jonathan49

Ok, this is going to sound stupid but I'm a total beginner in American petrol engine power. (I've just bought a race boat in the UK with Chief 502s by way of explanation, and I previously used diesels). Here goes:
American V8s seem to be mainly referred to by the cubic inch capacity; 502/540/572 etc.
Does this denote different manufacturers? Is one size a Chevrolet, another a GMC etc?
Do they all have the same mounting points/brackets etc?
Can you pull out a 502 and just drop in a 540?
Will all engines fit all drives? (I have 502s at 575 hp driving via Mercury ssm3a(uprated). My engines are dead so if I buy a pair of 540s will they drop in the same hole?
I'm sure I'll have more questions but thanks in advance for answers to my initial 'global overview' questions above.

Black Baja

iTrader: (2)

For the most part yes. There are some differences though. There are different deck heights (block) short or tall. The only thing this will affect is exhaust through the transom and .500" difference in intake manifold. There are also differences in exhaust port heights on cylinder heads. Aftermarket heads use .500" to .600" raised ports which will also affect exhaust through transom. There are different generations of blocks... Mark iv, gen 5 and gen6. Differences in generations are rear main seal which affects oil pans. Timing covers and block mounted fuel pump bosses or not. Mark iv has fuel pump boss newer Gen 5/ 6 don't. Also older motors mark iv used 3/8" bolts to bolt accessories to front of motor newer gen5/6 use 7/16" bolts. As far as the azz end of the blocks to bolt transmission/ belhousing all is the same. Other things you need to watch for is if the motor is internal or external balance. External balance 502ci uses a weighted flywheel and harmonic balancer these parts CANNOT be bolted on an internal balance 540. The motor will shake itself apart...

jonathan49

Many thanks BB, that's very helpful. So, the only difference I may have to deal with if I replace with a different size engine is exhaust through transom height, the actual join to the drive will be the same.. All the other differences are specific to the motor rather than the installation.
Are the mounting points/brackets different or do they all vary too?
As you can guess I'll just be buying replacement motors rather than getting involved in any rebuild so I'm mainly interested in the 'bolt in' process.
Many thanks

Black Baja

iTrader: (2)

Mounting points are all the same. The only difference is the size of the bolts.