A few pre assembly Twin cam asks

[kenny]

All components are now on bench cleaned and ready to go, just waiting for a few bits and bobs to arrive.

1) Just doing a final check on assembled refurbed standard head with the SE single groove cam on inlet and "standard" cam on exhaust.
Lift on inlet checks out to Mile's figures at .350 lift yet the exhaust is only .327 lift. This figure is not mentioned in his breakdown of cams and their lifts, any ideas please? I'm convinced it's ok but this figure is just not mentioned at all

2) Need to pick up a head gasket. I recall somewhere in the depths of my mind that when I built a high spec x/flow back in the late 80's the gasket of choice was as a BJ200 but I forget the maker and a google has drawn a blank......any reccomendations please.

3) The pick up pipe and the strainer tube. Do these come to a stop when drifting in or is a measurement needed, I'm sure I can see a lip but it is small. I will also be putting a smear of sealant on them too, is that ok?

4) The two sump bolt holes in the rear crank cover are plain and not 1/4 unc as per the rest of block.....should I helicoil them or just use nut and bolt fixings?..it's simple to do this as engine is on its stand, or is this correct anyway?

Many thanks once more in anticipation.

Kenny

3)

[elanman999]

kenny,
3, No there is no stop. You have to measure things.
4, The bolt holes shoud be tapped into the rear seal housing. You can use a nut and bolt but it then means you must take the engine out to remove the sump.
John

[rgh0]

kenny
I thought the standard cams were .350 lift also not the .375 lift quoted by Miles Wilkins on page 180 of his book or the .327 lift you have measured.

But its been a while since I measured up a standard cam so my recollection may be wrong. 0.327 sounds too small a lift and the cam may be worn on the nose, are all the lobes exactly the same and any evidence of wear?


regards
Rohan

[kenny]

Thanks Elanman, I'll check the books and see if a measurment is given for drifting them in (should have checked before I took them out)

Rohan, thanks for your comments there. It looks that I've got yet another "strange" problem on this rebuild.

Let me explain. As I said on a post a few months back the head I got with the car had cam stud and dowel damage on 5 studs and also was down to 65 thou shims.
I had the head fully reworked by a top and well respected Lotus machine shop (seats,guides,valves,shims plus the repairs and clean up) and they have done a superb job. To my surprise when I went to pick the head up the cams had been fitted so I thought everything was perfect.

I only stumbled on this measurement whist working out figures with John.Houston (fellow member) on his "unknown cam" and did a measurement on mine to compare.
My cams actually look like new so I'm buggered as to what the problem could possibly be...........I'm sure I'm doing the sums correctly but hope I'm wrong. Any further comments hugely welcomed or I'm on the hunt for another exhaust cam

Regards,

Kenny

[rgh0]

Kenny

What is the base circle diameter on your exhaust cam. Maybe the cam was reground on a smaller base circle to accomodate the recessed valves and they got the lift wrong?

Rohan

[kenny]

Rohan, I,m in disgrace I think
I did not want to take the cams out to measure them as it seemed a shame to disturb them after they'd ben set up at the machine shop "ready to go"
I'd been checking them with my digi vernier in situ.

I've just lifted them out now to put the Micrometer on them and readings were wrong which I gave you......I just mustn't have been getting proper readings with vernier in situ.

Base diameter mics to 1.208" and heel to lobe is 1.548".......I'm happier with that reading.

Miles wilkins book doesn't seem to say what the exhaust cam is when fitted with th SE inlet.

Thanks for the continued help with this and sorry about my mis reding of the sizes.

Regards,

Kenny

[rgh0]

Numbers look about right - standard base circle is 1.20 inch and its hard to measure direct with a micrometer so 1.208 could be easily measured.

1.548 give a .348 lift on the standard base circle near enough to .350 which is what I recall


regards
Rohan

[kenny]

Rohan, star man once more. Thats one more beer in my "I owe Rohan" diary

Kenny

[elanman999]

kenny,
Point 3, have just looked in my notes and the distance from the block to the bottom of the strainer (pushed hard against the spring) is 6.750in. But I do use the Burton competition sump set which has a different sump gasket. You need to measure how deep your sump is at the pickup point as if it has been grounded (like mine!) it might not be the same as my engine.
Cheers
John

[kenny]

Hiya John, 2 great minds eh ...Just logged in and you posted.

Thanks for that info, I'll do the measurments and see where we are. I assume the pipes want to be circa 1/4" from the bottom?

I still swear I can feel a lip though where the pipes will stop but may be wrong (as usual )

In the manual it just says tap them home

Thanks again though for you advice.

Cheers,

Kenny

[elanman999]

kenny,
Yes I allowed 1/8in plus the gasket which in my case =3/16 approx.
John

[rgh0]

Kenny
I just pulled a oil pick up tube from an old Lotus block I have. The tube top was 160mm above the block bottom face and this put it about one tube diameter from the bottom of the sump. Normal design for suction tubes is one tube diameter clearance so all this looks right.

The tube was pressed 34mm into the block. There is a very small step in the bore in the block at this depth of about a 0.5mm diameter reduction and the pickup had been fitted to this step.

The smaller diameter oil return tube has no stop in its bore and needs to be driven to a suitable depth to engage the strainer guide lugs before the sump is fitted but still clear the bottom of the sump when the sump is fitted

I would measure up to ensure if press the tube to the step in your block and then check clearance with the sump you have approx one pipe diameter to bottom of sump. If all is OK then press in. Once its in the block its hard to remove without damaging so ensure you get it right first time.

Hope this helps
Rohan

[kenny]

Rohan, that's spot on re. the small step. Thanks for other info too.
Will do the measurements as suggested.

Many thanks,

Kenny