Has anyone had trouble with a crane cam # h-272-2.I built a 350 bored .30 over with 1996 vortec heads and aluminum vortec intake.It has stock manifolds and 4 inch risers with thru hull exhaust and s.s steel exhaust tips.It does nothing but suck water back through the exhaust at idle , crane cams tells me it's not the cam doing it. What else could it be. It's in my 1986 19 foot thundercraft speed boat.

Thanks

Stock risers and manifolds don't like much more than 224* duration or they will revert water. Unless you have a leak at the manifold/riser joint the only way water is going to come back is thru reversion. If you plan to keep the cam then you will need to upgrade the exhaust or modify your current exhaust. You need to introduce the water and exhaust gas mix further downstream.

I use to run a 224/224 .465/.465 114+5 cam in a 360ci with aluminum Glenwood manifolds and 4" Fastglass short risers with no problems.

I currently run a 355 with a 226/230 .537/.511 112+2 hyd roller with the same exhaust. With the short risers it reverted water bad and I had to extend the risers 8" to prevent it from sucking water.

Short Riser



8" Extended Riser

WHAT IS YOUR IDLE SPEED (RPM) YOU MAY NEED TO SPEED IT UP . I HAD A 454 330HP THAT WOULD SUCK WATER AT ANY THING BELOW 750 RPM.

My idle speed is between 700 to 750, other people have built the same engine with out any problems.I see a lot of different opinions about how much cam duration it takes to suck back water. The cam i used has 216 degrees duration on intake and 228 on the exhaust.

Thanks for the pics, it helps to see what you are talking about. Any details would be appreciated as I have a 350 with unknown cam and Thunder Marine headers/risers. I am not familiar with the "Fastglass" water arrangement. i have thought about blocking the water injection point and tapping a connection to jump to a water cooled pipe, lastly then dumping the water down stream. Much the same as the water cooled exhaust on race boats.