502 Gen 6 Water reversion Issue
 

When the engine is in idle gets water reversion I’m using stainless marine manifolds and
2 set of elbows one set is 14 and other set is 20 inch long pipes measured after the elbow, The engine is not in the boat yet I’m running it on a wood pallet with plenty of drop in the rear part of the engine to give the same angle like it will be sitting in the boat but no luck neither sets prevent the reversion in idle.

I ran some test like running the engine with no elbows just the manifold with the water lines, and no water is found 100% dry. I noticed after running the engine in Idle for about 15-20 minutes I can see water drops between the head/exhaust manifold gasket only in the middle port right where it align with the elbow,I see the pipes are wet all the way in where it should be dry, water and exhaust meet at the end of the pipes.

How Can possibly happen using a hight performance exhaust with a stock cam


Here are the specs:Marine 502 Gen 6 crate engine, stock 435 HP, roller cam, single plane air gap merlin intake, stainless marine 4" manifold and elbows, electronic flame-Thrower marine billet distributors, 850 Holly 4150, Spark plugs MR43T gapped at .035-.040, 14* Degrees base & 34* advance

1995 Formula 252 LS

Your input will be very much appreciated.

Are the exhaust manifolds new or used? Is reversion occuring on both manifolds or just one side?

On both sides, I run it without the elbows and water lines just to check if is a head issue but no water is found after the test the manifolds are 100% dry. Could it be a timing issue because it runs but is not on time

Is this a car motor? If so you might have to much over lap. Also the stock timing shoulkd be 6-8 base.

As far as I know is a marine engine, I got it new from 1800Runsnew.com wich they only sell engine for marine application. It's the same GM base engine line for Mercruiser they said.

get a non digital timimng gun, a friend had a msd set up which might be like your flamethrower set up, and he could not time his boat right he ended up with 45 degrees thinking it was 30 and blew the motor. he was told on here to use a non digital gun just a regular old gun to set it. after the fixing the motor. good luck

Wrong. Straight up truck motor. Been there, bought that. Still, that cam shouldn't give much overlap. I ran the 454/425s with EMI thunders.

Get the engine timed and running smoothly and then test it. Cam timing being off can also cause reversion.
Double check the angle of the engine. The engine should be level or even lower in the back when at rest. Put a level on a valve cover to check it.
Is the engine getting to temp???? It could be some condensation from very cold water induced into the exhaust manifolds.

Wrong.... The 502 was never a Straight up truck motor and the cam is the same cam they install in the mag 454's on the back of the cam should be stamped 1622 it is a GM cam for the marine world same cam they ran since day one on all the mag 454's and 502 pull the rear plug on back of the engine where the cam is to check part number that is the fast way to check you will have to install a new plug.

The cam specs is 224/224 Part# 12551622 which is a very mild cam and water reversion should not possible.