OT: Fitting twin cam head on Lotus Kent engine

XJ
#1

Good evening everybody,

a friend is just about to put back the head of his Kent Lotus 7 engine. He is veeery experienced, but still careful not to mess things up. So he got himself a good book with a good reputation in the community.

Surprisingly, for me at least, the book instructs to adjust the camshafts in a way that the cam lobes “rock” on #4 cylinder (a good picture explains better what they mean). Then the timing chain should be installed over the cam sprockets and tensioned. I cannot find any hint on the position of the pistons - fair enough, he only let me have the pages relating to the valve timing … still, I can’t imagine that they might fail to give the starting position (e.g. # 1 TDC) right with the timing instructions. What am I missing?

Has anyone of you ever had the chance to work on these beasts?

Thank you all and enjoy the week end

Jochen

75 XJ6L 4.2 auto (UK spec)

#2

There must be a timing indication somewhere and this has to relate to something measurable, so likely tdc, and in a way that there is no valve collision and such that the cylinder that just fired is on the compression stroke.
Just like on ours, frontmost on the compression stroke, 0° on the damper, notch up, distributor pointing to the frontmost cylinder‘s wire :slightly_smiling_face:
Maybe they left it out because the engine is already set to tdc.
What engine is it - Kent? More cars with that engine, and a description online?

That might be a helpful forum: Xflow cam timing setting - Tech Talk - WSCC - Community Forum

David

#3

Thanks David,

the Kent engine was used on all kinds of cars from the Ford Anglia to the early Fiestas - I even think the first generation XR2 was still on a Kent engine - problem being that they didn’t havet the Lotus twin cam head.

My suspicion is that they somehow assume that the lower end has not been changed as, indeed, the book has a sketch depicting the markings on cam sprockets, timing marks on cover and timing notch on pulley. I’ll try to get hold of the earlier pages - maybe this is confirmed elsewhere.

Thanks anyhow - enjoy the weekend

Jochen

75 XJ6L 4.2 auto (UK spec)

#4

On a Europa, the car’s mid-engine configuration makes certain things challenging. There are timing marks on the front of the cam gears. During reassembly, the block is kept at TDC, the cams are inserted at approximately the correct #1 TDC orientation, and the bearing caps are laid and tightened. Then the exhaust cam gear is inserted into the timing chain, the gear is rotated one tooth at a time until the timing mark is flush with the valve cover surface, and the gear, chain, and cam are all jiggered and juddered until the dowel pin slides into the hole while preserving the alignment. The same is then done for the intake gear. Then you insert the chain tensioner, snug things down, and verify that the block is still at TDC and both cam gear marks are still aligned as well as they can be on a 45-year-old engine whose head has been skimmed. I found this to be quite challenging when I set the cam timing with the engine on the stand. But with the engine already in the car, those cam gears are inches from the firewall, you can’t see the timing marks without a mirror, and even with a mirror, parallax prevents you from accurately assessing their alignment. I was definitely not looking forward to doing it with one hand tied behind my back. What is advised is that you mark the back face of the cams before removing them. I used Tippex and a straight edge on the valve cover mating surface. They’re imperfect marks, but I photographed where both intersected with the straightedge, so they should be good enough for me to know if I’m a tooth off, which is the best you can do anyway.

Ew. I like the XK a lot more now, whether these help or not.

1 Like
#5

Thanks David,

though I don’t know much about Lotus, it seems that the Super Seven basically lives with a Lotus head on a Ford 1.6 litre block (even though pistons and crankshaft may be Lotus as well), while later Lotus designs have a full 2.2 litre own Lotus block.

Yet, based on today’s experience - we put the head on today - it looks like things are a lot more relaxed on the older design with a front engine layout. The crucial info was somewhat hidden - indeed it was the info that the head and the timing chain was to be fitted with the TDC mark on the pulley and the markings on the cam sprockets positioned in a certain way. As, indeed, the lower end hat been left unaltered, everything seems to have gone in smoothly - except that the engine manual failed to explain that you have to fit the tensioner prior to putting the head on, if the engine is installed in a Super Seven. We found out the hard way as, once the head is on, the front cross frame member will prevent installation of the tensioner. Engine had to be loosened and pushed up an inch to get enough clearance. For the moment everything is fine.

Thanks again for your thoughts and commitment!

Jochen

#6

No problem, I learned something about Lotus and about the Fords - you owe me a picture!

Does that cam design share the dowels I kept reading about?
David

#7

No, it seems the Lotus twin cam heads for the Kent engine do not share the same design. Yet, I didn’t get the chance to dive in deep enough as the owner had the head all prepared and within a difference of some 2° on the exhaust side everything fit perfectly. As described in the book he was able to loosen the sprocket and turn the cam with some pliers.

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Best

Jochen

75 XJ6L 4.2 auto (UK spec)

1 Like
#8

I’m confused. How does the Ford Kent engine differ from the Ford 116E that was used in Lotus Ford engines, a twin-cam Lotus head bolted to a Ford 116E bottom end?

#9

Sorry for the confusion, Kirbert!

The term “Kent” always seemed to be common for the 116 engine. So, no, it does not differ except for some Lotus goodies such as pistons.

The point I wanted to make is that the twin cam head on the Ford motors seems to be different from the twin cam heads used on Lotus’ own engine designs.

Cheers

Jochen

75 XJ6L 4.2 auto (UK spec)

#10

I asked because I looked up “Kent” and couldn’t find any reference to the 116E.

#11

Well, it cites the Ford Anglia as original user of the engine https://de.wikipedia.org/wiki/Ford_Kent - Google will translate, if necessary.

Best

Jochen

#12

Why translate!

:grimacing:
I also understand better now. The lotus engine wasn’t in the anglia though (so it says, that is), it does say, Aufgrund des Zylinderkopfes werden diese Motoren pre-crossflow genannt. Der Block mit 1,5 Liter Hubraum war auch die Basis für den Lotus Twin-Cam -Motor, der im Vereinigten Königreich in kleiner Stückzahl im Ford Escort der ersten Baureihe angeboten wurde.

David

#13

My FF had one in his Lotus 23B race car. Gotta presume there are differences between the race version and the street version, perhaps higher compression pistons and hotter cams. And the race car had a dry sump. Still, the engine looked exactly the same, with that trademark cam cover. Oh, and a pair of Webers, of course.

My FF is long gone, but one of his best friends is still around and we chat regularly. My FF pressured him into rebuilding his engine after he blew it up (!) even though the friend protested that he didn’t really know anything about the Lotus/Ford engine. He reports that there are places where oil flows backwards in galleys in the Lotus incarnation, and also that he had to buy a very special tap to make threads needed for something. He still has the tap. When it was all together, he told my FF that he needed to be there at startup to make sure the oil flows were working right. My FF ignored that, went straight to a race track, and promptly blew it up again. The man was a good driver, but not mechanically inclined at all.