3.1L blueprints

[sorealsosurreal]

so im building a 3.1L for my 240z starting with an F54 block out of a 280zx turbo. i used a sonic tester to measure the clinder walls and got a couple readings that are concerning me. the samllest being .075 which turns out to be almost 2mm and if i have to bore from an 86mmbore to an 89 that will leave me about .5mm of wall thicknes. being that these smaller measurments are towards the bottom of the cylinders will this really matter. can any one whos actually machined a 3.1L themselves give me any advice on this. thanks Matt

[BRAAP]

That seems pretty thin…

 

 

I recall some time back some discussion regarding the F-54 block having thinner cylinder walls than the N-42 blocks dispelling the F-54 block as the “superior” block for extreme performance use. I could be remembering that discussion wrong. I was not able to find those discussions in a quick search…

[jeffer949]

I remember that subject also. If i recall correctly it was brian(1 fast Z) that was the person who did alot of the testing. I would contact him as he is a BIG believer of the f54 blocks being junk. His L31DETT engine is on a n-42 block.

[e_racer1999]

IIRC the issue was that the F54 blocks were siamesed to allow for better cooling in the turbo motors, which in turn made the walls slightly thinner. Thus making the N42 block better suited for overboring

[sorealsosurreal]

okay well i looked really quickly and found an n42 block but its out of a 260z versus a 280z so the bore is 83mm vs 86mm. is there room to bore it out to 89mm anybody?

[Tony D]

The Japanese knew the N42 was what to use for 20+ year before someone on these shores took the time to rediscover it.

 

Normally anything less than 0.125" is considered too thin to be structurally sound, and you will want a liner in that case.

 

Braap recalls the discussion correctly.

 

BTW, the siamesing did not 'in turn' make the walls thinner. The casting was redesigned, with supposedly even cooling, the bores 'should' stay rounder, so the engineering rationale for the thicker walls of the N42 was no longer justified. The thicker walls of the N42 were used under the rationale that they needed all that extra beef to keep the bores round under extreme conditions.

 

In practice, the differences in concetricity is dubious, and the thicker walls of the N42 still work as well as ever to keep the cylinders round.

 

And as Bryan pointed out, some people don't run anti-freeze in their blocks (common in the 1960's when the L-Engine was designed) so thicker walls gives you 'corrosion capability'---unlike some of those F54 blocks that have paper thin walls due to corrosion pockets that have eaten away at the water jacket side of hte cylinders!

 

I think Bryan even experienced this on the DETT build!

 

No N42 came in the 260Z, the bore is 'not' 83mm because it came out of a 260Z. Look at the block serial number---the engine was replaced with an L28 some time ago.

 

There is no 83mm bore N42 block. They are all L28 86mm bores.

[sorealsosurreal]

ok so its probably just out of a 280z and he didnt know???

[1 fast z]

3mm wall thickness is as thin as I like to see on a boosted engine. On an NA motor you can go down to 3/32" and still be safe. Yes the main thing is sonic testing alot of blocks and finding one that isnt all pitted up on the inside from people cheaping out on antifreeze!!!!!! An N42 will always have more wall thickness than a F54.

[sorealsosurreal]

ok thanks for the info im going n/a but still the f54 block i have is just to thin. im hunting down an N42 as we speak. just sorta pissed considering this is a college project im getting graded on and if waisted the time i have preping this block. oh well what can yeah do

[e_racer1999]

The Japanese knew the N42 was what to use for 20+ year before someone on these shores took the time to rediscover it.

 

Normally anything less than 0.125" is considered too thin to be structurally sound, and you will want a liner in that case.

 

Braap recalls the discussion correctly.

 

BTW, the siamesing did not 'in turn' make the walls thinner. The casting was redesigned, with supposedly even cooling, the bores 'should' stay rounder, so the engineering rationale for the thicker walls of the N42 was no longer justified. The thicker walls of the N42 were used under the rationale that they needed all that extra beef to keep the bores round under extreme conditions.

 

In practice, the differences in concetricity is dubious, and the thicker walls of the N42 still work as well as ever to keep the cylinders round.

 

And as Bryan pointed out, some people don't run anti-freeze in their blocks (common in the 1960's when the L-Engine was designed) so thicker walls gives you 'corrosion capability'---unlike some of those F54 blocks that have paper thin walls due to corrosion pockets that have eaten away at the water jacket side of hte cylinders!

 

I think Bryan even experienced this on the DETT build!

 

No N42 came in the 260Z, the bore is 'not' 83mm because it came out of a 260Z. Look at the block serial number---the engine was replaced with an L28 some time ago.

 

There is no 83mm bore N42 block. They are all L28 86mm bores.

Thanks for the clarification, Tony.

[Careless]

ok thanks for the info im going n/a but still the f54 block i have is just to thin. im hunting down an N42 as we speak. just sorta pissed considering this is a college project im getting graded on and if waisted the time i have preping this block. oh well what can yeah do

 

it might be easier if you look for the car they came in rather than the block itself. you could buy a run down N42/N42 block/head carrying 1976 280z parts car from someone and then sell off the shell and associated parts.

 

College projects usually eat up money if you look at things like this. If you can't find it, then simply don't overbore your engine and look to other means for generating power. Higher compression maybe?

[Challenger]

I recently took a completely stripped and cleaned n42 block to the recyclers...

[sorealsosurreal]

it might be easier if you look for the car they came in rather than the block itself. you could buy a run down N42/N42 block/head carrying 1976 280z parts car from someone and then sell off the shell and associated parts.

 

College projects usually eat up money if you look at things like this. If you can't find it, then simply don't overbore your engine and look to other means for generating power. Higher compression maybe?

 

 

ACTUALLY I DID JUST THAT! im the proud new owner of a 1975 280z. It had the n42 block but not the head. an N47 if anyone wants it. my dad and i are now think of what to swap into it. the previous owner had taken it aprt to restore it and had money troubles and its been sitting in storage for who knows how long. came with brand new nissan sheet metal for the hood and fenders. everythings there just not together all for $500

[Careless]

lol +1

[sorealsosurreal]

:cry2:nevermind going to part out the 280z. but on another note the engine from it turned out to have nice beautiful thick walls. and i got all my ARP hardware yesterday. now in search of some pistons!

 

and with the other f54 block i think ive decided when the time is right to make a blow through turbo setup. i have the block, crank, rods, and a spare n47 head so why not????

[sorealsosurreal]

ok changed my mind again, thinking of a blow through setup on my 3.1L. what i need to know is what compression KA pistons would give me an 8.5:1 cr in a 3.1L with a 1mm headgasket and no deck of block or head. all the z calculators give you a choice of pistons but i dont understand how to put in an aftermarket pistons and convert the info they give you on the aftermarket pistons to the dishvolume it asks for on the calculator.

http://www.atlanticz.ca/zclub/techtips/calcs/engine%20builder/index.html

 

i plan to if i do this set up run the car on low compression till i have the money for the turbo parts. should i throw this into the turbo thread? i really hope this post makes sense. thanks everyone

 

Matt

[2eighTZ4me]

A few assumptions.... if you're building a 3.1L, that must mean you're using a Maxima diesel crank and 240Z (hopefully 9mm) rods. This setup by default gives you .6mm negative deck height (meaning the piston sticks out of the bore .6mm). If you're using a 1mm head gasket, compression is going to be pretty high, and you'd have to almost go with a custom dished piston to get below the 9:1 mark - meaning a really deep dish. (Also dependent on which head/chamber you use) You're also going to lose quench with a deeper dished piston, which will rob some performance.

 

Most (if not all) 3.1L builds I have read about are using a 2mm head gasket to compensate for the deck height and to preserve quench. Stroker turbo can be done, but with carbs, you're pressing your luck, as you don't have near the control over fuel/timing as you do with an EFI MsNs.

 

BTW - I have an SK blow-through surge box for triple Mikuni/Weber's that I probably am not going to use.....

[sorealsosurreal]

A few assumptions.... if you're building a 3.1L, that must mean you're using a Maxima diesel crank and 240Z (hopefully 9mm) rods. This setup by default gives you .6mm negative deck height (meaning the piston sticks out of the bore .6mm). If you're using a 1mm head gasket, compression is going to be pretty high, and you'd have to almost go with a custom dished piston to get below the 9:1 mark - meaning a really deep dish. (Also dependent on which head/chamber you use) You're also going to lose quench with a deeper dished piston, which will rob some performance.

 

Most (if not all) 3.1L builds I have read about are using a 2mm head gasket to compensate for the deck height and to preserve quench. Stroker turbo can be done, but with carbs, you're pressing your luck, as you don't have near the control over fuel/timing as you do with an EFI MsNs.

 

BTW - I have an SK blow-through surge box for triple Mikuni/Weber's that I probably am not going to use.....

 

 

Ok thanks for the heads up, I've worked on cars a lot (mechanic) but never built an engine before. Didn’t know that the KA pistons would surface out of the block. I was thinking of using an aftermarket KA low CR turbo piston for the build. I’ve skimmed through this write up on building a 3.1L stroker many times

http://www.geocities.com/row4navy/engine.html and I didn’t see the writer never mentioned his head gasket choice or what he did to the pistons whether they were shaved or not. So here's my question to you. If I used a 2mm head gasket and a deep-dish piston (no clue which one, pointers are welcome) would the CR be turbo applicable? as far as the carb vs FI I like the idea of a carb and it involves a lot less to worry about although I know that I would lose about all tuning capabilities

[2eighTZ4me]

Here ya go - try this link.

http://www.geocities.com/inlinestroker/

 

You'll see about halfway down the page where he describes piston choice. Based on his calculations (I myself have not made any, as I'm lazy) even with a 2mm HG, you're still looking at over 10:1, which is quite a bit too high for a turbo application. I was torn between doing that as well, and just ended up going with a NA stroker. I'm going to turbo the white daily driver in the near future.

 

You'd have to get a custom cut piston with a reduced pin height, such that the piston doesn't protrude out the top of the block, in order to achieve the compression figure you're shooting after. Then you lose efficiencies of combustion quench, as it is more favorable to have the piston very close to the combustion chamber at time of ignition.

 

I see that Top End Performance still "advertises" they have a 2mm head gasket, and I've heard other forum members using the Cometic gaskets, so hopefully, you won't get bogged down there. I have read other forum members having a tough time getting one, so be prepared to shell out for one. They aren't cheap.

[junglist]

 

 

I see that Top End Performance still "advertises" they have a 2mm head gasket, and I've heard other forum members using the Cometic gaskets, so hopefully, you won't get bogged down there. I have read other forum members having a tough time getting one, so be prepared to shell out for one. They aren't cheap.

 

I believe that Kameari still sells 2MM MLS headgaskets...although they are expensive as hell just like every other Kameari part: http://www.zccjdm.com/catalog.php/azcarbum/dt43033/pd858312/KAMEARI_L6_METAL_HEAD_GASKETS_