aaronz28

is there any concern with using platinum plugs in an old carbureted motor?

I have Rapidfires in my car now (equivilent to the AC R45s) and while the car runs and drives fantastic, in a very short amount of time, I'm getting a knarly black residue buildup on the electrode.

any ideas?

Plasticman

Have used Bosch platinums (original single side electrode versions) for many years now, with no issues EXCEPT:

Had a set in a 93 GMC Typhoon (4.3 liter turbo'd eng.) that had the center platinum electrodes working their way out to short against the side electrode. Evidently they had a problem with retension of the center electrode, and the local Pep Boys replaced them with no questions.

Residue on the electrode tells me the heat range is not hot enough for the type of driving you do normally. Is this happening on all the plugs, or just one or 2? I am assuming you are talking about the center electrode.

Plasticman

aaronz28

Here are two pix of the same plug... as you can see, the top looks fine, color is correct and clean, but on the bottom, its filthy and building up a ton of carbon... any ideas?

macdarren

I like the rapidfire plugs myself, they magically smoothed out my idle when compared to an equivalent champion. To my eye (and I am no expert compared to some of the guys here but) both of your plugs look kinda bad the second one is just farther along the path. I would say move up a heat range maybe, but I would suspect you are getting some oil into the chambers.....you don't say how many miles are on those plugs but unless they are really old I would tend to suggest you look at the general engine condition before plugs....maybe valve seals or guides?

aaronz28

Its the same plug..

the engine is fine, and the heads are fresh.. these plugs have less than 200 miles on them.

the guys who did the heads removed the little spring clip on the teflon seal... they do that on every SBC head they do. thier logic is that the spring makes the stem seal too positive and you get no oil on the guides... i can assure you that the engine condition if perfectly fine...

i'm wondering if there is a possible problem with stock points ignition and platinum plugs or, is it just that my carb is out of whack?
again, the motor runs like crazy and doesn't seem to load up at all as the plugs would indicate

thanks

aaron

macdarren

I see now that is just two shots of the same plug I thought you were trying to show a progression over time since from the angle of the first it doesn't look as bad as the second shot. You got me, 200 miles, maybe it is the carb/mix or something....I don't know if there is a reason to not run platinums, I have done it but never did it seem worth the money, they would look about like yours after a few thousand miles just like the rapidfires. Can't tell for sure if yours are, but I also use an projected nose plug....seems to help a little, I don't know if there could be interference if you had a high compression motor.

Regarding the valve seals, if it is all fresh then I doubt either of my ideas has any validity. My engine builders and buddies mostly don't like those teflon seals...most of the guys I know prefer an unbrella type that moves with the valve or some other wiper seal like the teflon but it is made of something else (viton?). I have been told that the wiper seals were primarily designed for race applications since as you mentioned they can actually so reduce the oil that on a street car the guides wear, not a big problem on a race motor that gets torn apart alot, also since the seal doesn't move any flex in the valve or just alot of miles can cause the seal to wear basically it stops working and then you get oil down the guide, again not a problem for the racer but on the street you get the neat effect of possible high initial guide wear due to lack of oil then seal leaks or fails due to just wear or a wobble from the now worn guide and then oil gets past the seal and past the loose guide...your removing of the clip might help both of those problems.

Again not your problem if all is fresh and I could be totally wrong (I am sure one of the forum engine experts will let us know) but I have been happier and had cleaner longer lasting plugs since I gave up the teflon wiper type seal.

Good luck.

Paul L

I saw that condition on my former 1979 Corvette. It was valve stem seals. Installed a new Crane set (with snap springs) and all was well. That was three years ago and the car is still running fine.

MikeM

[QUOTE=aaronz28]is there any concern with using platinum plugs in an old carbureted motor?


The only concern I would have is wasting my money. The platinum tip material is used to stop tip erosion from the wide gaps and hot spark of modern ignition systems. DNA to your point ignition.

magicv8

First look IMO either the plugs are oil fouled or the tank has cocacola in it.

Second look at the scum on the threads - you may have a head/manifold gasket leak or cracked casting.

Plasticman

It certainly can be an oil issue, and coming down the guides is a great possibility. But you have some faulty info there on guide seals.

1. Teflon PC guide seals should not be used on the street. They are great for race purposes (the one piece teflon seal is cheap, easy to install and remove, and has very low friction), but not for longivity. Removing the spring clips is even worse (since now it does not seal either), and depending on what else they did could (probably) be the source of your plug issues.

If they also removed the valve retainer "O" ring and the retainer shield, then you have a river of oil running down those guides. You will also have a caked up carbon mess on the backsides of the intake valves that will force you to remove those heads and strip/clean the valves. That caked up carbon on the backsides of the valves will restrict air flow through the valves in short order!

2. Non teflon PC seals, as used on later GM aluminum heads and sold under several brand names, such as Fel-Pro are very good for street usage. However I still recommend that the valve retainer shield and "O" ring at the retainer be kept in place. However, only the intake valves need the PC guide seals! The exhaust valves do not use the guide seals, since they need the extra cooling/lube oil, and will not cake up, since the valve runs hotter and is self cleaning (just like a self-cleaning oven). But the retainer shield and "O" ring should still be used on all the valves.

Good luck,
Plasticman

JohnZ

My Z is jetted 72/76 (vs. stock 68/76), with ordinary $1.50 AC R45S plugs and stock O-ring retainer seals, and the plugs look a little black (but with whitish-tan insulator nose), but with none of the deposits your photo shows; looks like the plugs are too cold to self-clean. Try a set of R45S and see how they look after the same mileage - I've never seen that amount of deposits on 200-mile plugs.

aaronz28

my valves do not have the o ring or the deflector cap on the spring..

they just have the white valve seals... and i'm pretty sure that they are teflon with the spring clip removed... the guys who did the heads claim that they do it on every set of street heads with no problems whatsoever... and the guides and valves are brand new.

it pushes a tad of oil on startup if its been sitting an hour or so after running, and it it will push a little cloud under full throttle acceleration.

but no oil aside from that which I can tell...

are those fuel or oil deposits on the plugs, is my question...

i've had 2 different carbs on the motor with very similiar plug results... both times using platinum plugs (the ones that crossreference to the R45s)

if it is oil, then i'll replace the teflon seals with the streetable ones.
if anyone has a part number for me
thanks

aaron

Plasticman

That is what I was afraid of! Those guys are use to building race motors, not street.

All your signs says valve guide oil is the cause of the deposits, and I agree that hotter plugs are needed to burn off the plug deposits. But, the root problem needs to be corrected. Also, those intake valves will have built up deposits on the back (port) side (and judging from what is seen on your 200 mile plugs, it will be thick).

As for the correct seals, depends on what diameter the guide bosses were cut down to. Here is a link to K-Line valve stem seals, but you need a paper catalog to know the sizes (website sucks).

http://www.klineind.com/cgi-bin/klin...ategory_id=125

Example: 11/32" stem seals come in .500" boss diameter (p/n KL1402 for 16 seals), .530" boss dia. (p/n KL1405 for 16 seals), and .562" boss diameter (p/n KL1407 for 16 seals). Note again that you really only need the seals on the intakes. Some put the seals on the exhaust, but even Chevy only used them on the intakes (example my 87 Vette L98 engine), as long as the shields and "O" rings are also used.

Your local parts store should carry either Fel-Pro or Perfect Circle brand. But you need the size first. I have used all 3 brands with good results on many heads, with no "come backs". Mostly I use the K-lines, since I buy them in bulk.

My other question is what are the red/orange particles on the plug threads? I certainly looks like either rust or perhaps Chevy orange paint? Are you seeing this on all the plugs, or just this one?

Plasticman

magicv8

IMO it is oil.

My 350 has been all over the USA in the last 5 years and does not push even a tad of oil on startup or at triple digit speeds. (You are answering your own question.)

builder

Aaronz28,

I can't believe that you have that much deposit on those plugs after 200 miles. To me they don't look like anything "clean" and "correct color". You have a problem somewhere. After 200 miles, your plugs should have no buildup and just some nice tan and ash colors.

Keep in mind that when you take the plug out, you actually have a part of the combustion chamber in your hands. Those deposits are on your pistons, heads and valves.

If the deosits were mainly on one side of the plug, I would check the position of the plug installed, and note its position compared to the valve. That would tell me which valve was the problem.

Your plug has deposits every where. I would say it is probably oil getting past the rings, and possibly some coolant mixed in.

Do all the plugs look like that, or is it only one?

If you can get some sort of lighted scope that wil allow you to look into the cylinder via the spark plug hole, look for areas on the top of the piston that are clean or "washed" near the outer edges. That will tell you that oil is getting by the rings and that they will need some attention.

From what I can tell, you have a much bigger problem than a heat range of plug. I'd look into the engine further. Swapping out plugs isn't going to fix the real problem.

MACDARREN makes sense. I never thought I knew more than the manufacturer of the valve seal to the point I would change the configuration or use of the seal. I don't think the head builder did you any favors.

But, these are just my opinions.

Formula Outlaw

Man that plug looks downright nasty...

CJS

My bone stock 283 powerpack plugs looked about 40% as bad as yours do. They were only screwed in just past finger tight. I changed plugs, gave it a full tune up, drive it like I stole it, and the new plugs look perfect.

MikeM

Gee! I thought this was the question.
"is there any concern with using platinum plugs in an old carbureted motor?"


I didn't know you wanted to know why your plugs looked like they came out of a landfill.

macdarren

PlasticMan,

I don't know I think we pretty much agree and were saying the same things....the newer PC seals made of whatever it is are what I have in my engine. The older umbrella seal also worked well but is a problem is you run dual valve springs.

I think the original poster has a valve seal or guide issue. I don't think platinum plugs are going to help, nor do I think there is a problem running them in an older car. My understanding is the platinum plug will mostly erode slower and might maybe heat up faster to help reduce normal deposits, however that plug is a long way from normal in a low milage street motor...IMHO.

Darren

Plasticman

Darren,

I agree completely. This is not a plug issue. Some plugs (hotter) may hide the issue, but it won't get any better.

He has a serious guide/seal oiling issue that will not improve. The airflow through the intake tract will decrease as the carbon starts caking on the backside of the intake valve.

Plasticman