what heat range plugs should I use?

82 GT · 10-09-2003, 07:37 PM

Based on my sig. below, what would be a good starting point for the heat range of spark plug to run.
I know every engine is different but I just want a good starting point and then I'll go from there after I read what the plugs indicate after awhile.

billheis · 10-09-2003, 07:49 PM

I think the old autolite # is/was 45. If all else fails just get plugs for 69 Mach I (351W 4bll) II'm asuming your using early windsor heads with the big plug.
Bill

82 GT · 10-09-2003, 08:23 PM

Quote:

Originally posted by billheis
I II'm asuming your using early windsor heads with the big plug.
Bill

Actually, the heads are '74. They are the 5/8 size(smaller plugs) and not the 13/16 size

billheis · 10-09-2003, 08:40 PM

Then a good starting point would be Autolite 25 which is stock heat range for 5.0. If you need to go colder then 24s I've always have had good luck with autolite but if your using another brand just cross the number.
Bill

82 GT · 10-09-2003, 10:06 PM

It's not a 5.0 engine. It's worked over 351w

billheis · 10-10-2003, 11:28 PM

They both use the same plug size and to be on the safe side go with the 24s. If its to cold they will just load up. If you go to hot you run the chance of detonation

82 GT · 10-11-2003, 03:49 PM

Well if #25 are for stock engines then a better starting point should be around #27-30 for what I have.
Remember, it's a 351w that's no where near stock.

You did help me though. Now I know where the base minimum starting point is. I think I'll start at #27 and work from there.

billheis · 10-11-2003, 05:44 PM

Sorrry I don't think I made it very clear. The higher the number the hotther the plug, lower colder. You want a colder plug not because of engine size but whats in it. You have higher compression and a hotter cam both will allow the clyinder to fill more. This usually means going to a colder (lower number) plug. You may even get away with using a 23. I hope this clears that up

jonnyk · 10-12-2003, 09:13 AM

I would recommend starting with 1 heat range colder than stock as well (24's). With your compression and iron heads you might still have to go one colder.

82 GT · 10-12-2003, 01:55 PM

Ok, now I understand. I had my theory backwards.
Thanks

10-09-2003, 07:37 PM	#1
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	what heat range plugs should I use? Based on my sig. below, what would be a good starting point for the heat range of spark plug to run. I know every engine is different but I just want a good starting point and then I'll go from there after I read what the plugs indicate after awhile. __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

10-09-2003, 08:40 PM	#4
billheis Registered Member Join Date: May 2001 Location: Fernandina Beach, FL 32034 Posts: 178	Then a good starting point would be Autolite 25 which is stock heat range for 5.0. If you need to go colder then 24s I've always have had good luck with autolite but if your using another brand just cross the number. Bill __________________ Bill Heiser 90 Convertable 5.0 LX, ported E7s w/ THumper valve job, TFS street, FR 65mm TB, B cam w/1.7 cobra rockers, kirban AFPR, Mac CAI, Mac Headers, off road h, 3 chamber flows, Crane ign. box, 3:73s, Art Carr AOD & 2600 converter

10-09-2003, 10:06 PM	#5
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	It's not a 5.0 engine. It's worked over 351w __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

10-10-2003, 11:28 PM	#6
billheis Registered Member Join Date: May 2001 Location: Fernandina Beach, FL 32034 Posts: 178	They both use the same plug size and to be on the safe side go with the 24s. If its to cold they will just load up. If you go to hot you run the chance of detonation __________________ Bill Heiser 90 Convertable 5.0 LX, ported E7s w/ THumper valve job, TFS street, FR 65mm TB, B cam w/1.7 cobra rockers, kirban AFPR, Mac CAI, Mac Headers, off road h, 3 chamber flows, Crane ign. box, 3:73s, Art Carr AOD & 2600 converter

10-11-2003, 03:49 PM	#7
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	Well if #25 are for stock engines then a better starting point should be around #27-30 for what I have. Remember, it's a 351w that's no where near stock. You did help me though. Now I know where the base minimum starting point is. I think I'll start at #27 and work from there. __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

10-09-2003, 07:49 PM	#2
billheis Registered Member Join Date: May 2001 Location: Fernandina Beach, FL 32034 Posts: 178	I think the old autolite # is/was 45. If all else fails just get plugs for 69 Mach I (351W 4bll) II'm asuming your using early windsor heads with the big plug. Bill __________________ Bill Heiser 90 Convertable 5.0 LX, ported E7s w/ THumper valve job, TFS street, FR 65mm TB, B cam w/1.7 cobra rockers, kirban AFPR, Mac CAI, Mac Headers, off road h, 3 chamber flows, Crane ign. box, 3:73s, Art Carr AOD & 2600 converter

10-11-2003, 05:44 PM	#8
billheis Registered Member Join Date: May 2001 Location: Fernandina Beach, FL 32034 Posts: 178	Sorrry I don't think I made it very clear. The higher the number the hotther the plug, lower colder. You want a colder plug not because of engine size but whats in it. You have higher compression and a hotter cam both will allow the clyinder to fill more. This usually means going to a colder (lower number) plug. You may even get away with using a 23. I hope this clears that up __________________ Bill Heiser 90 Convertable 5.0 LX, ported E7s w/ THumper valve job, TFS street, FR 65mm TB, B cam w/1.7 cobra rockers, kirban AFPR, Mac CAI, Mac Headers, off road h, 3 chamber flows, Crane ign. box, 3:73s, Art Carr AOD & 2600 converter

10-12-2003, 09:13 AM	#9
jonnyk Being stroked is great Join Date: Oct 1998 Location: Alberta, Canada Posts: 772	I would recommend starting with 1 heat range colder than stock as well (24's). With your compression and iron heads you might still have to go one colder. __________________ Novi 2000 now spinning off the snout of the 331... Mods Pics

10-12-2003, 01:55 PM	#10
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	Ok, now I understand. I had my theory backwards. Thanks __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

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