Lotus Elan

New Engine Build

PostPost by: Davidb » Sun Sep 10, 2017 3:01 pm

Rohan, should that McCoy cam spec be .460 lift? The .360 you mention seems a bit tame for you!
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PostPost by: rgh0 » Mon Sep 11, 2017 10:31 am

Davidb wrote:Rohan, should that McCoy cam spec be .460 lift? The .360 you mention seems a bit tame for you!


Sorry for the typo yes .460 lift I have edited the post.. Even for a "standard" road car i personally would start with a .410 lift cam minimum if I was rebuilding an engine :lol:

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PostPost by: rgh0 » Sun Sep 17, 2017 1:23 pm

Spent Saturday working on the engine as i got a set of suitable bearings delivered during the week from SJS for the unused Datsun L16 crank I had with the "correct" stroke. After talking to the eligibility officer it became clear that the standard stroke of 72.75 mm is the absolute maximum under the wording of the regulations and there is no allowance for manufacturing tolerances so this was the crank I had to use. I will take up this question with the CAMS historic commission as that interpretation allows for no recovery of worn cranks if the re-machining to undersized journals results in a slightly longer stroke by a few thou but I don't have time to argue now so I will proceed with the new unused crank.

Checked the stroke of the new crank with a dummy assembly to ensure it met the 72.75 mm or less interpretation which it did.
img_2901.jpg and


I then went to pull out the crank oil passage plugs to ensure the passages were clean and discovered the plugs were not correctly fitted and they were undersized and did not match the tapped threads in the crank. This Datsun crank had been supplied by a local "Lotus Specialist" many years ago and had been in my stock as a spare and it appears that he or his machinist did not pay attention to the actual plugs required which were 5/16 UNC grub screws. My other spare Datsun crank has different size threads for the oil plugs so I am not sure what is original, maybe both ?

When it came to fitting the chain sprocket on the nose of the crank I also discovered that the slot for the Woodruff key had not been milled deep enough. The standard key is 6 mm deep with a 2 mm slot in the sprocket and pulley and a 4 mm slot in the crank. The slot in this crank was only 3 mm deep. The easiest solution was to reduce the key height to 5 mm (by hand with a file), but I hate doing this sort of mod as it will trick someone up in the future but getting the hardened crank re-machined at this stage was just to much time. I used a chain sprocket with only a few miles on it. These need carefully checking before reuse as they do a lot more work than the cam sprockets and wear much faster

img_2905.jpg and


Having fitted the sprocket on the front and spigot bearing in the rear I fitted the crank to the block with new bearings and Redline synthetic assembly lube. I did not have the 5/16 UNC grub screws for the crank oil passages but fortunately I can fit them latter and will chase them up next week at my local fastener supplier.

I was reusing the existing pistons and rings and rods from this block as they were all in good condition when I pulled this engine out of the race car a few years ago. So a new set of bearings to match the new crank and new ARP 2000 rod bolts and they went in quickly without any problems. I use a conventional ring compressor and tap the pistons into the bore from the ring compressor gently with the wooden handle of a hammer. ARP say the rod bolts can be reused if checked for free length stretch but you are looking for stretch of less than 0.001 inch from original free length so I prefer to just change them when building a new engine.


The ARP recommendation is bolt installation stretch of 0.0055 to 0.006 inch which I measured with a stretch gauge. This stretch was achieved at 60 ft-lbs compared to the recommended torque of 55 ft-lbs if you don't use a stretch gauge. If building a steel bottom end that you intend to rev to 9000 rpm always use a stretch gauge.

img_2907.jpg and


Block with pistons and crank assembled and everything torqued up

img_2911.jpg and


img_2914.jpg and



Next is fitting the bearings and shortened jack-shaft

img_2917.jpg and



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PostPost by: 2cams70 » Sun Sep 17, 2017 2:25 pm

Hi Rohan,
I can check the unmodified L16 crank I have here if you want another check of the grub screw size. I would have thought it to be some kind of metric thread given the Japanese origin??
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PostPost by: rgh0 » Sun Sep 17, 2017 8:32 pm

Thanks that would be good to get another datapoint. I suspect the smaller of the two threads that I have not yet measured is orginal and it was drilled and tapped to 1/4 UNC when modified. I dont understand though if someone tapped it out why they would not put the correct plugs in.

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PostPost by: Chancer » Mon Sep 18, 2017 8:43 am

2cams70 wrote:Hi Rohan,
I can check the unmodified L16 crank I have here if you want another check of the grub screw size. I would have thought it to be some kind of metric thread given the Japanese origin??


I dont know if there is an ISO-Metric thread form for hydraulic fluid sealing, here in France pipe threads have d?nominations like 12/17, 15/21, 20/27 but they are all in fact standard BSP threads, they just didnt want to use the letter 'B' :D
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PostPost by: rgh0 » Mon Sep 18, 2017 10:54 am

There is a Japanese pipe thread and I think it is the same as BSP also. There is also the possibility that the passageways in the crank were sealed with grub screws with UNF, UNC or metric threads. As all my L16 cranks have been machined I am not confident any of them have the original plug thread still.

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PostPost by: SJ Lambert » Tue Sep 19, 2017 12:19 am

Hi Rohan, I was talking to the guys at Crankshaft rebuilders just the other day about the stretch figure for those same bolts. They agree with your figure on stretch with the caveat that it's best done with the "Blue" ARP "moly" (Ultra/Torque) lubricant - with the older superseded "white" packaged stuff the figure can be less - the "blue" mix gives the most consistent tensioning. I found when doing mine that once you edged over 5 thou stretch the bolts "tightened" and to get even another half thou required a bigger lean on the tightening spanner - I ran a torque wrench over all mine set at 55 lbs and none of the moved after having been stretched 5 and a half thou.
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PostPost by: rgh0 » Tue Sep 19, 2017 11:07 am

SJ Lambert wrote:Hi Rohan, I was talking to the guys at Crankshaft rebuilders just the other day about the stretch figure for those same bolts. They agree with your figure on stretch with the caveat that it's best done with the "Blue" ARP "moly" (Ultra/Torque) lubricant - with the older superseded "white" packaged stuff the figure can be less - the "blue" mix gives the most consistent tensioning. I found when doing mine that once you edged over 5 thou stretch the bolts "tightened" and to get even another half thou required a bigger lean on the tightening spanner - I ran a torque wrench over all mine set at 55 lbs and none of the moved after having been stretched 5 and a half thou.


Yes i used the blue packaged ultra torque lube. Yes, certainly the torque to get that final thou of stretch is significant. I tightened with a torque wrench in stages and measured stretch as i went and it took 60 ft lbs to get consistently in the .0055 to .006 thou stretch tolerance range. If I went back and tested those bolts at 55 ft-lbs they would not move due to the higher torque required to get their in the first place and the "stiction" which requires more torque to break then away.

If you tightened without a stretch gauge to the recommended 55 ft lbs even using the blue ultra torque lube you would risk under stretching a bolt and suffering fatigue failure after a short time.( been there done that ).

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PostPost by: 2cams70 » Tue Sep 19, 2017 11:45 am

I've had a chance to look at that unmodified Datsun L16 crankshaft again. It seems as though taper plugs aren't fitted or else they are fitted and then covered over with some kind of solder or there aren't any plugs fitted but the drilling itself is filled with solder. See pictures attached
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img_19631.jpg and
16 crank rear
img_19611.jpg and
L16 crank front
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PostPost by: rgh0 » Wed Oct 11, 2017 12:14 pm

L18 crank can be used with the 1500 block and some relieving is needed in the block casting and careful machining to get the counterweights to clear, not much different to whats needed for the L16 crank

I have struggled to see any real practical different between the 4 counterweight Nissan cranks and the 8 counterweight billet cranks apart from the cost :lol: They both have severe vibrations above 8500 rpm at the nose of the block. Technically the 8 counterweight crank is better but in practice the difference appears to be small.

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PostPost by: rgh0 » Wed Oct 11, 2017 12:32 pm

The engine build went into slow motion for a couple of weeks. I had ordered a new modular pump front cover a couple of months ago but that was delayed as there are none available anywhere in the world currently as far as i could find. I then ordered a new standard cover and this arrived a couple of days ago.

I spent the spare time working on the cam shimming and checking clearances on the head assembly. I cant continue with the final assembly until I get the sump and front cover fitted and then the bore and stroke checked by the official scrutineer and the block sealed to guarantee I am am not cheating on capacity.

Measured up the new front cover and back plate and all is good except for the relief hole in the back plate for the oil gallery plug. This has been machined slightly off the correct location and the back cover does not quite fit correctly as it hangs up on the plug when aligned correctly top and bottom. I need to just open up the hole a little, easy before assembly but a real problem if not picked up before assembly The relief in the back plate is also deeper than standard which is good for people who use BSP plugs in the NPT block gallery resulting in the plug sticking out more :D

Photo below shows a shiny new back plate below an older back plate so the difference in releif hole can be seen

oil-gallery-plug-relief-hole.jpg and


front-cover.jpg and




Aiming to complete the bottom end this weekend and then fit the head the weekend after with the scrutineer inspection in between and fit the engine in the car before the end of October. Getting tight for time for my race early November especially as I have my oldest daughters wedding in the next couple of weeks :shock:

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PostPost by: 2cams70 » Wed Oct 11, 2017 1:45 pm

Yes I had that problem with the new backplate in my assembly too!
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PostPost by: nmauduit » Wed Oct 11, 2017 6:38 pm

rgh0 wrote:I spent the spare time working on the cam shimming and checking clearances on the head assembly. I cant continue with the final assembly until I get the sump and front cover fitted and then the bore and stroke checked by the official scrutineer and the block sealed to guarantee I am am not cheating on capacity.

Rohan


Thank you for the update : would you have photos of the baffled sump before putting it back on, by any chance ?
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PostPost by: rgh0 » Thu Oct 12, 2017 12:07 pm

nmauduit wrote:
rgh0 wrote:I spent the spare time working on the cam shimming and checking clearances on the head assembly. I cant continue with the final assembly until I get the sump and front cover fitted and then the bore and stroke checked by the official scrutineer and the block sealed to guarantee I am am not cheating on capacity.

Rohan


Thank you for the update : would you have photos of the baffled sump before putting it back on, by any chance ?


yes I have photos I will post some this weekend

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