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I am taking apart an '88 H&E convertible. Selling most things but keeping a few things for myself. Specifically the engine and trans; the Delenair III; and a couple smaller odds and ends.
The hood is off and I got to thinking about keeping it as a spare. Then I got to thinking about the possibility of having hood vents added to it ala XKE style. These motors get wickedly hot it seems. Giving that heat somewhere to go just makes intuitive sense. Has anyone else done this? What is involved? About how much would it cost? They would obviously have to be somewhere that the drip rails needed for rainy conditions did not interfere with the intake manifolds.
I think these cars would look great with hood vents. JMO.
I've actually wondered the same thing, and have thought of doing it but didn't have time before getting the respray. However, if I recall correctly, I think Greg in France did an experiment and proved it didn't help with cooling while driving. The one benefit would be heat dissipation after shutdown, which alone might be worth it.
I routinely release the hood, take off my oil filler cap and pull the oil dipstick out a couple inches when I shut down to help the heat get out of the engine faster.
I suppose the aerodynamics would affect the ability of the vents to 'draw' air out at highway and above speeds. Placement on the hood would likely matter. Esthetically though two rows on the towards the outside of the hood starting about 60% back from the front with about 5 rows of vents about 6-8" wide might look really good...and help, even marginally, with heat dissipation.
I might make some inquiries to a few local body/custom shops and see what they think.
Correct I did do an experiment, and I thought to begin with that it made a huge difference, and posted that fact. Thereafter I had to do an about face and correct my first post.I found that in fact the first result was not repeatable and was due, I think, to an unusually cold summer morning. Sadly, as i would love some louvres but only if they did something, I proved that it made zero difference on the run. I did this by accurately measuring under bonnet temps with large holes cut in my spare bonnet, and those holes completely covered.
But, they did make a HUGE difference to under bonnet temps when parked after a hot run. I always pop the bonnet (hood) in these cases, but if you do not, under hood air temps stay above, repeat above, 80 degrees C for more than an hour! Opening the bonnet they drop within 5 mins. This is bad because it cooks wiring and rubber hoses of all sorts.
My measurements also proved that the air temp is hottest on the run just behind the radiator. A few pics of the test attached:
But, new readers may be interested to hear, what does make a HUGE difference to coolant and under bonnet temps, on the move, is unobstructed clean airflow into the radiator stack. I moved the auxiliary coil (Lucas cars only) and the horns, out of the middle of the airflow and gained more than 60 square inches of clean airflow. I also made a slot in the bumper to get better airflow to the radiator. These improvements reduced the time it took for the coolant to return to normal running temperatures after a hot stop (such as a jam on the motorway after a hot run, or a set of lights after a hot run) followed by a restart to cruising speeds from several minutes to under a mile. Horns and auxiliary coil before being moved out of the airflow
Last edited by Greg in France; 09-07-2020 at 02:50 PM.
Very interesting modification to add the extra grille in the middle of the bumper. More cubic inches of air has to be good.
If cutting vents and turning the metal looks to be prohibitively expensive I will consider cutting a hole like Greg did and inserting some kind of vents made to be functional off another model.
PS.....why is the little boy wearing a Ferrari hat? LOL
The bonnet louver inserts for the X100 XKR are a plastic type material and are separate from the steel bonnet.
You might find some good-used and fashion them into the bonnet?
wiring in your aux fan to a ten minute shutdown timer will do far more than hacking up the hood, it CAN be done and google can provide you with a few professionally done examples but the fan blowing for X time is far faster and better.
If your engine is scalding hot after shut down you need to asses the Rad, my car was egg boilimg hot before the new radiator core, now its of no concern.
If possible i would of matched the grille blade widths to more fit with the wiper grille but...not my car so ohwell.
Last edited by VancouverXJ6; 09-07-2020 at 06:12 PM.
Wasn't there an earlier thread on this and the conclusion was that the fitting of bonnet holes made no discernable difference to the temperatures. If it did l would have thought Jaguar would have fitted them as the did on the E type.
Although done right they can look good. https://www.jaguarforums.com/forum/x...-168215/page2/
That mod of Greg's makes me wonder how much better the UK Jag, with its long thin number plate that covers the bumper area only, is at cooling than the US or Japan Jag, where the number plates are squarer and project down to cover part of the lower grille. Air dam
That mod of Greg's makes me wonder how much better the UK Jag, with its long thin number plate that covers the bumper area only, is at cooling than the US or Japan Jag, where the number plates are squarer and project down to cover part of the lower grille. Air dam
Let us assume for the sake of argument that this discussion about how much number plates block air presumes the existence of a plate in the first place....
Front and Rear: Brown Front and Rear (exceptions): Black Rear only: Green
I wonder about the distribution of those states. A very heavy concentration in the Southeast and east of the Mississippi. The north and the "urban" coastal states (New England, DC vicinity, Left Coast) require them.
Personally, I wish I didn't have to use a front plate.
No surprise that the big brother states (northeast and west coast) require them. I'm surprised by Texas though. I lived in Ohio until the mid-90s, and they required them then. Glad to see they woke up. When I lived there, I had to remove the front plate on track days because it made a big difference on the Porsche 944T I was driving at the time.
Yeah, but Texas, Montana, Wyoming--the Rocky Mountain West in general, save those two bottoms ones require them, and they're not generally known for being "big brother" gummint-knows-best places. My working hypothesis for those states is that it increases the chance that at least one plate isn't covered in snow in winter or mud in summer....
SD SD
The answer is that it would make a difference, as the lower plate is partially covering the clean airflow entry to the lower grille. My belief is that clean (ie non turbulent) airflow into the radiator stack is a very important factor in allowing the radiators to cool effectively. When I relocated the horns and the auxiliary coil, it did make a difference.
Interesting about the turbulent vs. laminar flow. I wouldn't have thought it would have made such a difference. Unfortunately, the option of removing it is not available here.
At what speeds would this inflow become significant, however? Presumably not stopped in traffic, and at higher speeds there would be so much air being rammed through anyway. Some sort of medium speeds, I guess. Around town speeds, in other words.
My car gets on the warm side of the middle on two occasions: when sitting in traffic on a hot humid day (or stop-start busy roads), and, I have found, after I take it for a run somewhere, leave it in the sun, then drive back after say half an hour: there it will venture over the middle even on reasonably open roads. In other words, I can take it on a run to X, the temps will be bang on the middle (all times with aircon on full cold), but not bang on the middle coming back even on the same roads.
At what speeds would this inflow become significant, however? Presumably not stopped in traffic, and at higher speeds there would be so much air being rammed through anyway. Some sort of medium speeds, I guess. Around town speeds, in other words.
My car gets on the warm side of the middle on two occasions: when sitting in traffic on a hot humid day (or stop-start busy roads), and, I have found, after I take it for a run somewhere, leave it in the sun, then drive back after say half an hour: there it will venture over the middle even on reasonably open roads. In other words, I can take it on a run to X, the temps will be bang on the middle (all times with aircon on full cold), but not bang on the middle coming back even on the same roads.
SDSD
That is exactly why i decided to do something about the airflow into the radiator stack. I found that after a hot stop the time it took to get the needle back to its usual position was taking far too long. The reason for it, I believe, is that insufficiently clean airflow into the radiator stack will mean far less efficient heat removal. Enough to maintain the temps, but not enough to reduce them. The test I did was to unbolt the bumper and go for a test. The result was astonishing, coolant temps came straight down after a hot stop in a matter of a few hundred yards. My bumper slot is not as good a no bumper at all, but it makes a huge difference, and cooling, and temperature gauge watching, are just no longer issues for me. Speed is not the issue, even at high speeds in OEM configuration the airflow does not produce immediate coolant temperature drops. The pre-facelift XJS has all sorts of stuff blocking the radiator airflow, and that is the problem in hot ambient conditions.
Look at modern cars, they all have huge radiator intakes for a reason.
All well and good ramming it IN, but if cannot get OUT, oops.
Look above your transmissions, there was/is/might still be, a THICK sheet of foam insulation. Time has now released the glue, and most are sitting ON the transmission, which is all that is preventing that foam from falling out. Removing those remnants is simple, replacing it with the trans in place, NAH, not going to happen easily.
I used a THIN sheet of suiff from the local Hot Rod Supplier, way back in 1996, and the supplied Hi-Temp Glue. Still there, the Insulation, not that supplier.
That single thing made a HUGE difference to under bonnet temps, both running and when stopped.
Removing the trans fluid fiasco from the radiator 100%, added to the comfort. Trans cooler out the front, horizontally mounted behind the bumper, and like Greg, horns on each side.
2nd coil long gone.
Mesh main grille, and lower grille, we got waaaay too many large bugs to have those suckers open.
Sanden Compact A/C compressor.
Cruise bellows relocated outside the engine bay.
NO emissions stuff blocking air flow.
Cold Air Intakes from down just above the front lip spoiler.
All the "little" things that allowed this cat to survive in our Summers.
Grilles. Pedestrians last view. HA Trans cooler
Last edited by Grant Francis; 09-09-2020 at 08:02 AM.
09-07-2020, 01:27 PM
Hood vents
