350 mag alpha vortec head swap
04-22-2011, 10:44 PM
#41
I took the boat out again today. I am very impressed with the improvements. I am pretty sure it is lean on the primaries. You can almost hear it around 3600 RPM's sounding like it is laying over. When the secondaries come in it is like you are flipping a switch. The carb comes stock with 67 primaries, I am going to order 68, 69, and 70 jets and see what it likes. Other than that, the difference is amazing in the boat. Can't wait to really have it dialed in and use it all summer.
10-27-2013, 08:32 AM
#42
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So could you post an update on the engine combo? You went with the XM-270-HR cam correct with the vortec heads?
What lifter and spring combo did you end up going with? 1.5 roller rockers?
Getting ready to redo my valve train and just wondering what the results are after a few summers on it.
Thanks, Brian
What lifter and spring combo did you end up going with? 1.5 roller rockers?
Getting ready to redo my valve train and just wondering what the results are after a few summers on it.
Thanks, Brian
10-20-2014, 10:12 AM
#43
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I am thinking of doing this Vortec upgrade on the 350's in my boat. Did you ever get a responce to your question above, and what did you end up getting for your motor?
10-20-2014, 10:31 AM
#44
I ended up using factory rockers, some cheap ****ty valve springs with shallow retainers so I didn't have to machine the heads. The boat ran the balls for 2 years plus, but this spring before I had the cover replaced water came in through the cover, hatch, and since I wasn't running the cover over the flame arrestor it ended up getting in the motor and hydrolocking it. I drained it out, changed the oil a half dozen times, and ran it out this year. It sounded fine and ran fine, but it was down 200 RPM's from years prior, so it was a bit wounded. I ended up pulling the motor this year and I will be going with a 350 mag mpi for next season as my daughter is old enough to use the boat and I want it turn key and simple. the only thing I never got right was the carb tuning. I jetted up the primaries and it would help with that area right before the secondaries opened, but it was really rich down low and lost torque. I never pursued it, but there are lessons I learned in this:
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
10-20-2014, 11:33 PM
#45
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I ended up using factory rockers, some cheap ****ty valve springs with shallow retainers so I didn't have to machine the heads. The boat ran the balls for 2 years plus, but this spring before I had the cover replaced water came in through the cover, hatch, and since I wasn't running the cover over the flame arrestor it ended up getting in the motor and hydrolocking it. I drained it out, changed the oil a half dozen times, and ran it out this year. It sounded fine and ran fine, but it was down 200 RPM's from years prior, so it was a bit wounded. I ended up pulling the motor this year and I will be going with a 350 mag mpi for next season as my daughter is old enough to use the boat and I want it turn key and simple. the only thing I never got right was the carb tuning. I jetted up the primaries and it would help with that area right before the secondaries opened, but it was really rich down low and lost torque. I never pursued it, but there are lessons I learned in this:
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
10-21-2014, 06:18 AM
#47
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I ended up using factory rockers, some cheap ****ty valve springs with shallow retainers so I didn't have to machine the heads. The boat ran the balls for 2 years plus, but this spring before I had the cover replaced water came in through the cover, hatch, and since I wasn't running the cover over the flame arrestor it ended up getting in the motor and hydrolocking it. I drained it out, changed the oil a half dozen times, and ran it out this year. It sounded fine and ran fine, but it was down 200 RPM's from years prior, so it was a bit wounded. I ended up pulling the motor this year and I will be going with a 350 mag mpi for next season as my daughter is old enough to use the boat and I want it turn key and simple. the only thing I never got right was the carb tuning. I jetted up the primaries and it would help with that area right before the secondaries opened, but it was really rich down low and lost torque. I never pursued it, but there are lessons I learned in this:
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
I should have degreed the cam. I didn't and I used the old timing chain set. I did this on the cheap and in the boat. I should have yanked the motor and done it right.
I should have run better springs and had the guides cut down. The springs never gave me an indication of an issue, but I always wondered about them.
I should have spent more time setting up the carb. I think I left a lot on the table.
Don't get me wrong, it was a HUGE improvement over the stock motor, but the areas where I cut corners were apparent, as I knew they would be.
03-26-2016, 03:51 PM
#50
I guess I will keep this thread going instead of starting a new one.
New motor is a 96 350 mag MPI, bone stock but refreshed with about 25 hours on it now. Last year it would spin the 19 pitch Rev 4 to 4400 RPM. This boat spends most of the time pulling tubers and water skiers so I wanted more holeshot out of it. Dropped to a 17 pitch Vensura and now the holeshot is much better, but now it is spinning 5300 RPM with a full tank of fuel. It is pulling 51 mph which actually exceeds my expectations, but I don't want to spit a rod either. I honestly thought the MEFI 2 would have a rev limiter, but apparently it does not. I verified the tach was accurate against my digital timing light last season, so I am pretty sure it is actually pulling the RPM.
How high do you guys who run stock bottom end 350's spin them? It's not like I am going to be holding this thing at WOT for miles, but will surely run it WOT at times and don't want to worry about having a shortblock yard sale in the bilge.
New motor is a 96 350 mag MPI, bone stock but refreshed with about 25 hours on it now. Last year it would spin the 19 pitch Rev 4 to 4400 RPM. This boat spends most of the time pulling tubers and water skiers so I wanted more holeshot out of it. Dropped to a 17 pitch Vensura and now the holeshot is much better, but now it is spinning 5300 RPM with a full tank of fuel. It is pulling 51 mph which actually exceeds my expectations, but I don't want to spit a rod either. I honestly thought the MEFI 2 would have a rev limiter, but apparently it does not. I verified the tach was accurate against my digital timing light last season, so I am pretty sure it is actually pulling the RPM.
How high do you guys who run stock bottom end 350's spin them? It's not like I am going to be holding this thing at WOT for miles, but will surely run it WOT at times and don't want to worry about having a shortblock yard sale in the bilge.
