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Ignition Experts help! Power drop after changing plugs.
January 8 2006 at 9:50 AM
No score for this post James (Login Fairlane62)
from IP address 65.255.74.49

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I had Bosch DR8BC plugs in the 466 during initial start up and break in because Autozone was out of Autolite 45's and said the Bosch were equivalent. The Bosch's ran really well, they came gapped at .035 so I left them that way. I installed a fresh set of Autolite 45's yesterday, and gapped them at .042" for Duraspark ignition, and now the engine isn't as responsive, and has a miss at full throttle that gets worse as the rpm increases

I don't know if the Bosch DR8BC and the Autolite 45 are actually equivalent. Do you think the problem is with the plugs, or the wider gap?

Thanks,
James

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Anonymous
(Login powerstrokeace)
24.8.241.88 Re: Ignition Experts help! Power drop after changing plugs.
No score for this post January 8 2006, 10:04 AM

put the bosch's back in and see if it runs ok!

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Lem Evans
(Login l-evans7)
69.166.129.47 Try ...
No score for this post January 8 2006, 10:09 AM

the .035" gap on the 45s and see if that is it .

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Lem Evans
(Login l-evans7)
69.166.129.47 DR8BC...
No score for this post January 8 2006, 10:13 AM

does cross reference to a 45 .

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James
(Login Fairlane62)
65.255.74.49 Regapped
No score for this post January 8 2006, 9:11 PM

Re-gapped to .035 and both the Bosch and Autolite spark plugs do fine. The car pulls cleanly up past 7000 rpm like it used to. Apparently my ignition isn't able to push past the larger gap.

I'm running a Duraspark with MSD Ignitor II coil, so it seems that I should be able to jump the wider gap, but I guess I shouldn't worry as long as it runs ok.

Thanks to ya'll for your help.

James

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FoMoCo
(Login 68460)
24.11.111.122 Sure
No score for this post January 8 2006, 9:29 PM

wouldn't think .007 would make that much dif.

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James
(Login Fairlane62)
65.255.74.49 I agree
No score for this post January 8 2006, 10:09 PM

I agree, I double checked with a new gap tool and they were closer to .045" so it was actually about .009-.010" difference, but it still doesn't seem like it would make the car run that bad. I have seen the plug gaps eroded out to .055" on stock engines with duraspark, and they would still be running fine.

Thanks,
James

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Bob M
(Login Bob_M)
66.69.46.160 you have a lot of compression or boost?
No score for this post January 8 2006, 10:16 PM

I think cyl pressure effects how much gap your ignition can jump a spark across.

Bob M
http://fordifiedracing.com
http://bigblockfox.com


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Lem Evans
(Login l-evans7)
69.166.129.47 Two things ..
No score for this post January 8 2006, 10:21 PM

Agreed , 9 or 10 thou is not that much...but... 10 is a big % of 35 .
The stock engines were 8/1 and never saw the other side of 5000rpm , which I suppect is not the case with your engine .


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James
(Login Fairlane62)
65.255.74.49 10.3 compression
No score for this post January 8 2006, 10:30 PM

Bob and Lem,

Your right. It is a bit different from a stocker. I'm running 10.3 compression, and typically shifting at 6500-6800 rpm. With the wider plug gap, the car even idled bad, and then just got worse with higher rpm. It may be the compression that's causing it. Oh well, it's back to running good, so I'll just keep my plugs gapped at .035" in the future.

Thanks for the response,
James

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James
(Login Fairlane62)
65.255.74.49 Lem, one more question
No score for this post January 8 2006, 10:41 PM

Lem,

I ran Motorcraft BSF42C plugs in my previous 460. Does that also cross over to the Autolite 45, or is it colder?

Thanks,
James

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Lem Evans
(Login l-evans7)
69.166.129.47 Re: Lem, one more question
No score for this post January 8 2006, 10:50 PM

Yes it does . But if you take it to the track it would like the AR-33s better .

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Michael Jackson
(Login 269falcon)
205.188.117.68 Re: Lem, one more question
No score for this post January 8 2006, 11:35 PM

I ran across this answer on plug gaps in Tech Talk on the Drag Race Results Web

Same Plugs Gapped at .035 (Tighter Gap Insures there's No Missfires),A Wider Plug Gap Makes NO More power than a Plug that has No problem firing at say .018-.022 ,
.018-.022 Is the Normal Plug gap Used with a Magneto That's Ran in the 870hp+ 410 Sprint Cars Injected on Alky to Insure there's No Miss fires during Caution,Etc.

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James
(Login Fairlane62)
65.255.74.49 Thanks
No score for this post January 9 2006, 12:14 AM

Lem,
So are the AR-33's about one range cooler than the 45's?

Michael,
I guess the data you found proves out what happened with my engine. I had rationalized that a wider gap would result in a larger spark kernel which would improve efficiency. However, if there is no horsepower gain with the wider spark, it's better better to opt for the smaller spark.

Thanks,
James

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Charlie S.
(Login DblAdigger)
71.109.239.90 Another option would be to
No score for this post January 9 2006, 1:21 PM

up grade the ignition system so that it will fire the larger gap. The problems/symptoms you have are a classic case of weak ignition. Borrow a MSD 6A or equivalent spark box and see what happens. I think you'll be suprised.

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Lem Evans
(Login l-evans7)
70.157.226.53 Re: Another option would be to
No score for this post January 9 2006, 4:25 PM

Now you're talking . James could use a MSD 6 box . But , the bigger gaps do not seem to be productive .

This message has been edited by l-evans7 from IP address 69.166.129.47 on Jan 9, 2006 5:34 PM




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rick
(Login BBSTANG502)
69.2.87.147 what is the correct plug gap
No score for this post January 9 2006, 4:36 PM

with MSD 6al with coil and dizzy, for max power. thanks

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James
(Login Fairlane62)
65.255.74.49 Duraspark vs MSD
No score for this post January 10 2006, 12:09 AM

I have had some good success and some bad with MSD on other cars, so I like the simplicity and availability of the Duraspark since the car is primarily street driven. Of course that being said, most auto parts now carry at least one MSD 6A on the shelf, so availabilty is probably not the issue that it used to be.

Also, the Duraspark pulls good up to 7500 which is well past my powerband anyway, so would the wider gaps provide any additional power?

Thanks,
James

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Cory
(Login fordman300)
66.71.7.86 Re: Duraspark vs MSD
No score for this post January 10 2006, 3:22 PM

so what small 5/8 plug do you guys recomend for d3 heads crane HI-6 box and LX-92 coil. 10.5:1 CR
 
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