What spark plugs? R43s

KJG · 02-29-2012, 10:44:35 PM

I have a 1970 Camaro with a 4 speed. It has a 1970 block and cast iron heads. It is a 383 stroker 10.73:1. It has a 1978 hei distributor. Currently running ac r43s spark plugs. Which plugs are best for this combo.

Thanks for any help.

ProStreet383 · 02-29-2012, 11:47:06 PM

43 is to cold. 45 is what I would use. We had the 43's on our 355 with a tunnel ram and after about 300 miles they started to foul out. Installed 45's and never had another problem.

night rider · 03-01-2012, 01:05:54 AM

With 10.73 compression I think 45's would be too hot. Really depends on your cam too though.

I had a 10.18:1 355 wioth a 218/230@.050" cam that was making 212 psi cyl pressure. R44 and R45 was too hot for this combo and needed R43's

If your heads are the older style that uses the gasket seat, 13/16" wrenching then you need R4-S... If your heas uses the 5/8" wrenching and taper seat plugs then you need the R4-TS plugs.

At your compression I recommed R43S or R43TS

KJG · 03-01-2012, 02:12:32 PM

It does have the older style heads. I might try Autolight's AP 85 spark plugs with a .035 gap. The heat range is compared to AC's R43s and R44s, might be just right.

hhott71 · 03-01-2012, 04:22:24 PM

Quote:

Originally Posted by KJG

I have a 1970 Camaro with a 4 speed. It has a 1970 block and cast iron heads. It is a 383 stroker 10.73:1. It has a 1978 hei distributor. Currently running ac r43s spark plugs. Which plugs are best for this combo.

Thanks for any help.

Stock on a 70 350/300hp 10.25:1 compression engine was AC R44
The R44 is a 13/16" hex gasketed plug.

Many liked to use R44S for the extended electrode.

The Z28 used the R43 sparkplug with it's 11:1 compression.
Many liked using the R43S

If you need a 5/8" taper seat plug, the R44T or R44TS will work.

SO, using a R43S plug on your 383 should be just fine.
Maybe 42's would be better if you race it.

Skip Fix · 03-01-2012, 06:49:08 PM

OReilley told me this past week R44S are unavailable now only R43S and R45S.

I have used the 85s in my high compression 383 and 10.5:1 RAIV 400 Pontiac.

KJG · 03-01-2012, 09:02:35 PM

The auto lights are made in china, so that's out. So, I tested the coil and it failed. I replaced it along with a fresh set of ac R43S gapped at .035 and fired up. But, now I wonder if the gap is OK at .035. I also think I have a short somewhere because the fuse blows at accessory hook up at the battery. Still looking for it. Anybody have this problem?

High Country Z · 03-01-2012, 09:30:06 PM

I thought the plug gap for an HEI was .045

KJG · 03-01-2012, 10:05:24 PM

Yes, hei is usually .045 gap. I was hoping the closer gap would burn cleaner. But, the coil was not up to par and that was most likely fouling the plugs. I should open them up to .O40 - .045 and see how it runs.

hhott71 · 03-02-2012, 09:31:16 AM

Quote:

Originally Posted by KJG

Yes, hei is usually .045 gap. I was hoping the closer gap would burn cleaner. But, the coil was not up to par and that was most likely fouling the plugs. I should open them up to .O40 - .045 and see how it runs.

You will not see any difference.

KJG · 03-02-2012, 11:23:33 AM

Do you recommend leave the gap at .035? What would be best for performance?

Thanks for the help