'77 Datsun 620. THE Ratsun!

[Ratsun]

This has been a very long poject that started about 4 yrs ago and has been worked on in spare time. Unfortunately there was about three years of very very little "sparetime" available.

Anyway, I found this thing when I drove by the barn of the original owner who had just pulled it out to move some things around. I had been looking for a regular cab/shortbed to cut up and build for the track. However, when I found this Kingcab, it was just too nice to pass up. the price was right too and that always helps. It has NO rust on it anywhere and the interior was in great shape. It had been sitting for about 12 years, but after getting it home only minimal effort was needed to get it raod worthy again. I just pulled the cab for a good cleaning and put four new wheel cylinders and was on my way for the next year and a half or so. Unfortunately I got lazy and didn't insist on chaneging out the original cotton coated heater hoses before one of them burst and let all my coolant out and then didn't tell me!! The head gasket blew on it and put me down for a while. I finally got to it and then found myself coming down with a bad case of the "while I'm at it" syndrome. There is now a mean little Ratsun 4banger sitting under the hood just waiting for a solid ignition!!

Engine Specs:
Bored , radiused and polished block
.040 over custom built forged JE dome pistons= 11:1 comp ratio
6" race prepped rods (stock rods are around 5.5")
ARP bolts everywhere
balanced/blueprinted assembly
custom windage tray
reworked chambers/ported head w/new steel intake seats
custom reworked/ported intake from an sss
twin 44mm SU carbs from '72 240Z, will custom build needles after my Lc-1 wideband is installed
custom ground .540/290 cam
115lb. springs at 1.75" w/titanium retainers
lightened rocker arms
custom reworked valves
K&N filters
lightened flywheel
Centerforce II clutch kit
probably more too that I cant remember

Suspension upgrades:
Blistien performance shocks
Chevy S-10 front anti-swaybar
polly bushings
front sway bar moved to the back
more to come...

Brakes:
Front disc conversion with 11" cross drilled slotted rotors
Hawk racing pads
high temp performance brake fluid.
Rear disks to come...


I have gotten everything installed for the Megajolt and am awaiting it's delivery. It runs smooth on just the module so I am very excited about getting started tuning everything.

BTW, Bent is quite a guy and has been Extremely helpful. THANKS!!!

Here are a few older pics of the truck when I first got started building the engine. I will add more of it finished soon.
Thanks for looking.

[sierra2dr]

This has been a very long poject that started about 4 yrs ago and has been worked on in spare time. Unfortunately there was about three years of very very little "sparetime" available.

I know how that feels
The front resembles the UK spec Datsun Violet
All the best with the project

[Ratsun]

Thanks!

I finally got it all together and took it on a test run. I will be installing the LC1 this weekend and should be able to get the carbs dialed in a lot better. From what I can tell after the test run though this thing will be a beast!


Here are a few more pics of the engine build and the MJLJ install. It's still a work in progress so please excuse the messyness!!










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[Ratsun]

IMG]http://i204.photobucket.com/albums/bb26 ... 931248.jpg[/IMG]








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[dr.occa]

love the fuse block from the edis box.

[brentp]

Fantastic pics- and thank you for the kind words- and keep us posted on the project!

[Ratsun]

Thanks guys.


I did get the LC-1 installed and found that it was going WAY lean under load and WOT. After fiddling with the carbs all afternoon and getting nowhere I decided to get a cheap fuel pressure gauge and check that. I installed it tonight and found that I was running about 2psi at idle and droping below 1psi at WOT!!! No wonder!!! Hopefully it's just a clogged fuel line and not a bad pump.

It's deffinately getting closer though! I can't wait to start tuning that MJLJ.

[NWOleman]

Sweet! i been lookin for someone that used this setup on a L20 b or L18 datsun motor. How does is run? Also do you have a timing map for your motor? Any info you could give me on how your megajolt is setup would be great! Thanks

[NWOleman]

Sweet! i been lookin for someone that used this setup on a L20 b or L18 datsun motor. How does is run? Also do you have a timing map for your motor? Any info you could give me on how your megajolt is setup would be great! Thanks

[ggzilla]

This is a pretty well modified engine, so it will want a curve a little bit different from a stock L18 or L20B Datsun engine.

Attached is a MJLJ ignition map for a stock 1974 Datsun 620 with L18 engine, using these factory specs from the 1974 factory service manual:
Vacuum: 0/150mmHG (5.91 inHG) to 3.5/250mmHG (9.84 inHG) -- 3.5 distributor degrees
Centrifugal: 0/550 RPM to 10/2150 RPM - distributor RPM
initial timing: 12 BTDC/800 RPM - crankshaft RPM
So this map is 12 to 32 degrees mechanical, with additional up to 7 degrees depending on vacuum. It would probably perform better with the 32 degrees all in by 3600(?) instead of 4300 RPM.
When you try it listen carefully for pinging. Just as with the stock distributor it may need some fine tuning.

Of course the ignition map built into the MJLJ will run the Datsun engine OK too.

[NWOleman]

Thanks ggzilla! I owe you bigtime for this!