L28 Engine Build

[coupe72001]

I have started to lose compression and seriously blow some blue smoke. Looks like its time for new piston rings, which is a shame because they were only done 4 years ago.

I can buy an L28 engine on the cheap, but it is from a series one 280zx, with an N47 head and dished pistons. It has not been in a car for 3 years.

Questions:

Should I go for flat-top pistons, and if so which brand/where from?

Do I stick with my E88 head or change to the N47?

Will either head need modifications to suit flat-tops?

Would it be easier/cheaper to buy a 280zx series 2 engine that already has flat-tops and the P90 head.

Cheers,

D

[Ghostrider]

Questions:

Should I go for flat-top pistons, and if so which brand/where from?

N/A or Turbo is the end result??? as flat top pistons in an E88 or N47 will give a compression of about 10:1

Do I stick with my E88 head or change to the N47?

E88 EFI Head is considered among those that are supposed to know as THE BEST n/a head available. N42 & P90 seem to be the choice in turbo application but with either N42, N47 they have the same sized valves and combustion chamber volume.

Will either head need modifications to suit flat-tops?

Would it be easier/cheaper to buy a 280zx series 2 engine that already has flat-tops and the P90 head.

In my opinion this is the way to go, but I have been criticised before about this. P90 and flat top pistons give a comp of about 8.5:1 on stock bore and 8.7 at plus 1.0mm and is regarded as the best of the best in turbo heads as it was the factory choice at the end, but not always easy to find at the right price. Remember any L28 block is designed as a rear sump and will need to be modified to become a front sump engine, oil pick up etc. Drilling the front dip stick hole will block the rear oil return, but that's not a problem as you don't need it with the front sump configuration. Getting a new dipstick holder might be a problem though. I keep getting promised one from afar but nothing eventuates.

[coupe72001]

Thanks for the heads up.

To clarify I was thinking of staying N/A, and recycling my overpriced carbys and E88 head (as they have both been checked/rebuilt etc), unless there is good reason to do otherwise.

I have a mate shopping for parts in Japan as we speak, maybe I should put him on the case to search for dipstick holders. Do you know which model you need to poach it from to suit this application?

Cheers

[stagefumer11]

Note:: you can actually use the factory dipstick from in the block. Its only a press fit in. I removed mine quite easily. Then it was a matter of pressing in back in into the new hole

[coupe72001]

Thanks for the tip re: the dipstick.

I bought some flat tops today - I'm getting excited! If anyone can make recommendations about which engine components to replace the existing stuff with I'd love to hear them. I'd like this engine sorted out before it goes in the car.

[coupe72001]

Ok- I have stripped the L28 Block and had the bores and the crank polished. I have flat-tops and new rings and all the other parts I need to assemble. The N42 head is in better shape than my E88 head, so I am going to use it for that reason alone.

I am going to do a dummy assembly first (with the engine out of the car) to check that the valves clear the pistons. There are 3 pertinent questions though:

Has anyone run into major valve clearance issues before with an L28 and flat-tops?

Does anyone know off-hand what the tappet clearances for the N42 head are?

Does anyone know what color the L28 block was when new?

Any tips are appreciated. This is largely uncharted water for me, so I don't want to botch it.

Cheers

[blind_elk]

1. You should be able to judge possible interference of valves with pistons by putting a flat ruler across the face of the head with the valve fully open.

2. I'm pretty sure ALL L-series run the same tappets - .012 ex, .010 in, hot (.010 ex, .008 in, cold)

3. NFI

[OUTATIME]

gonna re hone the bores or they look alright?

[coupe72001]

Thanks for the tips.

The bores didn't require a hone, they polished up very nicely. (Just as well for me, as the pistons I scored on the cheap are the standard size - not an overbore). Likewise the crank polished up well, so I'll be sticking with (new) standard-sized bearings. I forked out for a performance harmonic balancer - avid readers will recall that I split my last stock harmonic balancer into 2 pieces, ruining my week. The balancer/crank/flywheel have been balanced, and the flywheel was lightened some as well.

As well as Mr Elk's ruler method, I will be applying a dollop of blue-tac to the top of number one piston, bolting the head and timing gear on, turning the motor by hand then checking out the indentations in the blue-tac to get an idea of valve clearances. It's a bit like something out of CSI. The boys at the machine-shop will measure the remains of the blue-tac and make the call about how much, or little, clearance there is. If it's too tight I may need to invest in a thicker (Nismo do a 2mm) head gasket.

Including paint and oil, I hope to keep the whole project under a grand. It's on track so far.

[Ghostrider]

Has anyone run into major valve clearance issues before with an L28 and flat-tops? .......... No! but I am using a P90 head, as my motor will be turbo.

.......... You may have to relieve the piston crowns for valve clearance.

Does anyone know off-hand what the tappet clearances for the N42 head are? .......... 0.010" for both

Does anyone know what color the L28 block was when new? .......... Blue

Including paint and oil, I hope to keep the whole project under a grand. It's on track so far. ............ how you do this?

My present cost list is over $3000.00 for my new L28ET build excluding machining.

[Ghostrider]

thicker (Nismo do a 2mm) head gasket.

Use this and your compression will go out the door! Probably drop to UNDER 8:1 which is N F G for your n/a motor. You want 10:1 in a good n/a engine.

Try relieving the tops of the pistons (Fly Cutting) for valve clearance IF necessary. as I said earlier.

[coupe72001]

Ok - thanks for that. I will fork out for the fly-cut if I run into trouble with valve clearences. (probably cheaper than the damn Nismo gasket anyway!)

I have mocked up the crank and number one piston, and will fit the head tonight if I get the tappet clearences spot on.

Actually, my how to build your Z engine book stresses NOT to recycle your rocker arms and lash pads when you change your cam, especially if you don't put eveything back on in the same postion it came off (eg number one exhaust rocker arm is to go back on over the number one exhaust valve - not somewhere else on the head.) When I had a close look I noticed that the rocker was not perfectly parallel to the cam. The left side of the rocker was actually touching the cam even when the cam nose was facing away from the rocker. Should I invest in new rocker arms and lash pads to try and fix this? I don't want to damage the cam.

Also I have started to go over budget. Ill tally costs after class and see what the damage is.

D

[coupe72001]

Ok... I have hit a snag. The crank doesn't spin freely when I tighten the bolts for number four bearing cap (this houses the thrust bearing).

It spins fine with all the other bolts tightened, its just four that locks it up. I measured the distance between the crank and the thrust bearing and there seems to be only a tiny (0.002 inch) amount of clearance on each side.

Anyone know what I might have done wrong - the manual suggests the crank should spin freely, even with everything tightened.

Regarding costs. I have forked out for brand new gaskets, bearings, rings, shims, welsh plugs and harmonic balancer only. Everything else is a decent second-hand item that has been cleaned/honed/polished or painted. The total costs have crept over a grand including all the machining, but hopefully it should stay the right side of $1,500.

[coupe72001]

Ok, finally have assembled and painted the short block and it all turns over by hand. There is buckets of valve clearance and number 4 bearing cap has been machined to let the crank turn freely. I am just waiting on new shims for the head so the tappet to cam clearances are right.

A 280zx turbo oil pump has come up on ebay. Do I want this? Obviously the car won't be turbo, but some other l28 N/A engines I know of are using this pump.

[Ghostrider]

Drew,

The US spec L28ET auto oil pump is the biggest of them all, you will find H 4 on the casting, but be warned, you also may need a new drive spindle, depending on your distributor drive.

L28ET oil pumps also come as H 3 & H 3.3 the most common manual version being the H 3.3

The L20ET pump is also an H 3

Cheers, D

[Ghostrider]

Drew,

If your talking about the one blax240 has, he is an excellent person to deal with. I have bought many items from him and can only recommend him highly.

Cheers, D

[coupe72001]

That's great to know - and your right, it is blax240.

I (will) have the L28ET oil pump, L28 (n42) block, L28 timing gear/cover and an L28 electronic distributor. Will the drive spindle I need have to be for an L28ET or can I get away with the non-turbo L28 drive spindle? Are they different lengths/shapes? I have never seen the L28ET drive spindle so I can't compare the two.

Cheers for you help,

Drew

[Ghostrider]

It has a lot to do with the distributor drive. The turbo distributor has a spline drive, but from memory the n/a distributor is an offset cam, so you might be ok. Just do it your way and if you get stuck let me know, as I have a couple of turbo spindles.

Cheers, D

[coupe72001]

It has a lot to do with the distributor drive. The turbo distributor has a spline drive, but from memory the n/a distributor is an offset cam, so you might be ok. Just do it your way and if you get stuck let me know, as I have a couple of turbo spindles.

Cheers, D

Excellent - I'll give it a go then!

I finally got the call and the head is ready to pick up - just in time for the long weekend!

[Ghostrider]

If you don't score the turbo pump from blax240, I have a H3.3 I might be tempted to part with, as I have an H4 & a new hi flow I bought from SWR some time ago. Send me a PM coz I might have something else that would help your n/a that I'm not to fond of advertising on here.

Cheers, D