Production of those was well under 1000 from memory.

 

Since there is no combustion chamber in the Pre HE head surfacing it will not increase compression any, merely loosen the timing chains.

 

MG wrong again, back to school! simple way to increase compression a little bit(any comp. increase i'll take it).

the PreHE factory head valves are RECESSED .050 deep into the head, that small chamber volume around the valves is reducing compression , look closely, so imagine when valve starts to open it has a small area of shrouding, and it only opens .375 anyway!
when the valves are closed the top of valve dont even reach the gasket surface level! anytime you do a valve job they will go deeper into the head= more chamber volume! BAD.

for my fix, i cut .050 off that surface and now stock valves are .050 protrusion above the surface(you followin here?). almost like .050 more lift! along with a GOOD thermal ceramic coating on surface including the roof of the chamber(dont want any heat escaping into coolant )

but the valves are also now taking up space in the chamber(more comp.). by now around 2 tenths ratio, hence my estimate of my 9.2 to1, with aftermarket Euro 9 to1pistons!
i bought new late redesigned pistons a curved bowl, so pressure will be centered in middle of pistons, also narrow low drag MOLY barrel faced rings!

my V12 also uses 3MM oversize inlet valves,(2MM exhausts), single piece forged Stainless steel ,ports are shaped and polished , bowls are carefully shaped for induced swirl into chamber!
latest valve flow testing indicates a 1/8" oversize inlet is like a 1to 2 MM higher lift cam some times more depending on other variables of the inlet tract! the larger valve head also takes up more chamber volume=more comp.

yes i am very familier with the curtain area of a valve, even when close to the cylinder wall,, big valves simply flow more air, period!

and i was concerned about the chain tension , but at engine assembly i examined it closely , and it looks to be a better tracking than factory, chain follows the sprockets with more contact,reduce wear!
BEEN 26 yrs so must be OK !

thank you OVER and OUT,, RON

i have many other modifications , porprietry at this time!

 

couple pix , lousy photography 26 yrs ago!

notice piston shape a bowl instead of flat bottom of bowl, latest designs today!

piston top bowl curved, not flat

 

Hi Ron, I’m aware and happen to agree with most of what you say.
The sole exception has to do with the recessed seat. The designers of the engine found additional horsepower with the seats recessed. Since they came from winning Formula 1 engine company Coventry Climax I’m inclined to believe them. Besides they actually had back to back numbers.
Im sure you’re like me you do everything you think will generate power put the engine together and then test it. I doubt you did the detailed back to back testing the factory did.

The only time I did back to back testing was porting. I hand ported one head ( and spent something like 120 hours porting and flow bench testing until numbers were somewhat similar.
Then I put the other head on my vertical mill and spent only about 30 hours doing it. At least 10 hours was calculating the proper XY axis to mill at To intersect the porting I did from the valve seats

Not only did I Same a lot of time but my flow numbers were significantly better.

 

MG , an excerpt from Walter Hassen about the danger of placing to much emphisis to air flow tests!

read last paragraph, do not place to much on air flow tests!!
Jaguar engineers found close to 10 HP, 12 lb.ft. torque all below 5500 rpm!

what you say!, this is out of the Jaguar book by Walter Hassen!

 

We read the same things. As for 10 horsepower, I’d rather have it than not.
I remember reading his comments about static airr flow tests. Especially the word Static. I don’t remember who explained it. But flow is meaningless by itself. More flow is only better if you can use it. At low RPM increased flow will cost you power.
However that was not the case with my first motor. I’d increased the bore and stroke so I was feeding more cubic inches. Plus as a race motor I was going to over 7500 Rpm by design. I was using Pipers camshaft for racing. Not a street motor at all. The springs I used ( From ( from Isky) promised to hold Over 8000 RPM without float. ( I wish I could remember details like seat pressure etc. lift and duration) Titanium was new back then and I didn’t know enough to be comfortable with it so I bought NASCAR SPEC Chevy valves and cut them down, something like 1.900.
Dale Earnhart ( sr) had Featherlite as a sponser back then. Featerlite had my customer put all the decals on the trailers So Dale got to know him. They both had Elk and once when I was there they were talking about how fast the Elk would eat away the top rail or two and then jump over it.
I spoke up and told them to use white oak instead of pine. White oak has tannins that taste really bitter to Elk and they won’t eat it. Once they tried it and found out that it works Dale was my buddy. He sourced the valves for me from his engine builder.

 

long story short , my oversize valves came from Grp 44 , suggested by Lanky ,chief engine builder for 44!
ron

 

Hi Ronbros,

I was just yesterday searching through the forums to reasearch info on this very subject and happen to see your question regarding 9:1 and 10:1 pistons. Presumably you have propably come accross a picture by now but just in case you haven't I thought I'd post this picture anyway.
I run a 1977 5.3 but have made some interesting engine mods in the 10 years since I built the race car from a standard road car. I upgraded the ignition and injection looms from the original 1977 to the 1981 P digital system. I also upgraded the inlets manifolds to Roger Bywater's High Torque manifolds together with the larger throttle bodies. the ECU was upgraded by Roger to use a 16CU ECU unit. The exhaust manifolds are tubular headers through two separate 6 cyl systems exiting either side just ahead of the rear wheels. Both air intakes have been cut off at the plenum and are fed throught the headlight box using 4in flex tubing. Air comes filtered by K&N filters.The diff is now 3.77 running through a 5 speed Getrag box. Last year running at Spa at the famous Spa 6 Hour meeting I ran a big end bearing. which was pretty good considering that I had been racing the car for 10 years with no issues at all. Probably a total of over probably 130 odd races, not including practice and qualifying. These engines are amazing. The latest figures |i had before the bigend let go was showing 328 bhp and 344 torques.
Searching Ebay for some bits and pieces I came accross for sale a set of brand new High Compression pistons still in their boxes. The engine has been rebuilt now using the 'new' HC pistons and has been slowly put together. Apparently there were only 360 10:1 engines prdoced by the factory. Looking forward to getting the car on the dyno for some new figures. Fingers crossed.
As you can see in the picture the 10: 1 piston is on the right. When measured with water the capacity of the bowl on the 9:1 is 23mil and the 10;1 is 13 mil. That's quite a bit smaller so should produce a little bit more bang!

Anyway I hope that this picture is of interest to you. Thought you might like to see a picture of my racecar on track.




Good luck

Regards
Paul

 

good find on the piston pix, thanks!
seems the pistons i use have a machined bowl shape ,not cast, so raises just another design , maybe Welsh Jaguar had custom made types?