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New GMC 305 question -- Plugs and gap?
#529966 Sun Apr 19 2009 01:19 PM
Joined: Nov 1995
Posts: 5,173
J
Unrepentant VW Lover
Can anyone tell me the correct plugs (and gaps) for a '65 305 V-6? The engine is in a 4000 series (ton and a half).

The engine is not running quite as smoothly as it should and has a little bit of a miss. I am going to pull the plugs to check the gaps, porcelain for chips & cracks, etc. But I have no idea what the gaps are supposed to be, actually ...

A quick recap -- The engine has new cap, rotor, points, condenser, coil, wires and plugs. Also, a freshly rebuild carb with a new mechanical fuel pump with a brand new electric back up (On the way to a show last year, the truck's mechanical pump failed and packed the crab full of diaphram bits, caused an engine fire and caused a lot of issues going home most of which have been corrected now except for this missing. A professional truck mechanic did the compression test, rebuilt the carb and double checked the timing and point gap. We have not yet pulled the plugs and double checked them.

Thanks,
John


John

'49 Chevrolet 3804

I've never been a NASCAR fan .. until now.
Let's go, Brandon!


Re: New GMC 305 question -- Plugs and gap?
John Milliman #530024 Sun Apr 19 2009 04:58 PM
Joined: Jun 2004
Posts: 8,436
W
'Bolter
I can get them tomorrow John if no one comes up with it between now & then. George


They say money can't buy happiness. It can buy old Chevy trucks though. Same thing.

1972 Chevy c10 Cheyenne Super
Re: New GMC 305 question -- Plugs and gap?
John Milliman #530095 Sun Apr 19 2009 09:34 PM
Joined: Aug 2008
Posts: 230
O
Shop Shark
here you go john i just dodged the rain drops out to the shop c44ns plugs and .035 gap

Re: New GMC 305 question -- Plugs and gap?
old dog #530098 Sun Apr 19 2009 09:42 PM
Joined: Feb 2008
Posts: 870
5
Shop Shark
Just a thought - when was the last time you adjusted the valves?


David Colter
pics * 1954 wrecker * 1948 Chevy 1-Ton
No act of kindness - no matter how small - is ever wasted ~~ Aesop
Re: New GMC 305 question -- Plugs and gap?
54TOW #530162 Mon Apr 20 2009 01:39 AM
Joined: Nov 1995
Posts: 1,188
S
Shop Shark
Old Dog & George -- Thanks -- I hope nobody got too wet. Was that AC-Delco on the plugs?

David -- Good question. They've not been adjusted since I've owned the truck and may not have ever been adjusted since they were set on the assembly line. Remember -- the truck has 10,000 miles on it -- 2,000 since I've owned it. What should they be set at?

v/r
John


The collective group of dedicated volunteers behind Stovebolt.com
Re: New GMC 305 question -- Plugs and gap?
Stovebolt Staff #530169 Mon Apr 20 2009 02:03 AM
Joined: Mar 2004
Posts: 3,106
'Bolter
Valves don't usually get too tight on their own, which would be the only way they would cause a miss. If they were too loose then they would be obvious, too much noise,
Scott


Scott Ward

2 1948 1.5-ton Loadmasters
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Re: New GMC 305 question -- Plugs and gap?
48bigtrucks #530177 Mon Apr 20 2009 02:29 AM
Joined: Feb 2008
Posts: 870
5
Shop Shark
I thought that a loose exhaust rocker could cause the engine to run rough, and it seemed like one thing not already done.

John, I have no idea what they would be set at - just talking shop and learning from the best.


David Colter
pics * 1954 wrecker * 1948 Chevy 1-Ton
No act of kindness - no matter how small - is ever wasted ~~ Aesop
Re: New GMC 305 question -- Plugs and gap?
Stovebolt Staff #530189 Mon Apr 20 2009 02:49 AM
Joined: Aug 2008
Posts: 230
O
Shop Shark
yea that was ac delco ,i didn't worry to much there wasn't any soap in it .

Re: New GMC 305 question -- Plugs and gap?
old dog #531038 Wed Apr 22 2009 07:40 AM
Joined: Feb 2008
Posts: 207
4
Wrench Fetcher
Here's a copy of a page out of my '72 GMC 4500-9500 owners manual.
http://image62.webshots.com/662/7/43/48/2348743480103559715JDkNRV_fs.jpg

if you need more let me know.


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