1972 E-type series 3 with engine number 7P50617SB. The original engine was stolen and this one fitted. I think it is a later Heron head as when fitted with 6 Weber twin chokes the bonnet is 25mm proud and won't close. I still haven't got the engine to run properly as it is too rich with the supplied jets. That's why I think it is the Heron head. I am fitting smaller jets and have reset the static timing to zero. I will give it another go this week.
I am an accountant and not a mechanic, therefore do things after reading the instructions. I can't find anything on the internet regarding the dimensions of these later cylinder heads. Can you help
Thabks
Eric

 

You have the timing at 0 degrees? Why?

You are in the XJ6 XJ12 forum, but you are asking about an e-type. You would do better in the e-type forum where people may be familiar with this issue or the dimensions. I guess by heron, you are referring to the flat style pre-he V12 head and not an XK6 head because you mentioned 6 webers. Wasn't this flat head used on all 5.3 with OPUS until 1982? Why would the head be a different size then? Why should the bonnet close if you are fitting aftermarket carbs? Is this a kit that is supposed to fit or are these just some trumpets that came with the carbs?

I want to say the height from the head to the top of the trumpets in some kits is 200mm. How high are yours?

 

To my knowledge, the Heron head is a hemi head and not a flat head. Therefore the height dimension may be different from the standard flat head, resulting in the bonnet not closing. The 6 Weber downdrafts are a standard v12 kit and the filters normally fit comfortably under the bonnet. Mine do not, so before I go to the extent of modifying it, I just need to satisfy myself that I've not done something stupid. The reason for the adjustment to the timing is that this head and set-up is supposed to work this way. The Heron head was designed to give a higher horsepower at a lower fuel consumption.

25 mm too high

one filter fitted

 

I think what you are asking is whether the port height on a heron head (which is the original) is different to that on the later HE head, because I am fairly certain that the two castings are dimensionally similar.
Which is an interesting question, and quite suitable to this or the XJS forum. Sorry I do not know the answer.
So if your engine is a non HE, then it is a flat top, and will be the same as the original engine. No changes were made until the HE engine around 1982.
BUT your air filter could be the problem.

 

Golden rule is "measure twice, cut once". I'm afraid you will have to cut something, hope it's not the bonnet.

 

Whatever it is, it sure is pretty

The older I get, and that is a lot, the more I realize how much there is to learn.

Here, the static timing at pure TDC??? Absent any other timing modification, such as centrifugal or vacuum, the engine would be very sluggish at idle or low throttle opening. In my experience most critters like some thing like 14 - 17 degrees BTDC.
Then as the advance devices do their thing, it all in around 35 degrees BTDC?

Do you have a manual spec at 0? And I guess that could well be and changes go from there.

Why do I have an image in my mind, of the carb V12 with flat manifolds and the carbs aside the heads rather than atop? Delusion, might well be...

Carl

 

Thanks All,
The Weber carbs and the filters are made for the E-Type V12. They have a low profile of 60mm. Looking at other installations, including Jay Leno, everyone else's seem to fit. I am clutching at straws with this one and am assuming that the engine cylinder heads have higher profile, otherwise why don't they fit? I did notice that with the original Stromberg carbs, the clearance of the their heat shields under the bonnet did seem very tight and higher than other Series 3's that I have restored. It just didn't sink in until I changed to the Webers. The reason for the change was that I could not get the Strombergs lean enough. With the Webers I can set each one. It is highly unlikely that the chassis and engine mounts are wrong as the car is straight.
Concerning the TDC at Zero - I am told that this is the case with this "Hemi" head - and 18 BTDC at 3000. I can but try.
Lastly, can anyone tell me where I can find the specs for Engine 7P50617SB ?
Eric

 

What is the distance from the head to the top of the carbs? Kits are usually around 160mm, maybe your intake adapters/manifolds are too tall?

As I recall, "heron" refers to the original V12 design, which is nearly dead flat. The HE gets a little swirl chamber but is still very flat. The hemi head is on the XK6 engine

I would try going to the e type forum to get a measurement from the cowl to the top of the engine, perhaps your mounts or something are a different size and the entire engine is sitting higher in the engine bay than normal?