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KA Swap in 620


Gio.&.his.Datsun

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Your '79 was the only year with a 4.11 differential. (assuming you have a standard transmission) All other years of 620 had a 4.375 and can easily be found and swapped... and they fit. Your engine will be revving higher at the same speed as the 4.11 so it will be putting out more torque. By fit I mean only the third member that is bolt in needs to be swapped. No need to swap the entire axle. This is the easiest and best bang for the buck performance upgrade you can make. The Ford 9" is an over strength over wide over heavy pig. It will need shortening, the leaf spring mounts moved and some way to connect to the Nissan driveshaft. Then there is the shock absorber location and emergency and hydraulic brake hook up. If you want gears go with the 4.375.

 

Don't mess with the vacuum lines other to inspect them for cracks and leaks. Learn more about what you want to do with your truck. Pull the wrong thing off and you'll be days on here saying it runs like shit.

 

Save your money on ignition upgrades. For your stock truck there is nothing better than what's on it now.

Forget header, they are a waste of money unless you totally race prepare the engine.

The stock carb is great if clean and properly set up. A $300 32/36 Weber is a good upgrade for it, but don't settle for a cheap Chinese knockoff. If you can't afford one leave it for now.

If your exhaust needs replacing have a shop custom bend a 2" and a larger muffler or a turbo muffler ....NOT a fart can! This ain't cheap so if the pipes are good just get a larger diameter muffler and adapt it on. If you have a cat remove and replace it with straight pipe

If your '79 has an air pump just take the belt off for now. It won't gain you anything but it will seem like it. If you don't need it for smog testing it's a start at removal. More on that later.

 

 

Smog equipment when removed, adds zero to the performance. This is because smog equipment only works when driving normally. At full throttle they are inactive. I think the '79 has a fuel shut off on deceleration so removing it actually wastes the gas normally saved by this system. So know what you are doing first.

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One caution on the aluminium Buick / Rover V8 engine!  This was the early days of Aluminium blocks.  Owners were not aware of the real necessity of maintaining proper coolant ph and approved mixture percentage level.  Most such blocks are really full of yellow corrosion products and may not have proper wall thickness[or coolant passage volume]  if you are lucky enough to de-crud the block!  Upside, you have a wide choice of left and right side intake and exhaust manifolds, some mix can fit almost any engine compartment and chassis combination.

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It would be great if there were more successful V8 swaps out there. There might be an opportunity for you to get up close and personal with all that's involved: Maybe even get to ride in it...Then you'd have an informed opinion as to whether you want to go down that path...For me, when I was younger...I too, wanted to have a V8 620 (I had a friend that had a V8 LUV)...it just never happened. Years later, I test drove a V8 Z: And it just didn't feel right to me...After having driven my friend's Z many times: I preferred that to the V8 Z. Good luck with whatever you decide: Ultimately, it's your ride and your decision.

Jersey.

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I think I'm going to beef up the engine a little, enough so I can have a daily driver with some meat and take down the ego of the lifted Chevy, Ford and Dodge trucks that dominate this area. I have a much much clearer direction as to what I want to do. Thanks for all the help and if I have any further questions I'll search these threads and maybe make a new one.

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Cars come with exhaust manifolds, which generally do a good job but an after market tubular header can extract more power out of an engine if...
 
The original manifold is restrictive
The engine has been modified for more power.
 
In 99% of the times the stock exhaust is just fine and a header produces no gains that are usable. They are loud, run much hotter, they always rust out, they don't fit properly and the always leak. The last three are more apparent on cheap headers. o $200-$400 to gain 3-5 hp @ 5k and nothing at driving speeds. In many cases a low restriction header alters the cylinder mixtures by over savaging and you loose torque at low speeds.
 
You have an L20B (a '78) do like I did. The L20B runs all 4 cylinders into a single outlet manifold and down pipe. The earlier L16 has 4 into 2 manifold and the exhaust down pipe  joins these two pipes into one and then to the resonator or muffler. The L16 exhaust manifold is arguably less disruptive of the exhaust flow and is sleek looking.
 
This is a '75-'77 exhaust on the left (yours is similar) and an L16 on the right. You can see the individual tubes keep the disruptive exhaust pulses separate for longer.
 

.............................4 into 1............................................................................. 4 into 2
IMG_20140901_121603984.jpg


m4kuUQQRwng3Pt5TJ2bAk7g.jpg Here is a header you can see the similarities with the L16 manifold. I did this for a $10 manifold and a $19 gasket. Don't expect much out of this, it's just cheaper than a disappointing header and... looks nice.

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At this point, your best bet is to learn how to tune your truck first.  

1.  set valve lash

2.  adjust timing to 10 BTDC at idle (or so) and experiment as you may find it runs best oevrall at 14 BTDC?

3.  Lose the stock carb and install the REAL Weber 32/36 from Pierce http://www.piercemanifolds.com/

4.  Tune the new carb, set the float height/drop and enjoy the drive.  

5.  get your brakes 100%, as you'll need those to be perfect if you want to add more power later.  

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Adapter plate bolts come loose so people tend to over tighten them and crack the plate. Use thread locker.

 

If you get the $300 replacement kit you pretty much get everything you need. Probably you will need to take your Hitachi throttle lever off and put on the Weber.

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