Five years ago, Davin with Hagerty built an iconic orange 396 cubic inch Big Block Chevy for Hagerty’s employee restored 1969 Camaro SS396. Since the car was used for Hagerty events all over the country, there have been some hard miles put on the car and it was not quite performing as a Big Block should.
The 396 was consuming oil and fouling spark plugs, and through a leak down test it was discovered that the piston rings were not doing their job. All of this bad luck for the Big Block prompted a new Hagerty project that was cataloged in a series of videos. So, if you’re a BBC fan you are in luck.
Previous videos showed everything from diagnostic testing to the engine removal process, machining and reassembly of the block. However, it was update number 11 that really caught our attention. As Davin reassembles the heads for the 396, he explains the basics of setting up spring height and checking for valve clearances.
Because of tolerances between the valve seats and the keeper land it is imperative to measure thoroughly to ensure the valve springs are set to the right height and are all set the same. While these heads should be fairly consistent because all of the valve seats were changed out, there are several ways to deal with inconsistencies.
Too much spring pocket is easily dealt with using shims, but not having enough spring pocket depth is a bit more complicated. Davin explains the different options from further machining the heads to using offset retainers to take care of the issue. After the heads are assembled the next step would be to make sure there is enough piston to valve clearance. Using a little bit of clay stuck to the top of the pistons is a simple way to test this before finally mounting the heads. With a target goal 425 HP, I for one cannot wait to see how this Big Block Chevy turns out.
Elizabeth is hardcore horsepower enthusiast with unmatched intensity for making things faster and louder. She wakes up for power and performance and only sleeps to charge up for the next project that’s heading to the track. From autocross to drag racing, Elizabeth is there with you, so stay tuned for her unique perspective on horsepower news, builds, tech info, and installs — with her, it’ll never be boring!