just finished my motor and im getting some reversion problems. i have narrowed it down to three things bad internal flappers, cam over lap but i dont think this is the problem and bad gaskets at the riser / manifold joint.

the motor is a sbc 8.1 com procharged with rhs proline heads cast 2.02 1.6 valves and stainless marine long risers. here is a link to the cam specs
http://www.cranecams.com/product/car...detail&p=23975

i think its the bad gasket at the joint causing a vac effect.

please someone help.

your cam is right on the line for reversion problems with wet exhaust,or it could be what you suspect,if you idle it up to 950 or close to that,it can help reduse reversion.

I had a same problem,what I did was add on to the inner pipe about 4 in,and took out the flappers and it did the trick,hope that helps

i agree w/mike t.idle up to about 950rpm.i have this same problem with one of our boats.i have a oversize cam and short silent choise risers.if i idle below 900 rpm thre motor starts to drink water,aboue that i am good.

Make sure you don't use the cheap green rubber gaskets. Use the nice thick ones that look like carbon fiber. I also had my risers extended through the tips.

just remember, leakage and reversion are 2 different problems. a quiky leak test for exhausts is to stand them up and fill with water till it just comes out riser end. then watch for drips coming down into exhaust port areas.

this is the old motor set up but its a good pic of the exhaust setup the water is injected right where the rubber coupling meets at the end or the riser.

that looks like a long enough riser for all but the most aggressive cams. so i would suspect a water leak. first thought was "how do you feed exhaust to the turbo?" then i saw the belt...

so you only added on to the internal pipe and not the external? my exhaust is even at the end i dont even know how i would add on to only the internal pipe.

If you want to do this right, your gonna need about $300 in stainless tubing and a very good welder. When we did mine, we cut the riser's off just past the elbow. Weld the inner pipe first and then outer. Leave the inner pipe longer so it runs into the tips on the transom. Tack each one and check that they are straight. The flange needs to sit flat on the manifold for it to seal correctly with the inner pipe inside the tips. Tack and check each one because they can be different. Don't even bother calling stainless marine, all they will want to do is sell you new risers.