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LZ 22 pre detonation


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Hey guys....As some of you know I blew my L20 up recently and put together a Lz22 and dropped it in my DD 521. I just passed the 500 mile break in and have been opening it up more. It has a rebuilt bottom end with new rings and honed cylinder walls and a rebuilt U67 head. Weber 32/36...matchbox dizzy and L20 stock mani and 3.8 gears Can anyone who has thus set up tell me what you have your timing set at? I have mine about 12tdc and it still has detonation on premiun. Should I scale it back to ten or something. Should I run the advance? Also.....I want to make this thing a ripper....its got balls now but only wakes up in the higher rpms.

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LZ22 with open L head should have a compression of about 9.84... that's up there.


Every engine is different, altitude, humidity, octane rating, compression, initial timing, air temperature all contribute (good or bad) to pre ignition and thus where your timing will be set. Since light pre ignition damages you engine over the long run you must retard the timing so that it is below this point even if it means going to 8 degrees. There is no set amount that works for this LZ motor. It is whatever it works best at. Just loosen the dizzy enough that you can twist it around by hand. Turn counter clockwise bit by bit until it just barely pings noticeably under load at low RPMs.

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Ok sounds good....I will dial it back a hair and see how it goes...I think I had it set perfect at first but had dieseling. Tried to fix that before I read it was normal and messed up my setting



Yup, my new dime has a LZ22 the PO knew like the back of his hand, and you just have to live with the dieseling I guess. Clutch kill!

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Try pushing the pedal a little and maybe it will help loose soem vacuum and kill it better.


Should should find a 38/38 weber,double opener. I like them!!!!!!!!!!!!


premium Arco is still not good as Premium Cheveron. Try that also.


Dial the dizzy to you think its best at. There is no science to it. Some cars can run 15BTDC down to 7BTDC.


Just run it hard on a hill then find the best spot. But I think its going to ping anyways just depends how much you push it and you just have to live with in its means. Meaning u push it right up to the point where it pings than back off on the gas. Thats one reson I stay away from high compression motors (esp with open chamber heads.)

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Dieseling? Just get in the easy habit of holding the brake and letting up the clutch as you turn the key off. Just enough to load the motor so it stalls right away. If you do it right, and it only takes a few tries, you won't even feel it. Eventually you do it automatically and don't even think of it, just like taking the key out.

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The 2.2 in Lisas 510 is 10* base timing and about 32* full advance. never have any problem with it dieseling when I shut it off the added compression should help with that, Like Mike said all engines are different but thats usally what Troy shoots for for timing and to really have a ripper at least go to a 38/38 to really feel the potential you need some 44 Mikunis or 45 Webers (IMO Mikunis are better)



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Dialed it in to 10 tdc.....adjusted the Carb accordingly and bammm its a ripper. I need a tack so I can see my revs and keep it in a safe zone but All in all I'm happy. 521 with a z22 and 3.8 gears moves out pretty well. After welding up my exhaust leaks there is very minimal ping now that I can hear what's going on.

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run the truck on the top end. Higher rpm.

if motor cuts out then your running out of air.

Be honest I would think that this would have happened. thats where a 38/38 would come in handy.


ON my truck after I put my U67 with cam the 32/36 on there would run out of air. So instead of fucking w/jets and ripping the carb apart to figure out jetting. I just slapped the 38/38 on there as it was only 4 nuts and wham running like a champ.

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The Carb that I bought had huge jets in it. I didn't document the size when I was in there but I know they were big. It kept fouling up the plugs when it was on the L20 with a bad cylinder 3. Now that its on the LZ....no flat spots .....no hesitation through out the rev to the top of fifth. Its actually running pretty damn good....like the motors just starting to wake up....its got one eye open right now. Now if I could just get a little cash to open the other one ha ha. Besides a 40O dollar sidedraft setup I couldn't tune what would wake this lil pig up more

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I have a long tube 510 header that I was gonna take the time to try to modify to clear the torsions ....U think its nismo but heard it isn't worth the power gains. Jeff mentioned the timing curve on the matchbox isn't very good either. Heard there is a particular single point dizzy that is desireable to run with pertronix that has a way better curve. Anyone know what dizzy that would be so I can start looking?

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the header I wouldnt even bother with. as since its a long tube that means it was for a L16/18. meaning the colloctor could hit the floor as its too far up on a L20b block or Napz block.Plusthe torsion bar in the way.

closest thing that would fit is the Top End Performance short tube header that needs ceramic coating!!!!!!


the dizzy might help but since you got matchbox already I would just adv the dizzy much as possible before it pings.

Unfortunaly the U67 head is more prone to detonation to you just gotta live with what you have unless you buy 94octane gas or something better $$$$$$.. I have run the SSS dizzy and I cant tell if it makes a difference or not. it just works when I install them. maybe if I had a LZ and it pings I would swap it in just to try it.


weber makes a double opener conversion where it makes the 32/36 almost like a 38/38. where it opens both barrels at the same time. this can give it a little more peppier response . Its up to you if you want to do this.

but remeber this was just a daily driver truck to save your 510 from daily driver use. I think you need to get back to the real prize. Fixing the back or your 510 that the tool box hit.

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Dieseling? Just get in the easy habit of holding the brake and letting up the clutch as you turn the key off. Just enough to load the motor so it stalls right away. If you do it right, and it only takes a few tries, you won't even feel it. Eventually you do it automatically and don't even think of it, just like taking the key out.


I agree with this post, you won't even notice once you get it down.

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