No way to track where the L18 came from. Heck, no way to track where the L16 came from unless you have the matching chassis data plate. Nissan didn't put that info out there; they may not have even kept that info in the first place and they certainly don't have it now.
James touches on the pointer for the pulley. If you don't have the original L18 pulley, you may not have the correct pointer for the pulley you do have. Typically the pointer and notched-pulley set has the pointer on the driver's side of the engine, where the single-notch pulley is matched with a degreed pointer plate mounted on the passenger side of the engine. Verifying TDC is Job One.
Tuning problems - L18/L16SSS hybrid with SU's
Re: Tuning problems - L18/L16SSS hybrid with SU's
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
Re: Tuning problems - L18/L16SSS hybrid with SU's
James wrote:Where is the pointer for the timing - is it on the other side?
I checked the two motors against eachother. The L18 has a different pointer, but it is bolted on in the stock location. I'm guessing that it's just an aftermarket pulley set that was attached, but I will verify that the TDC mark is actually at TDC. The PO told me that when he damaged the L16, he bought the L18 from a shop, and had them install it. Given the cylinder pressures, I'm guessing that it was rebuilt, or at least refreshed.okayfine wrote:James touches on the pointer for the pulley. If you don't have the original L18 pulley, you may not have the correct pointer for the pulley you do have. Typically the pointer and notched-pulley set has the pointer on the driver's side of the engine, where the single-notch pulley is matched with a degreed pointer plate mounted on the passenger side of the engine. Verifying TDC is Job One.
Yeah, I'm going to. I'll order some new floats for it first - might as well replace them if I have to take it all apart anyways. I need to do some more research and see what other parts tend to wear out in the SU's. I'd like to have a fully rebuilt set from ZTherapy, but that kind of money is not in the budget at the moment.James wrote:I would look at the float issue - might as well at this point.
Thanks again for all the advice and help! I think I've got enough work and parts for the car, now, to keep me busy for at least a month or so. I'm gonna try to get the new brake lines fabricated and installed next weekend, so I can get my new brake bits installed, but I'll try to make the time to check the TDC thing too.
~Laken
Re: Tuning problems - L18/L16SSS hybrid with SU's
TDC needs to be at the top of your list - too much timing and you are doing bad things.....
Aftermarket pulley - doubtful.
I'll take a pic of my car and my sister in laws car - I think I have access to both types and locations of pointers.....probably won't be until thursday or Friday
Aftermarket pulley - doubtful.
I'll take a pic of my car and my sister in laws car - I think I have access to both types and locations of pointers.....probably won't be until thursday or Friday
Finished is better than perfect......
Re: Tuning problems - L18/L16SSS hybrid with SU's
It's about time for some updates - a lot has happened with the car, and I'm still having troubles. 
On the positive side, I did get all the brake lines replaced, both rubber and steel, along with new wheel cylinders, master cylinder, and a few other bits. That was quite a project, but the brakes are MUCH better than they were now! I also got new air cleaners for the motor - housings that I can actually put real air filters in, as opposed to the 1/8th inch foam that was in use in the old housings.
More directly related to this thread, I verified that TDC on the crank pully matches with cylinder 1, and I got all the timing issues sorted out. I put myself through a crash-course in SU carburetors (including the 4-hour "Just SU's" video from ZTherapy) and started messing with those. Once I got the carbs removed I discovered a couple of interesting things...
I'm pretty sure these carbs came from-, or were refurbished by-, ZTherapy. They have a date and some writing engraved on the butterfly, and the writing looks like it could say "ZTherapy". Also, they already have the modern version of the floats, and they appear to have the bowl-to-nozzle fuel line that's described in the ZTherapy video. The dashpots and bodies were also incredibly easy to clean - all the grime and crud wiped right off with no effort at all - which could be an indication that they've been through the 22-G pore-closing process that ZTherapy mentions on their website. However, they still have needle valves in the bowls, rather than the gross valves described in the video. I'm thinking that might be becuase the date on the butterflies is from 2008. I called them to try to verify this, but nobody answered the phone. I'm wondering if ZTherapy might have some history with this car since they are based in Salem, Oregon, and that's where I bought the car from. I did replace the float-bowl gaskets while I had them torn apart, and I have an extra pair of floats now - the ones that were in there are perfectly fine.
Also, I discoverd that the throttle linkage was hitting the heat shield and preventing it from opening past about 70%. I little work with a Dremel tool solved that problem in no time.
After retuning everything again, the car was running absolutely wonderfully! It pulled strong and hard throughout the entire RPM range, there was no misfiring or plug-fouling, it was running smoother, quicker, and faster than it has at any other time since I got it! It put a grin on my face every time I drove it!
. . .and then after 4 days (about 70 miles) I noticed it running rich again. Now I'm back to the same mixture problem I was having before - it's running so rich at low-RPM that it's severely fouling the plugs and misfiring like crazy. It's a little better at higher RPM, but I can tell it's still running rich and rather poorly. I'm pretty sure it's not being caused by the dashpots/fluid, cause the pistons aren't moving at idle, and they seem to act exactly as they should under throttle. I checked the movement of the nozzles (for the choke), and that seems to be fine - they're moving up and down as they should be, and they are seated against the needle/piston when the engine is off. I can't figure any way that this could happen unless the bowls have too much fuel in them again. I know, now, that the floats are good, and I checked the needle vlaves by blowing and sucking on the fuel-inlet tube to make sure they were opening and closing the way they were supposed to. I can only think of two possibilities: either the needle-valves are bad (perhaps when I was testing them I was exerting more pressure on them than what they see from the fuel system), and/or the fuel pressure is too high. I remember reading something, somewhere, about the SU's not liking as much pressure as is supplied by the stock fuel-pump, so that a regulator might be necessary.
Thoughts and opinions? I'm running out of ideas here, so any advice would be greatly appreciated!
Thanks!
On the positive side, I did get all the brake lines replaced, both rubber and steel, along with new wheel cylinders, master cylinder, and a few other bits. That was quite a project, but the brakes are MUCH better than they were now! I also got new air cleaners for the motor - housings that I can actually put real air filters in, as opposed to the 1/8th inch foam that was in use in the old housings.
More directly related to this thread, I verified that TDC on the crank pully matches with cylinder 1, and I got all the timing issues sorted out. I put myself through a crash-course in SU carburetors (including the 4-hour "Just SU's" video from ZTherapy) and started messing with those. Once I got the carbs removed I discovered a couple of interesting things...
I'm pretty sure these carbs came from-, or were refurbished by-, ZTherapy. They have a date and some writing engraved on the butterfly, and the writing looks like it could say "ZTherapy". Also, they already have the modern version of the floats, and they appear to have the bowl-to-nozzle fuel line that's described in the ZTherapy video. The dashpots and bodies were also incredibly easy to clean - all the grime and crud wiped right off with no effort at all - which could be an indication that they've been through the 22-G pore-closing process that ZTherapy mentions on their website. However, they still have needle valves in the bowls, rather than the gross valves described in the video. I'm thinking that might be becuase the date on the butterflies is from 2008. I called them to try to verify this, but nobody answered the phone. I'm wondering if ZTherapy might have some history with this car since they are based in Salem, Oregon, and that's where I bought the car from. I did replace the float-bowl gaskets while I had them torn apart, and I have an extra pair of floats now - the ones that were in there are perfectly fine.
Also, I discoverd that the throttle linkage was hitting the heat shield and preventing it from opening past about 70%. I little work with a Dremel tool solved that problem in no time.
After retuning everything again, the car was running absolutely wonderfully! It pulled strong and hard throughout the entire RPM range, there was no misfiring or plug-fouling, it was running smoother, quicker, and faster than it has at any other time since I got it! It put a grin on my face every time I drove it!
. . .and then after 4 days (about 70 miles) I noticed it running rich again. Now I'm back to the same mixture problem I was having before - it's running so rich at low-RPM that it's severely fouling the plugs and misfiring like crazy. It's a little better at higher RPM, but I can tell it's still running rich and rather poorly. I'm pretty sure it's not being caused by the dashpots/fluid, cause the pistons aren't moving at idle, and they seem to act exactly as they should under throttle. I checked the movement of the nozzles (for the choke), and that seems to be fine - they're moving up and down as they should be, and they are seated against the needle/piston when the engine is off. I can't figure any way that this could happen unless the bowls have too much fuel in them again. I know, now, that the floats are good, and I checked the needle vlaves by blowing and sucking on the fuel-inlet tube to make sure they were opening and closing the way they were supposed to. I can only think of two possibilities: either the needle-valves are bad (perhaps when I was testing them I was exerting more pressure on them than what they see from the fuel system), and/or the fuel pressure is too high. I remember reading something, somewhere, about the SU's not liking as much pressure as is supplied by the stock fuel-pump, so that a regulator might be necessary.
Thoughts and opinions? I'm running out of ideas here, so any advice would be greatly appreciated!
Thanks!
Re: Tuning problems - L18/L16SSS hybrid with SU's
SUs like 3psi or less. What fuel pump do you have? If mechanical, do you have a 1/4" spacer between the head and the pump? It was OE, but sometimes gets lost and will result in more fuel pressure than stock.
How are you determining that your engine is running overly rich at idle?
Did you ever set the float levels?
If the neoprene seals on the needle/seats are solid, then they're unlikely to be bad.
How are you determining that your engine is running overly rich at idle?
Did you ever set the float levels?
If the neoprene seals on the needle/seats are solid, then they're unlikely to be bad.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
Re: Tuning problems - L18/L16SSS hybrid with SU's
I talked to ZTherapy today - they confirmed that these carbs did come from them. They also told me that they never used the gross valves in the 510 SU's - apparently they didn't work very well with the 510's unique floats and bowls. They said the stock mechanical fuel pump shouldn't be causing any problems (it does still have the spacer installed), and they said the needle valves usually last for 10 years or more (these carbs were rebuilt by ZTherapy in '08). They also told me that they've never seen or heard of this problem before. The only suggestion they offered was to check the tightness of the choke cable (it should have some slack before it starts moving the fuel nozzle). They also told me to make sure that there is no oil or grease around the nozzle itself, as many people try to lubricate these when they stick thinking it will help, when in reality it makes the problem worse. The nozzles are lubricated by the gasoline. I am guilty of that mistake, so that's one thing I know I can address. However, I kind of doubt that it's the source of my problem since the problem was occurring long before I ever disassembled the carbs.
I'm going out to take a look at everything again... maybe I can find something that I missed before.
I'm going out to take a look at everything again... maybe I can find something that I missed before.
Re: Tuning problems - L18/L16SSS hybrid with SU's
Well... I cleaned up the lubricant off the nozzles, adjusted the choke cables so they're a bit more equalized, and checked out everything else that I could without taking everything apart again. I didn't think I did anything that would have any significant effect, but it seems to be running perfectly again. I'm a bit puzzled, but I'm not complaining! I just hope it doesn't do this again... I drove it for about 100 miles and then let it sit (running) for about 20 minutes, and there's no sign of the rich mixture, misfiring, or plug-fouling. I'll keep my fingers crossed and just keep hoping that it continues to run this great!
Re: Tuning problems - L18/L16SSS hybrid with SU's
I've been working on the same/similar problem with my 510 for 3 weeks.- L20b with a DGEV weber.- It turned out to be that the timing somehow became too advanced by 5 degrees. I like it to be at 18 degrees at 800 rpm idle, and I have the mechanical advance more limited by shortened slots. I have a SSS distributor with Pertronix module. 'Hope this helps someone.