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Compulsive chicken choker
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6,470 Posts
Discussion Starter · #1 ·
I need to pick a set of plugs up this morning for my 1990's 305 Vortec. Halfords is nearest by far but they don't have the ability to cross-reference plugs from the number on the old plug. What is the modern equivalent car that uses the same plugs? I'm sure one of the Peugeots does but I can't remember.....
 

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Stroker
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5,576 Posts
It's a jungle out there

My Edelbrocked sbc came with Autolite 26 plugs in.

They were very close to a couple of exhaust tubes so called R*al Steal for the stumpy ones and got the Accel 416S plugs
(which fit a treat - but will have to see how plug leads get on as it's still close).

Anyhoo, as it happens the guy at RS queried what was in initially. He got me to double check heads so with torch and mirrors I could see that they did use the 'normal' 3/4" gasket plugs and NOT the 3/8" tapered ones put in by the pro builder.

I'm so glad the headers made me stumble across summat I took for granted was correct. Presume the mill may not have run or exposed threads in heads would have been scorched. :sniff:

Oh yeah, point being that chebby heads can take a mixture of short/long - tapered/gasketed plugs.
 

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Compulsive chicken choker
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6,470 Posts
Discussion Starter · #6 ·
How do I know whether the plugs should be long or short? I'm guessing short ones will cause problems by the spark not being inside the combustion chamber?

Kind of makes me smile when I hear an "expert" preaching that "all Chevy engines are the same and everything is interchangeable"!!!!!
 

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I'm Not Jed Clampett
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2,725 Posts
How do I know whether the plugs should be long or short? I'm guessing short ones will cause problems by the spark not being inside the combustion chamber?
I check heads where there could be multiple plug lengths (e.g. Rover v8) by getting a piece of welding rod, bending over the end to 90 degrees to make an 1/8" ledge, then put a spot of paint or tippex on the long side of the welding rod where I hope the plug seat should be. Poking this wire down the plughole and pulling it back till the wire snags the end of the thread will give you a good idea of the plug thread length, if your mark is still in the plughole you need longer plugs; if it's outside of the plug seat you need a shorter plug. This method works best if when you poke the wire in you make sure that the ledge on the wire isn't upwards where it might snag the roof of the combustion chamber and give a false reading.

Kind of makes me smile when I hear an "expert" preaching that "all Chevy engines are the same and everything is interchangeable"!!!!!
Hopefully none of those "experts" on here, just people sharing their experience so that we don't all end up with the same "been there f*cked that" tee shirt.
 

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Registered
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340 Posts
Champion's.... good for lawn mowers & chain saws/ maybe

definately DONT get champion,get AC43TS
DITTO........ do not use Champ / Chump plugs:shake::tdown: if you can @ all help it...
miss fire & dead cylinders loom:sniff:
My 1.4 pence / 2 cents. Cheers! Dr/Dee

Recommend AC or NGK.... Denso also a good choice...:tup:
 

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Compulsive chicken choker
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6,470 Posts
Discussion Starter · #10 ·
Where abouts on the heads will I find the casting numbers?

I've just tried the bent piece of wire routine to determine plug length, but as the car is fitted with rams-horn headers/manifolds its difficult to see.
 

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Stroker
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5,576 Posts
Hi,

the numbers are under the rocker covers.

I had a quick go on Summit, ticked all the boxes to try and get close to the right plug and it still listed both short and long tapered seating plugs :shock:
RS don't list their choice for owt past 1985 :S

KJ
 
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