The author’s (Bernie Wood) TD and TF at home in New Zealand
Well, it has been an interesting time! After breaking numerous rocker pillars and not having found any definite answer, it was time for “off with her head” – then, all was revealed. The inlet valves had been hitting the block.
This Laystall head, purchased new about 12 years ago, was a special-order high compression head.
But it seems that instead of leaving the head thickness standard and machining the chambers to suit, they appear to have kept the chamber area roughly the same and not sunk the valves in as deep and maybe machined the head. Thus, when fitting a high lift cam there was not enough clearance for the inlet valves as shown below. This was a so-called original head, the second one I purchased was from a refreshed mould and used 10mm ¾” reach plugs rather than the original 14mm ½” reach. How this effected the machining I don’t know.
Measurement with other my heads as comparison.
Laystall Oval Round
Head Head Head
Thickness 73.7 74.7 74.8
Depth Plug 11.4 13.2 14.7
Opposite 7 9.2 8.4
Centre 8.55 12.4 12.7
I read somewhere that Laystall heads were 75mm thick but I cannot verify this, I suspect it may have been 76mm as per a standard head. The critical point is just off the centre line where I get a depth 8.55mm, that plus 1.14 for the gasket, gives 9.69mm, not enough for a 10.5mm lift cam.
Not knowing quite what to do, I tried contacting the supplier but they did not answer my email. I do recall that at that time George Edney was manufacturing the Laystall heads, but he has had no online presence since 2010. There was some talk that Peter took over but then he had that big fire, so I doubt any records exist.
Ed’s note: withreference to the above paragraph please see the explanation of the current position at the end of this article.
I decided in the meantime to fit the original TF steel head, this was still dressed with valves and springs, so I had to pull the high rate springs off the Laystall head and fit to the steel one. No problems were noted and the engine was reassembled.
Everything was set up and off down to the testing station for its WOF (MOT) and about 3km there and back. A couple of days later I had time to go for a longer drive, got 800m up the road and the car just died. With a combination of rolling down hill, pushing and a tow it was back home and investigating again. Turned out no 7 valve was stuck wide open, off with the head again to find the valve stem had a slight bend at the top, not enough to worry at standard 8.3mm lift but enough to catch at 10.5mm lift.
Replacement valve ground in, engine assembled again, fired up and not running properly, with all the on and off’s I had managed to upset the front carb jet so it was jamming on the needle. Sorted that, then we had thunderstorms so a test drive had to wait a couple of days. Finally got in a 5km run before the rain came back and looking good so far.
Hurray some sunshine today! Out for a 24km run to the local Jaycar electronic store for some hi-fi parts. Running good up to the speed limit of 100kph, unfortunately quite a bit of traffic so no performance runs. When I got home, I pulled the plugs to have a look and found them porcelain white, just like what had happened with the TD. The standard GJ needles were not rich enough. Another wait while I got a pair of H1 needles, I should have realised this and ordered a pair in advance.
It would seem from comments I received after Part 1 was published that modern technology let me down. Either there was a problem with the app I was using on my iPhone to do the acceleration tests, or I was not using it correctly. The results it gave for certain measurements was not correct and I did not notice, so sorry for that.
I have repeated the runs and obtained better data.
Performance figures, purely as a comparison, single runs one way, no accuracy implied. These were done on the flattest straight piece of road I could find near me, maybe when the MGCC has its next drag days I can get some proper numbers in a controlled environment. After multiple runs, I could not get a standing ¼ mile time that made sense.
0-60 km/hr 05.0 sec 07.0 sec
0-60 mph 14.0 sec 17.0 sec
0-100 km/hr 15.0 sec 18.0sec
Well, what started out as any easy swop out turned out to be a nightmare. What I have learned (again) is don’t assume anything, as in measure twice cut once. The installation on the TD went so smoothly, I expected this one would be the same, how wrong could I be.
Now I have got the car back together and running, I am not going to do anything to it for a while. In March we have the New Zealand Pre56 Rally in Blenheim, so it is needed for that, it will get a good work out going from home, just north of Auckland, to the ferry in Wellington in one day, only 661km.
When I get back and winter sets in, I will be refitting the Laystall Head with a 1.2mm decompression plate which will give it about 9:1 compression ratio. Not sure about the 4-branch manifold as I haven’t done any further work on the pinhole leaks. I also have a 4.55 crown wheel and pinion to install and will probably do that at the same time.
Would I do it again, probably yes, all the dramas with flat tappets and worn camshafts hopefully gone forever. Only time will tell.
Aren’t old cars fun.
Ed’s note: Bernie mentioned George Edney and thought that he has not had any online presence since 2010. George is at ‘XPAG Engineering’, whose website is https://xpagengineering.co.uk
The Home page of the website says, under ‘Parts supply and manufacture’,…….
“We are the manufacturers and suppliers of the Laystall Lucas aluminium cylinder head.”
An email to info at xpagengineering.co.uk should find George.
Bernie also mentioned Peter Edney. Peter’s company is Classic Performance Limited and the website is https://www.classicperformanceltd.com
This period advertisement was included in the August 2020 issue of TTT 2 (Number 61), which also reprinted period road tests by Autosport magazine and Road and Track of a TD fitted with a Laystall Lucas head.