1971 LS-6 spark plugs

[Jack H.]

Interesting....

I followed the thread below and wondered what the 'General' had to say on the subject, so I pulled my factory original '71 owner manual out. It calls for R44TS for all 350 Corvette engines and R43TS for all 454 Corvette engines (normal driving conditions). Hum, must be an error in the book, eh?

[Jack H.]

Interesting....

I followed the thread below and wondered what the 'General' had to say on the subject, so I pulled my factory original '71 owner manual out. It calls for R44TS for all 350 Corvette engines and R43TS for all 454 Corvette engines (normal driving conditions). Hum, must be an error in the book, eh?

[Joe L.]

Re: 1971 LS-6 spark plugs

clem-----

Yes, I agree. ALL big block Chevrolet aluminum heads used the gasketed spark plugs; NONE were tapered seat type. This includes SERVICE replacement aluminum heads and, even, currently available GM aluminum heads for big blocks.

Part of what generates the confusion here is the fact that all RPO LS-6 engines were not the same. The RPO LS-6 engine used in 1970 Chevelles (and originally scheduled for use in 1971 Chevelles although no PRODUCTION examples were ever released for sale) used cast iron cylinder heads. These heads, for both the 1970 and 1971 model year, used tapered seat spark plugs. The Corvette LS-6 used aluminum heads and was equipped with the gasketed spark plugs.

GMSPO NEVER catalogued a spark plug for the 1971 Corvette LS-6 application. In addition, the R-44TS is shown in many references, including GM references, as being the correct spark plug for 1971 Corvette LS-6. ALL of these references are incorrect, though.

So, what is the correct plug originally used for the 1971 Corvette LS-6 application? I expect that it was an R44XL or, possibly, an R43XL.

[Joe L.]

Re: 1971 LS-6 spark plugs

clem-----

Yes, I agree. ALL big block Chevrolet aluminum heads used the gasketed spark plugs; NONE were tapered seat type. This includes SERVICE replacement aluminum heads and, even, currently available GM aluminum heads for big blocks.

Part of what generates the confusion here is the fact that all RPO LS-6 engines were not the same. The RPO LS-6 engine used in 1970 Chevelles (and originally scheduled for use in 1971 Chevelles although no PRODUCTION examples were ever released for sale) used cast iron cylinder heads. These heads, for both the 1970 and 1971 model year, used tapered seat spark plugs. The Corvette LS-6 used aluminum heads and was equipped with the gasketed spark plugs.

GMSPO NEVER catalogued a spark plug for the 1971 Corvette LS-6 application. In addition, the R-44TS is shown in many references, including GM references, as being the correct spark plug for 1971 Corvette LS-6. ALL of these references are incorrect, though.

So, what is the correct plug originally used for the 1971 Corvette LS-6 application? I expect that it was an R44XL or, possibly, an R43XL.

[Patrick H.]

Re: 1971 LS-6 spark plugs

Is it the orange car?

Patrick

[Patrick H.]

Re: 1971 LS-6 spark plugs

Is it the orange car?

Patrick

[Terry M.]

Yes *NM*

[Terry M.]

Yes *NM*

[Warren F.]

Re: 1971 LS-6 spark plugs

Thanks, everyone for your input.

Joe, have found some R44XLS on ebay, thought I would bid on these, do you think I should not, because of the S designation?

[Warren F.]

Re: 1971 LS-6 spark plugs

Thanks, everyone for your input.

Joe, have found some R44XLS on ebay, thought I would bid on these, do you think I should not, because of the S designation?

[Joe L.]

Re: 1971 LS-6 spark plugs

Warren-----

I think that the R44XLS will work perfectly for your application. However, I don't think that they were what was originally used. I'm not sure that the XLS-suffix plugs even existed in 1971, but they're what I would use today.

[Joe L.]

Re: 1971 LS-6 spark plugs

Warren-----

I think that the R44XLS will work perfectly for your application. However, I don't think that they were what was originally used. I'm not sure that the XLS-suffix plugs even existed in 1971, but they're what I would use today.

[Warren F.]

LS-6 plug mystery

Thanks, Joe.

[Warren F.]

LS-6 plug mystery

Thanks, Joe.

[Joe L.]

Re: LS-6 plug mystery

Warren-----

By the way, both the R44XL, aka GM #5612092, and the R44XLS, aka GM #5613870, are still available from GM and Delco dealers. I would recommend using the XLS-style, extended tip plugs, though. Of course, I'm not a big fan of AC spark plugs. Personally, I'd use the Champion-equivalent plug RN14YC.