Re: Reversion what is the impact?
 

One big one....Exhaust manifolds :cool:
500EFI and 525EFI have CMIs vs the stock 496 manifolds which will eliminate reversion in that cam range.

Re: Reversion what is the impact?
 

i am running a comp cams xm 262 cam,at oo6, int opens at 21,closes at 61, exh opens at 68, closes at 20, lift is 505/515, total timing is 34 degrees, also using a performer intake, stainless marine exhaust, harland sharp roller rockers,ign module is a tbolt 5,idle is 650 in gear-maybe should i raise the idle speed??

Re: Reversion what is the impact?
 

Simply put in an earth shattering, scientific equasion

Reversion + time + more reversion + time = DESTRUCTION

Eventually will have corroded valve stems that break,
or a whole host of other problems of varying degrees.

Avoid this plague , use the right marine cam, don't even trust the cam manufacturer. Have it put on a cam doctor.
Install shutter's in the exhaust. Stainless marine makes a pair for $60. Very cheap insurance.
I had custom copper elbows with about 15" rise made up for a 21' boat with big block that sucked water and recked 3 motors.
Exhaust has to be adequate for motor. especially where water mixes and exits water jacket.
On my 24 Formula with the silent choice , I shut the through hull exhaust off when slowing down to make sure no backwash happens. BBB

Re: Reversion what is the impact?
 

I will post pictures of my Merc 330 I just pulled this weekend. When we drained it, the first 16-20oz of fluid from the oil pan was water.... the corrosion on the engine was extreme.

Re: Reversion what is the impact?
 

How do "shutter's in the exhaust" work to prevent reversion?

What is a " cam doctor"?

Re: Reversion what is the impact?
 

Ray,

Any comment on this cam with stock exhaust for reversion potential. Any ptential fixes to reduce reversion if it is a problem with this paticular cam.

Bill

Re: Reversion what is the impact?
 

An old Indian trick is to use Rhoades Lifters. I am running a crane 100072 (228@050, 112LSA) and I have little if any lope at idle. I know without the Rhoades lifters that cam would have a lopey idle. The 'lopey idle' is what causes reversion.

Re: Reversion what is the impact?
 

what about the comp cams marine cam i have listed above-would it cause reversion??? comp says no

Re: Reversion what is the impact?
 

What is it about those lifters that has the effect that you describe?

Re: Reversion what is the impact?
 

They 'bleed down' at lower RPM levels, effectively making the duration and lift of the cam smaller. They act like normal hydraulics around 3500 RPM. They claim the same feature that makes them do this also helps them from pumping up at higher RPM's. I don't know about that, but we typically don't see that RPM on our boats anyhow.

They are popular in certain stock car racing classes that require a certain amount of vacuum at RPM. They allow the racers to run larger cams than they would otherwise.

This is my first expereince with them, but I know some car guys that swear by them.

http://www.rhoadslifters.com/default.html

They are also available thru Jegs, Summit, and others.