This exhaust manifold kit is for mounting stock manifolds to the heads on your Buick 401-425 Nailhead engine. These bolts are grade 8 stainless steel and are 1 1/4 inches long. These are ARP grade 8 stainless bolts and come with a polished finish. We also include extra thick flat washers. They are for the engines that use all 3/8 bolts in the heads. Please verify the fit to your engine before ordering. These bolts are much stronger than the stock bolts and are rated at 170,000 psi.
If you have the Stock manifolds that have the 4 longer bolts at the Rear of the manifolds, let us know at the time of payment and we’ll send the four longer bolts that are required.