1980 280zx with sbc swap build thread

[JH383ZX]

https://www.classiczcars.com/forums/topic/63403-considering-a-1980zx/

 

link to original thread

 

Howdy y'all, im new to this forum so correct me if im posting in the wrong place.  i have a 280zx with a 383 swapped into it, full manual valvebody 700r4, and lots of goodies in the engine.  s13 coilover conversion ect ect ect.

 

i just finished rebuilding the engine, and installed it back into the car.  i had it runnning briefly before i left to go back to arizona for college, but didn't get a chance to drive it.  when i come home for christmas i plan on continuing with it and get it reliably drivable.  I've done a few autoX races with it but the handling is not where i want it, mostly driver related(i need seat time more than anything), but the car tends to push hard and understeer significantly on corner entry, followed by more poor driver input causing corner exit oversteer. i do plan on moving the engine fore and aft to help with weight distribution, i also picked up a few scales from goodwill that i can use to corner weigh the car and better understand the balance, and my brother has a stock 83 zx that i can weigh to compare distribution.  after thats dialed in i do plan on upgrading swaybars to compliment the coilovers, if any of yall have some recommendations id be glad to hear them, i was looking at 1" front and 7/8" rear, or 1" for both if i can find it since the stock has the rear swaybar much too small in my opinion.  before that ill likely get an old stock bar from the junkyard and play with bolt hole spacing and how it affects handling so i can better understand swaybar effect before spending lots of money.  

 

feel free to ask questions about it, offer advice or show off your z, i plan on using this thread and the previous to keep track of my work as i go, so more updates as i get time to work on it

[JH383ZX]

trying to learn pictures, yall let me know if it decides to not upload them

[jhm]

Nice!  Thanks for sharing, and welcome to the Forum!  Hope you find any/all info you might be seeking; and please don't hesitate to share your knowledge and lessons-learned, as well.

 

What spring rates are you currently running?  You'll find that some folks prefer stiffer coil springs and lighter sway bars, and others vice versa.  Additionally, a lot of S30 drivers prefer a smaller rear bar (or even no rear bar at all) for better power-down behavior during corner exit.....don't know how that translates to an S130, but maybe something to consider if you plan to do a lot of auto-x.

 

Cheers!

[JH383ZX]

On 12/8/2022 at 10:37 AM, jhm said:

Nice!  Thanks for sharing, and welcome to the Forum!  Hope you find any/all info you might be seeking; and please don't hesitate to share your knowledge and lessons-learned, as well.

 

What spring rates are you currently running?  You'll find that some folks prefer stiffer coil springs and lighter sway bars, and others vice versa.  Additionally, a lot of S30 drivers prefer a smaller rear bar (or even no rear bar at all) for better power-down behavior during corner exit.....don't know how that translates to an S130, but maybe something to consider if you plan to do a lot of auto-x.

 

Cheers!

8kg/mm front and 7 rear on springs, and thanks for the advice ill play around with no rear swaybar and see how that works for me, i wouldn't mind a stiffer rate but ill have to figure out how springs are measures dimensions wise and if i can get stiffer ones, just depends on if my coilovers are a standard size or if its all oddball sizes.   ill play around with it a lot, and ill keep a journal of what changes i make and the effect on the car so that we can have some more available knowledge for tuning the s130 chassis. 

 

as far as stuff ive learned, ive learned a lot of lessons in how to deal with making stuff work for the swap, i learned how to rebuild and change valvebody circuits to make the full manual valvebody, s13 coilover conversion was fun, and learning the aerodynamics of these cars has been interesting, i designed a splitter in solidworks and tested it using string and tape, and ill redisgn it when i get back to texas.  the aerodynamic stuff is what got me started in going to college for aerospace engineering, but the love for combustion is gonna lead me to switching to mechanical engineering propulsion. if you can swing custom headers its worth it, i tried to make a lt1 header for an fbody work by cutting and bashing ect, it sucks but it works enough.  street tires and torque converters do help to keep the rear end live, my stock r200 has seen plenty of 60-160s, digs, late night pulls ect on a reasonably built 383.  i also like the single plane over the dual plane, the loss in low end torque gets mostly eaten by the converter anyways and it lets the engine rev a lil more, which i like on these cars.  theres also a lot of weight to be lost in these, im very very curious for the weight and im looking forward to finding out so much more on that topic, i bought 4 scales from goodwill for $20 and with a piece of wood i can do all 4 corners and gather more information.  with tires im still learning, i have nitto NT05 on mine and i like them, they dont fall off as harshly as some tires when you push past the limit, but its definitely much more defined over street tires. i will also be seeing how performance changes with them from temp, ive heard rumors they get greasy when they get hot, but ive yet to drive hard enough to get the tires to that point.  these cars are also terrible about building too much positive pressure under the hood which hurts cooling a bit, but as i figure out ways to improve it we will see.  vapor lock is also a big issue, i ended up, after 3d printed carb spacers dry ice in the gas tank ect, taking the old heater core and running fuel lines through it and letting it sit in a bath of water helps tremendously. also nitrous is coming soon, i have everything to setup a 50shot for it, so thatll be fun stuff.  

 

i have a lot of knowledge on my setup specifically, i did everything to it and theres no more untouched nuts and bolts on it, i love to talk about it, and im looking forward to gaining more knowledege and insight into this so i can make it better. itll be interesting soon to get back to back tests on effects of altitude, back in texas i was at 1000ft, in north arizona for college im at 5600ft, with the local mountain roads getting up to 8100ft!!! 

[JH383ZX]

finally weighed the car, need to corner balance a bit but it was 2656lb with full tank and all fluids no driver, 51/49 weight distribution so ill adjust the engine placement a tad and get it perfect, and adding the weight of the nitrous bottle should help  ill also adjust after ive weighed with driver, my friend weighs the same as i so when he gets back in town we will figure out the balance, my scale setup was two body weight scales from goodwill and some scrapwood, have to keep the other 3 tires at the same level for it to be accurate. but for $10 it doesnt get much better than that.  

 

when timing the engine after i got it running and idling a bit it was at 4* of total timing, shocked it even ran, dialed it in to 35 and shes much happier now, and after driving it she pulls hard! i gotta fix a couple trans leaks and somehow texas got pretty cold so once the weather breaks ill drive it some more.  trans was shifting perfectly, i love the full control over the transmission with the instant shifts.  carb needs some adjustment but thats to be expected with the cold, might add a resistor to the choke so it can stay a bit richer to warm up, i like a pretty lean idle so it revs a bit quicker coming out of corners, but the cold weather doesnt seem to like that.  but more seat time is needed to make some adjustments and get the car where i want it. 

[JH383ZX]

so im back in arizona now, enjoyed my time with the car, its having a wierd one of the head gasket if fine but its getting the valvecovers a bit milkshake like, thinking either condensation not burning off because the oil isnt very hot or the intake manifold is leaking a bit, but otherwise car is in great shape, gonna add nitrous this summer  

it does have a noticeable clunk going into gear especially if switching directions or downshifting, so i gotta track that down, and the gas tank needs some sealing

big plans for this summer include safety measures being implemented into the car, like a roll cage and 5pt instead of 4pt seatbelts, and a permanent fire extinguisher mount. ive only gotten the car above 160 a few times and generally try to keep it under 100, but even then i know this car will kill me the first chance it gets so safety is on the mind, especially once the mexico team reunites for the summer  

 

as far as driving goes i figured out or im starting to figure out how to load a lot of weight on the front tires before the corner and going in so that it doesnt push so much, and using more of the throttle to steer and control the angle coming out of corners.  its definitely a different driving style, than im used to but im getting better with it. turn in is very sharp, i may play with my toe settings a bit to see if going toe in/out feels better than 0 toe. for my drag and roll racing i need to spend time with the car and feel where the power really is, like i can feel once it gets above 3500 rpm it feels a lot happier and runs incredibly clean, and i can feel its still making power all the way up to 6000, but i havent figured out timing my shifts so that i can shift it cleanly at 6000. but for an iphone app 1/8th mile it said 5.87 to do the 1/8th from 0, not enough space for a 1/4, but im hoping in the 1/8th mile world thats faster than an 11 1/4 mile because i dont know whats fast for 1/8th mile. traction is pretty good for street tires, but theyll likely still be spinning through the 60ft.  

 

yall feel free to send thoughts, questions, $.02, ect, and if any of yall have experience with putting a jegs 10 or 12pt cage for an s30 into the s130 chassis let me know how it was, ill likely be removing some of the door to add more cage so some of it will be custom but the jegs seems to be a good starting point.