Rebuilding an L6

[Azon]

I have an L24 block sititng here with worn out piston rings and was thinking that I might as well rebuild it myself just for fun. My question is what exactly should I replace on the engine? Still not sure if I want to rebuild it to standard specs or not. Are there any lightweight pisons available for the L24? If so - where can I source these? Also is it hard to rebuild a cylinder head?

[Bruce]

I have been looking into rebuilding the L24 for my car as well.

I have chatted to a few guys who race them, and the general consensus has been, if you are sticking with the L24 just rebuild it to standard. If you want a bit more power get an L28 as a starting point. (I am waiting for pinch-a-part to have there $50 bare engine sale again).

[nat0_240_chevZ]

from another race guru....

 

"Use the l26 crank rods & pistons (overbore req'd if you use the 280zx pistons) you get a 2.6 or 2.8l with the stock engine number, (good for restorers)

 

Grab an early model 240z head (high comp, small cc's in combustion chamber), or gram an N42 from a zx shave 2mm from the botm face, shim the cam towers 2mm to compensate timingchain length. Also get unleaded valves which are larger (bet check cylinder clearance may need to notch bores depending on final size)

 

Get a reground cam, 30/70 or higher.

 

Get new bearings, big ends and main crank. New seals all round, new freeze/welsch plugs, new gaskets and use a good quality high temp, solvent safe sealers.

 

Use a copper spray on head gaskets or similar (permatex!!)

 

run stock 240z carbs with new needles and mainjet (or raise the needles not that easy but).

 

Good headers and exhaust. Should be on track for about 180-200hp from bugger all junk yard stuff.

 

Now lightening and balancing of crank rods and pistons is a must for free revving engines 7k +, also use good quality conrod bolts ARP or TensiStud i think.....

 

a quick vauge run through but very potent runner, good compression, revvy cam, and away you go.

 

nato

[Azon]

I have been looking into rebuilding the L24 for my car as well.

I have chatted to a few guys who race them' date=' and the general consensus has been, if you are sticking with the L24 just rebuild it to standard. If you want a bit more power get an L28 as a starting point. (I am waiting for pinch-a-part to have there $50 bare engine sale again).[/quote']

$50 for a bare engine? hmmm sounds interesting - what do they consider bare :shock: ? Adress of the place?

[Azon]

from another race guru....

 

"Use the l26 crank rods & pistons (overbore req'd if you use the 280zx pistons) you get a 2.6 or 2.8l with the stock engine number' date=' (good for restorers)

 

Grab an early model 240z head (high comp, small cc's in combustion chamber), or gram an N42 from a zx shave 2mm from the botm face, shim the cam towers 2mm to compensate timingchain length. Also get unleaded valves which are larger (bet check cylinder clearance may need to notch bores depending on final size)

 

Get a reground cam, 30/70 or higher.

 

Get new bearings, big ends and main crank. New seals all round, new freeze/welsch plugs, new gaskets and use a good quality high temp, solvent safe sealers.

 

Use a copper spray on head gaskets or similar (permatex!!)

 

run stock 240z carbs with new needles and mainjet (or raise the needles not that easy but).

 

Good headers and exhaust. Should be on track for about 180-200hp from bugger all junk yard stuff.

 

Now lightening and balancing of crank rods and pistons is a must for free revving engines 7k +, also use good quality conrod bolts ARP or TensiStud i think.....

 

a quick vauge run through but very potent runner, good compression, revvy cam, and away you go.

 

nato[/quote']

 

Thanks for the info - sounds reasonable.

[Bruce]

pick a part. They are located in Kilsyth and Campbellfield. They have weekly specials, the motors come up every couple of months.

A bare motor is a complete motor less any bolt ons as I understand.

no manifolds, distributor, starter motor, alternator, etc

cheers

Bruce

here is the web link

pinch a part

[Bruce]

Nato,

does what you are suggesting only apply to an L24 or can the same mods be performed on an L26/28 for similiar performance improvements????

 

cheers

Bruce

[nat0_240_chevZ]

well same goes for all motors...... up the compression, increase the rev range and = more power.

 

As fo starting with an l26 or l28

 

then yes go for the ground or new cam, then up the compression. either flat top pistons or shave the head or both within readon.

 

if you already have say a zx motor then your laughing, STD unleaded head with hardened valve seats etc, bigger valves (both in & out).

all depends on what your starting with, i wouldnt recommend spinning a stock bottom end to 8k+ without any balancing & lightening etc, as your asking for trouble.

 

new rod bolts would be a must, high tensile.

depending on which head you have and also pitson combination you can achieve almost any compression ratio you like, all comes down to application.

I "had" (note the "") an l24 with dished pistons and a head shaved within a shave of its life giveing excellent comp ratio, was able to spin it freely to 8500+ rpm as it had a lightened & balanced bottom end from front pulley to the gearbok output shaft. the cam picked up from about 2900rpm and pulled its hardest @ 5800 through to 7200 and would keep on going till 8k+ not sure how much but sounded like another 1000rpm as gauge stopped the needle @ 8k.

 

i used to have drag races with all the v8 commodore boys here and the 304's upto say the vs clubsport i used to be able to edge in front and stay there, gen3s used to beat me but remember we are talking a 240k L24 worked in a 2+2!!!

 

ill stop rambling now. but yes i did melt a piston #1 having it out with another gen3 (distributor moved/loosened while dragging and added another 8deg's of ign timing and bang, still ran well on 5 believe it or not.)

 

nato

[Bruce]

Thanks for the reply Nato,

Next question, What sort of comp ratios were you running, and what sort of fuel where you using?

Just wondering if you have found an optimum compression ratio that can still use pump petrol (premium unleaded)?

As an aside, a couple of mates who rally 1600's have had to run thicker headgaskets or rebuild there engines in order to bring down the comp ratios since they can't run avgas anymore.

cheers

Bruce

[nat0_240_chevZ]

My comp ratio was calc'd @ (roughly) 10.58:1 if i remember rightly,

 

was able to run regular if i wanted needed etc. but did run better on premo by far. still ate up the 5.0L commys on 91!!!!

 

You would be able to safely run about 10.8:1 with premo, although you must have a good base ign timing set along with a good advance curve.

 

I would recommend an electronic dizzy a MUST, get a dyno run done to check what curve you have and if req'd get a new or diff module to suit your req's.

 

I have a guy here that uses early holden ign modules and changes them depending on application and gets them to work in the 280zx dizzy, or other off the shelf bosch modules, all do the same thing just have diff curves, wiring configs.

 

i hear they tend to use the camira modules for the L engines 4 or 6 cyl....

 

 

nato