specing engine

[Peter loveday]

I'm putting together a loose spec list for my engine build and looking for some real world guidance on what is realistically possible. I've started to collect some bits but would appreciate some feedback around CR and cam choice.

I'm not going to give a power target but I would like a very rev happy engine which I assume would be limited by the standard crank. I have an N42 block in great condition which I will bore out to between 88-89mm wall thickness dependent. I will be running either Datsun spirt or Kamenari lightweight pistons and rods (139.5mm) with the usual other upgrades etc. The head will be a maxima n47 which I will port or have ported and I will likely go with 45/36.5 mm valves.
Looks like this would result somewhere around a 12:1 compression ratio which will fall a bit with unshrouding etc. What cam is realistic to keep Det at bay running 99 RON without sacrificing ideal ignition timing?

Perhaps I am looking at this the wrong way round, eg choose the cam and build around that eg the cam kit sold by mike .560" lift and 300 degree duration- what cr would be ideal.

Any particular manufacturer or specialist that would be recommended? kaminari, Datsun spirtit, Les colins etc

I realise these are some very specific questions

Thanks

 

[jonbills]

I think for an mn47 head, 12:1 cr is reasonable with proper ignition timing. Might even run OK on 95 RON.
I don't think there's any down side to bigger cams if you're keen on revs. A balanced rotating assembly should be good for 8k+. In Japan I understand 10k isn't so rare.

 

[jonbills]

What crank and displacement are you planning? If that's an L28 and 3.0 ish, I think an Mn47 will be about 11:1 cr esp if your pistons have valve cutouts. I read mn47 has 39 cc Chambers.
My engine is L28 with 88.5 kameari pistons and p90a head with 39 cc Chambers and my calcs give 11.1:1 cr

 

[richiep]

What crank and displacement are you planning? If that's an L28 and 3.0 ish, I think an Mn47 will be about 11:1 cr esp if your pistons have valve cutouts. I read mn47 has 39 cc Chambers.
My engine is L28 with 88.5 kameari pistons and p90a head with 39 cc Chambers and my calcs give 11.1:1 cr

I can't remember if we've discussed this before Jon - how much did the P90 head get skimmed to get down to 39cc? Or was some welding done too? That's a big old drop from the standard P90 chamber cc.

Peter - why the MN47? It has a good rep based on the chamber size and shape, and can be worked successfully on the intake side; it just has the negative of being a round exhaust port head with steel liners, meaning very little can be done with regards to port work on that side.

 

[SeanDezart]

Agreed with Rich on the head, being brutally honest - the N47 is a bad choice.

If we're agreed that an engine is not merely the sum of all parts, it should be constructed around the choices of inlet and exhaust manifolds together with the induction type (carb choice or ITbs).....to me these are essential questions to answer along with those already posed.

 

[Alphabettispaghetti]

I'm putting together a loose spec list for my engine build and looking for some real world guidance on what is realistically possible. I've started to collect some bits but would appreciate some feedback around CR and cam choice.

I'm not going to give a power target but I would like a very rev happy engine which I assume would be limited by the standard crank. I have an N42 block in great condition which I will bore out to between 88-89mm wall thickness dependent. I will be running either Datsun spirt or Kamenari lightweight pistons and rods (139.5mm) with the usual other upgrades etc. The head will be a maxima n47 which I will port or have ported and I will likely go with 45/36.5 mm valves.
Looks like this would result somewhere around a 12:1 compression ratio which will fall a bit with unshrouding etc. What cam is realistic to keep Det at bay running 99 RON without sacrificing ideal ignition timing?

Perhaps I am looking at this the wrong way round, eg choose the cam and build around that eg the cam kit sold by mike .560" lift and 300 degree duration- what cr would be ideal.

Any particular manufacturer or specialist that would be recommended? kaminari, Datsun spirtit, Les colins etc

I realise these are some very specific questions

Thanks

Given that Datsun spirit pistons are Kameari ones, re branded, I’d say Kameari, they’re cheaper also.

They also do matched components, if you email they’ll come up with a whole package of parts designed to work together.

 

[Tommi]

Given that Datsun spirit pistons are Kameari ones, re branded, I’d say Kameari, they’re cheaper also.

They also do matched components, if you email they’ll come up with a whole package of parts designed to work together.

We had this discussion before I believe. This is the response from Eiji after last time you brought this up. I left it at the time but you seem persistent.

“Yes there are those who don't know and brag about things. This can't be helped.
I have (name removed) and other manufacturers do the manufacturing for me, but the designs are mine. I design all of these parts in house as you know, but we don't possess production/manufacturing capabilities. They are definitely not Kameari or anyone else's copy. By the way, I grew up mere few miles from Kameari, and have known those guys for years.
We or Kameari or other shops do focus on L-engines, and thus after many years and many refinements and learning from trial & errors, the parts do become similar in looks, materials, weight, etc, yet with some subtle differences. Unfortunately some of the general public do not understand that, and there exists shops who do copy and re-name other people's products”

Please don’t keep slating Datsun spirit at any opportunity. It’s hard enough getting the real truth with these wonderful classics. More miss information helps no one. I’m sure you love Japanese classics as much as me so please don’t take this as a dig, I just have to stick by the truth.

Tom

 

[jonbills]

I can't remember if we've discussed this before Jon - how much did the P90 head get skimmed to get down to 39cc? Or was some welding done too? That's a big old drop from the standard P90 chamber cc.

Peter - why the MN47? It has a good rep based on the chamber size and shape, and can be worked successfully on the intake side; it just has the negative of being a round exhaust port head with steel liners, meaning very little can be done with regards to port work on that side.

It's only had a small skim. It had a lot of welding though! I'll probably skim it 0.5 to 0.7mm next time I take it off.

 

[jonbills]

We had this discussion before I believe. This is the response from Eiji after last time you brought this up. I left it at the time but you seem persistent.

“Yes there are those who don't know and brag about things. This can't be helped.
I have (name removed) and other manufacturers do the manufacturing for me, but the designs are mine. I design all of these parts in house as you know, but we don't possess production/manufacturing capabilities. They are definitely not Kameari or anyone else's copy. By the way, I grew up mere few miles from Kameari, and have known those guys for years.
We or Kameari or other shops do focus on L-engines, and thus after many years and many refinements and learning from trial & errors, the parts do become similar in looks, materials, weight, etc, yet with some subtle differences. Unfortunately some of the general public do not understand that, and there exists shops who do copy and re-name other people's products”

Please don’t keep slating Datsun spirit at any opportunity. It’s hard enough getting the real truth with these wonderful classics. More miss information helps no one. I’m sure you love Japanese classics as much as me so please don’t take this as a dig, I just have to stick by the truth.

Tom

It would be interesting to see some side by side pics. The pics I've seen before looked very like Kameari pistons.

 

[jonbills]

Agreed with Rich on the head, being brutally honest - the N47 is a bad choice.

If we're agreed that an engine is not merely the sum of all parts, it should be constructed around the choices of inlet and exhaust manifolds together with the induction type (carb choice or ITbs).....to me these are essential questions to answer along with those already posed.

I think mn47 is a good choice. There's no particular down side with round exhaust ports as far as I know.

 

[Tommi]

It would be interesting to see some side by side pics. The pics I've seen before looked very like Kameari pistons.

Yes for sure.....and kameari look like Datsun spirit ones and both of them look like any other high quality, forged racing piston of the same size. Only slight differences in skirt size, skirt coating, ring heights etc between them. The fact is I doubt many tuning companies have in house piston forging/manufacturing facilities, so all use the companies that specialise in that industry. But importantly they are produced to a clients design and that is where the slight differences are. Anyway....all great products sold by people with a passion for L series engines. I would buy products from either of them in a heartbeat.

Tom

 

[jonbills]

Yes for sure.....and kameari look like Datsun spirit ones and both of them look like any other high quality, forged racing piston of the same size. Only slight differences in skirt size, skirt coating, ring heights etc between them. The fact is I doubt many tuning companies have in house piston forging/manufacturing facilities, so all use the companies that specialise in that industry. But importantly they are produced to a clients design and that is where the slight differences are. Anyway....all great products sold by people with a passion for L series engines. I would buy products from either of them in a heartbeat.

Tom

Yep, fair enough. Both are excellent. Let's leave it there since we're way off topic!

 

[Peter loveday]

Thanks for all the feedback, a bit more detail on the current spec.

I’ll be using an l28 crank so yes will be around 3l. Induction will be through 46mm itbs - tract length to be optimised at a later date once running. Exhaust will be one of the last items to decide upon but will most likely be a 6-1 with equal length runners and I’ll fix down the diameter once I have a target power level.

Now the reason for choosing the (m)n47- as stated it has a small combustion chamber with near optimum design, it is in fact very similar to most aftermarket Chevy heads and I have a lot of material on optimising these (vizard books), inlet valves are small but that is not an issue as they would be upgraded anyway. The inlet ports may be a little narrower (not sure) but that only gives scope to improve the short side radius. As for the exhaust ports, I am yet to see any actual evidence that the linered ports are any more restrictive than any of the other heads. as far as I am aware, the big restriction in the exhaust port is around the valve bowl which the liner does not interfere with. If I manage to increase flow to the point that the liners are the bottle neck then the liners can be removed and further porting can take place. However before that point, porting the main runner will only reduce velocity and reduce low down torque.

With regards to either of the two companies I’d be happy to use either, I’d been planning a visit to kamenari when I’m next in Tokyo so they are likely to be my first choice.

Any more ideas on a suitable cam? I’m struggling to find any real data or suitable applications

 

[Alphabettispaghetti]

It would be interesting to see some side by side pics. The pics I've seen before looked very like Kameari pistons.

I've had one in my hand and compared to the kameari. It was an Exact copy.

 

[Alphabettispaghetti]

Does Les collins get his parts made?

 

[jonbills]

There used to be Kaminari body kits, but you definitely want Kameari for engines!

Schneider cams list lift and overlap and power band for their range. E.G they've got one near. 600 lift and 310 deg overlap that has power to 9k (something like that!)
You could look at their website, pick the power band you're after and call Kent cams and see if they can help you with a similar custom regrind.

 

[SeanDezart]

I've never heard of a linered head having them removed and not being finally junked.

Who makes quality round-ported exhaust manifolds ?

 

[Peter loveday]

I've never heard of a linered head having them removed and not being finally junked.

We will have to see how the porting goes then

Who makes quality round-ported exhaust manifolds ?

Me