L28 Fast Road Engine Rebuild - Advice Wanted!

AliK

Vehicle Dating Officer
Staff member
Club Member
Cast your mind back to when those with stock pistons were set aside as outcasts.

Think wisely and don’t allow yourself to be typecast as one of those collecting top trumps car parts to make a beauty pageant casting impression.

Take your time, build an engine with a budget that allows you to buy decent Castrol oils and the parts that matter in the long run.























Don’t let Mr Franky bully you into his cast - buy what is right for you!
 
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Woody928

Events Officer
Staff member
Club Member
Apologies for the extended absence on here, and thank you to everyone for their responses!

Factoid- the factory L-series rods are forged. So talking about replacing stock with “forged rods” isn’t actually the distinction people think it is. The upgrade element of the aftermarket rods comes in the lightweight H or I-beam designs and consistency of weight within a set. Factory rods can be prepped for hard performance use - just effort and money. The Maxspeeding rods just offer a more cost effective alternative these days.

Well you learn something new every day! Thanks for clarifying, that now makes so much more sense. So really the big distinction comes from fitting forged pistons over factory cast ones? I'm keeping up?

Depends which holes you use. I'd have to look up the factory advice for this (I've seen photos/diagram somewhere) but I think you could use the bellhousing bolts threads for the 'short' block safely and just try to avoid having a full engine (ie - with cylinder head in place) hanging off it too long. It makes my toes wince...

Kameari Engine Works can supply a forged piston to use with stock (forged!) L28 connecting rods and stock (forged!) L28 crankshaft. In 89mm size this would give you a swept volume close to 3 litres. That would be a good bang-for-buck off the shelf choice, but people are liable to point out that the stock L28 rod length is "not ideal"...

And that's one of the problems with asking a question like this on an open forum. There are many ways to skin this cat and many of the opinions and recommendations you will get are each as viable as another. Only you can say where you want to get to, and choose how you want to get there. You'd probably be well advised at this point to focus on stripping the base engine down, learning how it comes apart (which will help you put it back together again) and cleaning, bagging/noting the stock components (even if you're not going to use some of them) whilst not forcing yourself to make any decisions about modifying or aftermarket parts just yet. And reading the books. The books! Read the books.

Definitely read, and read again, the books.

Thanks Alan, it looks like I'll have to mount the long block way, I'll just be sure to make sure its only the block itself and the head and all ancillaries are removed!

Now that is very interesting, it seems like a more budget friendly compromise between the two perhaps! Fortunately I'm not looking for this engine to be the absolute peak of performance so the red length not being perhaps 'ideal' is less of a concern for me. Bang for buck and future proofing are however much higher up my list!

In your experience would boring out an F54 block to 89mm be wise though? From the reading I've been doing online it appears that could be pushing the limits of the block without re sleeving however this appears to be a case by case situation from what I understand (please correct me if I'm misinformed). Would it be perhaps wiser thinking of longevity to restrain myself to say 88mm bore?

I certainly now appreciate that this question has many different possible combinations and solutions, and have avoided posting on say Facebook as I know I'll likely only be told 'well I've done this and its great so you should do it too!' I'm trying to work out how to recover the engine from my lockup given current circumstances to start doing that exactly. I've certainly been reading the books about disassembly which fingers crossed will be the more straight forward element! Putting it back together correctly is what concerns me more.

I like the way you’re forging ahead with this, trying best not to cast a shadow on one option or another. Either way you choose will produce great results, I just wouldn’t want you to look back and see you’re own shadow cast over your engine while others have forged ahead, leaving you feeling limited by past choices while the world around you raises their limits.

fit forged pistons.

I see what you did there! :rofl: I'm trying to see whether there is a happy medium between a totally stockish rebuild and tweaking things a little to sprinkle just a little bit of extra magic to really give that grin factor when its all installed. I think Alans above suggestion could prove that happy medium albeit budget certainly has to be consulted! Also I have in my back pocket that later I can add a triple or efi setup for some extra umph should I feel its needed without having to open anything up ;)

I certainly don't need a bonkers top of the shelf adamantium engine just for bragging rights so I'm trying to sensibly restrain myself!

Please keep the thoughts coming, this is proving to be very educational for me!
 
Apologies for the extended absence on here, and thank you to everyone for their responses!





I see what you did there! :rofl: I'm trying to see whether there is a happy medium between a totally stockish rebuild and tweaking things a little to sprinkle just a little bit of extra magic to really give that grin factor when its all installed. I think Alans above suggestion could prove that happy medium albeit budget certainly has to be consulted! Also I have in my back pocket that later I can add a triple or efi setup for some extra umph should I feel its needed without having to open anything up ;)

I certainly don't need a bonkers top of the shelf adamantium engine just for bragging rights so I'm trying to sensibly restrain myself!

Please keep the thoughts coming, this is proving to be very educational for me!

Adamantium. What a 'Marvel'ous metal.

Dont EFI.

Electronic
female only
Injection
 

Makesy

Club Member
Adamantium. What a 'Marvel'ous metal.

Dont EFI.

Electronic
female only
Injection

Being comfortable with sexuality, I opted to stick with injectors....but that's just me ;)

Great thread so far @Woody928 ! Can't wait to see how this all comes together! I will likely poach some of this advice for my own use
 

Ian Patmore

Well-Known Forum User
You don’t need to go all out on the spends to get 200whp if attention to detail is followed and the right work done.

I'm trying to see whether there is a happy medium between a totally stockish rebuild and tweaking things a little to sprinkle just a little bit of extra magic to really give that grin factor when its all installed.


Richiep is quite right, easily abtainable without throwing more parts than needed at it, especially where the money should be spent where it is needed.

All do-able keeping within your stockish rebuild.
 

Woody928

Events Officer
Staff member
Club Member
Dont EFI.

:rofl: I think I'll likely stick with OER's or Mikunis

Add to favourites...
Welcome back woody

Thanks man :coolgleam:

Richiep is quite right, easily abtainable without throwing more parts than needed at it, especially where the money should be spent where it is needed.

All do-able keeping within your stockish rebuild.

Thank you for the reality check, I really do need to keep my budget in mind. It's very easy to let temptation and ideas get the best of you with so much info and altentives out there.

Realistically my next steps are to get the engine back, strip it and then hopefully get the block sonic tested to see where I stand before making any plans and doing anything rash.

I have also emailed Mr Mori San at Kameari for some advice as I hear he's very helpful.

Here's my 'modified' L28 for some inspiration,


after a quick balance adjustment today

:devil: So much want, I'm very excited for when this is all done! Lots of time and money to be spent in the meantime though...
 
:rofl: I think I'll likely stick with OER's or Mikunis



Thanks man :coolgleam:



Thank you for the reality check, I really do need to keep my budget in mind. It's very easy to let temptation and ideas get the best of you with so much info and altentives out there.

Realistically my next steps are to get the engine back, strip it and then hopefully get the block sonic tested to see where I stand before making any plans and doing anything rash.

I have also emailed Mr Mori San at Kameari for some advice as I hear he's very helpful.



:devil: So much want, I'm very excited for when this is all done! Lots of time and money to be spent in the meantime though...


Sounds like sensible steps. Mr Mori and OER. Add a Fujitsubo and you'll become a hero.
 

Ian Patmore

Well-Known Forum User
Most still thinking Woodys goal can be done by sticking an exhaust and triples on...very little talked about the internals, revving to 7k (woody's post 1) reliably isn't done just with forged pistons...

Woody, check everything you are going to re-use, e.g. don't presume the crank is straight
 

Turn & Burn

Club Member
You may have watched this already, but it really shows that you can get significant power without going overboard on the spend. Engine building really is the rule of diminishing returns. I’m building a stroked 3.2 and I reckon that I may only make 25bhp more than this. I’m thinking I’ll be lucky to get to get much past 260bhp flywheel and Aaron must be doing 240bhp flywheel on what is in terms of mods a very simple build and still on SUs. What a winner of a build!
 

Woody928

Events Officer
Staff member
Club Member
Most still thinking Woodys goal can be done by sticking an exhaust and triples on...very little talked about the internals, revving to 7k (woody's post 1) reliably isn't done just with forged pistons...

Woody, check everything you are going to re-use, e.g. don't presume the crank is straight

Thanks Ian, it dawned on me a long time ago there was far more to be done than bolt on's. The basic advice always seems to be 'well you want triples' which gets old fast as a statement. I'm going to focus on the bottom end first and then work my way up, clearly from the comments made I need to spend a lot of time working on the head. I'm getting the impression that balancing work will be vital to making the car rev highly and reliably.

Certainly diagnosing what I have first is essential. This is where having someone to walk me though everything would be super helpful. The books will however be my bible!

You may have watched this already, but it really shows that you can get significant power without going overboard on the spend. Engine building really is the rule of diminishing returns. I’m building a stroked 3.2 and I reckon that I may only make 25bhp more than this. I’m thinking I’ll be lucky to get to get much past 260bhp flywheel and Aaron must be doing 240bhp flywheel on what is in terms of mods a very simple build and still on SUs. What a winner of a build!

I've followed the Chanel for a while thanks, it's a great build and he's a really helpful bloke. Yes and no, that engine is using an LD28 crank which has a significant price tag attached these days... I remain hopeful for boring out my block and retaining the stock crank however I really need to find out how far I can safely bore out my block so I can work out what pistons will be available to me for the bottom end. Still waiting to get the engine back though :(
 

Ian Patmore

Well-Known Forum User
I see a huge discussion on internals has taken place...

Nice to see the video above with attention to detail, getting things working right.

Woody, I am not going to tell you what to do, as you must be out of short trousers by now. Consider;

Block, clean, remove oil gallery plugs so can clean, then fit NPT plug. smoothing off the under side of block, it removes roughness for oil drain quicker back to sump, removes cast material and can relieve where stress fractures can occur, esp if you plan at running at 7k. Paint inside. I have done this. Thoughly tap all holes to aid good assembly. Check deck surface is flat. On that note, I have a couple of z owner friends, both have had problems with machined parts that were "flat" when they aren't. This is probably down to the milling machine not been serviced, greased, swarf removed. I have seen the wear on Bridgeports mills, and the state they get into... so make sure flat is flat. What bolts, ARP? What about cooling, change the core plugs, drill out the water holes in the deck of the block?

Crank, check straight, polish journals, a few "free" hp and it has less wear on bearings. Don't skimp on bearings quality, e.g. Nissan. as good quslity is less likely to gaul.

Rod and Pistons, that is up to you, except to say the stock rod is perfectly good for "street" and even race applications. Consider getting them prepped, if not, the very least make sure they are part of a balanced set-up.

Head, some of this you can attempt, do, its not hard, some I have done. Cam, up to you, but consider whether it is ground onto an internal or externally oiled. If an externally oiled system, need spray bar, but you would need a set of appropriate cam towers, matched. It chucks the oil everywhere , and if you are running 7k rpm... Valve springs, are you going to get float at high rpm, what spring pressure, stock, or light...? What oil stem seals..? rockers, do you lighten for valve train inertia...?, what valve hats do you go for? if skimmed, tower shims or Kenmeari tensioner? Un-shroud the valves, will aid flow, but add cc to compression value, valve job, what can/needs to be done? Work out your combustion chamber cc, easy with chemist burette (I have one if you want) and have done. You could easily find when the cylinder head was cast, the dies have "moved" giving you un-even volumes. Can do some of the work here yourself in removing material. Do you weld the combustion chambers up, do you weld up the injector notches in the intake ports. What porting is done? Check thread holes and water passageways, check how head gasket sits, does it line up? What gasket do I go for? Check head flat on 3 sides. No point over-sizing valves, the N42 is already 44mm, any larger and your exhaust port won't cope, and become a restiction. Any valve/seat work, make sure the valves all sit at the same height. I have had a "Z specialist" do mine many years ago, and they were allover the place, so adding lash pads was a faff. Do you mod the head for better cooling at the rear?

Oil pump can keep up with your engine revs, and your water pump. I see you mentioned different rad, but a large % or people don't think of the thermostat, they open at varying heights, so are a restriction.

If using Ztherpy rebuilt carbs (by the way, they can be bored out if too small for engine cc), the N36 inlet manifold (from a 260z) has been said to be better than the 240z one, and add a few hp's. I still think it can be improved further (the N36). Inlet/exhaust gasket, make sure it fits and not cover part of any port, and do you port match? What studs here do you use? Think about how you fit the manifolds, they can be different heights, most stack bits of washers, yuck. I worked and had my intake notched so it was the same height as the exhaust, so clamping force is equal, less likely to leak. I see you mention header, size?

Plenty to discuss, rather than just what over-bore. I personally would leave and concentrate on things like above. A 1mm overbore just on its own isn't going to gain many hp, 3 or 4?.... Unless you go big, my next project, using the original Nissan block/head will have a 70% increase in cc over stock....
 

SacCyclone

Club Member
And throw in a baffled high capacity oil pan too?

dy6VYlf.jpg
 

Woody928

Events Officer
Staff member
Club Member
upload_2021-2-1_16-50-58.jpeg

Well its long overdue that I appear back from the dead, it looks like I nearly managed an entire years absence from here! I've been taking some time out for some well needed personal development while the world has been ending, the car had very much taken a back seat however I'm hoping to change that now.

I've also got my summer project out of the way which was taking up far too much time and money, its just got a few finishing touches to be added. It won't be to everyones taste however it's gone down my usual resto mod route, it'll now likely go up for sale this summer for something new assuming we're let out again.

72DA583C-121C-4630-8110-816CA766A5AA by Mark Woodrow, on Flickr

IMG_2211 by Mark Woodrow, on Flickr

Back to the engine anyway, having languished in my lockup for over a year and a half I've finally managed to get it stripped of all its extra weight and recovered it to the workshop. Several small battles with corroded bolts along the way as you'd expect. I've since got it onto its engine stand and finally begun the strip down work so that I can begin reworking it and damage assess the situation.

As of the weekend the bottom end was fully stripped, with all components bagged and tagged and the head has been set aside to be stripped and inspected next. On the whole it appears to have gone remarkably well so far, the books have been worth their weight in gold. I would have made so many mistakes without their guidance!

The bottom end looks in remarkably good condition to me, however I will wait for a machine shops full appraisal down the line. The head is pretty covered in carbon and appears to have had a head gasket leak around cylinders 3 & 4 albeit looks good on the whole. It'll need to be cleaned and stripped to work out more.

I'm currently doing a lot of online shopping and building lists of consumable items to be replaced, working out the essentials, the nice to have's and trying to build my ideal specification. I've very much woken up to the financial rabbit hole that a build like this can bring now that I've begun listing it out.

So what's the plan? This is as far as I've got to date and will need revision and adding to, however any and all input welcome.

At home I'd like to:
  • Remove casting flash from bottom end to help oil draining
  • Tap all threaded holes
  • Strip Head
  • Clean head
  • Research and look to DIY port and polish head
Machine Shop List:
  • Drill out oil gallery plugs (tap and plug)
  • Hot tank block to clean
  • Pressure test block
  • Deck the Block
  • Rebore block from 86mm to 88.5mm to suit new forged pistons (Use torque plate)
  • Inspect crank for wear, polish journals
  • Check and balance new rods and pistons
  • Dynamically balance bottom end with new rods, pistons, damper pulley, lightweight flywheel, clutch and crank
  • Hot tank clean head + pressure test
  • Skim head, three sides
  • Valve guides inspected and replaced where necessary
  • Valve seat reground to suit new valves (Three angle seats + new swirl polished valves to be provided)
Parts Specs
  • Kameari 88.5mm Forged Pistons
  • L28 Max Speeding Rods
  • Exedy Stage One Organic Clutch
  • Datsun Spirit Lightweight Flywheel
  • Kameari Racing Harmonic Balancer
  • Stock Water pump
  • Kameari High performance Oil pump
  • Kameari Adjustable Cam Sprocket
  • Complete Engine bolt replacement kit (stainless unless advised otherwise)
  • New bearings (ITM currently selected, haven't found an OEM source)
  • OEM Head Bolts
  • Full Gasket Kit
  • Timing Chain replacement Kit
  • New freeze plugs etc
  • DSI Swirl Polished 44mm, 35mm Valves
Cam choice still to be decided, have made various enquiries and considered various options from Kent regrind, Schneider, Kameari, Datsun Spirit etc. I have contacted DSI about their 274 .480 lift camshaft and am waiting to hear further. I would like to get a kit designed to work together either way so new springs, retainers, lash pads etc. I'm assuming cam tower spacers will be needed with the head skimmed?

Hoping to achieve a compression ratio of 10.5.1 however would appreciate advice in this regard and how to achieve it?

As you can tell this has escalated quite significantly, however I appear to have conflicting requirements with my build. While I know I could reach the originally suggested power goals with a stock bottom end, I do not feel that it will give me the revy engine characteristics that I'm hoping for. I also do not wish to ever revisit the bottom end again so would like to over spec for my requirements rather than over spec.

I realise that if done properly I could end up with a healthy dose of more power than I'd originally intended however I'm not intending to chase it. Fingers crossed that the above specs will lend themselves to an engine which will have been built with several insurances lending itself to reliability and longevity.

I also know that running stock SU's will be the engines limiting factor in its first incarnation however I will address this later down the line when I can justify the extra expenditure on something like a proper EFI setup.

Still need to make enquiries with several machine shops however realise that costs will go well over £6,000 with the above specs.

If anyone has a good condition stock oil pan then I'd be very grateful as mine is very battered and thin having clearly been exposed to the elements for a very long time.

Lots to do and discuss but that's where I've got to so far, pictures of a lot of the work to date can be viewed in the album lined below:

https://flic.kr/s/aHsmU3ac4R

A few teasers for you as well ;-)

IMG_2907 by Mark Woodrow, on Flickr

IMG_3235 by Mark Woodrow, on Flickr

IMG_3307 by Mark Woodrow, on Flickr

IMG_3363 by Mark Woodrow, on Flickr

Finally, I'd just like to thank anyone who's input into this thread so far, some of the information and advice has been invaluable, despite my long absence I've re read this resource a number of times!
 
Last edited:

Woody928

Events Officer
Staff member
Club Member
I see a huge discussion on internals has taken place...

Nice to see the video above with attention to detail, getting things working right.

Woody, I am not going to tell you what to do, as you must be out of short trousers by now. Consider;

Block, clean, remove oil gallery plugs so can clean, then fit NPT plug. smoothing off the under side of block, it removes roughness for oil drain quicker back to sump, removes cast material and can relieve where stress fractures can occur, esp if you plan at running at 7k. Paint inside. I have done this. Thoughly tap all holes to aid good assembly. Check deck surface is flat. On that note, I have a couple of z owner friends, both have had problems with machined parts that were "flat" when they aren't. This is probably down to the milling machine not been serviced, greased, swarf removed. I have seen the wear on Bridgeports mills, and the state they get into... so make sure flat is flat. What bolts, ARP? What about cooling, change the core plugs, drill out the water holes in the deck of the block?

Crank, check straight, polish journals, a few "free" hp and it has less wear on bearings. Don't skimp on bearings quality, e.g. Nissan. as good quslity is less likely to gaul.

Rod and Pistons, that is up to you, except to say the stock rod is perfectly good for "street" and even race applications. Consider getting them prepped, if not, the very least make sure they are part of a balanced set-up.

Head, some of this you can attempt, do, its not hard, some I have done. Cam, up to you, but consider whether it is ground onto an internal or externally oiled. If an externally oiled system, need spray bar, but you would need a set of appropriate cam towers, matched. It chucks the oil everywhere , and if you are running 7k rpm... Valve springs, are you going to get float at high rpm, what spring pressure, stock, or light...? What oil stem seals..? rockers, do you lighten for valve train inertia...?, what valve hats do you go for? if skimmed, tower shims or Kenmeari tensioner? Un-shroud the valves, will aid flow, but add cc to compression value, valve job, what can/needs to be done? Work out your combustion chamber cc, easy with chemist burette (I have one if you want) and have done. You could easily find when the cylinder head was cast, the dies have "moved" giving you un-even volumes. Can do some of the work here yourself in removing material. Do you weld the combustion chambers up, do you weld up the injector notches in the intake ports. What porting is done? Check thread holes and water passageways, check how head gasket sits, does it line up? What gasket do I go for? Check head flat on 3 sides. No point over-sizing valves, the N42 is already 44mm, any larger and your exhaust port won't cope, and become a restiction. Any valve/seat work, make sure the valves all sit at the same height. I have had a "Z specialist" do mine many years ago, and they were allover the place, so adding lash pads was a faff. Do you mod the head for better cooling at the rear?

Oil pump can keep up with your engine revs, and your water pump. I see you mentioned different rad, but a large % or people don't think of the thermostat, they open at varying heights, so are a restriction.

If using Ztherpy rebuilt carbs (by the way, they can be bored out if too small for engine cc), the N36 inlet manifold (from a 260z) has been said to be better than the 240z one, and add a few hp's. I still think it can be improved further (the N36). Inlet/exhaust gasket, make sure it fits and not cover part of any port, and do you port match? What studs here do you use? Think about how you fit the manifolds, they can be different heights, most stack bits of washers, yuck. I worked and had my intake notched so it was the same height as the exhaust, so clamping force is equal, less likely to leak. I see you mention header, size?

Plenty to discuss, rather than just what over-bore. I personally would leave and concentrate on things like above. A 1mm overbore just on its own isn't going to gain many hp, 3 or 4?.... Unless you go big, my next project, using the original Nissan block/head will have a 70% increase in cc over stock....

This is a hugely belated response, however I just wanted to say a massive thank you for your lengthy response Ian. I've referred back to your input several times, and having now started taking things apart am really starting to appreciate the level of detail required. Any further input gratefully received as you've clearly been there and done this many times before!
 
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Mr.G

Club Member
Very nice post Mark, I like the methodical approach you are taking.

I will be embarking on my own engine project later this year, with the help of some good friends and I will be taking a keen interest in your thread and photos.

I am sure you will be doing good research when it comes to finding a machine shop and a good one will always be worth travelling a distance to.
 
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