New Cam
 

I was planning on buying these new cams but was worried about reversion. Can anyone tell me if these will cause reversion. I have EMI thunder exhaust with short risers. The cams i have now are crane .
539/559 lift
228/236 duration @.050
114 degree LBA. I have no reversion problems.

New cam specs: Comp Cams 554/566 lift
234/244 duration
112 LBA

Thanks

Yes they wiill revert.

I can't believe you get away with the cam now.

I have EMI now and had to change my risers because of that issue.

There are several options
Call Chris Flores at Eddie Marine they can make anything and do an excellent job!

Don't know the reason for changing but there isn't going to be much difference between those cams if any. The ones your changing to will have more of a possibility for reversion but doesn't necessarily mean it will.

What in a cam do you look for to prevent reversion? I have a parts list for building the top ends of my twin merc 260/350's. I am looking at cams, but the whole reversions thing is new to me, as I have always been a hotrodder on the street. I am looking for good power and dead reliable, not a crazy race boat....I'll buy that once the kids are gone!

I am going to be running AFR 180 aluminum heads, full roller rockers 1.5 ratio, edelbrock air gap dual plane intake, and either edelbrock 600 or 750 carbs(carb recomendations are also welcome!). I would like to have WOT around 5200 or 5400 or so. Here are two of the cam grinds I am looking at.....
#1:
282/282, Lift .465/.465 114 lobe seperation.
Fair idle, 2,000-5,600 rpm


#2:
282/292, Lift .465/.488 114 lobe seperation
fair idle 2400-6000rpm

Thanks guys.

I recently took all my risers and manifolds off to look for water stains etc...No stains or white markings..Just black soot..so I guess no reversion...

I just wanted 2 new cams..I'm sure they are a bit worn..
What causes the reversion problem.. The bigger duration or the LBA

Just tore my buddys 454 down. he was running 236/246 114lsa flat tappet hyd cams, with stock center rise iron manifolds. That combo lasted many years, no reversion believe it or not.

I believe it.. I had no problems..But will I if I change over...Really don't want to spend money on longer pipes etc..then there goes my silent choice also...:daz:

Go with a 750cfm carb for that setup. 650 is in the small side for a healthy 350 with AFR heads. Those AFR heads are begging for a hyd roller setup and not those low lift hyd flat cams.

I ran the #1 cam for a few years in a .60 over 350 I still have as a spare shortblock. It had AFR 190s, Lunati 1.5 rockers, Performer RPM, Holley 750 with Glenwood aluminum manifolds and Imco short performance risers that mixed water in the same spot as stock risers. I had no reversion with that cam and it ran and idled very smooth.

The #2 cam will be on the verge of reversion with stock risers.
No exact way to tell other than pulling the riser after idling for a few mins and looking into the manifold.

Comp says this is the largest cam to use and not have reversion with stock risers. 12-236-3

Reversion is a function of cam overlap. When both the I and E valves are open at the same time. At idle is where the problem arises. Hence, longer risers that mix water further back and then dry risers.

I run 22" long dry risers on my 385ci SBC to prevent reversion with my 234/240 .580/.568 112+4 hyd roller.

i have a comp 306 cam witch is 222/222@50 ,268/270 duration with emi manafolds and short risers,and yes.if i idle below 900rpm for a few minutes the motor will start to drink water.

Im running crane 741 cams in my 500 hps with stock gill exhaust with the tall long risers that was stock on my 32 active thunder with no problems 2 years now. (knockon wood) Pretty sure this is the exact cam used in the 525's

specs 236/244 @.50
610/632 on 114 lsa

To keep this discussion basic, duration and LSA effect overlap and where, when, what it occures. LSA is a function of ICL and ECL not duration.

rssteiny - the 741's are on a 112°LSA and ground 5° advanced.. It looks like you have the 525EFI cams...ie: same lobes as 741 but ground on a 114°LSA.

Mine were 741 crane so maybe they are 112 as you say my mistake.

I am currently having water in oil issues with EMI thunder exh. Here are my specs, comp cams grind #CB 3016B / 3037B HR 12.
Valve lift. 612 .607
Duration @ .050 230 int. .236 exh.
L.S.A. 112.0
108.0 int. center line



would these specs. Create reversion ???

Update. I called comp cams and told them my specs on my existing camshaft and what I want to purchase. I asked about this new cam causing reversion. His answer was no ..it shouldn't ... the LBA is 112 and reversion is usually caused by LBA at 108 with bigger duration cam. He said at some point the intake and exhaust valves will be opened at the same time with no exhaust causing a suction in the exhaust.
I also called Eddie Marine and asked about reversion with this type of riser pipe. The tech said they can extend the inner 3.5" pipe (longer than as shown) further from the water oulet just in case it starts to creep up. The water comes out in the middle where you can see the larger section and the exhaust comes out on the right side at the end of the extention. Look at pic

http://i1071.photobucket.com/albums/...4/13039_lg.jpg