\'68 E-type Roadster

My '68 1 1/2 roadster has a crossover pipe running across the back of the engine (over no.2 cylinder) from the intake manifold to the exhaust manifold to (I assume) warm the intake Manifold for effeciency and smog purposes. I noticed that this crossover has been eleminated in the l969 and the intake manifold capped off. In l970 the crossover reappears on the 4.2 engines but in a different place (acroos the middle over no. 4 cylinder). Why the changes--could it be heat produced by the '68 placement of the crossover? What are your ideas on this. Anybody know why the changes.

Submitted by NE52-32043 on Fri, 09/24/2004 - 16:31

Guy,

Hot running is often the result of the mixture being too lean. If you haven't done so, do the carb adjustment per the manual to assure that you are running the right mixture.

Also, a few things you should check:
1. Check your hoses, especially the return hoses from the radiator to the water pump. If the return hose is soft, it can get sucked closed while running and cut off flow. Replace it if there is any question about its condition. Even when the top hoses have been changed, the bottom hoses are often neglected because they are more work to get to. If you squeeze them and they feel at all soft, change them.
2. Flush the radiator and inspect it carefully. Make sure it is not clogged. If it is, have it recored (not rodded out). Use a high efficiency copper core. Flush the block out while you are at it.
3. Change the thermostat and make sure that it is the correct thermostat for you car (i.e., that it will block the bypass and force the water through the radiator). An off-the-shelf thermostat from an autoparts store is not right. It must have the bypass shut-off that is correct for your manifold.
4. Fill your radiator/system with 50/50 quality anti-freeze (I like Prestone) and water, with a bottle of Red Line Water Wetter added.
5. Consider changing your fans/blades for a Coolcat set-up (www.coolcatcorp.com). NAYYY, just a happy customer who has the fans. They move a lot more air than the originals and are much more efficient at keeping the car cool. I have them on my '70 and they do a great job. I also have a Coolcat aluminum radiator, so cooling is not an issue even on really not days.
6. If all else fails, consider pulling off the water pump and checking the impeller. They do deteriorate over time and cavitation can damage the impeller and the block.
7. Re-tune the car and double check that the mixture is not too lean.

Hope that helps. If you do all that an it is still running hot..... Well, hopefully not.

Regards,
Steve

Submitted by guystarbrd@aol.com on Fri, 09/24/2004 - 02:26

\'68 E-type Roadster
THANKS EVERYBODY FOR SOME GREAT INSIGHT AND INFORMATION. CROSSOVER IS AS GOOD AS OFF IN HOPES THAT THE RUNNING TEMP ON HOT DAYS WILL COME DOWN AND GIVE ME THE CONFIDENCE TO TAKE ON SOME LONGER TRIPS IN SUMMER WHEN ITS NICE.
THIS "FORUM" IS A GREAT THING.

GSS

Submitted by NE52-32043 on Thu, 09/23/2004 - 10:00

My $.02 -- Remove the cross-over (unless you are concerned about being concours correct). It's worthless and only clutters up the engine compartment. You can get a cap for the manifold and close it off easily.

Steve Weinstein, JTC-NJ
'70 XKE FHC
'69 XKE OTS

Submitted by mfrank@westnet.com on Wed, 09/22/2004 - 21:11

Nope, this is incorrect. The original (rearward) crossover was NOT a water jacket connection. It actually routes the carbureted mixture over the hot manifold to promote vaporization. See photo.

Jaguar probably stopped using the system because it's (obviously)a pretty poor idea.

The interim cars had no crossover. Basically they had all the same fittings as the 1968,but with the holes dead ended. There was still some circulation within the manifold, and vaporization improvement due to heating from the coolant.

The final iteration added the "Detroit" standard setup of the day. A vacuum valve at the air cleaner inlet routes air over the exhaust manifold only when the motor is warming up. The "dead end" circulation of the interim design was also retained.

Submitted by jklein@genphys… on Wed, 09/22/2004 - 17:07

I can answer some of this:

The 1968 cross over is a WATER jacket connection which heats up the water with exhaust heat. The 1970 /71 setup is an air connection theat takes heat off the exhaust and routes that air to the carburators. It does this while you are cold via a vacuum operated flapper that shuts off the normal air inlet and uses the heated one from the crossover. BTW, this flow path also seem to have a considerably smaller corsssection as well so you are putting both hotter air and less of it to the carbs until you heat up.

Why the changes? I'm not sure. I imagine the first iteration, the water jaket heatup was a quick fix that they realized still added considerable heat after it was needed. The later setup shift back to the cold air intake path once you warm up. How and why 1969 got away with nothing I do not know?

That's my 2 cents worth.

BTW, the 1970 / 1971 cars do run much better when cold with the crossover setup intact and installed.

Jeff Klein
1970 SII OTS