1984 --5.7 / 260HP camshaft ? REPLACE

[kinger952]

finding conflicting inquires about rear main seal -- 2 piece ? is there a difference in camshafts for rear main seal or is it the same cam 431-5943 i am in need of 1 i have twin engines in boat starboard is SHOT dished lifters 2 of them wanting to replace camshaft

 

[Bondo]

finding conflicting inquires about rear main seal -- 2 piece ? is there a difference in camshafts for rear main seal or is it the same cam 431-5943 i am in need of 1 i have twin engines in boat starboard is SHOT dished lifters 2 of them wanting to replace camshaft

Ayuh,.... Welcome Aboard,.... Without knowin' the vintage of the motors, that question is unanswerable,.....

 

[76SeaRay]

In all my years of dealing with GM 350's and 5.7L engines, the two piece rear main seal on the crankshaft (and one piece rear main seal) have had no interaction with the Cam shaft. GM transitioned from the two piece rear main seal to the one piece in 1986. Not sure when Mercruiser made the change. All that said, I am making the assumption you have a Mercruiser based upon GM, however, as Bondo points out more information is needed. For example, engine serial number?

Edit: I should point out that the block for two piece and for one piece are different engine castings so that could have impact on the camshaft. That is another reason that the specific engine year, make, model and serial number are important. Same as it would be for any car or truck engine.

 

[kinger952]

In all my years of dealing with GM 350's and 5.7L engines, the two piece rear main seal on the crankshaft (and one piece rear main seal) have had no interaction with the Cam shaft. GM transitioned from the two piece rear main seal to the one piece in 1986. Not sure when Mercruiser made the change. All that said, I am making the assumption you have a Mercruiser based upon GM, however, as Bondo points out more information is needed. For example, engine serial number?

Edit: I should point out that the block for two piece and for one piece are different engine castings so that could have impact on the camshaft. That is another reason that the specific engine year, make, model and serial number are important. Same as it would be for any car or truck engine.

i will crawl in bilge later and get ser # thank you / i have found a cam but not quite sure if it will match
Hydraulic Flat Tappet Camshaft & Lifters

• 1957-1985 Chevy 262-400
• Lift: .488"/.510"
• Adv. Duration: 292°/302°
• RPM Range: 3000-6500
• mercruiser 431-5943 is a .400/.410 lift

• GM part# 340284, Merc# 431-5943
  flat tappet- 200/212 duration, .400/.410 lift
  

 

[NHGuy]

Something is not right with that duration. Find a marine cam. Or one that effectively copies marine stuff. You'll need large-ish lobe separation and far less duration than that (at .050) and still a good bit less at .006. That looks like a high compression car cam by it's numbers.
To get some details I'd recommend looking up the cams in Comp cams webpage to get a feel for your needed specs. Also figure out what heads are on the engine so you don't put in too much lift. If you use more than the setup can handle you run into things like spring coil bind and rockers that can't do the needed angle.
It's all a system, if you find out first what you CAN do you won't stick yourself with unmatched pieces that could damage things.

 

[Scott06]

Something is not right with that duration. Find a marine cam. Or one that effectively copies marine stuff. You'll need large-ish lobe separation and far less duration than that (at .050) and still a good bit less at .006. That looks like a high compression car cam by it's numbers.
To get some details I'd recommend looking up the cams in Comp cams webpage to get a feel for your needed specs. Also figure out what heads are on the engine so you don't put in too much lift. If you use more than the setup can handle you run into things like spring coil bind and rockers that can't do the needed angle.
It's all a system, if you find out first what you CAN do you won't stick yourself with unmatched pieces that could damage things.

yeah rpm range of 3000-6500 is not a marine cam...

 

[Bondo]

i will crawl in bilge later and get ser # thank you / i have found a cam but not quite sure if it will match
Hydraulic Flat Tappet Camshaft & Lifters

• 1957-1985 Chevy 262-400
• Lift: .488"/.510"
• Adv. Duration: 292°/302°
• RPM Range: 3000-6500
• mercruiser 431-5943 is a .400/.410 lift

• GM part# 340284, Merc# 431-5943
  flat tappet- 200/212 duration, .400/.410 lift

Ayuh,.... You need a cam for the '57- '85 Chevy, but with an Rpm range of Idle to 4800- 5000 rpms,....
Usually sold as a Marine, or RV truck cam,....