Piston squirters
 

In my lakester engine (blown alky hemi four) I'm considering adding nozzles aimed at cylinder walls below the pistons- which would also strike the undersides of pistons through part of their stroke.. The nozzles would receive full-time oil pressure, nominally 100 PSI. One reason is for piston cooling. The other reason is for better cylinder wall oiling. Prior to the just-finished rebuild, the pistons were badly scuffed (anti-friction coatings gone) and two were cracked. I'm not sure of the cause, but there are a couple of suspects. One is possible lack of cylinder oiling, due to extreme oil control measures (no cam in block to bleed oil, full-round crank counterweights to eliminate leading/trailing edges, crank scraper, efficient windage tray, and oilpan kickout)- and DOHC oiling is a separate drysump system. The other suspect is the finish of the bores in the steel sleeves (done per Smokey Yunick's "the smoother the better" edict), which might not retain oil well enough. So... in any case, I think dedicated cylinder wall oiling would be wise.
I don't know what volume of oil flow to shoot for- any suggestions? Or as a shortcut, any idea what orifice size for each of the four nozzles?

I have never done anything like that. But I have ran my oil pump with a drill with no lifter in one of the bores. Just to see how much oil came out of a .030 hole.
I was very surprised just how much oil came out of that tiny hole.

Are there any signs of pitting on the tops of the pistons that cracked?

How do those plugs insulators look out of those cylinders when viewed under magnification, any signs of shinny purple balls there?

Either of these two would be clear signs of detonation.

If the pistons where getting too hot due to the power level being made I would expect the exh valve notch to on its edges to show signs of overheating and or deforming first before the piston would crack.

How do the wrist pins feel, any tighter then you recall from when the motor was last put together?

Also what other things might be different about the motor that your having these issues now, I can see how too much oil control would eat up the skirts.

How would you implement the added oil feed holes?

Jack, we have some turbocharged imports down at my school. I can gauge several squirter holes and get back to you. It may take a week to pull a couple down to check.

Can you imagine having the oil mist system drilled into the rod throws? some expert drilling.

Maybe just drilling the Rod Caps Parting line is practical. Oh hey PMD did that.

The Boss Bird had scuffed and cracked piston skirts when we were using the recommended piston-to-wall clearance. We tried loosening the clearance (maybe .002" extra?....memory fading) and the problem disappeared.

The Pontiac piston is less massive than a hemi nitro piston so it was growing a lot quicker and binding in the bore.

I'll see if I can find a picture and post.

Edit: don't have pix anymore but the piston is at work in my show-and-tell stash so I can take a picture Monday.
The skirts would get 2 cracks on the side perpendicular to the pin bosses. The pin bosses are heavy and take awhile to heat up. 90 degrees from that, the piston and skirts are thin and heat quicker. So the piston goes oval while it is warming up.

I never could warm up to the idea of piston squirters being necessary since the crank is flinging oil up into the cylinders. But since the OEM's go to the expense on some engines, there must be a benefit. I'm willing to be educated.

Eric

Jack,might post over on Speedtalk.Tom

Good thought!
Those oil holes that use to be in the big end of the rods where for Cam oiling, but I bet they would help with lubing up the cylinder walls also.

We ran Piston Squirters on the 3.5L Le Mans race engines.
So for some applications it is an advantage. Same deal with extended high speed
like Jacks Bonneville Salt Flats eventual racer.

But drag race stuff and Bonneville racing is NOT the same requirements.

You have a 2 mile "run - up" before you actually start the first mile of the timed/speed
run. Jack will probably run on the short course until he can run 300 mph or higher.
The squirter parts are available and just need to be adapted to the 4 cylinder engine.

Tom V.

Tom: how do you aim the squirters? I'd think that all the air being pushed around by the pistons and rods would divert the oil from the direction that the squirter is pointed?? How much trial and error is involved ?

Eric

I have been doing over the road diesel engine work for over 30 years. Everything has bolt in piston cooling nozzles that spray onto the bottom of the piston crowns. Pretty much a direct shot throughout the stroke to control heat

Thanks Mike, I'll be interested in those factory squirter sizes;

Jack, PM me your address and I have a little assortment of the squirters and feed bolts to send you. The feed bolts have a little check ball and spring in them. BTW, the holes were from .027-.040" in the ones I checked.

Thanks Mike!

I saw on bookface this morning, Don @ DCI is modifying a block to put squirters in via the main tunnel. Interesting approach!

Great great idea doing it that way!
No extra piping to get vibrated apart of have to make retention brackets for.

I like that squirters-from-the-mains idea. However, I already had the engine ready to test-fire and install in the racer- hate to tear it back down. So I'm hoping to mount the nozzles in the block's pan rail- and attempt to come up with reliable plumbing.

Jack, the piston squirters I’m familiar with (6B and 6C Cummins) are plastic( yep, plastic) and fit in bosses in each main saddle. I’m pretty sure you could fabricate a common oil manifold that would fit in them in the side of the oil pan; the trick is going to be setting the angle on the squirters themselves. All the ones I’ve worked with are aimed at the underside of the piston to provide additional cooling to the piston head.

Thanks for the info. Yes, aiming them (to strike as much wall as possible) will be tricky.

Maybe just a typo mistake BUT you want the squirter oil to contact the underside of the piston and not the cylinder wall.

Tom V.

I like Don's approach to the issue. Easily done with the right equipment.

The squirter’s do not directly spray at the cylinder wall. If you did, your trying to do something different than how a pistons squirter (piston cooler) is meant to operate. The goal is to cool the pistons. The Squirters must hit the underneath side of the piston.

Newer style Diesel pistons have oil cooling passages inside the underneath side of the pistons. The squirters are positioned to hit the port holes for those oil passages for even more piston cooling.

Older types pistons with no cooling port (like a gas engine and most older diesels) just sprayed the bottom of the piston for extra cooling. Long hard pulls it keeps the pistons from expanding, the pistons last longer, less scuffing from less expansion. The oil acts as a heat sink, it is not for lubrication.

Here's the pix of the piston that got killed by binding in the bore.

To make a nitro engine survive, the thing has to be super loose.
Piston-to-wall has to be pretty sloppy
Mains need .007+ clearance (when you can grab the crank nose with your hand and make it clunk up and down, you're about right)
Valve guides need to be loose so you don't hang a valve and grenade the whole engine
If the exhaust valve heads are distorted a bit and won't seal after a run, it's ok.....they'll straighten up the next time you pour the coals to it.

Eric

That skirt damage was at .009"-.0095" piston to wall clearance. Problem went away almost entirely at .0115"-.012" The engine will tell you what it wants to be happy. Just have to look and listen to what it says.

Since I suspect lack of oil retention on my super-smooth cylinders, I want the oil to strike the walls. Due to restrictions on nozzle locations, oil will hit the wall for about half the stroke, and bottom of piston for the other half stroke.
Also... I've decided to remove the blower to get some experience with the engine under less stress. Hopefully learn enough to later run blown.

Could you explain, Jack, why you wanted a super smooth cylinder bore for your Land Speed/ "Texas Mile" type racing?

Tom V.

Tom, See OP.

“ (done per Smokey Yunick's "the smoother the better" edict) “

With Mike's help, design of the squirters is progressing. I've selected some Honda nozzles and machined hollow studs to mount the nozzles through one pan rail of the block. I need to machine an AN-3 male flare onto the exterior ends of the studs, but am having trouble determining the correct flare angle. AN flare fittings are nominal 37 degree, but I need to know the exact angles- I'm quite sure that the male and female flares are not identical angles. Anybody help?:confused:

Jack: I'm looking at my "Parker Tube Fittings Military Specification Handbook".
It shows the male and female ends to BOTH be 37 (+/- 1/2) degree.
If you want to make them slightly different, then you could machine one of them to the high side and one to the low side of the tolerance. But they have no intentional offset.

Eric

I had micro welding of the rings to the piston in the old turbo car -- coolers may have helped

Thanks Eric. I guess I was wrong to think that the male/.female angles were slightly different.

Mike G- to install the nozzles into the assembled engine is challenging! Similar to the situation with chamfering the interior of Boss Bird's oil passages, I had to invent a tool to spot-face the interior side of the nozzle stud holes which are within 3/4" of the crank counterweights (the as-cast block surface needed spot-facing to allow sealing washers to function). I expect to wrap up the installation in the next couple of days.
[Sorry for the poor quality photo of the mirror image]

Thanks for the update Jack. So I guess that means the Honda part numbers we came up with for the squirters were correct. It does look pretty tight in there. My Honda guru says in the Honda applications, they have had a few instances where a technician has not aimed the squirters just right. In operation, the counterweights have lightly contacted them and in a few instances, broken them off. This caused an immediate oil pressure loss in the Hondas. So make sure you have enough clearance in there. This is super cool stuff!

Of course, "next couple of days" became a week! And upon trying to crank it over, the Tilton starter just spun without engaging the flywheel. So... a couple more days spent adapting the solenoid from an older Tilton. S'pose it might work this time??:confused: