Sump Gasket - Rear Seal

[Roland]

Rohan,

I think I'll go with your 3mm each side, I know you have probably done a fair few of these joints. The two twin cam builders near me this morning were indicating similar over length.

Still undecided on sealant choice, I see the opposing choices on previous threads. The previous owner covered the rear seal in RTV and I think this was one of these narrow 5mm seals and looks like it never sealed fully. I started using Aviation Gasket a year back and I do like using it, tend to use it in preference to Wellseal now.

Tks

Roland

[2cams70]

If you are still interested in this topic I just remembered I think I do have a set of original unused Ford front and rear cork strips lying around somewhere. If I can locate them I can take some measurements and post them. Let me know if that's the case.

[MartinH]

Hello 2Cams70
I am very interested in this topic. Am in the process of renewing my sump gaskets as we speak. I have a 711 block. The old cork gaskets leaked. This time I ordered a set of paper/card material sump gaskets with neoprene for the half moons from SJ sports cars. I like the paper/card gaskets but the neoprene half moons look way to short (they are the right width) to be able to form an effective seal at the joint with the long sump gaskets, even once compressed/torqued down.

If you can find the length measurement for the cork type it will give me some indication as to whether or not my end seals are in the right ballpark.

Thanks
Martin

[MartinH]

Just started to read Rohan's excellent new work on the Twincam engine, (many thanks for what I am sure will be the new standard reference on the topic, a real altruistic piece of work.) In chapter 1 he mentions keeping old parts for reference. So I ran out to my workshop and found the old cork half moons I have just taken off my engine and measured them. 12cms for the front and 18 for the back. The new rubber/neoprene ones I bought are 12cms front and 19cms back.

I think I will have to review my previous comment that they appear way to short to form an effective seal. Maybe the action of tightening down the sump will close what looks like a considerable gap to me.

[Roland]

I am just in the middle of doing the sump today, the engine is in the car so I have a multistage process devised. Not easy doing this job with the engine still in the car.

I have just properly offered up both cork seals and they are not far off Rohan's 3mm over length and I don't think I will cut them (which is what Dave Chapman was advising).

Both seals are cork and 6mm wide:

Short half moon - 12 cm long
Long half moon - 18.6 cm long


Roland

[MartinH]

Thanks for those measurements Roland.

My engine is out for a gearbox change which makes things much easier with the sump gaskets.

BTW notice your loaction is Aberdeen. Would describe myself as an ex Aberdonian. My family are from there for many generations. I left about 30 years ago but do visit from time to time.

Martin

[Roland]

Martin,

I am actually a Londoner (Windsor) but my wife is from Aberdeen. We used to have a place here (Aberdeen/Banchory) and in Windsor but moved up here permanently when I retired. London is just too busy and I can actually drive the cars sitting in the garage on the roads up here.

Yes I didn't plan to do this gasket in the car. I was fitting some vernier sprockets and a nut escaped my arthritic left hand down the timing cover. Note I did speak with SJ sport cars briefly because I was tempted to buy the paper and neoprene gasket set, they kind of steered me back to the cork one as being better. In the end I didn't buy from them because they indicated the rear seal cork seal was 5mm wide and I already felt that was an issue in the gasket set from Kelvedon. I think there are all sorts of gasket sets out there, the classic team lotus set I have seems correct.

The seal lengths I quoted are uncut, I am just offering them up and they look correct and around 3-4mm overlength each end. If I am tempted to cut it would be 1mm each end but no more.

Roland

I decided to use Aviation gasket with Elring Dirko HT at half moon ends.

[david.g.chapman]

Just a quick clarification - I was writing that although I had cut the seals in the past, the last time I fitted the sump I did not cut the seals, and managed to fit them satisfactorily.

I imagine they will be easier to fit if the seals are trimmed, but you are sacrificing sealing pressure at each end of the seal, which might be important.

Dave.

[Roland]

Dave,

I have some jigs made up so I can set the seals without fitting the sump.

The front half moon set with no trimming but the back one didn't. In the end I had to trim the rear one down by 5mm approx.

Roland

[2cams70]

So I ran out to my workshop and found the old cork half moons I have just taken off my engine and measured them. 12cms for the front and 18 for the back

I'm not really sure how it is possible to gain anything meaningful from measuring already used half moon seals. They will have already been compressed. Sounds like you are happy with what you've found out yourself however. Digging around to try and find something at my place is no mean feat sometimes so I'll only make the effort if it's still required!

[rgh0]

I ended up deciding to trim to about 3 mm excess at each end after i did not trim a longer one many years ago and it moved sideways before seating in the groove and then not sealing correctly resulting in a serious oil leak when the engine was back in the car. Triming it to 3 mm extra meant it was partially seated in the groove before signficant compression started and I have not had a problem with them seating and sealing since.

cheers
Rohan

[MartinH]

I'm not really sure how it is possible to gain anything meaningful from measuring already used half moon seals. They will have already been compressed. Sounds like you are happy with what you've found out yourself however. Digging around to try and find something at my place is no mean feat sometimes so I'll only make the effort if it's still required!

My thinking is that if the already used half moons are the same length or in the case of the rear 1cm shorter, then the new ones should compress to give a suitable seal once torqued down?????

Martin

[Roland]

Martin,

I would have to agree with 2Cams, I didn't learn much from the seals I took out. Neither looked short once but the front one by example is 11.5cm. I would have come up short if I had used that.

I think this job is really one you probably get a feel for after doing a few and seeing how they sit before compressing. Measuring is tricky because the inner and outer lengths are obviously different.

Roland

[Hawksfield]

Hi All
This is a good gasket supplier I have used with success and uses a formed rubber type plastic half moon seal
All the parts are good quality and fit well as does the rear seal

https://www.ebay.co.uk/itm/203850482140 ... XQVT9S17aE

last rebuild

Hope this helps

[2cams70]

Hi All
This is a good gasket supplier I have used with success and uses a formed rubber type plastic half moon seal
All the parts are good quality and fit well as does the rear seal

<a class="vglnk" href="https://www.ebay.co.uk/itm/203850482140?hash=item2f766f81dc:g:2b0AAMXQVT9S17aE" rel="nofollow"><span>https</span><span>://</span><span>www</span><span>.</span><span>ebay</span><span>.</span><span>co</span><span>.</span><span>uk</span><span>/</span><span>itm</span><span>/</span><span>203850482140</span><span>?</span><span>hash</span><span>=</span><span>item2f766f81dc</span><span>:</span><span>g</span><span>:</span><span>2b0AAMXQVT9S17aE</span></a>

20211214_101234.jpg

Hope this helps

Good tip. Thank you. Looks like they use high quality controlled swell gasket material for the backplate gasket too. Better than what you get from Burtons and QED.