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.

Re: Reversion what is the impact?
 

That is a very interesting approach to dealing with reversion. Do you know of anyone else that run these to control reversion? Thanks.

Re: Reversion what is the impact?
 

I don't know of any offhand, but I originally was thinking of using them for their variable valve timing effect, so I would have more low end grunt.

Then I saw this:

http://boatheaders.com/reversion.htm

Where Lightning headers recommends them to reduce reversion. I was sold at that time, although I would like the rough idle sound.

Note that the info in the webpages is outdated, the Rhoads Lifters are now available as rollers.

Re: Reversion what is the impact?
 

Unfortunately I do not see them listed for a GM 496. The 454/502 lifter will not work because of the different oil galley in the 496. I think Crane and Morel are the only sources for the 496 lifter other than GM and the Morel is only good for the stock lift.

Re: Reversion what is the impact?
 

aren't they noisy???

Re: Reversion what is the impact?
 

I heard that too but don't have first hand knowlege.

Re: Reversion what is the impact?
 

Somewhere between solid lifters and hydraulic lifters. They don't 'tick' like a bad hydraulic lifter, they have a little bit of the solid lifter sound, not quite as loud but it is there if you listen for it.

I am still sorting out some issues w/water in crankcase, but hopefully I 'll be running this weekend. I'll let you know how they work on the water.

Re: Reversion what is the impact?
 

I just talked to Rhodes. No they do not offer a V-max lifter for the 496 but.... they will convert your existing 496 lifters to the V-max for $95. There is some question as to if the current push rod length will still work.

I asked about noise and was told it was "not too bad" and goes away above 4000 rpm. Reportedly this lifter design has been around since the 60's.

Why has this reversion solution not taken the high performance NA marine applicatiopns by storm? What am I missing here?

Re: Reversion what is the impact?
 

I think a lot of people are skeptical that they do as advertised. I know I was until I heard 1st hand from people that have run them. From those who I know have actually run them, they all recommended them. The only negative comments I have heard are from those who haven't run them, all 2nd or 3rd hand kind of info. As I said, I can't comment on actual performance gains yet, and actually I won't be able to compare it to a baseline anyway, but I can tell you I don't have a lopey idle where I know with normal lifters I would.

Another thing may be people don't know or think about them helping reversion.

Re: Reversion what is the impact?
 

Did you run this cam and get reversion before installing the Rhoades lifters or did they go in when the cam went in? If you did get reversion without the Rhoades lifters how much did these lifters reduce reversion?

Re: Reversion what is the impact?
 

Ok Am I missing something here? You guys seem to be making a big project out of this problem. I am running a 502/502 cam with a very tight 110 lsa I took my Stainless Marine risers and lengthen the exhaust tube 12" and I have no problem I also did this with a set of Gils on a blower motor. Am I missing something here?

Re: Reversion what is the impact?
 

Rage,

The Rhodes Lifters are my original installation. I feel I was pushing the reversion limits with the cam I am using, and thought I would try them. I installed them for reversion, and for the chance of a few extra ft./lbs down low. Keep in mind this is a small block 388, so the cam #'s don't directly correlate to your 496.

Mike,

I think your thread has been hijacked :D

This reversion thing is always coming up around here, and I think the more knowledge we share the better.

Re: Reversion what is the impact?
 

.

$$$$ headers or $$$$ blower and no reversion versus a $95 lifter conversion and no reversion.

Re: Reversion what is the impact?
 

Knowledge is sure what I am here for.

Yes the bigger the engine CID the more sensitive to reversion is what I read.

When you brought up the Rhoades lifter option I started another thread just on that to beat the bushes for more people that have tried them and their results. Feel free to jump to "Rhoades lifters eliminate Reversion from hot cams". That aught to attract some views and hopefully good feed back.

Re: Reversion what is the impact?
 

I do not know what Headers are on the 496 but cant the risers be modified in the same manor?

Re: Reversion what is the impact?
 

The 496 do not come with headers. They have an aluminum (Gil) exhaust manifold exiting into a 3" SS collector inside a 4" dia SS water jacket which is rather short. Probably could extend these risers pipes by inserting some 4" and 3" SS pipe but I have the later design corner transum exhaust tips on the Nordic Rage and have to make two 90 degree bends before the transum. This limits the length of possible extension considerably and would probably not have the improvement in reversion desired. I would rather not change the exhaust exit point in transum. So my interest in the lifter option.

Re: Reversion what is the impact?
 

What are your cam #'s? I tried a search on Crane's website with your OEM # but couldn't come up with anything.

If it were me, I would let Rhoads do the change for 95 bones, assuming your cam's # are 'big' You would not have much into it, maybe $250 total when you add gasket costs (assuming your motor is together) and two half days worth of work.

Of course, this would take boating time away

Re: Reversion what is the impact?
 

Mike,

The Crane web site is far from complete I have found. You have to call the Crane Tech line to get the timing card for this cam #. The cam is essentially the EFI500 so not huge but big enough to get me enough reversion to fry the o2 sensors located 1" above the stock exhaust manifold/riser junction. I've spent way more than $95 on o2 sensors already.

Actually the intake manifold and valve cover gaskets are rubber and new with new cam and heads instal this winter/spring so very reusable. The only open question is do I need different push rod length. If I send Rhoades a 496HO lifter they will tell me what if anything I need to do regarding push rod length. I cannot believe how perfect the Rhoades lifters solution seem to me. However I am still looking for some one who had reversion and got rid of it by switching to the Rhoades lifter.

Unfortunately I have run out of project time. I have been on this winter project since November (research phase) and my wife will now shoot me if I do anything other than drive the boat until this next winter. So I am looking toward the future here unless she takes a trip??????

Bill

Re: Reversion what is the impact?
 

The OEM0988 cam timing @0.050 is....
- intake opens 6.0 BTDC
- intake closes 44.0 ABDC
- intake duration 230
- exhaust opens 57.0 BBDC
- exhaust closes (1.0) BTDC
- exhaust duration 236
- LSA114
- Max lift Int 0.598
- Max lift exh 0.610

Re: Reversion what is the impact?
 

This thread branched off to "Rhoades lifters eliminate Reversion from hot cams?"

Re: Reversion what is the impact?
 

Mike,

Your 388, does it have knock sensors? Is it a Mercruiser or GM ECU? I am being told that the ticking noise from the Rhoades lifters closing the valves faster may be missdiagnosed as engine knock by the ECU/knock sensor programing.

Anything on this in your experience?

Bill

Re: Reversion what is the impact?
 

My motor is a "Herby" special, I built it myself. It is carbed with MSD ignition, so I don't have a knock sensor besides my two ears. I guess that could be another hurdle for you if you are going to Rhoads lifters. I think there are knock sensors available that are designed for solid lifters, you can ask around about those. I know some people just disconnect the stock ones, but if I had them, I would want to have their protection.