Our combination 4G63 backpurge/heatsink blocks are the perfect tool for DIY exhaust manifold builders. The 2" thick aluminum block will absorb transferred heat and reduce head flange warpage drastically. The block is also drilled so that you can backpurge the inside of the manifold runners and collector all in one setup. This weld ready kit comes complete with hardware, quick release purge fittings, and 10' of 3/16" ID silicone hose with a quick release coupler. The coupler is unique in that as soon as you remove it from the plug it shuts off all air flow so there is no need to add an extra shutoff valve downstream of your purge line.