Too whacked from work to do anything on the car tonight so I did some reading - always a dangerous thing.

I've always replaced my plugs with the same as was in there. Sorta makes sense - if it works don't change it. But for lack of anything better to do I used an application at championsparkplugs.com that suggested that the 1.7 engine should be running an RN4C. The plugs in the car are RN9YC. Thats 5 notches hotter. Their discussion on heat ranges say emphatically that too hot can cause engine damage. They also say go colder if you do a mod to increase compression. I really don't know what the rebuilder did to my engine way back when he put on oversized p&c put he did say the compression will be a little higher.

So what's the collective wisdom - is the RN9 too hot? Is there a generally accepted 'best' plug?

Throw those POS chumpion fark plugs in the St. Lawrence!!!!

Besides the fact that they are a big steaming pile of dog they do NOT have rolled threads like Bosch or NGK do. They are very hard on the plug hole threads and will some day cause you all sorts of problems.

If it's stock get Bosch plugs...just the everyday supers..no platium crap, just the regular Bosch plugs

NGK
ND

Good plugs

Bosch, best but just my opinion.

Get a 7 Bosch heat range plug for a daily driver 914-4. Should be great. Stay away from plat plugs unless your engine is still FI and in good order. Carbs have a tendency to foul plat plugs.

WR7DC for a good standard plug
WR7DTC or W7DTC for a mucho better version of that plug.

Good post, but a bit wrong. You don't need resistor plugs, and the extended tip ("D") plugs are for the VW water cooled engines, not the air cooled models. Bosch W7CC is correct, as is NGK B6ES. Along with thwe bigger bore comes an increrase in compression. If there's a question of heat range, the next colder plug should work. In this case, Bosch W6CC or NGK B7ES, but they're too cold, IME. The Cap'n

This is the first I've heard of water cooled vs. air cooled plug choices.
I've always used W6DCs in my '75 1.8 (L-Jet) without issue.
What's the difference, Cap'n???

QUOTE (Marty Yeoman @ Nov 29 2005, 12:04 PM)

This is the first I've heard of water cooled vs. air cooled plug choices. I've always used W6DCs in my '75 1.8 (L-Jet) without issue. What's the difference, Cap'n???

Combustion chamber design is my guess .............. Earlier 911s don't use extended tip plugs, either, except for the MFI engines. The Cap'n

QUOTE (Marty Yeoman @ Nov 29 2005, 12:04 PM)

This is the first I've heard of water cooled vs. air cooled plug choices. I've always used W6DCs in my '75 1.8 (L-Jet) without issue. What's the difference, Cap'n???

Combustion chamber design is my guess .............. Earlier 911s don't use extended tip plugs, either, except for the MFI engines. The Cap'n

echo?

echo...


echo...

Thanks for the correction Oh Krusty one. I don't have the Bosch #'s down all that well. I shouldn't have posted them.

I think I do remember that Bosch heat ranges go up with numbers, so 6 is a cooler plug than an 8 while ND and NGK's are backwards. 8 is cooler than a 6. If I remember right.

Yup. PITA, ain't it? The Cap'n

QUOTE (Mark Henry @ Nov 29 2005, 03:22 AM)

Throw those POS chumpion fark plugs in the St. Lawrence!!!! Besides the fact that they are a big steaming pile of dog they do NOT have rolled threads like Bosch or NGK do. They are very hard on the plug hole threads and will some day cause you all sorts of problems. If it's stock get Bosch plugs...just the everyday supers..no platium crap, just the regular Bosch plugs

holy crap - didn't expect that sort of response. So Mark, how do you REALLY feel obout champion

Consider the bosch thing done.

I cringe every time I see or hear of them in an aircooled