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Dave Nova
Dave Nova, Chevrolet Technician
Category: Chevy
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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Ive got a 366 Chevy that was supposed to be a 427 but when

Customer Question

I've got a 366 Chevy that was supposed to be a 427 but when I looked up the #'s on the block and heads it said its a 366. Are the bolt patterns for water pump, alternator mount, exhaust manifolds etc. the same as a 427? I already ordered a set of marine exhaust manifolds for a 427, will they fit? Can I put a 427 crank kit and a valve job to convert to a 427? Or can/should I just change cam and and valves? Its going in my boat and I was already going to have marine valves and cam installed. What is my best route to get the 400HP and good torque I'm looking to get. It may be possible for me to exchange the engine for a 502. But I would still be changing the valves and cam to a marine application. My bellhousing/flywheel bolted up fine to the 366 so I can use the transmission I already have. would the 502 bolt pattern be the same or is it different from the 366? Weighing my options on costs.
Submitted: 7 years ago.
Category: Chevy
Expert:  Dave Nova replied 7 years ago.
The 427 and 366 have the same bolt patterns for exhaust. The 366 and 427 use the same stroke, but the 427 has a much larger bore. The 366 is a tall deck truck engine and as such will use a different intake manifold. You would be better off getting a 427 if that is what you want. The heads and crankshaft will interchange with the 427.
Customer: replied 7 years ago.
What about the cam, are they interchangeable with a 427? Is the 502 exhaust/ bellhousing/ flywheel bolt pattern same as the 366/427. Thats really my only other option. They would exchange the 366 for a 502 since it wasn't a 427 like they said. but they don't have a 427 or a 454. I don't mind using the 366 as long as I can get the parts needed to go to marine application
Expert:  Dave Nova replied 7 years ago.

Camshafts are interchangeable between the 427 and 366. The 502 exhaust and transmission bellhousing bolt patterns are the same on the 502 engine. you can get the parts needed for the 366 to make it a marine application, but if it were me, I would opt for the larger engine. Its like having a built in power upgrade.