Newbie from Scotland

smokie

Well-Known Forum User
Hi, new to this forum just discovered it when i started looking about for parts for my Z. I bought a 240z a couple of years ago and haven't done much to it apart from running it to and from local shows. Its an early car but has been fitted with a 5.4 chevy engine. Given the current price of fuel and the 8mpg (if i keep the foot off the right pedal) then its time for the engine and box to come out. I've sourced an engine and 5 speed box from a 1980 280zx, plan is to keep it fairly standard for road use (its currently got dished pistons and an N42 head) maybe put in an uprated cam and a set of webers and a decent exhaust manifold ???. Would appreciate any advice on the engine build.
 

pmac

Well-Known Forum User
Hi, new to this forum just discovered it when i started looking about for parts for my Z. I bought a 240z a couple of years ago and haven't done much to it apart from running it to and from local shows. Its an early car but has been fitted with a 5.4 chevy engine. Given the current price of fuel and the 8mpg (if i keep the foot off the right pedal) then its time for the engine and box to come out. I've sourced an engine and 5 speed box from a 1980 280zx, plan is to keep it fairly standard for road use (its currently got dished pistons and an N42 head) maybe put in an uprated cam and a set of webers and a decent exhaust manifold ???. Would appreciate any advice on the engine build.

Its a very sound plan...............You will need (IMO) to change over to a set of flat top pistons and get some headwork(porting) done to get the best out of your proposed plan.
So... strip engine. Acid dip the block. Bore to suit new oversize flat top pistons. New everything else... core plugs. bearings timing gear oil/water pump.etc. rebuild and add moderately worked head with cam of choice and headers/manifold to suit. 1. 5/8" primaries will be best(IMO).
If you want any more help or need any bits n pieces just get in touch privately at pmaczc@madasafish.com as I dont like to get involved in public internet discussions.
Are you the owner of the chevy engined 240Z formerly owned by H**th T***s?
 

smokie

Well-Known Forum User
Thanks for your advice, not sure i'll go down the flattop route to begin with. I've just stripped the l28 and it doesnt look as if its done many miles, pistons are like new, if the machine shop dont reckon it needs a rebore then i'll stick with the dishes. Yes the car is H**ths old car. I only bought it because of the body condition, was never really keen on the engine. Currently trying to work out if i am better sending to the states for all the parts i need or whether there is a good supply of new engine parts in the uk ???
 
Thanks for your advice, not sure i'll go down the flattop route to begin with. I've just stripped the l28 and it doesnt look as if its done many miles, pistons are like new, if the machine shop dont reckon it needs a rebore then i'll stick with the dishes. Yes the car is H**ths old car. I only bought it because of the body condition, was never really keen on the engine. Currently trying to work out if i am better sending to the states for all the parts i need or whether there is a good supply of new engine parts in the uk ???

You can get all you need here in the UK, although you'll save a fair few quid if you bought from the states, even with duty/vat/shipping etc.

Seems silly to stick with dished pistons though?
 

andrew muir

Club Member
Hi Welcome to the club.
I thought I was all alone up here!
Where are you based about?
Yes 8mpg ain't good.
With the L28 you should be able to get 25-30 if you don't go nuts!
I am down in Peebles
:thumbs:
 

smokie

Well-Known Forum User
I've read so many posts on other Z web sites regarding flat top pistons and engine knock that i eventually came to the conclusion that i would be better sticking to the dished pistons and making do with the lower compression and hence lower power. Is there a real problem running flattops ? is our fuel of a high enough octane to avoid detonation ??
 

pmac

Well-Known Forum User
Thanks for your advice, not sure i'll go down the flattop route to begin with. I've just stripped the l28 and it doesnt look as if its done many miles, pistons are like new, if the machine shop dont reckon it needs a rebore then i'll stick with the dishes. Yes the car is H**ths old car. I only bought it because of the body condition, was never really keen on the engine. Currently trying to work out if i am better sending to the states for all the parts i need or whether there is a good supply of new engine parts in the uk ???

Yes indeed a fabulous condition early car.. :bow:

Seems silly to stick with dished pistons though?
Well I always try to give the best advice based on current NA tuning practice but I have no problem with the advice being rejected.:D
 

smokie

Well-Known Forum User
Hi Andrew, I'm even further north :) up in sunny Angus just north of Dundee. Used the car on a couple of classic runs last year and ran out of fuel on a couple of occassions (not good when you are in the middle of nowhere with the nearest petrol station over 30 miles away). 13 gallons dont go very far at between 6 and 8 to the gallon. Hope to take the 240 abroad later this year so reliability and hopefully good fuel consumption is one of my goals. Have you had your car at any scottish shows ?
 

smokie

Well-Known Forum User
Well I always try to give the best advice based on current NA tuning practice but I have no problem with the advice being rejected.:D


Your advice is very much appreciated and not wholly dismissed, Im listening ;)
 

andrew muir

Club Member
Hi I have been at a couple such as Biggar etc
Prefer shows based around circuits etc.
A bit more interesting usually.
Also my car isn't really a show car more of a daily driver.
Went to Spa last year and had a great time.
Plan to go back next year.
I think there is a chap in the s30 registar up in Kirriemuir he has a Samuri and a 2+2 I think.
He will be pretty local to you i would think.
 

woodjohn

Active Forum User
Hi Smokie, I think I may be the most Northern Z owner who looks in on the club. Feels a bit lonely up here since Vpulsar sold his one. I let my membership lapse as all the action was down South, and my 240 needs a complete strip down an rebuild. Incidentally I got my one from Montrose which is just a kick in the ar#e away from you. Got it 8 years ago but wifie reckons there are more pressing projects to be done first
 

pmac

Well-Known Forum User
Your advice is very much appreciated and not wholly dismissed, Im listening ;)

As always its down in many cases to the amont of money available. I understand that.
The whole conversation with you was kinda "Deja vu" as I spent an hour earlier today with a client discussing exactly the same scenario.
He has just purchased a similar engine to yours and has gone off to make a start on his build..
Using the existing dished pistons will be fine if you are looking for a budget build.And it will make a decent engine. But dished pistons just dont cut it in performnce NA engines.
To get more power and to justify having the Webers and a modified cam you really need to go for a considerably bigger compression ratio and have better porting etc to allow the head to extract the max from the cam and carbs.
In fact if you are sticking with a lower compression dished piston engine you could run that happily on a pair of SUs and a stock cam. That would cut costs dramatically.
Ultimately you are the only one who can make the final call:)

There is nothing different in building/tuning the L series Datsun/Nissan engine that doesnt apply to any other similar NA engine. The L sreies is just a Ford Pinto engine with more cylinders. There are no "special ingredients" or Magic Datsun fairy dust involved.:rolleyes:....................................

..........................................................
gets coat and leaves...... closing the door quietly on exit:thumbs:
 

smokie

Well-Known Forum User
Hi Smokie, I think I may be the most Northern Z owner who looks in on the club. Feels a bit lonely up here since Vpulsar sold his one. I let my membership lapse as all the action was down South, and my 240 needs a complete strip down an rebuild. Incidentally I got my one from Montrose which is just a kick in the ar#e away from you. Got it 8 years ago but wifie reckons there are more pressing projects to be done first

Good to know there are others up here with datsuns and wifes who simply dont understand..... We've done a few runs up your way with the highland car club, i think there's one planned for later this year, just hope the datsuns ready in time ???
 

woodjohn

Active Forum User
No chance of my car going to that, but if I am home from work I will try to attend that event , if you could post up the venue and date on the forum .
 

SKiddell

Well-Known Forum User
Smokie
You mention that on other sites "engine knock" has been mentioned

Beware of taking compression advice from some of the American sites, their octane ratings and availability of premium grades sometimes prevent compression ratios that some would consider "mundane" I'm currently running 12:1 admittedly on a full race spec engine and 98/99 fuel.
No det, pink, pre ignition, or knockmand revving to 8K

An N42 headed 2.8 engine with a good 40 thou skim off the head running flat tops on a squish of 38 thou will easily run at 11:1 on good fuel... good for 240 hp at the fly if set up right.
 

smokie

Well-Known Forum User
As always its down in many cases to the amont of money available. I understand that.

Ultimately you are the only one who can make the final call:)

There is nothing different in building/tuning the L series Datsun/Nissan engine that doesnt apply to any other similar NA engine. The L sreies is just a Ford Pinto engine with more cylinders. There are no "special ingredients" or Magic Datsun fairy dust involved.:rolleyes:....................................

..........................................................
gets coat and leaves...... closing the door quietly on exit:thumbs:

Thanks again for your comments they are really appreciated, i dont want to go OTT with the build or i would probably have been better buying a motor from Robello Racing :eek:

One of my concerns and my obvious lack of understanding regarding the change to flattops is the fact that, in the N42 head the valves protrude below the level of the head when they are open, i thought that this was the reason dished pistons were used ?
I dont want to build a car that is so focused that its only really suitable for the track, i want to use it on classic rallies and long distance touring events. i plan to run a standard clutch and gearbox, 15 pound flywheel, i already have an r200 diff fitted.
 

SKiddell

Well-Known Forum User
One of my concerns and my obvious lack of understanding regarding the change to flattops is the fact that, in the N42 head the valves protrude below the level of the head when they are open, i thought that this was the reason dished pistons were used ?

Hmm clearly we have some work to do here
The valves are only ever fully open when the piston is NOT at TDC, the overlap cycle When the piston is at TDC on the overlap cycle (180 degrees from TDC), the valves are only partly open (one opeing the other closing) this promotes scavenging .........helps exhaust draw, chamber evacuation and induction even then its at most around 4mm even on a mental cam

The dish was used on NA engines to reduce emmisions (longer burn) and on some turbo installations to help reduce compression.
 

pmac

Well-Known Forum User
Thanks again for your comments they are really appreciated, i dont want to go OTT with the build or i would probably have been better buying a motor from Robello Racing :eek:

One of my concerns and my obvious lack of understanding regarding the change to flattops is the fact that, in the N42 head the valves protrude below the level of the head when they are open, i thought that this was the reason dished pistons were used ?
I dont want to build a car that is so focused that its only really suitable for the track, i want to use it on classic rallies and long distance touring events. i plan to run a standard clutch and gearbox, 15 pound flywheel, i already have an r200 diff fitted.

Well its a brave man who owns up to a lack of knowledge.:bow:
Firstly then before you decide your final spec you should maybe buy/borrow/download a respected book on the subject of NA engine working and tuning. Then you will be in a better place to decide how to spend your hard earned wonga.
Skiddell and me are long term buddies and we would be pleased to advise/assist you but we are shy and retiring people and dont do "open forum" exchange of this kind of information etc.
I have given you my contact email. We are available to chat and talk.
And before anyone else pipes up i should just like to say neither of us has any interest in selling you anything or building anything for you BTW;) We are far too busy doing our own cars/engines now for most of this year.:p

So this now paves the way for others to wade in with whatever they need to say as Im off to get a mug of cocoa and put my slippers on.
Nite Nite:cheers:
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Hi smokie, welcome to the club.

Yes you have a nice car there!

When I started building my engine (about 12 years ago) it was around the time when LRP came in and there was hysteria about valve seat problems and knocking etc. I mistakenly bought a set of dished pistons for the build. I then decided to let an expert continue the mods and build. First thing he did was to fit flat-top pistons and machine 'cut-outs' for the valves (sporty cam). No knocking and engine still going strong.
 
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