing to bearing so it will handle the belt tension. Here's a photo. Obviously it isn't done yet or there would be a bolt holding the crank pulley on...


Steve Simmons

This thread was discussed between 09/02/2020 and 23/02/2020

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