Advice for Datsun 620 project

[Mistress620]

Hi guys. New guy on this site, and I was wondering if I can get some advice. I got this 1978 Datsun 620pick up which I called my "Mistress". I had it parked for months and now I'm putting my time to restore it and bring it back to life. I stripped down the body to sand down and clean up the rust and paint for the new paint job. I just have it all primered now. But What im asking for is question regarding about the engine rebuild. I took out the old engine and tranny out cause the block had a thrown rod and the tranny looked in bad shape. So I got a datsun L20b engine and a Datsun T-5 Borg Warner Tranny. The tranny looks in very good shape, and I started on the engine rebuild project. This is whats done so far:

 

*The cast Iron manifold was dropped, and I put in the earlier model exhaust manifold in and having a screw tube welded in its place to screw on the pipe for the EGR valve part on the Intake manifold{Damn smog accessories that has to say on}

*The A87 Closed chambered head was taken off. I'm currently doing a port & polish on the head, grinded down the inside of the head and smoothing it out, also widden the intake and exhaust ports to as wide as they can get on the gaskets, I'm gonna put in the 280ZX intake valves and have all the valves back-cut to 30 degrees after the 45 degree seating. The head is gonna get shaved down and have the valves widden for the bigger Z valves. also have the head cut to a 3 angle degree.

* The block is gonna get Bored and Honed 2 sizes over. All bearings are gonna get replaced for new ones. I wanna put in a Z24 crank and have it knifed edge, lighted, and re-balanced to 12,000 RPM. Replace all the piston rings. Lightened the flywheel to 15lbs. and put in a Datsun roadster clutch in.

 

So my question is;

Since I already have the Datsun 280 ZX valve springs, should I install them? Are they better or the same as the datsun L20b valve springs?

 

What other methods should I do to improve performance on my Datsun engine?

 

Sorry for the long story, but I just wanted to explain some things but any advice is helpful. Thank You

[datzenmike]

Z24 crank won't fit the L20B.

[Mistress620]

Yea I know, But They said that you have to shave down the counter weights to fit it in a L20b engine. I had got advise that this is what you do to make it a stroker crank for a Dastun L20b engine

[GLOZANO67]

Pics are always helpfull, I would like to see the new truck on the forum :P

[datzenmike]

Yes you could and also the block will need to be trimmed. Basically exchanging the Z24 block for an L20B block.

 

There's a reason that Nissan raised the deck height on the Z24 block by 2cm. When the crank throw and the rod form a 90 degree angle somewhere before the piston reaches half way down the cylinder there is maximum sideways pull on the piston. The shorter the rod and the longer the stroke the more the piston is pulled sideways in the bore. The stock Z24 rods are 165mm, the L20B rods you plan to use are 145.9mm. This extra side loading will increase wear and friction on the pistons and rings.

 

You might consider boring the L20N block to 89mm, a slightly smaller stroke Z22 crank (that will fit the L20B) and KA pistons. This will give you a 2.3 liter motor with less machine work and less stress on the motor.

[Mistress620]

Thanks I didnt know that the Z22 crank will fit in with no mill work. Imma try that. Im gonna post pixs of the project. But does anyone know if the Valve springs from the 280ZX is the same or an increase of performance when added to my w53 head?

[datzenmike]

The '78 came with a W58 head so either that is a much older L20B or someone swapped the head. The U67 head had larger valves and ports. (but didn't come in the closed chamber)

 

I don't know if the ZX springs are the same as the other L 4 cylinders or not. They won't increase performance but if stiffer will allow the motor to rev higher without valve float. I understand '67-'79 Roadster springs from the U 20 head are much stiffer.

[Mistress620]

how do you post up pixs, from my computer? Im trying but never done this and all my pixs are saved on my computer file

[76bullit]

There is a topic on how to post pics if you search it.

 

Basically get a photo bucket account and upload them there then you use the direct link to add the insert image button in the reply toolbar copy and paste the link.

[Mistress620]

Ok, Thanks for the help. Well heres the pix of my project:

 

This is how my truck first looked when I first got it.

 

I took off the wheels and put these 15 x 10 Alum. light weight sport wheels and did a 3 inch drop

Originally I wanted These wheels. The Solid Alum.

 

I then primered the outside body. Sanded down the paint to bare metal and sanded all the bondo off

 

This is how it looks now

[Mistress620]

Ill Post pixs of the engine project tomorrow

[74datsun620]

Very cool!!!!

[Mistress620]

OK, so here's the start of the rebuild. First I Stripped the front half of the truck down to sand down all the rust and paint that I didn't get. As you can see, I still have alot to go through

 

On my extra time that day, I painted the cluster and my new Grant GT steering wheel a metalic blue, and put in my tech meter.

 

I fitted this lower front sport lip off of a older BMW 325 series on my truck. It looked cool with the bumper and fenders on. no special cuts for the width but had to be trimmed from the sides cause the BMW front tire trims are futher back then the datsun.

 

Here's the Borg Warner T-5 transmission for a Datsun 1983 280ZX Turbo I'm gonna put in. Fits like a charm, just have to get the correct throw out bearing to press the clutch.

 

Here's the engine that came out of the truck when I first got it.

Sad the this L20b engine was a lost. pistons were damage, rod and crank...well you be the judge. and the head was a w58

 

Here's the new engine I'm building up. Plans: Piston Boring, Bigger stroke crank, Block honed, all bearings replaced, resurface the top of the deck, Flywheel lightened to 15 lbs, adding a Datsun Roadster clutch kit.

Pistons still look in good shape, and while taking off the head, I had a stubborn head bolt that broke off as you can see. Good thing its only one

 

Here's the A87 closed chambered head, still in good shape. Plans: Large 280Z Valves [Valves back cut 30 degrees from the 45 degree seats], 3 angle degree in the ports, resurfacing, Port & Polish.

 

Widen out the intake and exhaust ports on head.

 

Started on a port and polish on one chamber

 

Here are the Z valves. Still in good shape.

[Mistress620]

Hey guys when taking the head to the machine shop, what would you guys prefer the head to be resurface to? I heard that you can have it resurface to a certain amount. Also, can a L20b block be bored to 89mm? I just want to walls to be thin as hell to worry about the piston walls breaking down. Thank you

[Mistress620]

Sorry, I made a mistake about the Boring of the block, still trying to wake up. What I meant to say is that i don't want to bore the piston chamber so big that the piston walls are so thin that under pressure that they'll bust on me, So is 89mm as big as you can go, or is it pushing it? sorry for the misprint.:cool:

[banzai510(hainz)]

87 mm is ok for sure.

 

On your head makes sure not to port out the intakes so much that it get thin there also. that head heats up and bam u have a intake water leak inside the port.

 

Your going to spend alot of money on this????????

44mm valves and then need to get new seats and machine shop work.

 

also on the head I would do a just a minumum of the shave on the head. for longivity sake. If too much then you need cam tower shims.

 

since you got a squareport head you could get a Topend Performance(ck their website) header and have it Ceramic coated. then you dont need to worry about egr or other emmision stuff.

 

Hopefully with all these mods you going to put sidedraft carbs. otherwise a Weber DGV is barely going to handle this with out soem jetting work.

 

olddatsuns.com ck it out

[K_trip]

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