L28 Rebuild Advice

[HomeBuiltByJeff]

Hey guys,

 

Some of you may have been watching my silly videos pulling apart my L28. I am starting to formulate a plan for the rebuild of it. I am not looking for a balls to the wall track pig, but I am keen on doing some simple mods. 

 

I have been reading Datsunzgarage and I have begun to formulate a plan to go forward.

 

I currently have an F54 block with a P90a head.

I want to keep the crank, rods, and possibly the flat top pistons as they appear to be in good condition.

 

I am planning to get the head shaved, as mentioned on Datsunzgarage so I know it requires the cam to have shims under it to keep the chain tension in spec. 

 

I obviously also plan on replacing the bearings, gaskets, etc, but planning on just going with stock items.

 

I also need to replace the cam anyway, as it has a bit of corrosion I am not happy about. This is where I am needing some advice. I want this car to be streetable, I am not looking for a super lumpy track pig. I want to try to retain my valves just clean them up and lap them. There is a small, but noticeable wear line on the last rocker (others seem pretty good), which lines up with the most corroded cam lobe. Do I need to get all new lifters with a new cam? Is getting them resurfaced a more cost effective option.

 

I was advised that if I did shave the head and raise the cam, that I would need longer valves? I am wondering, if I get the head shaved, can I then get a cam with higher lift and just add more lash?

 

Basically my whole aim, is to do 99% of it myself at home. I realise I will need a machine shop to shave the head, and possibly get them to thoroughly clean the head and block. Is there anything else I MUST do?

 

Also to note, I am thinking I will run triple webers, and an exhaust to be determined.

Let me know if I am stupid, or if there is a better way.

 

Jeff

 

[GregTas]

Why are you so keen to get the head shaved? Does it need it or are you doing it to bump the compression?

 

If it's only a very minor skim I wouldn't think it would create too many issues with the chain.

[HomeBuiltByJeff]

Why are you so keen to get the head shaved? Does it need it or are you doing it to bump the compression?

 

If it's only a very minor skim I wouldn't think it would create too many issues with the chain.

Sorry, I should have been clearer. Yes I was planning up upping compression. My idea, is to try to do a basic rebuild, with a few relatively simple upgrades, that others can watch, and potentially do at home themselves.

[GregTas]

You could always leave the head and put higher comp pistons in. Could be easier.

[scott]

no point using a P90 for a street car, clean up a n42 as it will be suited better for what you want.

What fuel setup are u running, carbs or efi?

U can get rockers resurfaced, any L builder can off this service. Try M.i.a engine service or stuart wilkins motorsports

[dat2kman]

Get an N42

For same $$$$ spent, better bang for buck.

 

You can rip 120 thou off a p90, and bring the chamber down from 53cc to around 44cc, the benefit of p90 is the better flowing ports compared to other STANDARD heads.

Valves are different heights.

The Kameari timing chain tensioner kit solves a few issues, many are using these, with good result.

If budget allows, look at using longer rods, and shorter pistons, for improved rod length to stroke ratio

 

Go talk to Clive Cams for your cam, it'll most likely need to be a welded up, then ground down, 72-74 deg, nice tractable unit.

He has all the various grinds on CNC machinery.

[gav240z]

Get an N42

For same $$$$ spent, better bang for buck.

 

You can rip 120 thou off a p90, and bring the chamber down from 53cc to around 44cc, the benefit of p90 is the better flowing ports compared to other STANDARD heads.

Valves are different heights.

The Kameari timing chain tensioner kit solves a few issues, many are using these, with good result.

If budget allows, look at using longer rods, and shorter pistons, for improved rod length to stroke ratio

 

Go talk to Clive Cams for your cam, it'll most likely need to be a welded up, then ground down, 72-74 deg, nice tractable unit.

He has all the various grinds on CNC machinery.

What he said basically.

 

If you want an N42 I have 2, would swap 1 with a P90a if it suits you?

 

I would not shave the P90, it's the wrong way to go about upping compression in my opinion. Much harder to add material back than to take it off.

 

P90's are better when they have combustion chambers welded up (more expensive).

 

The Kameari timing chain tensioner kit is a bit expensive (for a budget build) but gives the motor a nice sound (like an S20 motor).

 

I would almost buy 1 for that noise

 

Your existing camshaft can be reground to suit profile you need. Don't worry about corrosion on it. As mentioned speak to Clive Cams. Go 74 degree cam (that's what I want in mine).

[HomeBuiltByJeff]

What is the benefit of the N42 head over the P90a? Does it increase the compression?

 

no point using a P90 for a street car, clean up a n42 as it will be suited better for what you want.

What fuel setup are u running, carbs or efi?

U can get rockers resurfaced, any L builder can off this service. Try M.i.a engine service or stuart wilkins motorsports

I am planning on running triple webers with this build. They both look like good options for shops. Are there any decent engine shops on the South side of  Sydney (my laziness trying to save an hour driving  ).

 

 

What he said basically.

If you want an N42 I have 2, would swap 1 with a P90a if it suits you?

I would not shave the P90, it's the wrong way to go about upping compression in my opinion. Much harder to add material back than to take it off.

P90's are better when they have combustion chambers welded up (more expensive).

The Kameari timing chain tensioner kit is a bit expensive (for a budget build) but gives the motor a nice sound (like an S20 motor).

I would almost buy 1 for that noise

Your existing camshaft can be reground to suit profile you need. Don't worry about corrosion on it. As mentioned speak to Clive Cams. Go 74 degree cam (that's what I want in mine).

A swap could definitely be on the cards. Can I keep running the standard valves with a clean and a lap? I assume they would have to be the matching N42 valves.

 

So I assume the Kameari chain tensioner is something to offset a shaved head. 

 

Overall does my plan sound worth while? As I said, for a fun street car that I don't hate driving because it is so temperamental.

[C.A.R.]

   

   

   

   

[chris240]

What's scary is I know that scene is around 2 minutes into the extended version of thriller.

Welcome back LF...

[Howdy]

G'Day Jeff,

What you have in mind sounds good. What ever way you can get higher compression is OK but need to try to keep the port size reasonable and they do respond very well to a good port job on the inlet ports. Not sure which pistons are in your motor but if they are dished, it might be cheapest to find some flat top pistons and keep that head. I'd find another good rocker from somewhere, should be plenty around. The triples might get a bit fat in traffic and not like idling for too long, especially with a cam. Plugs tend to foul easily especially if you go with BP-7s which are a suitable heat range for higher comp and triples. They might need a reasonable tuning effort to get good enough for Sydney traffic. Trouble is the air flow velocity is a lot lower with decent size triples and a longer duration cam. Personally I don't think anything under 44mm carbs is worth the trouble and expense as they just use extra fuel. But man they do sound good. I found twin 2" SUs  work very well for a city car and are a cheaper alternative but you need to stuff around with the linkages a bit, port out the manifold and modify the air box which are all easy jobs. 240Z carbs are a common straight swap also. If it was me I'd go with 45mm triples, a decent set of headers, 2.5" exhaust, 9.5 to 10.5:1 comp - max you can get with that head (98 oct fuel) 72 deg cam, nice port job, recurved dizzy to suit, BP7ES plugs and keep it to 7000RPM / 7500 max - she will like to go higher but don't. Any higher you will need a good harmonic balancer, rod bolts and a good full engine balance including clutch. Optional extras would be a proper engine balance, lightened flywheel and HD clutch. And limit the heavy city traffic as she will be for the open road - old school with soul and character mate. One option you may not have considered is fuel injected individual throttle bodies which would be a bit easier to tune, more suitable for dual purpose driving and still sound awesome.

[HomeBuiltByJeff]

G'Day Jeff,

What you have in mind sounds good. What ever way you can get higher compression is OK but need to try to keep the port size reasonable and they do respond very well to a good port job on the inlet ports. Not sure which pistons are in your motor but if they are dished, it might be cheapest to find some flat top pistons and keep that head. I'd find another good rocker from somewhere, should be plenty around. The triples might get a bit fat in traffic and not like idling for too long, especially with a cam. Plugs tend to foul easily especially if you go with BP-7s which are a suitable heat range for higher comp and triples. They might need a reasonable tuning effort to get good enough for Sydney traffic. Trouble is the air flow velocity is a lot lower with decent size triples and a longer duration cam. Personally I don't think anything under 44mm carbs is worth the trouble and expense as they just use extra fuel. But man they do sound good. I found twin 2" SUs  work very well for a city car and are a cheaper alternative but you need to stuff around with the linkages a bit, port out the manifold and modify the air box which are all easy jobs. 240Z carbs are a common straight swap also. If it was me I'd go with 45mm triples, a decent set of headers, 2.5" exhaust, 9.5 to 10.5:1 comp - max you can get with that head (98 oct fuel) 72 deg cam, nice port job, recurved dizzy to suit, BP7ES plugs and keep it to 7000RPM / 7500 max - she will like to go higher but don't. Any higher you will need a good harmonic balancer, rod bolts and a good full engine balance including clutch. Optional extras would be a proper engine balance, lightened flywheel and HD clutch. And limit the heavy city traffic as she will be for the open road - old school with soul and character mate. One option you may not have considered is fuel injected individual throttle bodies which would be a bit easier to tune, more suitable for dual purpose driving and still sound awesome.

That is what I am talking about! I live in the sticks (Bowral) so traffic is not an issue. I am thinking I should take Gav up on his offer to swap for the N42 head, but I am trying to find what compression that should give me with the flat top pistons I have. I have have read one place that said 10:1 (which is perfect) where another said something like 11.5:1 (which is way too high for me).

 

The triple webers sounds great, so I am happy to live with the downsides. I know nothing about carbs, so I may as well jump off the deep end. I am stubborn enough to learn or die!

 

When you are talking about the porting required. Are you talking about cleaning up the ports and matching them to the manifold, or are do you mean I have to really get bigger valves? 

[gav240z]

Hi Jeff,

I don't know if my N42s have a complete set of valves so may need to source more as p90 valve stems are longer than N42 so can't be directly swapped.

 

I also took a camshaft out for my E31 head (internally oiled) swapped for the external spray bar set up on early cars.

 

Re: comp ratios if I recall correctly flat top pistons with an N42 head yields a 10:1 compression ratio.

 

There was an online L-series engine calculator years ago on Ozdat.com but I think it died.

 

You could try this though!

http://atlanticz.ca/zclub/techtips/enginemodellingsoftware/index.html

 

However it's not entirely accurate so use it as a reference point not the gospel.

 

I was just down your way yesterday, should have dropped by with the heads ?

[gav240z]

I would talk to James Flett at MIA engines in DeeWhy also about your options, budget and want you want to farm out in terms of machine work etc..

[HomeBuiltByJeff]

I was just down your way yesterday, should have dropped by with the heads

You should have dropped me a message, I was working on the car the whole day. Even just to say hi.

 

 

I would talk to James Flett at MIA engines in DeeWhy also about your options, budget and want you want to farm out in terms of machine work etc..

Well, If I can get away with just putting the N42 head on I may have very little machining to do. 

I would like to give the porting a go myself, and obviously all of the assembly. As you may have guessed by now, I don't like getting anyone else doing the work for me. If I can do everything myself, I will.

[ZED83]

I wouldn't recommend to anyone buying kameari twin idler gears. I had them on my 3.2ltr build, didn't even last 5000ks before it started tearing the chain to pieces.Yes they sound great, but a Waist of $700 in my opinion.....

Edited October 21, 2017 by ZED83

[TOO60Z]

I'm with MJ on this one,it's gonna be a thriller! Don't believe anything you read by forum experts to be gospel P90 valves are shorter as the chamber is deeper in the head. Comp ratios are fickle which rely on accurate measurements of piston to deck height,chamber volume, head gasket thickness and bore diameter plus any valve reliefs in piston and so on. Machine shops exist for a reason, they are tradesmen with years of experience and are in business to do the correct job but also to make money. Put an N42 on it with a bigger cam and no valve reliefs and you will die, and be back at the machine shop to do it all again. I don't set my house on fire just to have a go at putting it out myself.

[C.A.R.]

[HomeBuiltByJeff]

So with an N42 head, on my F54 block, with my flat top pistons, and a larger cam (72 degree??) what valves would I need to source? Do I need aftermarket? Or do I need N42 valves?

 

I do plan on taking the case and head to a machine shop, to at the minimum get them cleaned and to make sure the head is straight, etc. What else must I do? I am not looking at building something that revs to the heavens, I am more looking for a simple build that I can do at home. If it turns out that upping the compression is a stupid idea and it is better to just do a clean stock rebuild, then so be it, but I am sure there are a few things that can be done by someone at home if you take your time, and do it right.

 

I will be building my 911 engine myself when all my custom parts come back from the US, and that is stupidly expensive (probably in the realm of 20 times the budget of this engine). So this build is hopefully going to be a lot simpler, and more straight forward.

[AndBir]

So with an N42 head, on my F54 block, with my flat top pistons, and a larger cam (72 degree??) .......

 

It is mentioned in the Overview of Engine Heads on this forum (and talked about on various other forums) that :

 

"The N42 heads have hardened steel seats so it can run unleaded petrol. The head was used on fully dished pistons which meant that there was no quench in the design. It has been stated by some forum members that if you run an L28 with flat top pistons with an N42 head and standard petrol that you may experience some knocking.  It has also been said that the N42 is the preferable head for high compression NA motor because it already has large ports, BUT the chambers need modification for higher compression, better flame burn & better quench."

[Howdy]

When you are talking about the porting required. Are you talking about cleaning up the ports and matching them to the manifold, or are do you mean I have to really get bigger valves? 

 

It depends on what your final specs on the motor are but if it is higher comp, 72 or 74 deg cam and 45 webers then a high flowing inlet port will enhance that extra breathing in the medium to upper RPM range. Bigger valves would help in a higher spec motor but probably are not necessary for this build and the money could be better spent. If you do your own porting, take the time to learn the basics about port flow as first timers would be more likely to make them flow less than more. Pay particular attention to NOT ruining the port's shorter radius which is the usual number one mistake, and don't highly polish the inlet ports (exhaust yes so carbon doesn't stick but inlets need to be kept reasonably rough to aid flow and keep the fuel mixed with the air) and there are areas on the L series heads where you can hit water if you go too Gung-Ho. If you are at all unsure about doing it, just clean up any casting irregularities, match the ports to the manifold & gasket and carefully smooth the port to seat to chamber transition, lap the valves, polish the chambers and leave it at that.

 

Bleedin obvious stuff is measure your comp ratio (need a piece of perspex, bit of grease and a burette) balance all the chambers and do your piston to valve clearances from 30 deg BTDC to 30 deg ATDC on the exhaust stroke but I reckon you already know that. (Can weld a piece of hardened steel to an old valve to cut the valve reliefs if you need them).

 

Not so bleedin obvious stuff is if you get the cam ground, you may need taller lash pads so the rocker wipe pattern remains centralized. You may also need heavier valve springs depending on the profile and intended revs.

 

IMHO I don't trust even the best machine shops as I have picked up major faults in machining so many times, from the most highly regarded workshops, things that would wreck a new engine in minutes but may not be picked up by an assembler who does not double check the measurements and clearances. So my advice is even if you farm out work to a machine shop you will still need to check it carefully anyway. I too prefer to do everything myself and only farm out machining I can't do at home because I don't have the equipment.

[C.A.R.]

Backyard Jeff, Buy these two books:

 

 

 

Read both cover to cover, then ask any questions that the books don't answer.

[HomeBuiltByJeff]

When you are talking about the porting required. Are you talking about cleaning up the ports and matching them to the manifold, or are do you mean I have to really get bigger valves? 

 

It depends on what your final specs on the motor are but if it is higher comp, 72 or 74 deg cam and 45 webers then a high flowing inlet port will enhance that extra breathing in the medium to upper RPM range. Bigger valves would help in a higher spec motor but probably are not necessary for this build and the money could be better spent. If you do your own porting, take the time to learn the basics about port flow as first timers would be more likely to make them flow less than more. Pay particular attention to NOT ruining the port's shorter radius which is the usual number one mistake, and don't highly polish the inlet ports (exhaust yes so carbon doesn't stick but inlets need to be kept reasonably rough to aid flow and keep the fuel mixed with the air) and there are areas on the L series heads where you can hit water if you go too Gung-Ho. If you are at all unsure about doing it, just clean up any casting irregularities, match the ports to the manifold & gasket and carefully smooth the port to seat to chamber transition, lap the valves, polish the chambers and leave it at that.

 

Bleedin obvious stuff is measure your comp ratio (need a piece of perspex, bit of grease and a burette) balance all the chambers and do your piston to valve clearances from 30 deg BTDC to 30 deg ATDC on the exhaust stroke but I reckon you already know that. (Can weld a piece of hardened steel to an old valve to cut the valve reliefs if you need them).

 

Not so bleedin obvious stuff is if you get the cam ground, you may need taller lash pads so the rocker wipe pattern remains centralized. You may also need heavier valve springs depending on the profile and intended revs.

 

IMHO I don't trust even the best machine shops as I have picked up major faults in machining so many times, from the most highly regarded workshops, things that would wreck a new engine in minutes but may not be picked up by an assembler who does not double check the measurements and clearances. So my advice is even if you farm out work to a machine shop you will still need to check it carefully anyway. I too prefer to do everything myself and only farm out machining I can't do at home because I don't have the equipment.

That is some fantastic advice. That is the sort of thing I am looking for. I think I will try my hand at some light porting, but like you said, mostly just cleaning it up and matching it to the manifolds.

 

I am starting to think it may not be worth the hassle of upping the compression. It sounds like just bolting on the N42 head. Possibly just do the light head porting, and a cam, with my current head and see how it goes. 

 

Where should I send my cam to be re-ground, and if I keep the current head what grind (72 degree still)? Obviously to still match up with webers and an exhaust to match.

[HomeBuiltByJeff]

Backyard Jeff, Buy these two books:

 

 

 

Read both cover to cover, then ask any questions that the books don't answer.

I have already got and read the first one, as it is what I have been using to date. I will order the second one now.

[dat2kman]

I wouldn't recommend to anyone buying kameari twin idler gears. I had them on my 3.2ltr build, didn't even last 5000ks before it started tearing the chain to pieces.Yes they sound great, but a Waist of $700 in my opinion.....

That's funny, all the others that are using them, don't seem to have any issue.

Might be how you had the tension set, as anything more than gentle thumb pressure, whilst tightening the four capscrews, will cause excessive wear.

 

Oh, and as mentioned, for cam grinds, CliveCams in Melbourne, he bought all of Wade Cams when they closed, it just added to what Clive already had.

He knows the grind numbers you will need.

Edited October 22, 2017 by dat2kman