Rollered or flat tappets?

[mmayea]

I am replacing my engine and would like to know what the difference is between rollered and flat tappets. I have the option of going either way but I not sure what I should do. Any sugestions would help.

 

[braindead0]

Re: Rollered or flat tappets?

With the same cam profile? Roller tappets (generally) allow for more agressive cams to be used.. I suspect in this application there's no reason to spend the extra $. Of course, if it's just a few extra $, in theory it means less wear and tear on your cam.. but I've never seen one wore out..

 

[Skinsk]

Re: Rollered or flat tappets?

Most marine engines use roller lifters.. Due to the extra strain that a marine engine suffers under it's constant heavy loads.<br /><br />Scott..

 

[MrBill]

Re: Rollered or flat tappets?

Just as the name infers...roller tappets have a roller on the bottom, that rolls over the cam lobes. Flat tappets are...as you would expect, solid and flat on the bottom. Cams are different for each and must be matched to the appropriate type of lifter (tappet).

 

[SlowlySinking]

Re: Rollered or flat tappets?

mmayea, roller tappets have less friction than flat tappets, this equates to more HP at the prop and less wasted to friction. Unless the price difference is outrageous go with the rollers.

 

[loadnet]

Re: Rollered or flat tappets?

I agree to go with the rollers.. <br /><br />You'll pick a wince more HP and the engine will run much quieter....<br /><br />PB

 

[flashback]

Re: Rollered or flat tappets?

Skinsk I respectfully disagree, most marine engines I have seen have flat tappets unless it is built for racing..............

 

[rodbolt]

Re: Rollered or flat tappets?

Hello<br /> Most GM high performance 5.7 L are roller tappet. most marine engines are still flat tappet. I expect that as more and more 5.7's are built we will see more roller lifter cams. its funny but I am intalling a pair of 340 hp MPI marine power 5.7L in a boat and the heads and block have Hecen en Mexico in the castings<br />I suspect the 3.0 will be made in china soon.<br /> Having an aggressive cam makes water reversion a big big problem. I have seen to many hot rod auto wrenches trying to put aggressive cams in boats. most with disaterous results. my advice is to make sure the engine, whatever you get, is a marine power package not a close copy.<br /> good luck and keep posting

 

[Skinsk]

Re: Rollered or flat tappets?

Guess I'll have to re check my mercury intro class again... <br /><br />Scott..

 

[conimicut1]

Re: Rollered or flat tappets?

Rollers are now used in most new GM v8s. They allow a higher lift and more power. But you have to use a roller cam with roller lifters. Some high performance roller cams require a special distributor gear, make sure about this if you buy one. I suggest that if you deceide to get a roller combo, get a marine cam, that will prevent the water reversion issue mentioned. There is an overlap with technology for car and boat motors, but it is not identical, especially cams. I'd also suggest getting better heads, the heads and cam are a team. A marine vortec v8 should have rollers and much better heads and alot more HP, get a marine engine package if your engine is toast. Then consider fuel injection, more HP and better fuel economy but its pricey! All of these ideas are best used in a newer boat that needs a motor, not an older one that is not worth as much. Don't spend alot of money on a boat that will not be worth it.<br /><br />Check this out, I'm sure there are other suppliers:<br /><br /> http://www.ebasicpower.com/engines/base/

 

[flashback]

Re: Rollered or flat tappets?

skinsk, I may have been too quick on the trigger. from what i understand, most of the new boats 2000 and up that have the magnum 350 do have roller tappets....I guess I was thinking older as I don't have 25 thou to put into a new boat. most of my experience is with engines 15 years old. you know, the 2 thou boats..