Question to the Group - N42 Rebuild

[Travel'n Man]

Question to the Group –

I am getting ready for an engine/head rebuild -

Here is what I am planning on doing – any suggestions? I am wanting to keep it basic and nothing too wild. I am going to be sending the car off to the body to have the engine bay detailed and repainted. The engine will be painted the correct Datsun Blue. This is my first rebuild and my buddy that is a ASE Certified Master Mechanic will be handling this project for me. I am not underestimating his skill level, but I know there is a lot of knowledge with our membership and would like to hear your recommendation. I only plan on having this engine out one time and want to get it right.

Share your thoughts - thanks in advance!

Block – N42

• Hot Tank Block

• Polish Block Head Surface

• Polish Block Timing Cover

• Polish Block Valve Cover

• Bore & Hone Cylinder Walls

• Install New Piston & Rings - Oversized .040

• Install New Rod Bearings

• Install New Main Bearings

• Install New Oil Pump

• Install New Water Pump

• Install Timing Gear Kit

• Install New Engine Gasket Kit

• Install New Freeze Plugs

Stroker Rods-Shortened? (Questioned)

Lighter Flywheel?

Head – N42

• Hot Tank Head

• Resurface Intake Gasket Side

• Resurface Head Gasket Side

• Resurface Valve Cover Gasket Side

• Shaved Head .080 (Questioned)

• Copper Shims Cam Tower (Questioned)

• 3 Angle Valve Job

• New Rocker Arms

• Hardened Seats

• New Valve Stem

• New Valve Guides

• New Isky Coil Springs–Retainers–Lash Pad

• New Valve Seals

• New Camshaft – Isky Stage II (this was the techs suggestion at Isky)

• Clean and Repair all threads

• 2mm Metal Head Gasket (Questioned)

• Reassemble and valve adjustment

• Square Port for Header – Ported to match

• Ported and Polished Head

Edited July 22, 2010 by Travel'n Man

[Walter Moore]

That is an impressive looking list. I don't know what to say except good luck.

[S30Driver]

Looks like a very comprehensive list.

Only thing I can think of offhand is a quality grade 10.9 stud/nut kit for the intake / exhaust / carb setup.

[Nigel1943]

I'd say your compression is going to be a touch high with 0.080 off the head and 0.040 oversize pistons (flat tops ? )

[Zedyone_kenobi]

Why not high pressure/high volume oil pump

Get your pistons coated with a low for low friction

Larger oil pan to hold an extra quart

Also, I would avoid shorter rods. They will make for increased side loads on the cylinder walls. I would go for a longer rod if you have to build a stroker, you will get more torque out of it.

[Marty Rogan]

Why would you want to shave off .080 off the head? If it is that badly warped, you might want to find another head. Your compression ratio will also go way up. Only shave off as much as you absolutely have to.

You also might want to re-think the metal head gasket. I looked into that recently. Then I came to realize, that the head gasket is a fail-safe for the engine. If the metal headgasket does not blow, then you will start blowing your new internal engine parts! I ended up going with a new stock gasket from Car Quest. Their "OEM Replacement" line is the same part that Nissan supplies, at only about 40% of the cost.

Just my 2 cents.

Marty

[Diseazd]

I'm not totally sure, but I don't think the chambers are deep enough to take .080" off of the N42. The P79 and P90 have deep chambers.We shave those heads .080, use the longer early L28 valves and shim up the towers and springs .080" to keep geometry and cam sprocket height correct, but I don't think you can do that with the earlier heads. Maybe someone else can chime in on that subject. Guy (Don't forget to buy Isky's lash pads for the Stage II cam to keep rocker geometry right)

Edited July 22, 2010 by Diseazd

[Lazeum]

I would do what you've just said but I would go with flat top pistons and different head.

Since you're going to do all the work, I'd choose a P90 head that's got closed chamber with better knock threshold over the N42.

I would also use a smaller head gasket to keep the quench effective with the setup.

I wouldn't use metal head gasket either. I'd rather see the gasket blowing than my new custom head being wrapped in case of failure somewhere.

Compare to what you're going to pay already, a used P90 should not be that much more money.

I have a F54 block with flat tops, P79 head made by Rusch Motorsports. Torque & Power are very nice compared to my previous combo with same block & stock N42 head. Comp ratio was too high, timing had to be retarded by a lot to make the engine running with no detonation.

Cams were different though so that would also explain power differences...

[Travel'n Man]

Thanks to all that have responded - this is fantastic!! Please post your personal thoughts and I will go over with my buddy to get the best of all worlds and put them together in my engine bay. Great stuff here!

Thanks to all!

Any lighter flywheel recommendations?

Edited July 22, 2010 by Travel'n Man

[240ZMan]

I used to run an N42 head with .030" over flat tops and a Delta Cams regrind (probably not quite as much overlap as the Isky cam you're considering). I was not able to run full advance in the 4500 rpm range on warm days due to detonation and had to back timing off. Shaving the head .080" would obviously make it worse.

I later swapped to a P90 head which I did shave .080" and using my butt dyno could not tell the difference from the N42. Head gasket in both cases was Felpro.

Unless funds are unlimited, I would recommend you use your N42 head, a stock HG, and take the money saved by not shaving the head and buying a metal HG and use it to have the head ported. I suspect you will gain far more from that.

Edit: just thought about this a little more and you might want to go with the 2 mm HG to lower the compression a little more, at least based on my experience. Better to have a slightly lower CR and be able to run full advance.

As for lightened flywheel, I had a stock one machined down to 16.5 lbs which I'm still running and love it. But if I had to do it again today, I'd spend a little more and buy a Fidanza given they can be found for around $250 now and then. Back then they were never less than $400 so the $150 for machining/resurfacing was a good deal.

Edited July 23, 2010 by 240ZMan

[Mike B]

Any lighter flywheel recommendations?

I re-read an old issue of "Zcar and Classic Datsun" magazine recently (Sept/Oct 1998) where they were building an ITS car. It noted that the 70-71 Z's have a flywheel that weighs 17-18 lbs and the ones in later years weigh 22-24 lbs. Probably not the lightest one out there, but it should be pretty easy to find one cheap.

-Mike

[Travel'n Man]

Dave Rebello has completed my N42 head - cam - porting - flat top pistons - 240 rods - compression 10:1

Car is due out of the body shop this week for refreshing of engine bay - going with black from the firewall to the front of the radiator support - 110Red from the radiator support to the end of the car - engine bay taken down to raw metal - excess holes welded.

Engine going to be dipped - bored - honed this week - engine block to be 110 Red (same color as car)

Header and Heat Shield Jet Hot Coated

Engine rebuild and install over the next 10 days..........pictures to follow

Edited September 6, 2010 by Travel'n Man