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What are the practical RPM limits of a basicly stock 318 or 360? Any real weaknesses in the short block?

How big of a cam can you stick in one without spending $$$$?



RPM limits of a stock small block are in the 5,000 range, depending on the condition of the motor. The biggest concern with the Mopar small blocks are timing chain issues with a motor in the 125,000-150,000 mile range. The amount of care the motor has seen is another consideration with a high mileage motor. 318s are tough, 360s a little bit weaker in the crankshaft. Either will out live most GM smallblocks.

Pre Magnium small blocks: The 318s have small original 2bbl carbs with restrictive single exhaust system. They also have small intake ports and tend to run out of air around 5,000 rpm, most stock 318s couldn't rev high enough to hurt themselves. A 4bbl carb and dual exhaust through even the stock exhaust manifolds and a good double roller timing chain & gears can really wake up a 318. If your planning on turning some rpms, or do some serious racing, you will want to step up to the 340/360 heads or to the newer maginum heads. A 340 cam really wakes up a 318, but with springs and clearance checking, you can do up to the mid 450s lift without much fuss. Factory Mopar small blocks have a decent factory balance, once you get past the intake and exhaust restrictions, the valve gear and oil capacity will be your rpm limiting factors. Past 5500-6000 is really pushing the stock rod bolts and lubrication system, imho.

A pre-maginum 360 is a different critter. Most are low compression, but all have the bigger port heads, and come with either a large 2bbl or a 4bbl carb from the factory. 360s have a cast crankshaft, not an issue with breaking, but seem to wear more then the 318 cranks. In factory trim, a 360 can turn enough rpms to cause damage. Cam choice is about the same as a 318, but the bigger port heads and more cubic inches provides pretty stout performance pretty cheaply. Both weigh about 50lbs more then a sbc, but have angle plug heads from the factory.

I perfer a 727 over the 904. Back in the day, I would heavily abuse my cars. I could break built up 904s, but really had to give extra effort to break 727s. Gene