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Old 11-30-2004, 05:50 PM
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Rich at idle but pinging on tip in?

Hiya folks.. well I finally got my timing issues resolved.. I pulled the manual for the zz4 and found they suggest 10 degrees and vacuum advanced on ported.

So Im trying to adjust my idle mixtures screws on my Demon ZZ4 crate carb and having some problem..

I keep getting some pinging on tip in acceleration. Meaning when cruising down the road and lightly accelerate in a high gear the motor pings. If I put more or less pedal it'll go away but generally its about 10% throttle open. So I know Ive got the timing set correctly for my stock ZZ4 and figuring theres a carb tuning issues.

Ive checked for vacuum leaks etc can find any. So the BG instructions say that the idle mixture should be 1-2 1/2 turns out. With the screws out 2 turns the pinging pretty much goes away but runs horribly rich at idle (black smoke etc). So the only way I can get it to run normally at idle is about 3/4 to 1 turn out on all 4 screws. This however is causing the pinging to be more pronounced.

It seems weird that Im getting an overly rich idle but getting a lean (pinging = lean right?) situation on tip in..

Anyone have any suggestions?

Thanks!

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Old 11-30-2004, 07:21 PM
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set-up

I really don't think 10 deg of initial timing is enough. If you call barry grant they will tell you there carbs need 16 to 18 degrees of initial to idle right....

The tip in pinging can be caused by a few things. what plug are you running ( heat range) what octane fuel are you running???

keith
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Old 11-30-2004, 08:16 PM
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Im running 92 octane, which should be fine for a 10 to 1 engine. The factory specs for the motor is 10 degrees btdc, and the carb is a zz4 crate engine demon specificly designed for this motor. My assumption would be that if Barry Grant speced out the timing for his carbs differently it would state so in the installation and configuration guide.

The plugs are the factory spec heat range, I dont remember the # off hand.

Theres gotta be some simple solution to this, something Im missing here

Thanks for looking guys.
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Old 11-30-2004, 10:31 PM
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If it's too lean at part-throttle, maybe going a bit richer on the primary main jets would help.
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Old 11-30-2004, 11:10 PM
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The idle screws will not affect the pinging, or how rich it runs after the throttle plates start to open.

They should be adjusted to get the highest smoothest idle, the depth of each screw will probably be different.

Sounds like you need more advance, but that will cause more pinging. If every thing else is to specs, then I would start going with bigger jets.

Troy
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Old 12-01-2004, 05:33 AM
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tune

The reason i asked about the plug's is because some times if your on the edge of the plug being to hot it will do what you are describing and going 1 heat range colder will fix the problem.

92 octane is ok for a 10.1 engine if you have the tune correct.

I would call barry grant and tell them whats going on with the idle. I would bet they are going to tell you that you need more inital timing......There carbs have a problem with running rich at idle. If you do a search of this site i am sure you will find plenty of threads with people having the same problem. I bought a barry grant off a guy for next to nothing because he couldn't get the idle fixed.... Glad i know what to do to correct it beacuse i got a good deal on the carb....

I would disconnect the vacuume advance and set the timing at 16 initial and about 34/36 total and i can almost guarnantee that all your problems will go away......

Keith
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Old 12-01-2004, 11:06 AM
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Generally a ZZ4 engine will run best with about 14 degrees initial timine. If you're getting detonation off idle, the advance curve in your distributor may be coming in too early. That can cause a situation like this. Another thing to look at is where you have the float levels set in the windows. Raising them up slightly will start the fuel flowing a little sooner, which may help your situation.
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Old 12-01-2004, 11:58 AM
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Re: Rich at idle but pinging on tip in?

Quote:
Originally posted by JoeS
Hiya folks.. well I finally got my timing issues resolved.. I pulled the manual for the zz4 and found they suggest 10 degrees and vacuum advanced on ported.

So Im trying to adjust my idle mixtures screws on my Demon ZZ4 crate carb and having some problem..

I keep getting some pinging on tip in acceleration. Meaning when cruising down the road and lightly accelerate in a high gear the motor pings. If I put more or less pedal it'll go away but generally its about 10% throttle open. So I know Ive got the timing set correctly for my stock ZZ4 and figuring theres a carb tuning issues.

Ive checked for vacuum leaks etc can find any. So the BG instructions say that the idle mixture should be 1-2 1/2 turns out. With the screws out 2 turns the pinging pretty much goes away but runs horribly rich at idle (black smoke etc). So the only way I can get it to run normally at idle is about 3/4 to 1 turn out on all 4 screws. This however is causing the pinging to be more pronounced.

It seems weird that Im getting an overly rich idle but getting a lean (pinging = lean right?) situation on tip in..

Anyone have any suggestions?

Thanks!
This is in reply to you part throtle problem.I'm not real sure if those carbs are like holley's but if they are you should try and check the back 2 barrels to se how open they are.if they are not open enough that will give you problems with you're 4 corner idle system.The front two barrels from the underside if you look at them should only be open no more than 1/2 the idle circuit slot.If you hve to crank the idle past that position then you should try and se if there is a adjustment screw for the back two barrels.It should be located on the base plate of the carb,it's very small.By opennig the back two you should be able to close the front two some,giving you more idle and part throtle control.Hope i helped out.

Last edited by robertg; 12-01-2004 at 11:58 AM.
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Old 12-01-2004, 12:30 PM
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Pinging at tip in would be due to vacuum advance.

Long cams will often burn rich at idle due to the large overlap. Get's really bad with poor compression for the overlap. These longer cams will often make more vacuum at 1200 than at idle. The extra vacuum will pull the advancment to unacceptable levels. A big cam with alot of gear does this more often than not.
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Old 12-01-2004, 01:18 PM
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Unplug your vacuum advance, plug the hole in the carb, and see if it still pings. If it doesn't ping any more then you need an adjustable vacuum advance canister for your distributor. If it still pings, and you know your base timing is correct, then you either have too much (or fast) mechanical advance or you are running too lean and need to richen your jets a little.

EDIT: You might also want to try and put your vacuum advance on to full manifold vacuum and then set your initial timing back a few degrees. The vacuum advance will kick in at idle (unlike ported) and give you the few degrees you lost when you retarted the base timing a little. It will also give you less timing at cruise because you set it back a few degrees and everything after idle between ported and full vacuum is the same. Doing that, you will retard x degrees at cruise for every x degrees you take out from initial and may stop the part-throttle pinging...

Last edited by fried_guy; 12-01-2004 at 01:27 PM.
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Old 12-01-2004, 01:22 PM
Technical Support Barry Grant
 
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It is very common for the Vacuum Advance to come in too quick for these engines. The distributors NEED to be recurved to get the engines to perform properly especially if the fuel isn't a true 92 or 93 octane.
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Old 12-01-2004, 01:52 PM
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I agree, it sounds like your advance is coming in too quickly. I get the same thing if I am towing a heavy trailer, I have to back the advance off to get it to stop. I also run cheapo gas which doesn't help.
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Old 12-02-2004, 01:49 PM
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Thanks guys.. I'll give those things a try this weekend
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Old 03-18-2005, 04:17 PM
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So what was the final result of your tune up on the ZZ4. Iam about ready to start mine and am looking at some old posts and yours keeps comming up!
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Old 02-18-2006, 07:45 PM
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Well, once again, lots of experts with NO good info to give.

I have been fixing these dists for a long time now. This came about with the fellows at Limeworks Speed Shop in Whittier, California, as they use ZZ4 engines in just about EVERY from the ground up car they build, and had severe pinging issues with EVERY one of those ZZ4 engines until we got together and fixed the distributors and to a lesser extent, possible vacuum leaks.

We found the dyno heros had done their mayhem quite well with the ZZ4, making them ping to beat the band. We used simple hotrodder's logic and fixed the problems.

First problem, vacuum advance is connected to ported vacuum source, WRONG, pulls in too much timing at acceleration and cruise rpms. If the engine needs ported vacuum advance, the mechanical advance just ain't right.

Second problem, to compensate for the dyno telling its stupidity, the mechanical curve on the ZZ4 is set to start at 1,300 rpms, limit at 5,500 rpms, way, way, way too high.

The fixes Limeworks and I came up with that work:

1, limit the vacuum advance pull pin travel to .086 inch of travel, 8 crankshaft degrees of vacuum advance and source it FROM FULL MANIFOLD VACUUM ONLY, NO PORTED VACUUM. A simple stop can be built from a scrap piece of sheet aluminum or steel, held in place with two 6/32 screws. This will take the idle timing to 18/19 degrees, just where the engine wants to idle at. 69120 vacuum advance is correct, just needs to be stopped down in degrees and fitted to full manifold vacuum, not ported.

1, mechanical advance. The curve pulls in way too slow, done that way only to compensate for the incorrect ported vacuum advance overtiming the engine at acceleration. Changing just one spring to a lighter one, sourced from an early points dist, will make the mechanical advance start at between 850 and 900 rpms, stop at 3,200 to 3,400 rpms, just where that engine likes it. 41 weights and 375 center that are already in the distributor are the right pieces for the machanical advance, just not sprung right for real world and correct manifold vacuum useage.

The initial should be 10/11 degrees.

Mechanical total will be 32/33 degrees

Idle timing will be 18/19 degrees.

Vacuum advance will do what it is intended to do, be a load compensator, not a timing overadder.

These engines like more timing when they are on light to no load, as at idle to cruise loadings. Ported vacuum souring just doesn't do that, it pulls degrees in during acceleration, along with the mechanical advance, just where we don't want or need it. Load compensation is just that, more timing when the engine is not loaded, less when it is, as in acceleration.

This works, and I have done it to many ZZ4 dists for people that listened to others and did it the WRONG way with ported vacuum sourcing first.

Anyone want the pics of just what to do, e/mail me and ask for "ZZ dist pics" in the subject box. sparkman451@earthlink.net Disregard the spam filter, it'll open when I respond to you with the pics.

Now, for the carb/manifold leaks.

Some, NOT ALLl ZZ4 intake manifolds don't have a carb pad large enough to seal off the carb from leaks from some of the vacuum passages on their bases, especially some Holleys and Edelbrocks. the pads aren't large enough to support the full base of the carb, the gasket droops and leaks occur.

What Limeworks and I came up with is to use a gasket on each side of an Edelbrock 2732 sealing plate. This plate is large enough to seal the gasket between it to the manifold and between it and the carb base and is not thick at all. To check for leaks, flow UNLIT propane under the carb with the engine running and see if two things occur. The idle should change a touch, and the exhaust should smell like burned propane. No idle speed change/smell, no leaks.

Like I said, Limeworks and I have done the distributor mods described above to many, many ZZ4 dists, and not one person was unsatisfied with them. It fixes the pinging and performance issues with the ZZ4 engines, and others in the crate GM family that also use that distributor, ZZZ, ZZ3, ZZ383, ZZ430, ZZ503 carb'd and 454 motorhome.

Now, I used to work at Holley, and sorry, tech@bg, but I wouldn't use a Barney Grunt carb for my lawnmower, let alone my car. And, I wonder just why Summit quit carrying them, what, no warrantee support, that is the word I got from Summit.

I get a lot of flak about the way to correctly fix a ZZ4 dist, from those who aren't seeing the real world of it all, dyno heros and magazine artile readers that the articles are sourced from other distributor/dyno heros for the most part, but I have never seen anyone drive a dyno around the block, and the setups for them are usually to add way too much timing and jetting to be effective for the real world.

So, that's the way they come ouot of the factory, and they don't get real world'd, they just ping away and mnake things worse, until a guy like me comes around and disagrees with all the "experts", offers the right way to fix it.
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