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LSx FAQ

What spark plug should I use with my AFR cylinder heads?

The following list of spark plugs are suggestions for getting your engine up and running. In order to determine the correct heat range for your application, we recommend pulling your plugs and inspecting them a few times under typical operating conditions; commonly known as reading the plug. Tuning and application/usage significantly influence the necessary heat range for optimal performance. Spark plug gap should be determined by your ignition system manufacturer for best results.

- NGK #TR55 for normally aspirated, pump gas engines with a compression ratio between 10:1 and 11:1

- NGK #TR6 for engines with high compression(greater than 11:1) or running power-adders using Race Gas

What should I torque my bolts to?

We recommend using ARP head bolts or studs versus the factory (torque-to-yield) GM bolts. Make sure to follow the recommended torque specifications supplied with your fasteners.

Are there any other special parts that I need with my MONGOOSE cylinder heads?

With the exception of the perimeter valve covers on 97-98 motors, your AFR cylinder head will accept all factory GM components. 97-98 vehicles you must use Center-Bolt valve covers versus the factory covers.

Can I use AFR large-bore cylinder heads on my small-bore block?

Yes, you can run our cylinder heads on your small-bore(3.898"-3.905") block. In order to do so, you must use a head gasket with a 4.125" or larger bore; such as the Cometic #C5318-040 or the Felpro #1041 head gaskets.

What head gaskets do you recommend using with the MONGOOSE cylinder heads?

- For small bore(3.898" to 3.905") blocks with our #1510 and #1660 cylinder heads, we

recommend using the Cometic #H1294040S head gasket

- For blocks with a 4.00" or larger bore, we recommend using the Cometic C5318-040 head

gasket

Can I angle mill my MONGOOSE LSX cylinder heads?

Unfortunately these cylinder heads can only be flat milled, because of fitment issues that would arise with the intake manifold.