Beautiful Snowflake
Q I'd like a little information on a pair of big-block heads I have. I've seen the Winters Snowflake stamp on aluminum intakes but never on heads. I know a little bit of the history of Winters, in that GM used them for some of its castings. These heads have the snowflake cast on the top of the exhaust ports on both outside ports. They are square-port heads, with a strange C-shaped exhaust port, casting number 14011077. These were on a 454 that was in a '68 Camaro that I bought several years ago and am now restoring. I went through the engine and put in a hydraulic roller, some forged flat-tops, and a few other things. Thought I'd try these heads and see how they worked. Not sure if they have hardened seats, though. Do you have any idea what I have here? Thanks.
Bob Moody
Via e-mail
A C-ports, D-ports, whatever you call them, these were the baddest GM big-block cylinder heads throughout the '70s! They were released as a performance part (never on a production engine) back in '69. The actual part number is 14011076 and it's referred to as a C-port. These heads are a refinement of the original big-block aluminum heads that were in production on hi-po 396s and 427s, which featured a round exhaust port. Through testing, GM found that raising the exhaust port floor and installing a vane in the center of the port prevented the formation of negative pressure in the exhaust runner and inhibited reverse flow. These revisions produced a 25 percent increase in exhaust flow over the original round-port aluminum heads. As produced, these heads featured 2.19/1.88-inch valves, a 114cc open chamber, and port volumes of 290 cc on the inlet and 103 cc on the exhaust. For street use, the C-ports are a perfect fit, and don't worry about the seats, because they're hardened.
The next revision to the aluminum big-block cylinder heads came in the early '80s when Chevrolet released the famed Bow Tie aluminum heads. These were not very street-friendly with their 0.600-inch raised exhaust port, which did not match up to many street headers. They were released to satisfy the Pro Stock drag racers campaigning GM big-blocks.
Pump You Up
Q I have a Chevy 350 four-bolt main block and a set of mid-'70s over-the-counter 492 casting heads with 2.02/1.60-inch valves, screw-in studs, and guideplates. The heads have what appears to be a factory port job or someone paid to have a nice job done. I'm planning to put this engine together for short trips to the video store and such. And considering that it will not be raced, I'm looking for a lot of low- to midrange torque and power. Compressionwise, I'm looking to get as close to 11:1 as possible so I can still run 91 from the pump. Can you recommend a cam that will give me the radical Pro Stock sound but produce the low- and midrange power I'm looking for? This engine will be going in a '70 four-speed Nova with 3.73:1 gears and a posi. Thanks.
Scott Rhyne
U.S. Navy
A This must be the Internet at work, as this is one of many letters I've gotten lately from readers thinking they can squeeze pump gas with high-compression ratios. That's just asking for pre-ignition and detonation problems. Yes, with electronic engine management and the benefits of EFI, you can step up the compression. However, with poor cylinder-to-cylinder fuel distribution from wet fuel carbureted inlet systems, and the retained heat of cast-iron heads, you must be very careful how much you squeeze the mixture before ignition.
Moving on to your camshaft, you could run a ton of overlap to bleed off cylinder pressure, allowing you to run more static compression. This would give you the Pro Stock idle quality you mention. The only problem with this route is that the engine wouldn't have any useable power until about 4,500 rpm. In my book that's not "low- to midrange power." Comp Cams has released a new line of very popular cams appropriately named the Thumpr series. These hydraulic flat tappets came from a design concept originally created for sports car endurance racing. The Comp team of engineers incorporated the early exhaust valve opening, the long exhaust duration, and a generous amount of intake and exhaust overlap to maximize your engine's nasty idling characteristics without negatively impacting streetability. Two camshafts are offered that would work for you based on how radical you wish to be. The conservative sort that I am, I would recommend going with the Thumpr cam, grind number 279THR7. This specs out at a healthy 227/241 degrees of duration at 0.050-inch tappet lift, 0.479/0.465-inch max lift, ground on a tight 107-degree separation angle. If you're feeling frisky you may chose to go with the Mutha Thumpr, grind number 287THR7. This big'n comes in at 235/249 at 0.050 inch, with 0.489/0.476-inch max lift, and also ground on 107 centers. Both of these camshafts will give you the "Boy Racer" exhaust note you're looking for. It will be quite loud and also have a nice, choppy idle quality.
We'd recommend sticking to a max static compression ratio of 10:1. If you were going with aluminum heads, we'd give you a little more room. If you were building a reverse flow cooling engine, like a late-model LT1 or LT4, we'd let you push the compression to the 11:1 range. Online, I've seen some posts recommend crazy numbers like 12.5:1 on pump gas on the street! This just isn't going to happen without a seriously knock-limited spark calibration. With the cast-iron heads, and for only street use, you'll be better off on the safe side.