madkaw

Damn, I'd like to just find one TB cheap, and you got 6- lol You would run a MAP sensor of some kind would be easiest.

Still plugging away here with carb tuning. Swapping around the wideband to the other bank of exhaust ( advantage of duals), from the back to the front cylinders I noticed the front carbs were starving. The odd thing is that I have to run the mixture screws 1/2 turn richer to get a smooth idle. So I suspect air leak, but can't pin anything down. I have replaced all O-rings ( 50mm X 2.5mm is what I found) and not much difference. Sprayed down everything with starter fluid with no response. now I can live with this because I can tune it in and the motor runs really well-- -EXCEPT for #6. By looking at the plugs 6 is sputtering rich with small black spots diluting the tan underneath. I can use a hose and listen inside the carb inlet and hear the sputtering occurring. I suspect it's the accelerator pump leaking fuel by the packing, though I have changed it once already. With a mirror I can see nothing happening on my side of the butterfly. Trying to come up with an idea to seal off the accel chamber to verify this issue. I've looked down the accel pump hole and can't see any obstruction to keep packing from sealing. Anyone ever try an Oring to seal the pump? I tried tightening the cap as much as I care too, since I know this isn't the way it was made to seal.

Putting together a FI set up and looking for a 240sx TB or a TB without a bunch of extra plumbing like a zxt TB

I thought it was your graph. I was interested in the MN47 info for my own project, but it's good for comparison here. Wish I could pick your brain over on the MN47 stuff you did sometime.... but for now, it's Derek's spotlight!

Not sure if this is your work Blake.

I'm confused, I don't see an option from your choices above for flat top motor, but you keep mentioning it. Yes a P79/54 flat top would be best for na , but your 54 has dish pistons as you stated.

Amazing talent to put all this together. Thanks again for documenting all this for us wishers. I feel an extravagant expenditure in my future. Megasquirt is already in place.

More importantly is whether the Mikuni intake(if you used one) cleared the bolt holding the thermostat housing. The Mikuni shorty intake #1 runner hits the rear bolt of the thermostat housing. You might miss this if your not careful. The intake will not seal because it is being held of the head by this bolt. Not sure what you are using that hole for, but doesn't have anything to do with the Mikinis.

I had the mysterious high oil pressure on my last l24, the thread is on here. Only went away when I changed blocks. Latest L24 runs average numbers.

I wouldn't trust that head either . Like John said, sell off what you don't want. I had all kinds of issues with SS valves (SI), nothing wrong with stock Nissan valves for street. I'd try the cam, I think it would be plenty streetable. I'd try a P79 or p90 with that cam, no oversized gasket needed.

So many factors to consider, but the curve does seem late.

My Mikunis are giving me a bit of a fit lately. Strange issue of the car dying or wanting to die at idle. The engine acts like it is running out of fuel. I can watch the AFR gauge slowly but surely go way lean as the engine starts to idle rougher and eventually it will die. It is kind of arbitrary when it happens, at other times it idles okay. In the past I have always been able to have a good idle with these carbs. I installed a fuel pressure gauge so I can drive and watch, because I am still dealing with transition. I suspected it has been a fuel supply issue. I have cleaned my tank, replaced fuel pump, bypassed my regulator, replaced fuel lines, replaced fuel filters. The pilot adjustment(idle) screws are pretty new and I can not find any issues with them. The carbs have been off and cleaned several times. The float adjustment has been checked and adjusted per Mikuni manual. I examined the needle/seat assembly and they look new, which they are pretty much since I bought them. Checked sync of carbs. I have watched the engine die and the pressure gauge shows 3.5 psi , so I think the supply is okay to that point. So would an issue with one cylinder kill the whole motor? If I had an issue with an idle jet with just one hole do this, or more likely a whole carb? I have the original needle/seat assemblies which I think I will swap back in to see if that makes a difference. I DO know that I am missing the accelerator check valve balls, which I got today(via Amazon, pack of 100-anyone need some-LOL) They got lost during one of the carb cleaning processes here lately. Float adjustment. So I have always done the inverted lid and measuring distance between top of float and lid at 12.5mm. The manual also gives you a height for the fuel in the bowl-24mm. It's not very user friendly since the measurement is from the center line of the butterflies upward, so you have to do some math to a get a number to measure from the top of the carb. When I did the math and measures the fuel height was off by 4-5mm-WOW. Can that even be right? I like this method better because that's actually what's in the bowl. I went with it and increased the fuel height and the car ran alright and seemed better in transition, but nothing to do with idle, still dies and idles rough. Curious if anyone else has gone down this route with fuel height adjustment ? I'll take some pics and get back with everyone

Cool!

I'd say if the cam is installed correctly it is NOT causing your idling issue alone. I can idle at 10 as well as 20 with not much change of idle. 10 thou off the head will not change valve timing enough to cause issues as you describe. Most cam profiles have a bit of advance machined in them just so they can be installed 'straight up'

You need more info if you want help and not guesses

FAQS section

Very nice!

Post up pics of your other work!

So got the trans back but engine wouldn't go past 4300. It was like hard ignition Rev limiter. Anyhow, just for others that might run into this , it turned out to be my VR circuit inside my MS. There was pots that are supposed to be adjusted a certain amount of turns . There was a place to measure voltage to make sure the pots were adjusted properly and mine was off by 1v. This is a pull up voltage circuit so that 1v didn't allow my CAS to work properly. FYI

Very nice Ryan. With regards to the fuel routing subject- I am trying to figure yours out?

1.65" intakes

So my engine runs perfect with the old dizzy and wires. What I did discover when swapping over and restarting the engine was that my battery was shot. 5 years old and killed many times. Makes me wonder how much of an issue that was causing with my MS3X

I actually have the set that came with the Mikuni kit, but didn't use them. They are very short so starting a nut on them is a bitch. I shaved down some older studs that had shorter threads on one end of the stud. I probably could have used the shorter Mikuni ones if I didn't thread them all the way in, but I didn't like that. Another words you will find a very small amount of error is allowed when sizing them because they will run into the runners .

I wouldn't put to much weight on what the short runner will or will not do. My car felt plenty torquey down low and would pull all the way to 7K-and it's a 2.4. The Mikuni shorty manifold is a bitch as far as mounting . It also has clearance issues with the thermostat housing which i believe I covered. I also would not worry about gasket matching the runners. The anti-reversion is there for a reason.

I'm with Leon, go with the P90. Better combustion design than the 47 and the CR loss would be made up with running more aggressive timing on the P90. I'm betting your friend was running dished pistons. The progression to turbo would be easier.