New Engine Build

[gjz30075]

Turns out my crank is an L16; 4 counterweights. Thanks to 2cams for the clarification. Rob, I have no plans
for the crank.

[rgh0]

A bit of detail on my understanding of cranks

L18 cranks came in both 4 weight ( Datsun Stanza) and 8 counterweight versions (Datsun 180B) in Australia not sure about the rest of the world. I believe they both can be machined to replicate a Ford 1600 crank though I have only seen it done with the 8 counterweight version. A 1600 crank can be used in both the 1500 and 1600 blocks if you use the right rods and pistons.

The use of an L18 crank in a road car is not really warranted as there are lots of good second hand Ford 1600 cranks around as well as new cranks that are being made for Formula Ford engines which cost less than machining a L18 crank. If you have a race class that allows long stroke engines then an L18 crank will be cheaper than a billet crank.

The L16, 4 counterweight cranks balance well and the counterweights are reduce to match the reduced big end journals. A 4 counterweight crank has a larger spacing between the various elements that balance each other out so more potential for internal crank flex but this does not appear to be a significant problem. Twin cams with both 4 and 8 counterweight cranks appear to vibrate strongly around the nose above 8500 rpm due to the fundamental secondary couple unbalance that all 4 cylinder engines have that comes from the pistons and rods reciprocating mass not from the crank itself.. Maybe a 8 counterweight crank is a little better but I don't think this is significant. It is more important that you use light weight rods and pistons to minimise this vibration. I have seen some people use vibration damper front pulleys to try to reduce these vibrations but I have not tried them myself, theoretically it could help but I get acceptable results using lightweight JE pistons and Carrillo rods

If building a Lotus 9xx engine for high revs you also have this problem as the aluminum block is more flexible and the standard pistons and rods are very heavy so lightweight rods and pistons are even more critical.

cheers
Rohan

[Davidb]

Rohan, as a side issue-what about the BDA and BDD used in Formula Atlantic back when? They were eight counterweight and the engines would rev safely to over 10,000 rpm--I have heard of 13,000 rpm from one race car builder. How different are they to the Twin Cam crank. Full disclosure: I have one of these cranks in my Twin Cam.

[2cams70]

Sorry to disagree Rohan but the Datsun L16 (1,600cc engine) is what was fitted to Datsun 1600 and Datsun Stanza models. The L18 engine as you stated is what was fitted to the Datsun 180B model. The L18 is longer stroke compared to the L16. All L16 crankshafts are 4 counterweight and I was of the belief all L18 cranks were 8 counterweight but I could be wrong on this as I haven't pulled apart many L18 engines.

See picture attached. From left to right L16 late type, L16 early type, and 3020E Lotus. The two L16 cranks are from Datsun Stanza's. The late L16 is lighter weight with reduced metal in the webs and counterweights. I am told this type is not suitable for LTC conversion. If anyone wants an L16 crank let me know! For me it worked out best to buy an off the shelf crank because unless you can do the machining of the Datsun crank yourself the labour costs are prohibitive and you need to make up a custom flywheel as well.

[gjz30075]

Now that we've severely hijacked Rohan's thread, my Datsun crank has 'N8240' cast in it. Does this
mean early or late?

[rgh0]

Its always a good day when you learn something new. I had always be told Stanzas where an L18 engine not L16. Just goes to show you need to always be careful what you believe.

cheers
Rohan

[Davidb]

Rohan, any comment on my query on the BDA/BDD cranks?

[rgh0]

Rohan, as a side issue-what about the BDA and BDD used in Formula Atlantic back when? They were eight counterweight and the engines would rev safely to over 10,000 rpm--I have heard of 13,000 rpm from one race car builder. How different are they to the Twin Cam crank. Full disclosure: I have one of these cranks in my Twin Cam.

I presume they were a special forging or machined from billet with the longer stroke and 8 counterweights and similar in design concept to the current billet machined 8 counterweight race cranks.

With the right rods and pistons a 10000 rpm bottom end is not that hard. 13000 rpm is pushing it but I dont see why it would not be possible with enough development work. Like I said before running above about 8500 rpm requires frequent rebuilds which would not have been a problem back in Formula Atlantic days for the professional teams.

In an Elan also not much point trying to build an engine to run at those 9000+ pm revs as the power band gets very very narrow with the twin cam head and you don't actually get much more power. More useful in a light open wheel race car with Hewland gear swapping to match the circuit and a 4 valve BD head --- like formula Atlantic

cheers
Rohan

[2cams70]

Now that we've severely hijacked Rohan's thread, my Datsun crank has 'N8240' cast in it. Does this
mean early or late?

My late L16 crank has "W7040" cast in. The early L16 crank has "230" cast in. Maybe your's is L18?
Note there was also an L20 (2 litre) engine but I think the crank stroke is too long for any Kent block.

[gjz30075]

Now that we've severely hijacked Rohan's thread, my Datsun crank has 'N8240' cast in it. Does this
mean early or late?

Maybe your's is L18?
.

I was told it was an L18 by the guy I got it from but, at this point, I really don't know.

[SJ Lambert]

Time to cosy up to our local friendly pilots as far as that avgas ban goes eh Rohan!!

[rgh0]

If you google the web you will find there are 4 counter weight L18 cranks - just did not come from a Stanza I guess

cheers
Rohan

[rgh0]

I spent the day cleaning up the block and measuring up the two spare modified L16 Datsun cranks I have.

Wired brushed every machined exterior surface of the block ( top, bottom, front, back, oil pump, fuel pump) and then cleaned with solvent, Cleaned out all the oil passages with a rag, solvent and pull through. Cleaned out all the bolt holes with rag and small screw driver and solvent.Cleaned all the inside surfaces, bores and bearing mounts with solvent.... Now ready for assembly

I have 2 spare L16 cranks and need to decide which to use:

One has a stroke .25mm / 10 thou longer than standard due to a machining error when it was made and has 10 thou under size mains and 20 thou under size big ends . My racing class has recently introduced engine measurement and sealing and my class requires standard stroke. I don't know if a .25mm / 10 thou longer stroke will be acceptable, as standard stroke must be kept.... but no tolerance is specified! I need to talk to the eligibility officer. I have all the bearings for this crank but may not be able to use it.

The other one is correct stroke at 72.75mm and its mains are standard and big ends 10 thou under size. An L16 crank at standard stroke has to have big ends 10 thou under size as a minimum. I don't have any spare bearings for this crank but i ordered a new set from SJS today. They will ship Monday and I should have by Wednesday in case i need to use this one. I find I can often buy bearings quicker and cheaper out of the UK than in Australia despite ACL bearings being made locally. This is the darker crank in the photo, I have not used this one and had forgotten I had this one nitrided . The other crank was not nitrided and has had about 8000 racing miles with no wear.

Picked up my new McCoy .460 lift 300 degree seat to seat inlet cam during the week from Clive Cams. I had it checked to confirm its to the specification i expected as i got it from a friend rather than direct from John. My friend had purchased two but broke one during assembly so he used another cam set and i brought his unbroken one. I also had it drilled and tapped to accept long sprocket bolts. This allows the bolt down past the first cam bearing and reduces the risk of breaking the cam which is very real with a high lift cam at high RPM. The long bolt needs to be hollow drilled and grooved and cross drilled to allow oil to flow down the cam from the first bearing to feed all the other cam bearings.

Did a bit of work on the water pump and front cover also.

cheers
Rohan

[Certified Lotus]

Time to cosy up to our local friendly pilots as far as that avgas ban goes eh Rohan!!

I never had a problem getting avgas. Lots of local airports who are very willing to sell it to you. My "home track" ( New Jersey Motor Sports Park) has an airport next to it. We would drive over with a pick up truck full of red 10 gallon gas containers and fill up.

Thanks for providing a detailed description of your new build Rohan ! We are all facinated to "watch over your shoulder".

[nmauduit]

I also had it drilled and tapped to accept long sprocket bolts. This allows the bolt down past the first cam bearing and reduces the risk of breaking the cam which is very real with a high lift cam at high RPM. The long bolt needs to be hollow drilled and grooved and cross drilled to allow oil to flow down the cam from the first bearing to feed all the other cam bearings.

I recently ask QED about long sprocket bolts and tapping accordingly the camshafts for a build I'm scheduling, and they said they had never done the longer bolt ... which I've found a bit surprising. So I guess I'll have to source a long tap and do it myself. By how much do you get them pass the bearing ?