SR20DET --> 1986 300ZX Questions

[Ashkenico]

Hello everyone! I am new to these forums and this is my very first post.

I suppose I should begin by saying that I love my car. I purchased my car with a full understanding that it would be a project car and a pretty big restoration job. I will create another, separate thread explaining what all I am going to restore later.

I currently have the stock 20+ yr engine and it has a horrible 305k miles on it! I had a mechanic look at it and he told me that although there's nothing big wrong with it that would cause it to not run, there are many many small issues with it that has him stumped. The engine is misfiring to the point I am getting like maybe 12 MPG (luckily I live very close to work). There's a pressure leak somewhere so it has problems starting up, though it runs fine when it warms up. Its constantly pumping exhaust AND petrol into the cabin so I have to drive with the windows down, but my clothes still smell bad when I get out. And something new just started happening with my transmission: It refuses to go into 1st and 2nd gear when the engine is running! I have to turn off the engine, put it into 1st then start it up. 3rd sometimes acts up, but the other two gears are fine.

So I was thinking...I could spend 2x as much money rebuilding that engine with all its issues OR I can just buy a gently used engine with low miles and swap it out and be done with it.

I do NOT know much about car mechanics. I am an EE major so please forgive me if I use incorrect terminology or come off sounding otherwise stupid.

I have done some research on various engines that can be put into this car, and apparently a whole lot of engines will fit with little or no modification to the engine bay.

Two things concerned me with getting this new engine: Power and fuel economy. I sort of want to balance out the two but when it comes down to it, fuel economy is more important to me since I am not a car-person at all and im not a competitive show off like most dudes are. (this is my very first car, actually).

Anyway someone told me that the SR20DET should fit nicely in that car with no modifications to the bay, which is nice. I can get one with ~30k miles for 1k even + ~250 to ship and can pay someone 500 to perform the swap.

I am here for clarification, really as I am sure that many of you know much more about engines than I do.

What is the true fuel economy for that engine? I was told that I should expect around 25-30 mpg for the non-turbo model. Is this true? Also, are there any special things I should know about engine swaps? I asked the seller about what comes with the engine and he told me that everything is included, even the transmission, and all I would need to do is find someone that knows how to wire in the ECU.

The last thing I want to happen is that I buy this motor and then there is some other expense that prevents the proper installation. I don't want any surprise costs.

Sorry for the long post, and thank you for all that respond!

[Ace2cool]

Hey, welcome to NICO! I moved your thread to the "Classic Z Technical" forum. The Z32 forum is for the '90-'99 300ZX. The guys in here will probably be able to help you a little bit better than we could.

[evildky]

I do not recomend a pallet motor especially one taht isn't fomr the US, when you buy a pallet motor you are buying a miles unknonw engine, they might telly ou it has aobut 30k but the truth si that unless ti includes a cluster, ti is milage unknown and most likley is they decided to sell ti as a pallet and nto a clip it's got a lot more than 30k miles on it, I've had nothign buy bad luch with pallet motors, and I assure you ever "low miles JMD engine" I have bought (3 of them) have had more miles and smown mroe ware that the "high miles" engine I was replacing, if you watn to buy a used enigne get one from a reputable auto recycler, a good reputable recycler will document the miles and running condition before they pull the engine and offer a period warranty and you won't have to wait on a container to find out what you get

also I never suggest someone swap in a smaller engine, it just doesn't make any sence to give up displacement, more displacement = more potential power at lower rpm

people who say it's cheaper to replace than to rebuild have generally never priced a rebuild, and as witht he swap the more work you do the less it costs, if you pll and disassemble your engine and it doesn't require overboring or oversized pistons you should be able to rebuild the block and both heads for under $1000, if you are paying someone else to do the removal and reinstal taht figure could easily double

as for fuel economy, you should be able to get high teens in city driving, and high 20's on the interstate cruising at 55, mixed driving can get you anywhere in between, as for economy of having a smalelr engine pushign a heavier car than it ever came in who knows, probably better than the vg but worse than a 240sx

now if it's power you are after, you can look into a vg30et swap/conversion, you can look for a wrecked donor or just collect the bits you need to convert your's or a salvage vg30e to turbo, follow the link in my sig to my turbo converted z31

[zmainiac]

Where do you live? Is the car a turbo or not? There is no point to swapping in another engine. You can get all the power you want out of a vg. I am shooting for 800 plus Hp this year. What are your goals for the car. If it is not a turbo a turbo swap will make it way more fun. I can help you fix it. A stock vg should last forever. Did the mechanic do a compression test?

[Ashkenico]

Thank you for your responses, and yes, I had forgotten that this car is now considered a 'classic' just this year. Here's an answer to a few of your questions, best I can:

Lets see...this current stock engine is a non turbo. The engine that I was going to replace it with is also non-turbo and has been pressure tested.

I live in Texas. I am NOT interested in more power, fuel efficiency is most important. I can care less about turbo charged engines. This 'upper teens' that you mentioned is just unacceptable to me. There are more modern engines that provide both more power and more efficiency than this one. I do not want this engine. Like I said, its just missing too many small things, and the previous owner(s) have done modifications that they should not have. So even if I did pay to get this engine rebuilt, I would also be paying for new hoses, a new EGR valve, new electrical connectors (which are apparently hard to find) and a whole lot of other things I just don't want to be bothered with. I will be more than happy to post pictures of my oddball engine if you don't believe me.

I can totally under what you said about buying an unknown and undocumented motor. The seller did post pictures of the replacement motor and it looks really clean. I know for sure that the motor and transmission comes with a warranty. I will ask him if he can prove the mileage on that engine.

[zmainiac]

You will need the following new parts for a different motor swap. Custom: driveshaft, motor and transmission mounts, custom wiring, modifications to the shifter location. Maybe a different front crossmember(for rb engines). My 86 na got 30 mpg on the highway. I brt with a good k&n filter, headers and a decent exhaust you would do a little better. There is a color coated writup on how to swap all the vacuum hoses and it doesn't cost that much. There is a rare vg20et that came in the japan versions that probably bolts right in but they are hard to find. It should get better milage.

[Ashkenico]

Heh, yeah I remember reading something about the shifter location may be a bit off-centre but thats cool. Do you think that the SR20DET is a good engine? Someone told me it has a poor intake or something.

[evildky]

you might be able to get better milage form an n/a vg than I can btut hen I was less cocerned wiht milage and more concerned with performance, and like I said high teens in city driving, I get only about 11 mpg city driving my tundra, I can get 20 on the highway, but I live in the city not the burbs

the sr20det is an overly popular engine with the s13/s14 crowd, if economy is the prime concern the sr20 is availabel as an n/a in the US but only in front wheel drive, it can however be converted to rw configuration

also the ka24 would eb an easy domestic availbel swap

and wiht any of these swaps you son't need to change your trans or driveshaft, you will however need t swap over the frotn half of the trans case and perhaps the countershaft bearing

[Perrenial Badass]

I average about 21.4 MPG inter-city driving per tank in my 86T. Would be better if I was ever on the interstate. NA should be getting better mileage than that as well, but it depends on how quickly you decide to get up to speed as well. I stay out of boost.

I think your mechanic might not be very competent if he is incapable of tracking down exhaust and gas leaks that are getting into the cabin. If the pressure leak is causing starting issues, then it should be easy enough to diagnose. Leak down test for the heads, compression test for the rings, and use starter fluid to test for vacuum leaks.

You never mentioned what transmission type you have, auto or manual.

Fixing your car back to stock can be pretty cheap, boneyards in my area sell running motors for $150 with a warranty. It would come with the EGR valve and such but no alt, PS pump, compressor, etc. Putting another $350 into maintenance items when you drop this motor in would make the car reliable for many years to come.

Buying an SR would be the same amount if you have one local, or a grand imported. You then have to pay to have mounts made up and have to wire it all in. It would still be wise to do all the maintenance such as timing belt on it, I'm not an SR guy so IDK what that would set you back. I would expect the price to be similar. I think SR20s in the Silvia came with the 71C, which is the same transmission in manual NAs so you might not have to modify the driveshaft.

In the end, it is probably cheaper to buy a Civic or a Sentra than to rebuild a VG or swap in an SR or pretty much any non-stock motor into your Z. I think that if your primary concern is fuel economy and you have the $1K do drop for an SR, that your best choice would be to sell the Z and buy something with better gas mileage to begin with. Probably not what you wanted to hear, but true.

[Ashkenico]

yeah, selling the z is not an option. the money im putting into it is well worth it because i love the body shape and small size. It is my money after all and in the end, ill have spent only 4k for a complete resoration, and i think ill be aking out like a bandit.

[Ace2cool]

Do I smell a $500 economic beater Civic? :

[Ashkenico]

well..thanks for your input anyway, i'm out.