madkaw

I know nothing about Datsun Spirit or the owner and he seems to be liked, but I have reservations about Stephens build . I'm not knocking anyone but this thread is about avoiding detonation or why we have it. Of course not hardly anyone brings the important numbers to the table(HP) except 30 ounce. That engines sounds like a hoot!! My L24 put out 155 rwhp on 2 different dynos, so I think the numbers are accurate . My early e-88 head , similar to the e-31 has 41cc chambers. CR is around 9.55 . My engine builder who builds spec Mazda race engines never did an L motor. Just by looking at the chamber design and knowing my smaller cam profile he advised staying under 10. The only ping I get, and it's not all the time, is around 3000rpm. This seems to vary by what has I use also- as in name brand.

Guy, Your engine is not just like Stephens- there are big differences. The biggest is the p79 head with high quench compared to the open chamber n42. Combustion chamber design is everything when it comes to detonation. Stephen is running and old design open chamber more prone to ping . His pistons aren't to high either if you look at the numbers- there actually too short. All these little or big things depending how you look at it - add up to why one engine acts differently . The n42 is a great all out race head if lots of work is done to it, but the p79 and 90 heads are much better street modded heads . The serious Z engine builders don't give out all their secrets, but if dig around over at hybridz you can pick up some good stuff .

Thanks for closing out the thread. Too many of these help me thread have no ending and no one learns anything.

Holy Zhit , Man I wish I lived closer. Maybe it's better that I don't .

Stephen What about your timing curve? I'm assuming the pinging you hear in 3rd and 4th is in 3000 rpm range? This is the range I hear pinging on my motor. I attribute mine to a timing curve that isn't that great- comes in too early- and my triples that seem to go lean in this transitional rpm range. OEM HG is 1.25 correct? That puts your squish around .040 - this is not optimum from what I read. When the head was redone I am assuming the fine details were done like removing or smoothing excess spark plug threads to eliminate hit spots? All these things add up from what I have researched . Combine that with the L series motors that are prone to detonation compared to other aluminum head motors, then you have little margin for errors on a high CR motor

Looks like it was done right on a solid platform. Is it worth 50k - yes! The right buyer will see the value in this particular small market and see that there no way you could build that car for less. Now if you are saying that I'm not going to pay that much for a 1970s refinement then that's a different story. If you want a completely modded out Z car done right, the values there- IMHO

It seems primarily in the rear control arms where all the noise is coming from. I think I will change them out this winter and be done with it. It's frustrating when I have gone to great detail to eliminate rattles and make the level of refinement high on this car to just have it ruined by barn door creaking over bumps.

So could you feel a difference in the handling that was worth noting? My car winds up being my daily driver when the weather is good. It hasn't seen a second of track time yet, but will eventually in a limited amount. So maybe I'm fooling myself to even have urethane in there. I would love to do a direct back to back drive of two cars set up with a stiffer springs and sport shocks, but one rubber and the other urethane

Don't doubt your engine runs great. I am a little surprised that more dyno testing is not done by the members on here. I'm talking mostly the guys that have substantial money invested in a motor and that can probably afford the 100$ it takes to confirm your butt dyno. The dyno in your case would let you know if your HP is limited by detonation. We are not talking bragging rights, but maybe verification the big $$ you spent on your Rebello or whatever is putting out reasonable power. I'm trying to get to the dyno next week to see what gains I really got from my Mikunis. It feels great on the butt dyno, but I don't trust that and the direct comparison to the SUs would be great. As far as the advanced cam, I thought retarding the cam got you closer to valve bashing the advancing - but I might be backwards on that. I run my cam slightly advanced to get the Intake valve closing number correct.

I already have the loud exhaust and stereo. The stereo will drown out the noise, but it's loud enough that other people can hear it. I posted over in hybridz and I think I will try the zerk fittings and grease. At least it's easy maintenance to squirt some grease in there.

I second the look at the clutch fan. Maybe thermostat got hung up?

I know this isn't the first squeaking urethane bushing thread but I do have a question. I have the black bushing that were purchased many years ago, but don't have many miles. They squeak bad- especially the rear arms. I have tried re lubeing them, but they start squeaking again after a while Did they make black ones that were not graphite impregnated? How do you tell if you do or don't have them?

I'm with Carl, your numbers seem weird. I remember reading about your build and thought it curious that the builder had to reduce the cam lift to increase clearance. Reading countless threads of other builder's( Braap, 1fastZ, and others on Hybridz), the guys that do many of these motors, piston height above deck is usually positive in stock configuration. I believe Braap said he measured and almost all motors were .019 +. That's more then what your forged pistons gave you. So what HG thickness are you running? Trying to figure your head to piston distance. My point being is the squish distance is very important on these motors to fight detonation. Getting outside this distance makes these motors more prone to detonation. Now from what I have read you want to stay less then .035 . Some run as close as .022. Their claim is it makes a profound difference in power in achieving MBT. Also head cooling is a issue with these motors the more power you extract from them. This is most prevelant in track conditions or hard driving. Maybe you should go with a cooler thermostat.

Wade is describing 'old school' timing tricks- which can be effective in some cases where factory setting are very conservative. I would be a little worried if you couldn't recognize pinging though. Like Leon said, dyno is the only real way to see if there is any gains.

Plug n play would be huge - optimistically watching!

Somehow I missed this thread until now. This is very interesting and waayyy over my head as far as understanding code and all that stuff.. I wish you luck. I have purchased the MS3X for my car being it was the closest to plug and play-and it's a far cry from it. But, I wanted an Standalone system that I didn't have to actually break into the ECU and make changes. This will be primarily hooking up wires and tuning. I would also love to see dyno comparisons between the stock EFI and something like you are developing or MS.

Might want to add piston to head clearance and HG specs also. The get ready for more opinions then raw facts;)

He won't get it, but lots of nice bits on there.

Saw a pretty s130 silver and black on rt 37 between Bloomington and Bedford

" the floats pass the drop test"- your talking pistons. As mentioned earlier it could be the front carb float . I would examine the needle assembly for smooth operation. It sounds like fuel is being cut off by a sticking needle and seat. The fuel slowly seeps into the float chamber when you stop and fills it for normal operation, then you take off and empty it again. I would pull the float chamber top after it dies or get a visual method outside the float chamber to check level Also as suggested - check all connections around the dizzy for looseness

It's those unexpected things that kill the schedule . I guess your having the engine rebuilt by someone else or are you doing that also. The bodywork usually is the time killer, so it helps the car is pretty solid

Your going to have to do better with your post. I am struggling to read your run on sentences. I would love to help you, but I need to understand you. Have you degreed a cam before ? Did you have the timing cover off when you installed the new cam so you could count the sprocket teeth.

You need to give us waaayyy more info then that. What's it doing? Spitting? Hitting but not starting ? Turn over easy? Like said above - sure its nothing else? Verified spark? Degree the cam?

No, you want to see what the total MECHANICAL advance is. The vacuum from the no load scenerio in your garage would probably pull in additional timing.

You sure have pinned yourself into a corner. Don't know your abilities but 5 months is unrealistic for some shops, let alone one person . I wish you luck and watch with interest.