water reversion
05-11-2004, 04:12 PM
#3
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It depends on total valve overlap (primarily). That is a function of duration and lobe seperation angle. Just for reference my cams have ~51* overlap (if memory serves correct) with a 111 sep angle and a 226/234 durations. These cams reverted some water with stock exhaust and imco ss risers, but not much. They reverted quite a bit with the stock cast iron risers. I think the imco risers mix the water further back than the emis with alum risers, but not sure. What is the seperation angle on the cam you listed?
BT
BT
05-11-2004, 04:55 PM
#4
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It shows to be 54* on the ex. I bought the cams from Summit, high performance marine 3000 to 6000 rpm. One motor was already built, then read that might have a reversion problem. Could I up the idle to help rid of the problem if it does have a reversion problem? Two fresh motors dont want any problems.
05-11-2004, 06:16 PM
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Not sure if you mean the overlap is 54*? If not, and if you can give me the lobe seperation angle (something like 114 would be nice) I should be able to tell you the valve overlap. I would also suggest calling EMI with the engine specifics. They should be able to give you solid guidance. If you do have a problem you could up the idle rpm some, but must pay attention not to hurt drive shifting into gear. Or, you could weld extensions onto the riser exhaust gas chambers to move the water/gas mix further back. A final thought is possibly advancing the cams 4* to get the exhaust valve closed earlier. This would have the outward affect of moving the torque curve of the engine down the rpm scale, which is sometimes a good thing for a boat. Just depends on your situation. There are some really knowledgable people round these parts (OSO) that can verify if advancing the cam would be a good play in your case.
BT
BT
05-11-2004, 07:51 PM
#6
MarineKinetics
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pimcotrans
The part # for that cam is 134561. Crane does not build a 135461.
Cam Timing: TAPPET @.0042
ADV Duration
296*/306*
[email protected]
236*/246*
[email protected]
.553/.571
ICL 109*/ECl 119*
LSA 114*
Overlap 73*
Here is the timimg card:
http://www.cranecams.com/?show=brows...61&lvl=2&prt=5
I have a customer who has run these same cams from a previous build, I will obtain some first hand feedback.
Bob
The part # for that cam is 134561. Crane does not build a 135461.
Cam Timing: TAPPET @.0042
ADV Duration
296*/306*
[email protected]
236*/246*
[email protected]
.553/.571
ICL 109*/ECl 119*
LSA 114*
Overlap 73*
Here is the timimg card:
http://www.cranecams.com/?show=brows...61&lvl=2&prt=5
I have a customer who has run these same cams from a previous build, I will obtain some first hand feedback.
Bob
05-12-2004, 08:49 AM
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Taking it one step further RM, would you say that the important number on a cam card regarding reversion would be EVC degrees atdc? Seems logical that's what matters regarding cam grinds and reversion. My EVC is 24*, Pimcotrans is 36*.
BT
BT
05-12-2004, 09:43 AM
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Missed the part # 134561, bad typing, I guess. Any info would be great. What kind of hp could i see from this combo? Factory rectagular port heads, mild porting, gasket matched the intakes, stock size valves. I am glad I found OSO, just wish I knew about it before I started ordering parts.
