Stroker Questions

I have a 360 that I am rebuilding and stroking to a 408 inches. This will be a street engine that I would like to be very reliable and streetable, with a kick. I'm hoping to get around 450 horsepower, while still running pump gas. Since I live in Denver, I know the altitude will have an effect on the power among other things. I would like advice on what crankshaft, rods, pistons, cam, and etc that I should use. I'm already planning to use tti headers/exhaust, an Edelbrock Air Gap intake, and a Holley Street Avenger 770 carburetor. Everything else is up for grabs. One other thing is I'm not sure how to tell what my torque converter is in my 727 transmission. I can read some numbers off the ring gear but if you have any idea how to tell this would help with the cam.

Dan Frazzini
Via moparmuscle.com

Dan, with your goals, there are many different directions you can go. Starting at the bottom end, a cast crankshaft is a reliable alternative at your power level, as are stock rods and even hypereutectic pistons. These budget parts will come together as a nice mild street engine. If a little more cost is acceptable, I would go with a forged crankshaft, Scat I-beam rods, and moderately priced forged pistons like the offerings from Probe. In either case, go with a good moly ring, like that from Speedpro. I would also go with a compression ratio of 10:1 with iron heads, and another half point if you go with aluminum.

Your intake and carburetor choices are good pieces, and will work well on the stroker. As far as the cam and heads, the better the heads, the milder you can go with cam duration for a given power level. This will improve drivability and fuel economy on the street. If the budget allows, a set of Edelbrock heads are a good starting point, and can meet your power goal in out of the box form. To get more from the heads, some porting helps these heads significantly. With the Edelbrock heads and the rest of the combination as described, you can make 450 horsepower with a cam as small as Comp's XE268. If you want something with a little more bite, look at some of the grinds from Hughes Engines. These will deliver more power because of the faster acting lobes delivering more lift for a given duration level.

As for the torque converter, assuming it is a factory style unit, you can first identify it as either an 11-3/4 or 10-3/4-inch unit, usually referred to as 11 or 12-inch converters, respectively. Most likely it is the 11-inch piece, as these were more common in later small-block 727 transmissions. These came in high and low-stall versions, but which one yours is cannot be easily identified. You can do a stall test by power braking the car, and if the stall is in the 2,500-2,900 rpm range, it is the high stall, and if it is closer to 1,900-2,200 rpm, it is the low stall. The factory high stall 11-inch converter was just about the perfect street torque converter as supplied by Chrysler.


Low-Buck Solid

I am building a hot 318 for my 1970 Valiant. I like the idea of being an underdog, and I am serious about building the 318. I have a set of flat-top forged pistons, and the block is .040-inch over-bored. I have a stock, forged crankshaft, and a set of heavier rods. I know that I am going to need some rpm to pull power out of this small engine, and have the heads to do it. My heads are ported MP aluminum heads, not the Edelbrock style heads. These are fully ported, and flow in the 270 cfm range.

My question is about the cam. I want to use a solid-lifter cam, and I am looking to spin the engine reliably to 7,000 rpm. I have already selected a Competition Cams MM Series, with 243/247 degrees duration. I have a complete early 273, which is where my forged crankshaft came from. This was a solid lifter four-barrel engine, and I was thinking I could source the entire valve train for the 318 from this engine. Are these factory parts going to get the job done in my 318?

Bill Samuta
Via moparmuscle.com

Bill, in an application such as you are describing, I would go with an aftermarket valve train. Those 273 parts worked with a cam that was very mild in comparison to the grind you are using, and the 273 had very low spring loads as compared to the springs you will need for 7,000 rpm with that fast rate solid cam. The pushrods will not be up to the job, and they will fail. The stock rockers tend to gall on the shafts with high spring loads. You can make them work by using good hardened shafts, and minimally honing to increase the clearance, or better still, having the rockers bushed. The oiling can be improved with banana grooves at the oil holes supplying each rocker. This will get the rockers to live, but you may also consider using a positive adjuster rather than the interference thread adjusters of the originals. At the end of the day, a roller tipped rocker will be a far better choice, especially with the high lift of your cam. The plain tip of the stock rocker will generate far more side loading with the 273 rockers, and accelerate the valve guide wear.