Lotus Twin Cam Sump - 4 Bolt To 6 Bolt Lip Seal Conversion.

[ceejay]

Here's A Project For The DIY Fabricator Perhaps.

From the vast quantity of parts that are still available for the Lotus twin cam engine, the pressed steel six bolt sump has become a scarce and much sought after item.

But Many Twin Cam Owners May Not Be Aware That Old Four Bolt Sumps Can Be Converted To Six Bolt Sump Seal Arrangement.

Read more at the link below about the conversion process. (And put your name on the list if you are interested to learn how to do the conversion and fabrication)
http://elantrikbits.com/lotus-elan-blog/?p=779

Ceejay

[rgh0]

This project of Ceejay's (Colin) came out of discussion with me when he was looking for a 6 bolt sump for a customer who wanted a fully baffled sump to the design in his Ebook. I had a couple of spares but was reluctant to sell them as I had them earmarked to go with blocks and heads and other bits I had for complete engines. All the other engine builders I know in Australia were in the same situation as supply of 6 bolt sumps had totally dried up here and from what I read on LotusElan.net the situation was the same in the USA and UK and Europe. Maybe South Africa is a potential source of 6 bolts sumps but the cost of getting them from there would not be cheap or easy to do.

I remarked that I had a couple of 4 bolt sumps from old 120E block 1500 engines I had purchased and had always thought a conversion to the 6 bolt arrangement was possible with some "relatively simple" but quality critical sheet metal work. I had kept them, thinking one day I would get around to giving it a try. I offered Colin one of my 4 bolt sumps to try it on and one of my spare 6 bolt sumps as a loan to use as a pattern, if it worked OK he could keep it as long as he converted the other 4 bolt sump I had, for me.

A few weeks later Colin had done a great job and I had another spare 6 bolt sump in my stock which now will also go into another complete engine build and he had the basis for this new Ebook.
I hope it helps alleviate one more shortage area.

Maybe one day I can convince Colin to make door window frames !!

cheers
Rohan

[ceejay]

Hey Rohan.

At first glance the sump project looked reasonably simple, but there are a few things that became apparent,
and that was with the sheet metal forming, accomplished with good old fashioned hammer forming technique.
(Be much easier with a press die, but that costs big$$ to make)
The first project is the hard one, the rest not so hard, but still very fiddly to get right.
But if there are spare 4 bolt sumps out there, don't throw them out, they are worth their weight in gold.
Col

[AlfaLofa]

There's a 4-bolt sump for sale here:

http://www.ebay.co.uk/itm/Early-LOTUS-F ... 4ad8e89bd6

[ceejay]

That's a good buy for someone in the UK.
Ceejay

[DJ908]

All very interesting.

Is it possible therefore to change the rear (and front?) crank seal on a 4 bolt crankshaft motor to the same seal/s used on the six bolt crankshaft and have the sump modified as indicated here?

It would still leave me with that chatter you get from the spigot bearing in the back of the crankshaft, a noise which I have learned to accept but which can sound rather alarming at times.

Robert

[rgh0]

With the six bolt crank and the needle roller spigot bearing it uses I have not had any problem with chatter from this.

cheers
Rohan

[DJ908]

Rohan

I am somewhat envious of those with their 6 bolt crankshafts for I am well aware that the installation of the needle roller spigot bearing was the means of eliminating that rather ugly chatter or bark that occurs occasionally on starting the car. But there was no way I was going to persuade Lotus to change my crankshaft at the time just to overcome that problem. It was in essence a Ford problem ? as the supplier of the short blocks to Lotus.

I have often wondered whether it might be feasible to machine the existing crank to take a needle roller bearing but in my case I rather suspect the money to do so would be better spent elsewhere on the car.

The fixing of the weeping rear crank seal is a good example of what I would consider a more important issue to be solved. So my prime question remains. Is it possible to fit a lip seal to the four bolt crank for that would allow me to have Colin's team modify the sump to suit?

Robert

[rgh0]

Hi Robert

I think it would be easiest and cheapest to replace the crank with the 6 bolt crank and to replace the rods with 125E rods if you still have the earlier rods also at the same time (though not absolutely necessary).

The problem with using the 4 bolt crank with a modern lip seal is that the seal location diameter on the 4 bolt crank is smaller that the flywheel mounting diameter so you cant slip the normal one piece lip seal over the end of the crank shaft. It would be conceivable to use a split seal design but these are relatively expensive assuming you could find one to match the crank and it is not the sort of thing you get for a few dollars off the shelf at your local bearing shop and would require fabrication of a special split seal carrier to match this seal and the six bolt crank sump.

I am sure you could fit a needle roller into the end of a 4 bolt crank if you really wanted to. IIRC the bronze bush is larger in diameter and could be replaced with a sleeve and a needle roller bearing.

cheers
Rohan

[types26/36]

Is it possible therefore to change the rear (and front?) crank seal on a 4 bolt crankshaft motor to the same seal/s used on the six bolt crankshaft and have the sump modified t

You may find this thread interesting as it contains pictures of a modification on a four bolt crank engine.
lotus-gearbox-f37/crankshaft-rope-seal-t962.html#p72335

[billwill]

Rohan

I am somewhat envious of those with their 6 bolt crankshafts for I am well aware that the installation of the needle roller spigot bearing was the means of eliminating that rather ugly chatter or bark that occurs occasionally on starting the car. But there was no way I was going to persuade Lotus to change my crankshaft at the time just to overcome that problem. It was in essence a Ford problem ? as the supplier of the short blocks to Lotus.

I have often wondered whether it might be feasible to machine the existing crank to take a needle roller bearing but in my case I rather suspect the money to do so would be better spent elsewhere on the car.

The fixing of the weeping rear crank seal is a good example of what I would consider a more important issue to be solved. So my prime question remains. Is it possible to fit a lip seal to the four bolt crank for that would allow me to have Colin's team modify the sump to suit?

Robert

Would it not be easier to simply fit the bottom end of a Ford 1600 Xflow?
http://www.lotuselan.net/wiki/Torquing_ ... am_Rebuild

[ceejay]

It is amazing how many variables can crop up within a certain topic. The four bolt sumps pretty much had a reputation for being weepers of oil. The conversion of the old style sumps to the later lip seal (6 bolt) is an obvious choice. I wonder just how many older four bolt sumps are out there hanging up in sheds/garages awaiting to be reborn as six bolt sumps.

Rohan mentioned to me during discussions re his sump conversion that quite some time ago he sent a couple of old 4 bolt sumps to the recyclers, and of course he regrets doing that now...but at the time, a conversion had not been done, so the old style sumps were seen as having little value.

But things are now different, and it would be odds on that many other people have done the same thing.

To be honest, during the past thirty odd years of Lotus ownership, the thought of converting the old four bolt sumps to six bolt arrangement had never entered my head.

The crank seal conversion certainly brings an older engine into line with a more modern configuration and the options to build a better engine with easier to source parts are there, not to mention the increased reliability of six bolts holding the flywheel to the crank if you are using the high end of the twinks rev range.
Col.

[billwill]

But are the 6-bolt cranks and flywheels available so that a 4-bolt engine can be converted to a 6-bolt engine?

[ceejay]

A quick google search will reveal plenty of suppliers of upgrade parts such as; cranks, flywheels, and rear seal housings. There is no shortage of parts for the twink.

[jk952]

I have a banged up 6 bolt pan, but the flange is good - if someone is interested, would work well for a 4 to 6 bolt conversion (my plan was to have it straightened or more likely rewelded but found a good one.)
Jack