300+ rebuild

[Vladislav]

On 3/3/2026 at 3:06 PM, Geoff Weeks said:

You can't rip the liquid apart by physical action alone. 

Maybe it's not fine to flood up Larry's thread but seems I should toss a pair of nikels to this basket.

Paul's explanations were wrong (or maybe we are both wrong with him as he clever addmits sometimes). The effect of cavitation is predicted by taking the fluid body apart. It's possible if you "pull one end" and "hold the other". For example in a centrifugal pump some portion of fluid is forsed to go to the outside due to spinning but the incoming fluid is hold down because of excessive resistance in the suction channel. Or similar effect can be achieved on a surface of impeller blades. Big impellers have section of blades made by the same principal as a plane wing. That "assymetrical ellipse" shape produces difference of pressures on different sides of the wing. More curved side gets lower pressure what helps getting the plane up. And same effect is used in leaned (not straight) boat sales.

Ok, that's a rocket since but the point we deal regarding cavitation is fluid is broken down in a certain point. So a bubble occures there. That's not gas in fact. It's vaccuum. It could be gas filled to some minor grade because of intensive evaporation to the vacuumated volume but what has meaning is that volume is under notably lower pressure than the whole fluid body.

When that bubble moves from the area with conditions which produced it to area with normal conditions normal pressure in the fluid presses it down immediately. And as long as fluid doesn't compress as gas it produces big hit in that spot. It's pressure wave spreads over surrounding fluid and since fluid is super-conductive for stress it achive structural parts of the device.

During cavitation we have a kind of "hammering" to empeller blades, pump housing or a cylinder sleeve (here the effect is stimulated by pressure jumps in the combustion chamber if combustion isn't going right, for example being detonative). Ok, constant hitting to a structural element makes material brittle which is followed by chipping out and making cavits.

This way general reason for cavitation to take place is incorrect movement of fluid in a certain passage. For centrifugal pumps the most typical reason to cavitate is higher revs than they are designed for. And clogged suction side too or sucking from very low level. 

[Freightrain]

No problem Vlad.

You have way more knowledge than me about that stuff.  I have never thought that hard about it, as I just learned about cavitation when I bought my new 2000 Ford Power stroke pickup and keeping the ph level in the anti freeze checked to keep pitting to a minimum.

 

As for the manifold, I did buy some thin wall inserts and new 3/8" studs that I will be installing tonight in hopes to get that all back on the engine and running again.

I will post pictures.

[Freightrain]

Back to square one.

Was able to fit in my small mill at home.  Drill/tap insert thread insert.  I also took a quick pass across the mounting surface with a face mill.  Got rid of the rust and rough pitting.

It's all back together and running.

Question to the guys in the know:

Does the valve train not get much oil?  Valve tips are not getting much.  A few more then others.  The rockers are getting oil at the shaft as you can see it drip out but the rocker tip not so much. These are the rockers from the 237 and they didn't oil much.  I did clean them and used air pressure to make sure the rocker passages are clear.  Moving rocker up/down you can feel air spurt out at the tip.  It didn't seem to have issues on the 237 with wear or anything.  Is this normal?

 

The studs I got were just a smidge short on thread length so I had to stack up a couple washers to make sure the nut didn't bottom out before tightening.

 

[mrsmackpaul]

Dunno about the valves and the amount of oil

Joey or Geoff will know, I just set the valves and send it, yeah I'm not super anal

 

Paul

[Freightrain]

5 hours ago, mrsmackpaul said:

Dunno about the valves and the amount of oil

Joey or Geoff will know, I just set the valves and send it, yeah I'm not super anal

 

Paul

The 237 ran for the last 9 yrs as such.  I noticed the lack of oil back then.  It still leaked at the valve covers enough to think it would be flooding the heads.  It was always damp in spots.

[fjh]

6 hours ago, mrsmackpaul said:

Dunno about the valves and the amount of oil

Joey or Geoff will know, I just set the valves and send it, yeah I'm not super anal

 

Paul

You should be ok with the oiling in my estimation ! have you tried the jakes? that will tell the tail if enough oil is getting up there!  push the solnoid down see if they fire off!

[Freightrain]

2 minutes ago, fjh said:

You should be ok with the oiling in my estimation ! have you tried the jakes? that will tell the tail if enough oil is getting up there!  push the solnoid down see if they fire off!

They always have worked.  Haven't tried it on this motor yet.

There is oil getting to the heads, but it is the rocker tips that seem to be marginal at best.  A few have oil drooling out of the rocker tip.  Most basically nothing.  Granted there is not much spring pressure, valve lift or RPM that would wear the rocker faces.  I always question it because on a gas engine if you have the valve covers off....you are getting soaked even at idle.

[fjh]

8 minutes ago, Freightrain said:

They always have worked.  Haven't tried it on this motor yet.

There is oil getting to the heads, but it is the rocker tips that seem to be marginal at best.  A few have oil drooling out of the rocker tip.  Most basically nothing.  Granted there is not much spring pressure, valve lift or RPM that would wear the rocker faces.  I always question it because on a gas engine if you have the valve covers off....you are getting soaked even at idle.

I would personally run it for a bit before getting carried away!  Get the engine in the truck and work it hard  the best you can I understand its a toy but you don't want to baby a new set of liners and rings You  need to warm it to operating temp then  and work its ass for the first bit preferably loaded! Nothing ruins a rebuild faster than idling to long!

 

Just sayin!

[Freightrain]

Absolutely agree.  I can't wait to kick it in the ass.  Even though I am not heavy I am not afraid to make smoke!

[fjh]

Don't be afraid to put some brakes on while driving it hard ! Road dyno it ! Put boost gauge and pyro in and drive by them!