Spark plug heat shields

MaineShark · 01-20-03, 06:05 PM

I recently pulled my plugs for a compression test, and found two of the boots partially melted. Not good, for obvious reasons. There is a shield over the plugs at cylinders 5 and 7, but none of the other pairs have this. Are the other three shields missing, or were they never there?

Are there heat shields I can buy (stock or aftermarket) to protect the other six plug wires? I'm going to be replacing all eight, and I don't want to end up melting the replacements...

Joe

billybob · 01-20-03, 06:43 PM

MaineShark,

www.ecklers.com

put in part numbers

A8065 - left rear right front

A8066 - right rear left front

Bill

Vette/Berlina-coupe · 01-20-03, 08:18 PM

Hello JOE- Those aluminum-shields have nothing at all to do with heat my friend (excepting to hold-in heat that cooked your wire-ends), --they are there to block rf-radiation (radio-freq.) from propagating into your radio (especially AM), -so that you don't get the ticking at idle and buzz at higher-rpms! The other plugs are effectively shielded by the engine-block etc., and you should have a complete set of contiguous shield-shells up to and including over the distributor (black-plastic is clad with aluminum on its underside) which should really all be grounded to be most effective I believe. Also FYI, -while touching on subject of the radio, if you pull-off your right-hand knob&rotor on most oem-Delco's, there's a tiny-hole just above the knob-shaft that you can poke-in a small/flat-bladed screwdriver and delicately adjust for max.-reception (antenna-up, and on some weak-station around 1400kc-AM), -which can often make a big difference in radio noise-rejection... -Bob vH
:TALK

[Re: JohnZ&nomadNeil(below): -T'aint-so my friends, you're missing the orig.-question, --the steel/heat-shield extending along the upper & side -regions of the R&L/exh.-manifolds is not what is being referred to here (they serve to radiate excessive heat back as to keep the eng.-compartment significantly cooler); -my reply is concise/accurate, --so why confuse the issue... ]

JohnZ · 01-20-03, 08:48 PM

Quote:

Originally posted by Vette/Berlina-coupe
Hello JOE- Those aluminum-shields have nothing at all to do with heat my friend (excepting to hold-in heat that cooked your wire-ends), --they are there to block rf-radiation (radio-freq.) from propagating into your radio (especially AM), -so that you don't get the ticking at idle and buzz at higher-rpms

Wrong - all SB Chevys with cast iron exhaust manifolds have a galvanized steel heat shield surrounding each pair of plugs - attaches to a 1/4"-20 tapped hole in the block just below, and centered on, 1-3, 5-7, 2-4, and 6-8 pairs of plugs; the shields are there specifically to shield the plug boots from exhaust manifold heat. The chrome/stainless steel IGNITION (RF/radio) shields are a different animal, and are in addition to the spark plug HEAT shields. I see lot of cars with the plug heat shields missing, as some Bubbas don't bother to re-install them when they R&R the exhaust manifolds (same Bubbas that leave the front starter brace off and then wonder why the car keeps eating starter noses).

Nomad78SA · 01-20-03, 10:22 PM

You can get the heat shields at any of the major suppliers for around $7.00 each

JohnZ is dead on with what he says. One of the shields will have a hole in it for the sensor that mounts in the head.

I got a couple around here you can have if you want them. I think I painted them blue at one time to match the block on my 78SA.
Neil in Tenn

billybob · 01-20-03, 11:36 PM

MaineShark,

For clarification I have posted an image from my AIM, these are the plug shields to which I am refering.

Anything that will protect against direct heat could be considered a heat shield.

For example the starter heat shield which is nothing more then a small hunk of aluminimum attached to the starter to deflect some of the direct heat from the manifolds. It still gets hot but its indirect there by lowering the amount of heat absorbed by the starter.

Think multi layer, light up a propane torch put your hand above the flame, hot and it hurts. now do the same thing but put a hunk of metal in between the flame and your hand. You still feel the heat yet you are less likey to burn yourself.

These shields do basically the same, its not 100% but is enough to offset the direct absorbtion.

Simple environmental physics.

Bill

MaineShark · 01-20-03, 11:41 PM

Yup, those are they. Three are missing. The melted boots were both on unprotected plugs.

Neil: thanks for the offer, but I think I'm going to look locally, to save shipping. Plus, I don't think blue will go with my car

Joe

JohnZ · 01-21-03, 10:05 PM

[QUOTE
[Re: JohnZ&nomadNeil(below): -T'aint-so my friends, you're missing the orig.-question, --the steel/heat-shield extending along the upper & side -regions of the R&L/exh.-manifolds is not what is being referred to here (they serve to radiate excessive heat back as to keep the eng.-compartment significantly cooler); -my reply is concise/accurate, --so why confuse the issue... ]

[/b][/quote]

Yes, 'tis so - the original question was clearly stated - the individual shields around the spark plugs (which are heat shields), as posted further down on the picture of the A.I.M. page, were the subject, not the ignition/radio RF shielding you discussed. There were never any steel heat shields along the upper and side regions of the exhaust manifolds on his car - never even considered anything like that.