blackhawk

Thanks everyone for the lesson. Like I said, I always new what reversion was, I just didn't know exactly how it happen. So now the million dollar question.

How do you know if reversion is occuring?

blue thunder

Detonation, high oil temps, loose spark plugs, tuliped valves, rust on plugs, blown holes in piston(s) and finally... meltdown.

BT

Vinny P

Don't forget when the tulip of the valves snap off after getting cold water dripped on them..

CCPerformance

Blue Thunder:

I've seen reversion causing rust on valvetrain and bores & perhaps in extreme case hurt valves or completely hydraulicing a motor. How would it cause detonation, increased oil temp and blown pistons (I'm assuming that both of these are a result of detonation).

Water injection has been used for years to control excessive cyl temps & detonation. How is water creating detonation?

Scott

Guys I thought I would throw in a picture of my motors and a question since this thread did start about HP500 reversion. I was wondering with the merc risers if reversion would still be much of a issue? I do have a different cam it's a Crane 168731 and yes I did change the springs they are now Comp Cams double that have a normal seat pressure instead of the 170+ pounds I used to have
I have never seen any evidence of it like steam out the exhaust or rust in the valve trane.

Cord

The best way to tell is to run the motor, idle it for a while and then shut it down. Take the exhaust off and look in the port. If you see water, you have a problem.

blue thunder

CCperf... water would take space in the combustion chamber thus increasing the effective compresion ratio of your mixture. Too high a compression and you get detonation/heat. Too much heat on the piston may first show up as high oil temps. I have an engine on a pallet in my garage with the loss of exhaust valve head checkmate454 mentioned. This was due to what I described above.

BT

CCPerformance

Hey BT:

I'm not busting your balls I'm just trying to learn soemthing here.
I don't doubt that a valve head may snap or tulip due to thermal shock(cold water on hot valve) or overheating. But I'm confused. Are you suggesting that both conditions are happening simotaniosly. How can a cylinder be so hot as to burn pistons and valves and also be taking on fresh cool water at the same time? Its either hot or cold, not both. Although I guess this could take place after the motor is run hard and you then go to idle I can see the water damaging the valve which would in turn impede the efficiency of exhaust gases out that would increase cyl & oil temps.

Did this occur at idle speeds or at cruise speed. even if a motor reverts like niagra falls at idle, it most likely goes away at speed. If this is at idle and detonation was so catostraphic as to cause this damage would you not hear the rattling and or wash out plugs due to excessive water?

blue thunder

CC.. If you suck in a small amount of water through the exhaust valve, then it closes, you have effectively increased your compression ratio, because the water takes up space in the combustion chamber. Lets just says it take up enough volume to create a compression ratio of 20:1. What octane fuel would you need to prevent detonation with a 20:1 compression ratio?

In my case I never heard any pinging. Probably due to open exhaust. I'm sure it was happening. I was at about 4500rpm when it blew. I think what happens is as the exhaust valve looses its seal due to tuliping, the suction of water increases and things go bad in a hurry. I had been having an oil temp problem on this motor before it blew up. I don't think there is a hole in the piston... but I haven't tore into it yet to see. That will be my winter job, if nothing else lets loose in the mean time. I think holes in the piston are more often caused be a lean condition over a longer period of time. Remember... all this is just my .02.

And lastly... stop bustin my balls!!

BT

DanB

Get the new issue of Hot Rod mag. Good article explaining the basics of cam design.

Dan