high compression l28 on pump gas?

[Tony D]

" and my catalytic converter is fresh and new"

 

Joe Isuzu went and changed companies didn't he? Now he's building Nissan L-Engines. Whoodathunkit?

[Ghettodeffender]

So to all you nay sayers, those of you whom said this build would not pass smog. It passed with flying colors!!!

[ctc]

Can you post the results? Would like to see the levels.

[Noddle]

CTC, is that your silver 240K ?

[steve260z]

[Tony D]

You also said you were going to "buy a smog" as well... Clean piped cars still exist.

[Ghettodeffender]

I did not "buy a smog" that was plan b if the Z wouldn't pass. So now you all know that this engine build will pass california smog testing.

[Ghettodeffender]

Heres the smog certificate.

[BluDestiny]

That's a clean running engine

[SuperDan]

Heres the smog certificate.

Wow. who would have thought.

My stock 77 280 has a pretty fresh rebuild on it and was not quite that clean when I had it smogged a few months ago.

So what were the final specs on this engine? 10:1 and the 480/.480. Duration(In/Ex): 274/274 cam?

[josh817]

California sounds horrific for vehicles. RIP
:[

[randy 77zt]

You can take the old z distributors apart and adjust the advance curves.That little plug on the back of the vacuem advance can has an adjustment under it.a l28 motor with 10-10.5 -1 compression will need a sorted distributor to work.Probably would need a retard down to 26-28 btdc at wot.That is what the vacuem can on the dizzy if for.The engine will criuse better at 36 btdc or so.Another problem is old injectors.There is a point in time where you have to quit buying used parts .Back in the 70's the gas didint have injector cleaner.If you pulled out the injectors and sent them to a good shop like Kinsler or Rc Engineering for a flow test you would probably find a big difference in flow on the set that came out of the car.Some flowing %60 -some flowing %90+ .If a guy knows how to tune the car It can be made to run well and pass smog.The gasoline is supposed to be burnt in the engine -not in a cat.A cat convertor is not a band aid for poor tuning.If you run a bunch of unburnt fuel through a convertor it will run hot and plug.A cam might reduce some Nox emissions becuase it would reduce cylinder pressure at the 15/25 mpg dyno test.but it usually will increase CO and unburnt Hc.I ran my 77 with a stock l28e for awhile with some clean up mods-like new injectors and a custom rebuilt distributor by me with a new advance curve.The car was very nice and smooth-but would run if you needed it too.

[Ghettodeffender]

Wow. who would have thought.

My stock 77 280 has a pretty fresh rebuild on it and was not quite that clean when I had it smogged a few months ago.

So what were the final specs on this engine? 10:1 and the 480/.480. Duration(In/Ex): 274/274 cam?

Yup that was the final build specs, i will say i have to have my timing WAY advanced for this build to have the power it should, however i have no ping problem and it runs clean. I'm surprised the motor even idled at stock timing when they tested it but it did.

[Davey G]

What octane rating are you running? 91?

 

I'm having something similar built, but will be using 93 octane here in Texas, and won't need to pass smog.  My requirement is that it run on pump gas w/o majorly retarding the timing.  Anxious.

[Ghettodeffender]

What octane rating are you running? 91?

 

I'm having something similar built, but will be using 93 octane here in Texas, and won't need to pass smog.  My requirement is that it run on pump gas w/o majorly retarding the timing.  Anxious.

I run it on 91 octane but the timing is very far retarded to run on it.

[Gollum]

Yup that was the final build specs, i will say i have to have my timing WAY advanced for this build to have the power it should, however i have no ping problem and it runs clean. I'm surprised the motor even idled at stock timing when they tested it but it did.

 

Generally a high compression motor requires less timing to make peak torque. There's a difference between requires and can run timing figures. Higher compression will also ping sooner thus most people don't think they can run as much timing. There's two things going on here in most cases, in that yes the overall timing potential has changed, but required timing for peak power has changed too. The only way to be certain about what timing requirements are for peak power is to run a race gasoline and check timing figures, then mix 50/50, and extrapolate for pump gas. 

 

Yes race gas will LET you run more timing, but it also burns differently than pump gas. Just because people put in race gas and turn up the timing and get more power doesn't mean ping is what's holding you back on pump gas. Pump gas has it's own, different, timing for peak torque. Yes a high compression motor might be ping limited, but you can't really be sure until you find out where best torque occurs.

 

The other factor is that usually ping sets in around peak torque OR BELLOW. That's not where peak power is, is it? At lower RPM ping has more chance to happen, at higher RPM it doesn't. You can literally "out run" ping to some extent. The higher RPM you get, the closer you can get to best torque ignition timing, if your motor has ping issues down lower.

 

 

All this to say....

 

Did you run stock timing when you got the smog test done or were you advanced? And how much advance are you running now versus before?

 

They're supposed to hookup a timing light and check that you're within 3 degrees of stock at idle.

[Ghettodeffender]

Generally a high compression motor requires less timing to make peak torque. There's a difference between requires and can run timing figures. Higher compression will also ping sooner thus most people don't think they can run as much timing. There's two things going on here in most cases, in that yes the overall timing potential has changed, but required timing for peak power has changed too. The only way to be certain about what timing requirements are for peak power is to run a race gasoline and check timing figures, then mix 50/50, and extrapolate for pump gas. 

 

Yes race gas will LET you run more timing, but it also burns differently than pump gas. Just because people put in race gas and turn up the timing and get more power doesn't mean ping is what's holding you back on pump gas. Pump gas has it's own, different, timing for peak torque. Yes a high compression motor might be ping limited, but you can't really be sure until you find out where best torque occurs.

 

The other factor is that usually ping sets in around peak torque OR BELLOW. That's not where peak power is, is it? At lower RPM ping has more chance to happen, at higher RPM it doesn't. You can literally "out run" ping to some extent. The higher RPM you get, the closer you can get to best torque ignition timing, if your motor has ping issues down lower.

 

 

All this to say....

 

Did you run stock timing when you got the smog test done or were you advanced? And how much advance are you running now versus before?

 

They're supposed to hookup a timing light and check that you're within 3 degrees of stock at idle.

I had it at stock timing, barely ran but passed with the figures above.

[Connor280ZX]

Heres the smog certificate.

Wow, that's impressive. Not only that you've passed, but were so far below the thresholds... So I guess it's safe to say that a cammed L28 will pass ca smog?

[Ghettodeffender]

Wow, that's impressive. Not only that you've passed, but were so far below the thresholds... So I guess it's safe to say that a cammed L28 will pass ca smog?

Yeah, although a more aggressive cam probably wouldn't.

[Leon]

Wow, that's impressive. Not only that you've passed, but were so far below the thresholds... So I guess it's safe to say that a cammed L28 will pass ca smog?

 

No.

 

It's safe to say that a cammed L28 running lean with retarded timing and a new cat might pass smog. I'd be interested in how that car tests 6-9 months from now...