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Problem with Compression or Timing on High Compression L20b causing pinging


510SSS

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How about from Pipercross? http://www.burtonpower.com/parts-by-brand/brands-o-to-p/pipercross/600-series-air-box.html, which Airbox would fit my Dual 40mm Solex/Mikuni setup? How about this Viper Cold Air Induction Kit?: http://www.burtonpower.com/parts-by-brand/brands-o-to-p/pipercross/viper-cold-air-induction-kits.html this sounds like it would be effective at lowering intake temps, anyone with experience with airbox installs, give me a shout out.

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My first post said to turn the timing back. If accurate*, 5 degrees BTDC should probably work but 5 degrees is not in any manual. This is a 'one of a kind' engine and there are no published timing settings. Rough guides maybe but I would set it lower and lower until it goes away... this then becomes the normal for your combination. *By accurate, I mean it may say 5 degrees but maybe the mark on the pulley is out, maybe the mechanical advance is too much and should be dialed back. If the vacuum advance is disconnected and a timing light put on it, the engine revved over 3-4K the total advance should only be what? 32? 34? See if it is.

 

If dialing the timing back does not fix this then the causes of pre ignition/detonation should be reduced. Again, heat is the biggest cause.

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I've been having a ping issue with my ~9.8 compression LZ22 (stock Z22, stock U67 w/ mild cam). I thought it was timing, but pulling it back did nothing except make it difficult to drive. Because of when it's pinging, I've mentally narrowed it down to lean fuel mixture/not enough pump jet, although I haven't done driving tests and pulled plugs to confirm 100%.

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Pump jet? Accelerator pump? It only shoots one squirt of fuel to transition from slow to the primary barrel IF the throttle is suddenly opened. It doesn't do much for prolonged acceleration or load.

 

If at low speeds under load (but before the secondary opens) replace or increase the size of the power valve. It's held closed by vacuum and opens by spring pressure when manifold vacuum drops... hard acceleration. It's job is to richen the fuel mixture under load. If your carb was rebuilt it's easy to mix up the bottom screws that bolt the throttle plate section to the main carburetor body. The screw under the power valve is hollow to allow the vacuum signal up to the valve. If a solid screw is mistakenly put back in... no power valve. My 710 carb was this way. It didn't ping but when fixed had more pull

 

If at high speed WOT it could be the high speed enricher. It does basically the same as the power valve but differently

 

Please don't say "But I don't have the stock Hitachi carb" :lol:

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Well considering I already put a timing light on it and the timing is correct, (already own a 10mm socket btw), idk why you need to give advice with attitude, must be you're only was of stroking you're internet ego... Either give some constructive criticism or stfu, keep you're personal inadequacies to yourself please Flatcat19 (this means you). Not rich at all, in fact im broke, just trying to make my Datsun run properly and not ping, so I can drive it.. :ninja: :sick:

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Anyways, back to the topic of this thread, I will take another look at the timing see if I can dial it back abit without making it not start. I will do the test with 100 octane race gas and see if it's really straight compression related, or if I need to have the distributor re curved. I am going to try out those new BP7eS NGK's tormarrow and see if that makes any difference. I am also interested in not having my fuel boil from excess ambient heat (live in Cali not Washington) so if anyone can recommend an Airbox that would work for Dual 40's please help me out with any tips you have.

 

Thanks for everything Ratsun community.

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Well considering I already put a timing light on it and the timing is correct, (already own a 10mm socket btw), idk why you need to give advice with attitude, must be you're only was of stroking you're internet ego... Either give some constructive criticism or stfu, keep you're personal inadequacies to yourself please Flatcat19 (this means you). Not rich at all, in fact im broke, just trying to make my Datsun run properly and not ping, so I can drive it.. :ninja: :sick:

My comment was made is reaction to your lack of providing the info asked about.

 

People asked what your timing was set at, you never answered.

 

Every response I have seen you make had been in relevance to spending money to loop hole past said problem.

 

Buying more parts will not fix your car. Tuning it properly will.

 

Say/think why you will. It's not just my queries you're skirting.

 

Verify cam timing. Verify ignition timing. Verify stoich. You're car should be fixed and purring.

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You want suggestions? I know what I would do...

 

Set on headers? Wrap em.

I'd personally would rather use the stockanifold. Not many of us will regularly travel fast enough to be concerned that the L16 manifold is too restrictive(ha).

 

Cold plugs, set timing.

 

Install an A87 or W53 closed chamber head.

 

 

I'd be willing to bet any combination of what's listed above would lessen/eliminatebyour pinging

U67s have just been reported to be pinging prone.

 

With a beastly engine combo, I'd also invest in a wide-band AFM. I'd always be worried about my motor investment.

 

 

EDIT: Added thought...did you say you have bigger valves? I wonder if heat is getting sucked back in to the combustion chamber as the exhaust valve opens. Just thinking here...downside to having too free-flowing of an exhaust. No scavenging effect/less vacuum.

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Wow dropping some knowledge instead of BS, you're catching on I think. I can't just give you all the info right away you are asking for considering my car is back in the shop due to the pinging, and I can't just run down there (considering the 510 is my only car...) Anyways, thanks for the help, I will look around for a stock manifold and maybe close my exhaust up a bit to 1 3/4 or something, if that really can help to mitigate my problem. (anyone else have experience with exhaust being too open?) Ya I was thinking about getting a wideband and perhaps changing up my carb jetting based on the results.

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Does anyone think it could be caused by Fuel Pressure at higher revs? I just had a thought that it only happens on harder acceleration, so perhaps it needs an electric fuel pump with regulator? Right now I am simply running the 240z mechanical pump, and I'm not positive it's enough to keep up with the carbs.

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As KoHeartsGPA suggested, I will second him and recommend a heat shield. It makes a world of difference. It is even more of the problem with the Mikuni manifold as it puts the carbs directly over the exhaust, versus the long Cannon manifold that puts out a bit. (But we wouldn't know because no oics :D) Long story short, I took off my stock mechanical fan and eliminated constant and assisted moving air, which caused carburetor heat soak within 10 minutes of driving, even on a cool night. I first made a heat shield out of license plates I stole off a neighbors car (kidding), and it works. I made a nicer one that would have been less than $15 if I went out and bought materials. You don't need any extra heat reflective BS; just some sheet metal and metal band. I made this with a bench vice, body hammers, and other general tools. I can touch the bottoms of the carburetors now and they are barely warm. Not saying this will help at all with ping, but it keeps the carbs cool.

 

F32DD4A5-DA37-4C86-A600-329DAAC5DDA0_zps

 

If you have the Mikuni manifold, there are two bosses with threaded 6mm female holes.

9D6794AC-F11D-44A7-8660-FB76873703C1_zps

 

 

 

Oh, and stay away from T3. Their "bolt on" products aren't always bolt on.

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I don't think your fuel pressure has anything to do with the pinging.  If you are not getting any gas or your car is bogging then it can be the fuel pressure or fuel pump. Pinging is caused by hot spots on cylinder walls and/or, carbon build up in cylinder head or low grade gas or your timing is way too advance.

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Assuming all things are in order (cam timing correct, no vacuum leaks, good fuel pressure, float level correct) your problems really just sound like tuning. Get the distributor re-curved, put a set of NGK B6ES plugs in it, double check your firing order and verify TDC then move on to carb jetting.

 

I have run 2.5" exhausts in many 510's so that's not your problem. I actually prefer the larger tubing size.

 

Did you say your car's at a mechanic's shop? And he know how to check things like cam timing and firing order? If you're not comfortable with that shop, find someone else. I know a few guys in the north bay that have lots of 510 experience.

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His problem is NOT connected to firing order, or the thing would bearly run, if at all.

And I really doubt cam timing would do it.

Remember, he says this is just at high load.

 

510SSS, just start with simple, known cures for ping.

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Ok cool thanks guys, Yes I do have the Mikuni manifold, I am starting to think that may be the problem, because its right over the header. What company makes a heat shield that is bolt on for the Mikuni manifold? I would fab one, but have school and work, don't really have the time right now. I will try to get some pics of the engine bay, if I get down to the shop this week, I will double check the firing order, and make sure that the Mechanical Advance is not over 32-34 degrees, I will get back to you guy's thanks alot. Also, anyone have any more info on an Airbox with Inlet setup? Can that be run in conjunction with a heat shield?

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Best to find a mechanic that knows Datsuns.  It's getting harder to find ol skool mechanics that knows how to use a vacuum gauges, dwell meters or even adjust points. Most new ones only know how to plug in a reader and read the codes and replace parts, unless, of course, they have been schooled in the art of tuning a car by listening to the car, using a vacuum gauge to adjust air/fuel mixture or how to properly set points, specially dual points.  Best practice is to ask them if they worked on a Datsun before and if they said yes asked them which Datsun and how long ago. 

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Yes, an air box can be used with a heat shield.

I'm using an old 240Z air filter assembly, that I cut the 2-carb back out, and welded in a plate to match with my 4 carb mouths.

Then attaching 4" hose to run up behind the left head lamp, where I have ventilated the sheet metal.

 

But people make them ready made, I've seen them all over the net by a number of companies.

 

 

DSC07864.jpg

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You're not going to find a heatshield to buy. You need to make one, or have one made for you.

 

I have a template of the one used by Nissan Motorsports, way back in the day. I could make you one, but you'd have to do the final fitting and mounting. This particular design was originally made to use with springs to hold it to the intake runners, but I have made them in the past that bolt to the bottom of the intake. It's best to support it at the front of the carbs too.

 

A simple air box can be fabbed by using a foam filter backing plate, like the ones from ITG http://itgairfilters.com/product/jc50-big-twin-carburettor-filter-jc50/

 

You can buy a blank from them and cut your own holes to fit your carbs.

 

ITG-jc50-page-001_zpszhkwfmoy.jpg

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