Poppet reducer

[bloodman]

While researching various sites to improve my knowledge of my recent powerhead failure I came across a thread on cold seize. These guys were talking about a failure on a high performance merc and felt the failure could have been cold seize as temperatures were low. To reduce the chances of this happening in the future it was thrown out that you could restrict the poppet some to reduce the flow of cold water as pressure increases and opens the poppet. Thus some heat would be kept in the engine. This rush of cold water when the poppet opens is apparently believed to contribute to the problem. Of course the restriction would be removed when in warmer conditions. Thoughts?

[esdbass]

When you say " hi perf Merc" were these guys talking about a 2.5 L true Hi perf merc like a 260,280, or a 300 Drag motor? if so the Popit is removed from these motors all the time and thus they were discussing making a restricter of some type to adjust water flow through the block based on water temp of the lake. Jay Smith has posted on this quite a lot on the 2.5 Hi perf page. These restrictors are actually adjusted in size in these 2.5 motors based on water temp.

If it was a 3L XS Hi perf motor I don't think restricting water in the same way is the issue ( yes Eric Simon has a Popit diverter ) that increases water flow through the block dramatically and cools the engine almost too well if a 1/2" restrictor is not used, but I think following proper warm up AND cool down procedure in cold water is probably where your cold seize problem came from and it's not something that is covered in any owners manual that I am aware of? Don has outlined proper warm up and cool down procedure at length, it may be a sticky on this board?

[bloodman]

You got it. And it was the 300. The bottom line was stated that since the piston and bore are made of same material, aluminum, the expansion rate would be the same, thus no need for t stats or poppet. And cold seize should not be a problem.

Just thought it was interesting read. Made me wonder even with a properly warmed up engine like mine was, whether the hard acceleration to get on plane opened the poppet and the sudden rush of cold water in the block caused ar added to the problem. Maybe a little less of that cold water flying in the block at speed would be nice. Anyway no matter what, you wont find me doing any sudden hard acceleration, even after proper warm up again in cold water. Of coarse I already know better than running it wide open and proper cooling before shut down.
Don is a pretty dang good teacher.

[esdbass]

The T stats open on a properly warmed up motor before you take off. It's when the engine temp drops when your watching the temp gauge that this happens. On a 3 L opti getting to 120* before taking off is the critical temp that needs to be achieved. When you come down off plane after a run you just need to keep the motor idling for a little while till the temp starts rising back to the 120* range then you can shut it off

BTW: Not standing on it at take off in real cold water is always helpful I think

Don I'm sure will be along to clean up anything I might have not gotten just right but this is my understanding of it.

On my Hydro Tec 250 XS R&D Powerhead with Eric Simon's Popit diverter because of it's extreme cooling ability it's actually sometimes takes a while to get the engine temp up to 120* in a neutral idle and I have a 1/2" restrictor in place so it's something I watch for both at warm up and after comming off plane BUT it make my motor run much cooler WOT than the stock set up

[bloodman]

I am gonna assume something here. I dont know if I am on the right track or not so feel free to correct me at will.
I assume that since the t stats are on the top of the head that the temp sensors are nearby also. I am also assumming that water enters the block from the bottom of the block.
I know that the lower cylinders are usually the ones that go first. Could it be that this cold water pouring into the block under power and when the poppit is open somehow is coming into play here by hitting the walls of these cylinders before it warms at all? Just a thought???

[esdbass]

Don's best at answering that for you but typically #6 runs the hottest and thus is most likely to fail. Having your injectors flowed and then putting the richest one in #6 can help a little.

[bloodman]

Guess we need the pros knowledge on this one. Thanks esdbass.

[esdbass]

No problem I'm sure Don or Redline will be able to fully answer your question and it's a good one

[EuropeanAM]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bloodman &raquo;</TD></TR><TR><TD CLASS="quote">I am gonna assume something here. I dont know if I am on the right track or not so feel free to correct me at will.
I assume that since the t stats are on the top of the head that the temp sensors are nearby also. I am also assumming that water enters the block from the bottom of the block.
I know that the lower cylinders are usually the ones that go first. Could it be that this cold water pouring into the block under power and when the poppit is open somehow is coming into play here by hitting the walls of these cylinders before it warms at all? Just a thought???</TD></TR></TABLE>

You've basically hit the nail "on the head". Your "understanding" of the system's designed function is correct.

Attempts to modify the configuration of the poppet valve can be "troublesome", at best. Even the "poppet diverter" must be fine-tuned with a restrictor, to bring water pressure and thermostatic control back into range.... the PCM on these engine monitor to ensure that thermostats/temperature come up properly (and even sometimes set faults if they don't).

Additionally, specific water pressures are expected, and when you fall substantially below the "expected water pressure threshold", faults set then as well.

The best method is to have a Smartcraft Instrument configured to monitor engine temp! Watch to ensure you've reached the 120 degree mark.... make your first acceleration (especially in cold water temps) a GRADUAL one.

And of course, before shutdown, allow a 60 second or so idle period, while monitoring to ensure temps have stabilized at 120+ degrees (and remained in that vicinity).

95+% of cold seizures are either "operator induced" (failure to allow adequate warmup time), or caused by debris in a thermostat that PREVENTED the engine from coming up to temperature (which the operator should have seen if monitoring temp on a Smartcraft Instrument).