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Machining cylinder head for more compression?


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On 1/8/2021 at 5:48 PM, z shredder said:

Hello,

I am looking at buying an L26 engine for my 240z the plan is to use the l24 flat top pistons and a decked e88 cylinder head to get more compression.

The ozdat calculator says that with a 1.25mm thinner head gasket and the l24 pistons I will get a compression ratio of 10.5/1 is this equivelent to machining 1.25mm of the cylinder head and using the stock head gasket?

Is it even possible to remove that much material?

Endurotec +060 Pistons Set Of 6 suits Nissan L26 | eBay

You need at least change the piston's to higher quality ones, that raise your compression. A big cam and weber carb setup is a must if you want to have some power from it.

You could also lighten the flywheel and some good headers are needed.

Then offcourse the head.. 

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Thanks for the offer but I am not going to spent 1500€ on a cylinder head 😁

Do I really need new pistons? Until now I was planning on using L24 flattop pistons.

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On 1/9/2021 at 6:22 AM, z shredder said:

Well I have 2 options using the E88 head from the l26 or using the E88 head from my l24 I heard that the l26 had bigger valves and that's why I wanted to go with this. 

You're getting a lot of advice about the fine details to get that last 10-15% of power from an engine.  It looks like you are starting with an L24 and have the option of buying another L26.  Both factory stock engines, maybe?.  It will help you to define what you want the engine to do when you're done.  You can spend a lot of money on parts that won't help you reach your goals.  Plus the money you can spend removing or modifying perfectly good parts to install the unnecessary parts might be wasted.

The parts all need to work together.  Expensive pistons that never see more than 6000 RPM are probably a waste.  High CR with poor fuel is a waste.  A ported head with a poor exhaust system is a waste.

You started your thread with machining a head, but machining a head should be in the middle of your list of things you need to do to reach your goals.  You need a plan first.  Plus you need to know the quality of the parts you're starting with.  If the L26 has already been bored you won't be able to use your L24 pistons in it, for example.  But you might be able to use the L26 crank in the L24 block.  Example.   Since you're limited in finding parts and spending money, many of the suggestions made won't be reasonable for you.

I'd get the parts and see what's usable.  You might find cracked heads, trashed cylinders, damaged valves, etc.  Don't spend too much money until you know what you have in front of you.

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5 hours ago, bartsscooterservice said:

He lives in Germany, they have high octane fuel

Not really.  They have 98 RON which is the same as 93 pump octane in the US.  The US uses (RON + MON) / 2 method.

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So was there Nissan sedans in Germany ? Are they in JY’s there ? Is or was there a variant of the Maxima for that era ? That would be the head to get

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On 1/10/2021 at 6:19 PM, z shredder said:

Do I really need new pistons? Until now I was planning on using L24 flattop pistons.

You have a 1973 240z engine L24?  YOu know that these engines have flattop pistons that just come above the deck of the block? there was a service newsbulletin telling that these heads of a 1973 are different so watch out..

Btw..  Your a student?  (I have never seen a student with the money for a restauration of such a car) .. have you thaught this through?  Don't think "ow it's easy" ..     

There is a firm here in the Netherlands .. it sells 240z wrecks!!! for 10-15000 euro.. and about EVERY part needs to be repaired or renewed.. There are a lot of people that look through a pair of pink glasses at their cars but don't realise that these resto's cost a LOT of money. (I hope yours is not as bad..)

≥ Datsun 240Z (bj 1971) - Oldtimers - Marktplaats.nl

I always tell people if you want a good reliable car you have to invest the money for a new car..  otherwise you will have a lot of brakedowns and exasperation. (irritation to the MAX!)

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7 hours ago, dutchzcarguy said:

You have a 1973 240z engine L24?  YOu know that these engines have flattop pistons that just come above the deck of the block? there was a service newsbulletin telling that these heads of a 1973 are different so watch out..

Btw..  Your a student?  (I have never seen a student with the money for a restauration of such a car) .. have you thaught this through?  Don't think "ow it's easy" ..     

There is a firm here in the Netherlands .. it sells 240z wrecks!!! for 10-15000 euro.. and about EVERY part needs to be repaired or renewed.. There are a lot of people that look through a pair of pink glasses at their cars but don't realise that these resto's cost a LOT of money. (I hope yours is not as bad..)

≥ Datsun 240Z (bj 1971) - Oldtimers - Marktplaats.nl

I always tell people if you want a good reliable car you have to invest the money for a new car..  otherwise you will have a lot of brakedowns and exasperation. (irritation to the MAX!)

This reminds me a bit of this cartoon I used to watch as a kid called phineas and ferb were they would build crazy stuff and everybody asked "aren't you to jung to build (insert something crazy)?"

and they would just reply with "yes..... yes we are" and continue building.

As a Kid I never really spend much money on anything since the age of 5 to save up to someday buy a cool car. I also got some finencial help from my parents because they didnt want me to ride a motorcycle.

And about the car yes it WAS really bad, lots of rust, bad suspension all around, bad wiring and so on......

Right now all of the structural rust has ben fixed the car has a complete new floor pan welded in by welder/chassis builder for free by trading him spare porsche 914 parts 😀 I can weld so I will repair the rest of the rust myself.

I removed all of the suspension (A-arms, Struts, sway bar, steering, brakes) even the differential and tank everything got new bushings and all off the surface rust painstakingly removed so that I could paint all of it, while at It the underbody also got painted/undercoated.

Aswell as the new bushings I also installed kyb gas struts because the old ones were not good. I also removed all of the rubber seals, all of the glass, all bodypanels, interior to restore.

The dash was cracked so i used filler and lots of sanding to repair it all of the gauge glasses were so crappy that you couldn't see the gauges I removet them and polished until they were clear again.

So I basically tore down the car to the bare chassis in a small garage with no lift so working with a jack and jack stands.

"have you thaught this through?" well I think I am doing pretty ell for a 16 year old with a limided budget. This is no half a$$ed restoration! I already have all of the restored suspension, brakes, steering and differential installed, the car is getting ready for paint and

removing the engine block (cylinder head and everything else is already removed).

A restoration doesent have to be horrendously expensive if you do all of the work yourself and spend your money smart!

I will upload a few pictures of the car so that you get an idea.

Edited by z shredder
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My '73 pistons aren't valve notched like your's. Maybe a European, N. America thing?

I would highly recommend new nuts for the TC rods. They're one use locking and I can tell you from experience and many other's experiences I've read, reuse of the old ones and they'll eventually come off. Small price for 2 new pinch nuts and peace of mind.

Looks good. 👍

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34 minutes ago, siteunseen said:

I would highly recommend new nuts for the TC rods. They're one use locking and I can tell you from experience and many other's experiences I've read, reuse of the old ones and they'll eventually come off. Small price for 2 new pinch nuts and peace of mind.

Looks good. 👍

I reused and lost one once when I hit a bump on the highway.  Luckily I heard it come off and I was able to get home and replace it with no damage.  I did lose the poly bushing and the cup washer.

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1 hour ago, z shredder said:

Pictures

IMG_20201024_122624.jpg

 

If your front end groans and moans when you go over speed bumps and driveway ramps it's the rear poly bushings working the back of the TC rod.  Eventually it will break it off.  Most people use rubber on the back.  It doesn't really see much use when braking like the front one does.

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I don't think any original standard  Nissan pistons have cut outs like that.

on the compression rod, I have these, which are cheap and effective. 

https://www.thezstore.com/page/TZS/PROD/23-4190

I had poly bushes both sides before I fitted them, and I had a lot more roll after I fitted them which I think shows how much load they were taking. 

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13 hours ago, jonbill said:

I don't think any original standard  Nissan pistons have cut outs like that.

I agree, no L motor has that..  so this engine was already restored at one point.

16 hours ago, z shredder said:

well I think I am doing pretty ell for a 16 year old with a limided budget.

I'm surprised and very happy that a 16 year old is restoring a 240z!!  

Also ..  NICE pictures, i now think you did'nt bite off more than you can shew..   Most (very) young people start an resto but never finish it.  You'll get it finished i think!!

On the rubber and poly stuff..  I personal HATE the poly.. rubber is MUch more forgiving.. the poly makes it to stiff. I have seen broken suspension, just because the poly was to hard.. did not give.

I don't know where you live in NRW but i'm a few km of the city Goch/Kleve. Dld.   I think it's fantastic that you restore a Datsun when thought of "a cool car" 

I drive a 240z now for 20 years (restored myself.) and is ready for another restore haha.. and it's the small boys that walk on the hand of their mother that shout: OH MOM look at that BEAUTIFUL CAR!  👍  I had that more than once.  (These little boys grow up to restorers haha) 

Also people that start to video the drive by hahaha...   

With my just restored 280zx (on this site: 1979 slick roof 280zx) people spontaneously stop and say what a beauty!!  (It's almost impossible to drive that car without someone complement it or getting a thumbs up..  once a roadworker shouted realy loud: Nice DATSUN!  HAHA.. 

The most i'm excited about people who now are starting to put some thumbs up when they see me drive my almost as new 300zxtt !!   I drive that car now for 15 years (only in the summer) and the only thing i got was a jealous look!  People are clearly changing their opinion..

Show us your progress, we all love pictures!   AND.. if your not sure how to do something also let us know, we (all) are here to help.

Edited by dutchzcarguy
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That pulley (where the fan normally is on) is a bit out of line?  The belt looks a bit of a ghostbelt on that pic. haha.. it's there but not completly it looks like it disappears..

You know of course those carbs are not the original ones?  If it's a engine that was never apart it's time to take it apart completely and inspect every part. (install all new gaskets and oilseals!)  If it's a euro version block it probably has a E88 head and about 162 hp. (But with these carbs that could be a bit less or more..)  As it has a starter on it, you could do a compressiontest before you buy it, that should be around 10 Bar.  (155-160 psi) and best is that every cylinder has the same pressure.

Watch out the engine could get a bit jumpy when you get the starter running..  take out al the sparkplugs.. look if there was extra oil in the bores. it will influence your compr. data..

Bring a good flashlight and a full battery. 😉 

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On 1/10/2021 at 6:19 PM, z shredder said:

Thanks for the offer but I am not going to spent 1500€ on a cylinder head 😁

Do I really need new pistons? Until now I was planning on using L24 flattop pistons.

No problem. Just depends on what you want though. Maybe its better suited for someone who is doing an early 240 restoration and needs the correct E31 head for it.

It's not lying in my way anyhow. I intend to keep it as a spare because by that time in the future they are even harder to come by. I am willing to sell it to a fellow z enthusiast, but i'm not santa claus

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On 1/14/2021 at 11:24 AM, dutchzcarguy said:

That pulley (where the fan normally is on) is a bit out of line?  The belt looks a bit of a ghostbelt on that pic. haha.. it's there but not completly it looks like it disappears..

You know of course those carbs are not the original ones?  If it's a engine that was never apart it's time to take it apart completely and inspect every part. (install all new gaskets and oilseals!)  If it's a euro version block it probably has a E88 head and about 162 hp. (But with these carbs that could be a bit less or more..)  As it has a starter on it, you could do a compressiontest before you buy it, that should be around 10 Bar.  (155-160 psi) and best is that every cylinder has the same pressure.

Watch out the engine could get a bit jumpy when you get the starter running..  take out al the sparkplugs.. look if there was extra oil in the bores. it will influence your compr. data..

Bring a good flashlight and a full battery. 😉 

I would throw that carbs in the bin, they don't belong on a japanese car 😑

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On 1/13/2021 at 3:27 PM, z shredder said:

I am probably going to buy this L26 because the price is good and it's not to far away. 

IMG-20210113-WA0002.jpg

I once went to Schut in Soest , the netherlands. He had some original datsun engines laying around. You could give them a call.

industrieweg 29, soest. tel +31 (0) 35 6010668

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If the L24 is still ok and servicable, I would put it back together and run it like that until you know what you want to do. Like @Zed Head said, doing one mod without the other will not do much, but empty your wallet.

I'd drive it around for a while, enjot it, and think about what you want from the engine. Then gather all the parts for an engine project. You could use the L26 as a starting point.

I think the biggest buss for your money is a lightened flywheel. It doesn't add any horsepower, but it certainly gives a standard engine kick in the a$$ response. Very revvy and a little touches at the traffic lights, but managable once you get use to it.

My wife keeps stalling mine, but then she refuses to drive it because it's got no power steering, no power windows, no power mirrors, blue tooth or navigation, this list goes on.

Looks like you are having fun restoring it so far. It's your project, so you can do what you want when you. Just my 2 eurocents.

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Besides my L24 spare block i do have another L26 with a Restored E30 ! head  (No not E31  a E30!) , it came out of a Z that was souped up!   Never used it myself but it looks like a nice step up.. 

A E30 head is the head of a L20 6 cyl. Nissan engine, and together with a L26 it makes a nice compression number around 10,5 i think?  

Has someone else experience with this combination L26 with E30 head?

 

I could sell the L26 with a E30 head..  prices would be like this one i just found on the dutch marketplace: 

EDIT: he changed the price of 3500 euro to "bieden"( translation: make a bid.)

≥ Datsun L28 Motor Gereviseerd - Overige Auto-onderdelen - Marktplaats.nl

Edited by dutchzcarguy
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