Finally some good attention to these Forgotten heads that many Jaguar XJS owners with their V12 dream of making them into the powerful Engine that deserve to be can’t Wait.
This chamber was very successful. Made the Jaguar V12 a long production engine like about 25 years or more long. The HE combustion chamber is but 1 part of the HE package. The design allowed a very lean mixture past peak EGT. High compression was another part. Bosch (Lucas labelled) fuel injection was another part, a tall rear gear ratio another part and a GM HEI (again Lucas labelled) another part that had the required punch to ignite the lean mixture. The system was a more sophisticated Mopar ELB with the lean burn baked into the combustion chamber and piston design. At full throttle the system ran regulation A/F ratios. To give you an idea of how good they were when set up according to the book - I say that because idiots who had no idea how to read, had no mechanical aptitude or understanding of basic mechanical principals - would start changing things when the engine started stalling or running rough. So when set up back to factory, they would get about 21 IMP gallons (not USG) to the mile. The HE still had more power than a pre HE at WOT. Here's the thing, the pre HE is a far nicer engine for performance. A pre HE revved up is unbelievably smooth, it's just the early injection system wasn't great. Also many pre HE's had 3.31 rear ends the HE had 2.78 or something. The pre HE had very heavy pistons too. The weight of them was ridiculous. I'd love to see what DV might do to a pre HE head. Pre HE heads are called Heron heads. As you mentioned they're just flat. The combustion chamber is bowl in piston. Be interesting if DV could come up with a piston and porting for the pre HE. People have generally found the HE head doesn't respond very well due to the recessed exhaust valve. Gains made tend to move the torque band around rather than increasing power production past 350hp. This was found by Jaguar who introduced the 6 litre HE in the 1990s and that really was the pinnacle. It had torque below 2500rpm, whereas the both the 5.3 pre HE and HE were pretty gutless until the rpm went over 3000. Part of that was the weight, the other the rear gear, the other the turbo 400 in them and the other part was heavy pistons. I'm sure with the DV treatment the limitations we mere plebs can attain from the HE will be surpassed. You see, the pre HE is comparatively easy though getting NA power over 400-450 from a pre HE is still pretty difficult. It rises to that range then after that it is the law of diminishing returns ie the large amount of money spent starts to yield smaller and smaller returns.
If I remember correctly, weslake was involved in the design of the head. The exhaust port actually reminds me of a Ford side valve v8. They were that flat on both intake and exhaust
Since we are on the subject... Im running a set of endyn "soft dome" pistons i.e. Larry Windmer,they are in a air cooled VW thats 13:1 on pump gas . That HE head used the same principal and 12:1 on premium fuel!!
In the phone pics what is the 3B 4B and 5B about looks like different chambers? I would like to see the total setup on the non HE heads and piston. The diesels do great on fuel economy so interesting that they could not adapt that similarly to gas.
Michael May "fireball" head. Originally, it was supposed to center the swirling charge over the exhaust valve and spark plug at tdc to make for a rapid burn. The idea works, but I am not sure they did it to the full extent at Jaguar. I think Group 44 used the Heron head (chamber in piston) design for more flow and outright hp.
Michael May is an amazing guy who started turbocharging road cars in the early 70s. He‘s born in Germany but lived in Switzerland most of his life. He sold most of his stuff here in Germany an was well known under his companys name „May Turbo“. He started racing in the 50s and won early races by just installing a movable rear wing to be able to drive with much higher corner speeds. No one back then knew about the advantages of wings until he used it on his Porsche 550 and was faster than the Porsche factory team. Porsche made a protest and even if there wasnt anything about wings in the rulebook, they banned it because May was about 4 sec faster per lap as the factory Porsche. He is still alive, now 90 years old!
Finally some good attention to these
Forgotten heads that many Jaguar
XJS owners with their V12 dream
of making them into the powerful
Engine that deserve to be can’t
Wait.
It should be fun! Thanks!
This chamber was very successful. Made the Jaguar V12 a long production engine like about 25 years or more long.
The HE combustion chamber is but 1 part of the HE package. The design allowed a very lean mixture past peak EGT.
High compression was another part. Bosch (Lucas labelled) fuel injection was another part, a tall rear gear ratio another part and a GM HEI (again Lucas labelled) another part that had the required punch to ignite the lean mixture. The system was a more sophisticated Mopar ELB with the lean burn baked into the combustion chamber and piston design.
At full throttle the system ran regulation A/F ratios.
To give you an idea of how good they were when set up according to the book - I say that because idiots who had no idea how to read, had no mechanical aptitude or understanding of basic mechanical principals - would start changing things when the engine started stalling or running rough. So when set up back to factory, they would get about 21 IMP gallons (not USG) to the mile.
The HE still had more power than a pre HE at WOT.
Here's the thing, the pre HE is a far nicer engine for performance. A pre HE revved up is unbelievably smooth, it's just the early injection system wasn't great. Also many pre HE's had 3.31 rear ends the HE had 2.78 or something.
The pre HE had very heavy pistons too. The weight of them was ridiculous.
I'd love to see what DV might do to a pre HE head. Pre HE heads are called Heron heads. As you mentioned they're just flat. The combustion chamber is bowl in piston. Be interesting if DV could come up with a piston and porting for the pre HE.
People have generally found the HE head doesn't respond very well due to the recessed exhaust valve. Gains made tend to move the torque band around rather than increasing power production past 350hp. This was found by Jaguar who introduced the 6 litre HE in the 1990s and that really was the pinnacle. It had torque below 2500rpm, whereas the both the 5.3 pre HE and HE were pretty gutless until the rpm went over 3000. Part of that was the weight, the other the rear gear, the other the turbo 400 in them and the other part was heavy pistons.
I'm sure with the DV treatment the limitations we mere plebs can attain from the HE will be surpassed. You see, the pre HE is comparatively easy though getting NA power over 400-450 from a pre HE is still pretty difficult. It rises to that range then after that it is the law of diminishing returns ie the large amount of money spent starts to yield smaller and smaller returns.
Great info! Thanks!
Wow, first an awesome series on TBI swirl ports, now a Jag V12. Sweet!
Looking forward to Mark coming out with lots of cool Jag parts!
If I remember correctly, weslake was involved in the design of the head. The exhaust port actually reminds me of a Ford side valve v8. They were that flat on both intake and exhaust
,,,,,,,,,,,,,,,,,,can't wait to see how much you deepen that exhaust bowl,,,,,,and blend it .....,
I like the sunken exhaust area.
Since we are on the subject...
Im running a set of endyn "soft dome" pistons i.e. Larry Windmer,they are in a air cooled VW thats 13:1 on pump gas . That HE head used the same principal and 12:1 on premium fuel!!
Good info. Thanks
My wife thought I was looking at an owl.
🦉😂🤣
Interesting design, very different for sure. I’ve ridden in a couple of jags-and they pulled pretty hard for a full-size luxury car!
😂😂😂
ha ha! that's a hoot!
In the phone pics what is the 3B 4B and 5B about looks like different chambers? I would like to see the total setup on the non HE heads and piston. The diesels do great on fuel economy so interesting that they could not adapt that similarly to gas.
Mark may bring this head Saturday and explain it. Thanks
Wow, that is very different from our beloved v8 stuff, neato.😎👍
It is pretty cool! I like working on different designs. Thanks
Is the swirl in the exhaust stroke direction different from the intake stroke direction, as well as in every case?
If I understand your question? Yes.
Interesting concept .but undecided on how I like the design ..
I am with you.
Have you seen the pistons yet? Maybe they will need some work done to them also?
I haven't.
@@servediocylinderheads I added a couple to list
@markniblett4857 Thanks, Mark!
hi, what year is that cyl. head? or years it was used???
No idea
This could be educational.
I hope so! Thanks!
I'm just some flub on the internet - but that design looks terrible. Basically a "bathtub" style chamber with an extra bathtub inside. Hope I'm wrong.
Funny!
more jaguar head stuff f
@@overbuiltautomotive1299 D.V. has them, he said he would do a video on them finalized. Thanks
Michael May "fireball" head. Originally, it was supposed to center the swirling charge over the exhaust valve and spark plug at tdc to make for a rapid burn. The idea works, but I am not sure they did it to the full extent at Jaguar. I think Group 44 used the Heron head (chamber in piston) design for more flow and outright hp.
Stay tuned for part 2! Thanks
Michael May is an amazing guy who started turbocharging road cars in the early 70s. He‘s born in Germany but lived in Switzerland most of his life. He sold most of his stuff here in Germany an was well known under his companys name „May Turbo“. He started racing in the 50s and won early races by just installing a movable rear wing to be able to drive with much higher corner speeds. No one back then knew about the advantages of wings until he used it on his Porsche 550 and was faster than the Porsche factory team. Porsche made a protest and even if there wasnt anything about wings in the rulebook, they banned it because May was about 4 sec faster per lap as the factory Porsche. He is still alive, now 90 years old!