Which Spark Plug for GT40?

[ricofrancois]

Hi guys

I have a 1997 Nautique 196 with GT40 EFI 5.8. The owner manual mentions the Motorcraft AWSM22 / Autolite 763. They've been discontinued and the replacement is according to Autolite the 764.

I just want to make sure I get the right one. The gap should be 045, is this the case for all 764 or do they come with different gap sizes?

Thanks

Eric

[74green]

I used the 764s at .045 in my 5.8 GT40

[ricofrancois]

Thanks, I will get the Autolite 764.

[h2oski]

The Ford GT-40 is a 5.7 not 5.8... Chevy makes a 5.8 though... I'm just say'in

SkiDim GT-40 spark plugs

-Scott

[seth]

Thats weird. Im pretty sure my Gt-40 says 5.8 right on it, and it sure feels like a 5.8 rather than a 5.7.

[ricofrancois]

Yes I am pretty sure mine says 5.8 and the 1997 owner manual GT40 specifications reads 351/5.8 310BHP

[ricofrancois]

It looks like the 5.7 is on the 350 block not 351

[DanielC]

The Ford is the 5.8. The Chevy is the 5.7

Ford bore and stroke, 4.00 X 3.500

GM bore and stroke 4.000" x 3.48

Sorry, the Ford has more cubic inches. It is bigger.

[jasper]

350 in^3 = 5.73547 L

351 in^3 = 5.75185 L

GT-40 = Ford = 351

[NigelC]

I believe the PCM part number is RP030007 for a set of 8

[h2oski]

Dang, I knew it.... I should have sat on my hands.... I tried to help and got it backwards.... at least we know now....

[gtxragtop]

From my research I've found the following:
I have the original factory plugs on my 1996 GT40. They are AWSF-22C. According to the autolite chart, they map to 103.
The 764s which map to AWSF-32C are a hotter plug and belong in the non GT40 engine which I see in my PCM manual. The
PCM manual states that AWSF-22C maps to Autolite 763 not 764. The 763 is no longer produced. So I plan to use 103C which should be the correct heat range for this engine to prevent detonation. The AWSF-22C in there now are burning very cleanly.

http://www.autolite.com/sites/defaul...ref_0311_0.pdf

[gtxragtop]

103 is the standard copper core plug
AP103 is a single platinum plug
APP103 is a double platinum plug

I see that a number of Marine parts vendors are selling the 764 as the replacement for the GT40 engine. I suspect that they lumped the GT40 into the PCM 5.8
lower horsepower category by mistake.

[east tx skier]

I have used xopper AL764 in two different high output 351s and have never had a bit of trouble. I think the lower horsepower 351s take an AL24, but memory may have faded. Let us know how the 103 world for you.

[gtxragtop]

I have used xopper AL764 in two different high output 351s and have never had a bit of trouble. I think the lower horsepower 351s take an AL24, but memory may have faded. Let us know how the 103 world for you.

764 is one range hotter plug. With a hotter plug there is a possibility of pre-ignition (pinging) that can take place. Since it is one range hotter, probably not
an issue. I'll let you know about the 103. I really do not expect much difference from a 764. The AWSF-22C in the engine are the original plugs with 667 hours on
them and they still look new. Hard to believe they are original but given that they have a trace of black engine paint on them as if they were sprayed when the engine was sprayed at the factory leads me to believe they are original. Anyway they have the perfect very light tan color on the insulator tip so why change when they work so well.