Hey guys, I have a 77 xjs with the pre HE engine. I guy is parting out 2 xjs that he claims is from 77 as well, although he doesn't seem to know a lot about them. Are there any visual differences between the pre HE and HE engines? Or is it simply a casting code I have to go by?

With the low compression rate, I plan on picking one of these engines up if the price is right to twin turbo it on a stand to make it easier.

Cheers

 

As I understand things, one way to tell is by looking at the spark plugs. Pre-HE spark plugs are almost vertical; HE plugs go into the head at an angle, canted towards the centerline of the engine.

Cheers
DD

 

I think the biggest giveaways would be the fuel rail. If that is just a square section tube shaped like a captial D (seen from B bank side/left side of the car), it is at least an HE injection system...

 

Doug is right.

The HE have the plugs angle towards the centre of the V.

The PreHE has the 3 front plugs angled towards the front of the car, and the 3 rear plugs angled towards the rear of the car.

The square fuel rail is OK, but a lot were retro fitted with that rail a long time ago, so not as 100% as the plugs.

 

Thanks for the replies. Unfortunately, the guy selling did not tell me the heads were sold. Engine is fully apart minus the pistons, do you think the pre he engine is worth $150 for everything minus heads?

my plan was to build a coil on plug system with a new intake and twin turbo on a stand, and drop it in the xjs when it's ready. Without the heads I'm not sure if it's worth it even though pre he engines are hard to come by

 

Not worth having. better to look for a complete engine.

 

The ideal setup would be 1989 block with 1 piece rear main seal and flat heads., Although if you are going to turbo charge a HE would be a good start and easier to get hold of.

Reshape the chambers to low CR and improve flow. My modified heads on a 5.3L would have a CR of approx 8:1 with a flow increase at all lift points, with most of the increase at low lift.

These heads have a measured volume of 32cc with spark plug installed

 

Hypothetical but if one could acquire 'new' old stock HE parts exactly as seen in your picture for a couple hundred US would that be a worthwhile purchase? Totally new OEM in the box looks exactly like your picture.

 

 

These are not stock heads, they have had 100's hours spent matching ports, re-shaping chambers and de-shrouding valves. But for a couple hundred $$ if the heads are complete and new would be a worthwhile purchase.

All the sharp edges have been removed and the step around the intake valve laid back to improve low lift flow. The spark plug has also been de-shrouded. The bottom photo shows the intake valve seat with a 4 angle job to improve flow further.

Stock chamber


Modified chamber

 

Well not EXACT. I ment that exact engine component. I don't have the part number off hand but yeah a new set OEM for well under $1000.

Do you have any resources on the modification process? I've read about deshrouding but its like most things where everyone has an opinion on what is or isn't necessary. I've even run the question by Roger Bywater and found yet more confliction opinions on this level of modification.

I ask because I'm at the stage where everything less than a 5-digit repair bill is done and my straight piped car is performing flawlessly but I have this nagging feeling its not near the full potential. Next step could be things like this, I'm also looking at hydraulic extrusion to smooth/enlarge the intke runners before ceramic heat coating them to go with better exhaust manifolds...there are a few options they arr just abit pricey and deserve sober consideration.

 

Have a read through this thread, unfortunately thanks to Photobucket most of the pics are gone

https://www.jaguarforums.com/forum/x...-build-170908/

I built a flow bench to test before and after modifications as I modified the heads. I think page 12 has my findings with respect to the manifold.

When I flowed the heads they flowed the same at max lift as they did with no intake valve installed, so this would suggest that unless you install bigger valves (1.71" is about the limit in a HE) there is no point in opening up the intake ports or intake manifold runners. I also flowed the heads with the IM installed and flow did not drop outside of my uncertainty. A larger plenum is a MUST though and I do plan on making a larger plenum for the stock runners.

These heads were ported using the teachings of David Vizard. I was not planning on increasing valve size and I am running a stock camshaft. So with 6.7L we should have maximum power at or about 5500rpm.

 

Doing 1 thing in a stock engine is not necessarily going to make a big difference, so just de-shrouding valves in an otherwise stock head may not give results. My resource is a friend who has built a LOT of high performance Jaguar V12 race engines, I have followed his advice and listed below is what I have done.

His advice for a stock engine is to increase the size of the plenum with a 100mm square section tigged to the stock runners and the TB's moved to the front. If you open the engine to modify install the biggest valves you can get into the chamber. HE limits the valve size so this is where the power limit is with the HE engine NOT the pocket exhaust valve flow. The head will crack if the intake valve seat is too close to the step.


A list of what has been done to my engine.
De-burring and matching all the ports. These are NOT polished but left with a 60 grit finish to promote fuel suspension.
Tidying up around the valve guide.
Blending the seat into the bowl.
Modify the exhaust port to remove the horrible square bump.
Polishing the exhaust ports
Multi-angle valve job.
De-shrouding the valves and smoothing the chambers.
Much tighter squish due to piston coming 0.040" closer to the head.