Lotus Elan

Timing chain touching front of inside of case

PostPost by: thehackmechanic » Sat Feb 23, 2019 3:12 pm

Hey, folks. I've been lurking for quite some time, as as this forum has more twin-cam info than the Europa forum.

I bought a '74 Europa TCS 5 1/2 years ago with a seized engine, and have been slowly rebuilding it. After an 18 month wait, I got my hands on a Dave Bean cartridge water pump with its inner and outer timing covers. I've spent the past two months carefully test-fitting the covers doing a little fettling. There appeared to be a problem with clearance of the timing chain as it comes down off both of the cam gears; it was touching or almost touching the front of the inner surface where the cork gasket sits. In test-fitting, I found that if I shoved the head all the way forward on the bolts, it increased the clearance just enough that I felt comfortable assembling it.

So, yesterday, I finally assembled and sealed the front covers, dropped the head on, shoving forward as I did during test-fitting, bolted down the head, and put on the chain, gears, and tensioner. Unfortunately, now that I've spun it a few times by hand, I can see that the chain is still very very close to the inside timing chest surface of the front part of the head where the cork gasket is. This photo shows the chain coming down off the exhaust cam gear. It looks the same where the chain comes down off the intake cam gear.

img_8192.jpg and


If it's not actually hitting, it's certainly close enough to be catching the tiny (and I mean TINY) amounts of RTV that have squeezed out of where the cork gasket is at the back of the chest:

img_8190.jpg and


It looks like the cam gears themselves are about in the middle of the chest. I've measured the thickness of the Bean inner cover (the backplate), and it's about ten thousandths thicker than the original, but since the chain is so close to the inside portion of the head itself, I'm not sure that the extra thickness of the backplate thickness is the root cause of the problem. It almost seems like the crank sprocket itself isn't far enough forward. I didn't take it off the crank when I rebuilt the engine, so it hasn't moved from where it was.

The crank has a set of stock symmetrically-sized thrust washers on it. It does look like there's ample room to move the crank slightly forward with asymmetrically-sized thrust washers. Is that what I should do?

Any other suggestions?

Thanks.

--Rob Siegel
'74 Europa TCS, 20k miles, stored since '79, resurrected in 2019
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PostPost by: miked » Sat Feb 23, 2019 7:25 pm

Rob,
Just some thoughts. The crank sprocket (with standard crank) should be in the right place as will be the jack shaft sprocket. The jack shaft position is dictated by the locking horse shoe plate thing and sprocket back spacer. Is it possible that you have non standard cams with different depth/length that are moving the sprocket positions.
I would aire on the side of what is new. The front water pump cover and back plate can't influence anything to do with the cam chain position in my mind. So what about the cams and sprockets?
Have you any others to check against. I have a built up head in the garage for a twin cam i am doing for a friend. I could try to measure from some point on the cam shaft thrust collar on a cam to the rear of the sprocket.

Cheers Mike
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PostPost by: miked » Sat Feb 23, 2019 8:05 pm

Just measured from a cam shaft face (what sprocket sits on) to the rear of the thrust collar/guide (part that stops cam moving fore and aft). This is 1.370 inches.
This should help determine where the sprockets sit, assuming they are bog standard.
Mike
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PostPost by: 2cams70 » Sat Feb 23, 2019 9:54 pm

Did you remember to install the spacer in between the jackshaft and its sprocket?
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PostPost by: thehackmechanic » Sat Feb 23, 2019 11:41 pm

@2cams70--> I see the one you're referring to shown in the parts book as #7, X026E0017Z, "adaptor." I have no recollection of a spacer behind the jackshaft gear when I took it apart, and I did not install it with one, unless it's somehow pressed into the front of the jackshaft or the back of the gear. I'll see if I can determine this without taking the thing apart. Thanks.

http://rdent.com/manuals/europa/tcparts/engine/ef.htm
'74 Europa TCS, 20k miles, stored since '79, resurrected in 2019
'73 BMW 3.0CSi
'72 BMW 2002tii, '73 BMW 2002
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PostPost by: miked » Sun Feb 24, 2019 12:12 am

They can be stuck to the jack shaft and only come away sometimes with a few taps with a soft hammer. A light interference fit.
I thought you said the chain was close both sides. You would think this would only cause one side to run close.
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PostPost by: thehackmechanic » Sun Feb 24, 2019 4:29 am

@miked--> That makes sense. Yes, it's close on both sides. I found a photo of the jackshaft without the gear on it. Am I correct that this shows the spacer attached to the end of the jackshaft?

Thanks.

--Rob

img_8172.jpg and
'74 Europa TCS, 20k miles, stored since '79, resurrected in 2019
'73 BMW 3.0CSi
'72 BMW 2002tii, '73 BMW 2002
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PostPost by: StressCraxx » Sun Feb 24, 2019 4:45 am

Hello Rob,

I have done the same Dave Bean conversion as you have. The clearance on mine is adequate. Is it possible you have swapped the jackshaft sprocket with the intake cam sprocket?

Regards,
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PostPost by: miked » Sun Feb 24, 2019 8:18 am

Rob,
Yes, that looks like your spacer sat on the end of the jack shaft. If you dont mind me saying, a lot of silicone on that back plate.
Having a gasket there should mean using a lot less. I only use Wellseal. Thin coat brushed lightly on each mating surface. Need to be careful of not blocking the chain oil hole in the back plate. Others may use different products but Wellseal always works well with gaskets.
Cheers Mike
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PostPost by: 2cams70 » Sun Feb 24, 2019 9:39 am

Yes it looks like the jackshaft spacer is installed correctly and I agree that looks like a lot of silicone. What is the thickness of the paper gasket you used between the backplate and the block? Standard thickness is quite thin - around 0.2mm. If the gasket is thicker than standard, plus the extra thickness caused by the silicone plus the slightly thicker than standard Bean backplate these factors all combined could cause the issue you describe. Did you check too that the front oil gallery plug is clearing the hole in the backplate and that the backplate is not hanging up here? It looks reasonable in the pictures but best check to be sure.
For my engine I decided not to use any sealant here. You will find that gasket paper manufacturers will state not to use any sealant of any kind in combination with a fibre gasket - you won't hear that from the sealant manufacturers of course because that's not in their interests!! You will never find an OEM using sealant on a fibre gasket. Particularly since your water pump housing assembly is new and presumably flat sealant should not be required.
For my engine I threw away the backplate gasket supplied in the kit. I found it to be poorly made with the screw holes and coolant passages not lining up properly. The quality of the paper used was suspect too.
I selected a gasket paper as thin as possible with "controlled swell" properties and cut my own with an exacto knife, hole punches and scissors. "Controlled swell" paper under the influence of heat and oil swells to completely fill gaps between the sealing surfaces. The paper I used is supplied by Mahle in a roll under part number JV100. I figure Mahle as a worldwide OEM supplier should know a thing or two about gaskets. It's freely available through various suppliers in the USA but being in Australia I had to import mine specially as there were no local suppliers. Although other gasket manufacturers can supply "controlled swell" automotive gasket paper this at 0.4mm thickness was the thinnest I could find.
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PostPost by: Craven » Sun Feb 24, 2019 11:49 am

Paper gasket looks quite thick, Jackshaft with spacer.
p1020912.jpg and
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PostPost by: thehackmechanic » Sun Feb 24, 2019 4:37 pm

Thanks, everyone, for your input. My current theory is that several issues are conspiring to reduce clearance, but let me step through the comments.

[email protected]> I confirm the 1.37" measurement from the camshaft face to the rear of the thrust collar. The cam gears appear to be the stock Ford-stamped parts.

[email protected] StressCraxx-->I don't think I accidentally swapped the jackshaft and intake cam gears because the intake gear still has the timing mark on it.

[email protected], 2cams70, Craven-->Yes, the backplate gasket IS a little thick. The gasket that came in my Payen gasket set that I bought 5 1/2 years ago was about five thousands thick, but over the years of sitting, it shriveled and dried up like a leaf in November. I bought a replacement backplate gasket from RD Enterprises. It is about 15 thousandths thick, so an extra 10 thousandths.

img_8170.jpg and


[email protected], 2cams70-->The gray RTV isn't as thick as it looks; it was scraped down to a uniform thin coating with a putty knife before the covers were mated. Nearly all of it was scrapped off the area surrounding the oiling hole. I spent many nights reading the pros and cons of using sealant on the gasket and if so, what kind. I'm aware that the factory manual says to use nothing, the Wilkins book says to use Wellseal, and Rohan says to use Locktite Red Aviation Gasket Maker. I'm being advised by a guy here in the United States who builds twin-cam engines to use what he refers to as "silastic" (silicon and rubber RTV) with an RTV primer (Dow 1200-RTV) applied first on the metal surfaces. If I have to tear it down and do it again, perhaps I'll try something else that's thinner than RTV, but I doubt the adhesive is causing the clearance problem at the top of the head.

--There appears to be enough clearance between the chain and the backplate as the chain comes off the crank gear, but even down there it's tight. I measured it with feeler gauges at about .046". The picture below is a little out of focus but I think you can see the clearance. If I had that much at the top, I'd be overjoyed.

IMG_8118.JPG and


--The Dave Bean backplate is a little thicker than the original backplate by about 8 thousandths (old backplate 0.0444, new backplate 0.452). So, yes, between the thicker backplate and the thicker gasket, that's about an extra 18 thousandths.

--The new iwis timing chain, measured at the widest part of the link plates, is a little thicker than the original chain (.445" compared to .430"). At the roller pins, it's .502" compared to .490".

Because of these last two points, my current theory is that the combined extra width of the new backplate, gasket, and timing chain is just enough that it makes the clearance problematic. If you add those together, taking half of the difference in chain thickness, it's .024" Seems reasonable, right?

I need to think about what to do about it. If I tear the head and the front covers off, yes I'll source a thinner gasket and will likely try a different sealant.

Thanks again.

--Rob Siegel
'74 Europa TCS, 20k miles, stored since '79, resurrected in 2019
'73 BMW 3.0CSi
'72 BMW 2002tii, '73 BMW 2002
'72 BMW Bavaria
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PostPost by: vincereynard » Sun Feb 24, 2019 5:12 pm

As the chain is tight for both cams, the jackshaft and crank are probably not the problem.

As you say it is probably a combination of a few tight tolerances combined.

I would be inclined to remove the gasket and, with a flat glass and engineers blue, check the plate for flatness. Then either make up your own gasket from very thin paper or not use a gasket at all.
https://www.ebay.co.uk/itm/362507069936

This stuff and Wellseal are very similar. Permatex is thinner and brushes out easier. I used both.

As someone has already stated ensure that the chain lube drilling is clear.

I have a burton cartridge on my twink and be aware that as the housing is thicker the water pump pulley needs to be set about 8mm further back for the fan belt to line up. My engine was originally built by gibbons and the belt was way out.

Vince

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PostPost by: types26/36 » Sun Feb 24, 2019 5:56 pm

thehackmechanic wrote:.I bought a '74 Europa TCS 5 1/2 years ago . After an 18 month wait, I got my hands on a Dave Bean cartridge water pump with its inner and outer timing covers.-Rob Siegel

I know its of no use now but a Europa does not drive the alternator from the crank pulley and subsequently does not put much side loads on the water pump bearing, hence there is no adjustment on the Vbelt and normally the Europa water pump lasts a very long time, unless you got the Bean kit at a very good price I doubt I would have gone to the expense and associated problems of a Bean cartridge kit..........hindsight is a wonderful thing :D ........if the problems are too great you could always revert to the standard set up and sell the Bean kit :roll:
Last edited by types26/36 on Sun Feb 24, 2019 7:55 pm, edited 1 time in total.
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PostPost by: RichardHawkins » Sun Feb 24, 2019 7:16 pm

Rob,

If you have to take the timing chest apart again, use the opportunity to do a dry test assembly. You can fit the head wth only the timing chest back plate, install the chain, and then see and measure all the features that may be of concern.

Our engines are now approximately 50 years old and have probably been apart several times. Parts are often not of original manufacturer quality. Not all previous owners knew what they were doing. Check everything you possibly can and trust nothing. Over here in the UK a friend bought a replacement timing case (I think from QED) that didn't fit. As the UK is a small country taking it back and demonstrating the error was not difficult, but very frustrating.

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