twoup1200
Magnolia, Tx, USA
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Joined: 10/23/2004
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I own a 93 georgie boy on a 92 p-30 chassis and 454 engine. This weekend I installed thorley headers. Along with the headers I installed new plugs, wires, dist rotor and cap. It fired right up and idled well. Today I took it out for a test run. About a week ago I checked the timing and it was right at 8 dbtdc. I run regular gas but have never noticed any pinging. When I went out for the test run today I noticed a slight pinging while accelerating easily. When I got on it harder the pinging went away, at least I think it did. Is it possible that headers could cause this pinging? Do I need to time it differently with headers? I really don’t want to retard the timing, don’t want to run higher octane gas either. Any suggestions?
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RJgonfshin
Winston Or, USA
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Joined: 06/08/2003
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Are you sure it's not header ringing, which is very common, and is one reason why I hesitate to install headers again. Some engines w/ certain headers can ring quite loud, and I would say that it does sound like pinging somewhat.
Rich
' 98 Flair, 454, Onan Microlite 4k, Intel PD 9155 w/ wizard, Sta-power 1500 watt Inv, 2 6v batts, ammeters, Oly Catalytic Heat, hauling 2 Bent Bikes and sometimes towing a Tracker F&S boat.
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twoup1200
Magnolia, Tx, USA
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RJ
I've never heard of header ring. I suppose I could try retarding the timing to see if it goes away. I think the factory spec is 4 dbtdc. Other threads recommend 8. Mine was set to 8 when I bought it.
If retarding the timing doesn't do it I guess it must be header ring as you said.
Thanks
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MELM
GA
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If I haven't forgotten too much about the TBI Chevy engines, you are only setting a reference timing for the computer to work with. It adjusts the timing based on the inputs from a bunch of sensors, and the nominal setting just gives it the range it needs to operate as designed.
When you reconnect that wire after setting the distributor, the timing probably changes. I suspect you can rotate the distributor several degrees and not see any change (after the computer compensates) at the timing mark.
Now, on the old ones with carburetors, vacuum and centrifugal advance mechanisms on/in the distributors, timing setting does make a difference.
Mel & Mary Ann; Mo'Be (More Behave...) and Bella
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hud3ma
N. Cen. PA via Ware, Herts, England, UK
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Quote:When I went out for the test run today I noticed a slight pinging while accelerating easily. When I got on it harder the pinging went away, at least I think it did. Is it possible that headers could cause this pinging?
To address your basic question...yes, it is quite possible that the headers caused the pinging by changing the fuel charge density at specific throttle positions and engine loads. The headers are scavanging more of the incoming fuel charge out of the combustion chamber during valve overlap than the stock exhaust system did, and this probably leaves a lean mixture in the chamber during compression that is prone to pinging.
The oxygen sensor detects the increase in the amount of un-burned fuel in the exhaust charge and responds by further leaning the mixture and / or advancing the ignition event, both of which simply make the pinging worse.
* This post was
edited 01/16/05 08:26pm by hud3ma *
Mike & Karen
...and Ziggy, the Golden Retriever
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pchuckie
Pemberton twp, NJ
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I'm going with "hud3ma" he sounds like he knows what he's talking about.
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Fishreed
Burton, Michigan USA
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Joined: 09/26/2004
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HUD3MA,
I concur with your diagnosis, but what does the guy do about it short of a reprogram job on the engine's computer?
TravelMaster 1986 23ft, Chevy G30 5.7 TH400 Tranny. 350M V-8 295hp and 360 ft lbs torque, Mobil One Synthetic, Tru-Cool Tranny(4490) and Engine Coolers (M7B), Bilsteins shocks on the front. Monroe 555 HDs on the rear.
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Jim83Itasca
La Quinta Calif
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Joined: 09/16/2003
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twoup1200 I would first add (to a low tank) premium fuel and see what happens and if the ping goes away.
If you have a vacuum canister on the distributer (I have never looked at a 93) your standard vacuum advance from the factory can be as much as 25º and that will drive you nutso.
My reason for that remark is "light throttle pressure" brings on the ping but full throttle does not, full throttle means no vacuum and the distributer vacuum is out of the picture.
If you find that is the case a "Crane cam" adjustable vacuum advance kit will do you well since it can be set for a min/max vac advance.
Also the 8º base timing is good!
Mine is 10º base 24º mechanical all in by 2900-3100 RPM for a total of 34º plus the advance (vacuum) is a 10º A.C. Delco so just light footing it down the road at speeds the max advance is 44º
part # 1973577 at your chebby dealer. Good luck
Jim
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winepress
Santa Barbara, Ca / Lake City, Co
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Joined: 09/20/2004
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The "knock sensor" should respond way before you can ever hear a pinging. You might have a bad one.
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Nomadac
Columbus, IN
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I have a set of Doug Thorley headers on my 1983 454 in my Suburban and have not had any pinging casused by the headers. Some headers are more prone to noise, but header ringing, never heard of this before. Doug Thorley header are of good quality and not like the cheaper headers on the market. I think the other suggestions to check would be advisable.
Arnie
2003 Travel Supreme MH
38KSO1 Cummins ISC 350HP
Car Dolly w/1996 Toyota RAV4 2WD
1963 Pontiac Grand Prix
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