7.4L & 454 Magnum.
02-07-2005, 07:16 PM
#11
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Re: 7.4L & 454 Magnum.
Originally Posted by Slick02
7.4 has a 2 bolt main, and as far as the rest,,,like I said, thats my opinion, but if the 7.4 was that strong with a 2 bolt main and cast crank,,,why did Mercruiser go to a 4 bolt main and steel crank in the 454 magnum,,,its not like they wouldnt cut a corner if they thought they could get by, prime example was the use of the alpha drive behind a big block in 1987, they found out real quick that that wasn't the ticket.
I don't even think you can tell from the Merc serial number..
All 502's are 4 bolt.
All Gen 5 and Gen 6 are 4 bolt.
As far as WHY Merc "went" to a steel crank, etc. It's simple... The base crate motor that "was" the 330/7.4 has cast parts. The base crate motor with the rect port heads had steel crank and forged pistons.
Merc didn't want to incur any additional expense in "monkeying around" with the parts combo, as if would have COST them money to mix and match any more than they did.
02-07-2005, 08:09 PM
#13
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Re: 7.4L & 454 Magnum.
OK, I stand corrected. I thought Mark IV's after about 1988 were all 4-bolt. My 1989 was and I though they would be consistant with that. Again, there are a lot of early 2 bolt main big blocks making big power with no apparent problems.
02-07-2005, 08:18 PM
#14
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Re: 7.4L & 454 Magnum.
Originally Posted by Whiteknuckle
OK, I stand corrected. I thought Mark IV's after about 1988 were all 4-bolt. My 1989 was and I though they would be consistant with that. Again, there are a lot of early 2 bolt main big blocks making big power with no apparent problems.
Mine was an '89 with a 2 bolt...
