Is it reversion, if so how?
 

Ok here goes. Rebuilt both 502 Gen IV new cams and used Gill exhaust with long risers. Ran it for 2 hrs and while flushing noticed a clacking sound and had water in the oil of one engine. The machine shop listened to it and thought it was a bad lifter (new with cam).

I pulled the risers and exhaust and saw #7 looked wet. I have since pressure tested the cooling system (Block heads intake to 50 psi air) no leak down. Pressure tested exhaust manifolds with both air and water with no signs of leakage as well as oil cooler.

Have not pressure tested stainless risers due to not knowing how to plug the 3 holes at the discharge side. Any suggestions on how will help.

My question is would a bad lifter or any other valve train issue cause reversion? If my risers check out OK I'm stumped.
Thanks for any input!
:(

What cam are you running ? I was told that Gill's can not have more than 230 in duration

If only #7 was wet and #8 was dry ,,,then i think its not reversion !
Usualy its on both sides of the block .:eek:

#8 Might have been wet however I am running the same cam in the other engine with no water in the oil. Is it possible the cam is degreed wrong? Or???

That may be an option,,,or,,,,,,haedgasket ?????

Not sure if this is correct, the factory 420 cam (228°/236°) was Merc built with Gils.

You need to make sure you are using the right head gaskets you can mix match heads to any generation block but you need the right head gasket or you will fill the engine with water. The coolant holes in the heads are diffrent from generation motors

What cam are you running?

An exhaust valve not sealing well can cause reversion. A bad lifter would only cause reversion if you tightened the rocker down too far and held the exhaust valve open. Not sure exactly where the limit is with Gil exhaut but it's somewhere in the area of 230-240 degrees @ .050.

Thanks for your input everyone. Both engines were rebuilt the "same".
Same head gaskets same cams, I'll get specs on here soon to answer questions. One runs good no water in its oil.

Here are the specs for the cams in my 502's

Pace Performance PN#12353920 - Flat Tappet Hydraulic Camshaft & Lifter Kit (228,238- .540,.540)

All models big-block Chevrolet V8 1965-66 California, 1965-68 with federal emissions. All non-emissions truck and all 1966-92 for off-highway applications. This is also an excellent marine cam. Good idle, daily performance usage, mild bracket race, 9.5 - 10.75 - 1 compression ratio 3000 - 3400 cruise rpm. Basic rpm 2200 - 5700, 6500 rpm attainable with proper valve springs and lifters. Technical Notes: These are hydraulic flat tappet camshaft kits. The duration at .050 lift (intake/exhaust) is 228/238; valve lift is .540"/.540"; lobe centerline is 114. These new generation of camshaft kits are designed and manufactured by Crane Cam Co. for GM Parts Division. All kits contain one (1) camshaft and sixteen (16) tappets.

I'll be pressure testing my risers and checking valves.

Exhaust valve not sealing well or the exhaust valve not following the cam well (broken spring, weak spring, not enough spring pressure), or sticking exhaust valve can cause reversion.

dgood,
Do yourself a favor and just modify the tail pipes. I had the same problem when I built a 502 yrs ago. I ened up extending the inner pipe by 1.5"-2" and the problem stopped. At idle I could see the water climbing up the ID of the exhaust pipe. I had a solid roller cam in it. Not sure what it was. But those three little holes in the inner pipe introduce the water into the exhaust stream and bingo.. reversion.
I cut the outer pipes and then extended the inner one, put a ring aound it with three grooves (2-6-10 oclock). Used a piece of rod the size of the difference between the inner and outer pipe. The two pipes can grow at different rates so you dont want to weld the inner to the outer.
That would solve a reversion problem.. not the easiest, but it is final. Find someone in your area that can weld SS and go for it..

Hope this helps.
Dick

I could not agree more with Dick (mr. Gadgets). Extend the pipes a little and solve the problem.
That cam with 238* exhaust duration nsounds a little big for that exhaust. I have seen the exact problem that you are having....one engine reverts and one does not. We lenthened the risers and the problem went away. I would bet good money that you have a reversion problem. I can not explain why one would do it and not the other. I quit trying to figure it out and just fixed it:drink: Good luck.
Eddie

even with two idenical engines...they rarely are, theres always differnces here and there, the way the cams are ground, how far a valve is in the seat from a valve job, timing, carb adj and idle speed....all could effect it if you are on the edge....Rob

BUT ,,,,still wy isn't it in #8 only one side ??????????

Can that be ???????:party-smiley-004:

Certainly. Depending on the exhaust, some do not have equal risers because of the offset of the engine. There are just to many factors....just like what was listed above. Just a half an inch in where the water enters the exhaust could be all the difference needed if you are on the edge. I think the cam is to big at 238 deg. to use with that exhaust. It doesn't really come as a surprise to me that it reverts. I'm surprised that both engines aren't doing it. Like was said, a little extension to the pipes should fix it.
Eddie

Thanks everyone for your input. I will try as suggested and update the post.

Just came from the machine shop and with the intake off saw signs of water (IE rusty) in the aft intake ports on both sides. Is it possible for reversion to suck into the intake side of the head??? Doesn't make sense does it?.

When I found the problem, I fixed it before rust could occur, on the engine test stand. I wouldnt think it would get to an intake port. Maybe someone else can share their experience.
If you have excessive water psi in the block, it could have damaged the intake gasket??? Any signs of that?

I have had a bent exhaust valve (obviously not sealing) and found that water was pulled into and puddled in the MPI intake plenum. Of course, I new I had a problem because the engine was missing.

How does the reversion put water in the oil ?

A few ways.

1) leak down after shut down (past rings over time).

When I found it, running the motor on a test stand, I would run it for 5mins or so and the oil was milky. I changed the oil and tried it again and same thing. I could see the water walking up the inside of the exhaust pipe, at idle.
I was told at that time, it would enter the exhaust and go right past the rings in the oil pan.. Seemed to happen very quickly.

i was told that gil headers had promble merc. made the idle at 900rpm that stop the water from coming in. i agree with these guys :ernaehrung004:go dry then you don t have to worry .:cool: thats wt i am going to do:cool: had same deal going on my motor . good luck :ernaehrung004:

Check your intake manifold and make sure it was sealed properly. This lets water into the oil sometimes when the bolt around the water jackets aren't tightened enough or if the intake is touching the block and not letting the gasket get squeezed properly.

I ran a 240/248 with wet GILS before and the engines are still purring like a kitten for the guy I built them for. No issues except they need bigger fuel tanks and deeper pockets.

It could be reversion though.

The good thing is that you are running them in on a test stand. Awesome call on your part.

Good luck and keep us posted.