delsol

We've got a set of 454's running Gil manifolds, we noticed a small amount of water sitting in the bottom one of the manifolds during routine maintenance.
The cams are Comp cams;

duration @ .50 int .220
exh .231

lift int .581
exh .598

ground on a 110 degree centreline

In researching info here i have read that some find the gil to be a possible reversion issue.

The risers are standard bravo risers with 4" single wall ss extensions welded on to the end to extend out the transom.

If this could be an issue there are 2 possible solutions;

replace with another system ie; imco powerflo's -- along with some extensions/tips to extend out the transom

or
cut the risers just behind the elbows and replace with 4" OD inner, and a 4.5" outer tube straight out the back of the transom -- creating dry exhaust right to the end -- this would also increase the ability to flow with the larger tubing...

Any insight?

Thanks, Dave

kreed

iTrader: (2)

I was always told you need at least a 112 centerline in a marine application with wet exhaust.

Hardin Marine

Dave,

I'm unsure really what your self-modified tail pipes look like but the camshaft you have is what's causing the reversion problem your experiencing as the standard riser wasn't spec'd for your camshaft selection.
When Mercury chose to run a camshaft very similar to yours but with a wider lobe separation and a .05 more duration on the HP500 they too had to have special tailpipes with more rise and fall built into them to rectify the problem. Here's the style of pipe required to solve your reversion problems. Your lobe separation choice and duration is what's creating the vacuum in the top of your manifold and sucking the water back into your engine.

Are you running the original equipment turbulators between the manifolds and risers?

http://www.hardin-marine.com/p-13408...-polished.aspx

Sincerely

cliff_m_b

Another possible option I believe would be to use Rhodes "Bleed Down" Lifters. A little bit noisy but seems to solve the reversion issue which occurs at idle.

pantera232

I just welded on ss pipes 10" long.. But before we welded i had some one stand outside the boat and get them aligned up dead in the center that way we wouldnt burn the outter rubber hose... We grinded the pipes to fit perfect and we had it up and running that day... Reversion was gone and nothing has melted .

delsol

Pantera
you welded single wall pipes onto the ends of the risers?

That is what we did, -- but it doesn't get rid of the reversion as the water is introduced at the end of the original riser this way. the only way to do it is to lengthen the double wall also so that the water is dumped at the end of the pipes.

Or as been said here get a cam specd that doesn't cause reversion....

FIXX

iTrader: (2)

you have to weld extension on the inner of the 2 pipes..you will need to cut both pipes and step the inner pipe so it sticks out further for welding..extend the inner pipe then add to the outer pipe..then you will need to cap the ends and drill relief holes for the water to dump..as stated earlier do you have turbulators?? thease are supposed to burn off any water that reverts back into the pipe..

delsol

there are no turbulators installed, where can we get some?

Mr Fixall -- that is exactly what we are thinking about -- although we are now looking at just replacing the cams.

weighing it out...do fix the problem or make it so the problem can't affect it??