[jlm69]

I have a question regarding RAV heads. I tried looking up info on plugs but had no luck.

I needed to buy spark plugs for my 303 heads, so I figured that the R45S AC Delco plugs for 1969 / 1970 Ram Air heads would work, but they won't screw into the heads, so I obviously bought the wrong ones.

What should these heads be using?
Do they use the same as the 400 version of the V head?

[tom s]

I think they take a longer plug because of the small chambers.Ben a couple years since I built one with the 303s.Tom

[Kenth]

MPC REV.11-1-69 says R43N for the 303 cui. engine.

[25stevem]

The threads are all the same, so yes you need a plug with longer threads .
The most important question however is what heat range do you need.
A r45 series plug would be too hot for the power level that 303 will make .
As posted above a 43 sounds right for flat out full throttle, but if you might be concerned with loading up while your doing basic tuning then I might go for a 44.

[JSuchma]

RAV 400 is part number 5612072 R44S, 303 took part number 5612425 R43N.

[Jim Robertson]

I am using the NGK R5671-8 (extended tip) in a 400 head street setup. We are dynoing this coming weekend. So we will know if these will perform or not. These use the crush washer and incorporate a “normal” 13/16 hex head.

[jlm69]

Ok...

So first I tried a R45S and it didn't go in far enough.
I went to PEP Boys and asked for R43N plugs & picked-up R43S plugs and same thing. They were too short. When the counter person tried looking up R43N plugs the only thing that came up were R43S plugs which listed them for RAM AIR Pontiacs so I thought ok, I'll give it a shot, but as I said no good.

I tried looking up the R43N plugs thru Summit Racing, it comes up as "2,000+ Results Found For "rain", WTF!!

I changed it to R43 and it comes up with "ACDelco Conventional Resistor Spark Plugs 19362248" which still seems to be too short with a .372 spark plug reach.

Attached is a photo of a R43S and R45S side by side. The dimensions for the R43S plug reach comes out about .060" shorter so it obviously didn't even reach the chamber.

On the actual head, the dimension from the threaded area to the first step where the plug's washer sits is about .7145". So, both of these are way to short.

I'm going around in circles at this point!!!!!

[jlm69]

Where can I pick up the R43N plugs if I can't even find them thru Summit Racing???

Doe the R43N plug have a longer reach (threaded end ) to it??

[jlm69]

Plug photos

[jlm69]

Just looking at Amazon...

Would this be better for me to get?
It has a longer reach.....ACDelco GM Original Equipment R43XLS Conventional Spark Plug

[tom s]

here you go
https://www.ebay.com/itm/13441658480...yABEgLUF_D_BwE

[tom s]

Did you buy them?Tom

[jlm69]

Yes I did!!!!!

[jlm69]

Thank You Tom!!

Thanks Everyone for your comments.

Lou

[tom s]

Saw they had sold,figured

[chrisp]

https://www.ebay.com/itm/35431951189...-53481-19255-0
Could have saved some $$$$$$$$
Others look used

[johnta1]

I think R43XLS is the replacement plug for the R43N.

These are NGK equivalents for 43N / R43N:

AC NGK part# NGK stock#
43N B7ES 1111

44N B6ES 7432

R43N BR7ES 5122

R44N BR6ES 4922

[Jim Robertson]

Just looked at the plugs during the dyno session and the these are R5670-8. Sorry for the confusion. These plugs performed great.