Pressure Testing a Block

[Tim Ayers]

Originally Posted by rockfla

Tim



My good friend and Flathead (and A & B motors) specialist re-builder here in town runs his up well over 100. I believe he goes to 130psi.

Wow. Interesting. Thanks for posting that, Robert.

[flatjack9]

Originally Posted by GB SISSON

Are we talking pressure in the cooling system here? Don't most radiator caps have something like a 15 lb cap? I woulda thought that was 15 PSI, but maybe the terminology is different. If we are driving around with 100 psi in our radiators, no wonder it's such a ****show when we pull the cap before it cools down.

The pressure I am talking about is cylinder pressure. Think about it, when you take a pressure test, you'll get readings well above 100 psi. Cylinder pressure when running is considerably more. So 50 psi is nothing compared to what the engine sees.

[Tim Ayers]

Originally Posted by flatjack9

The pressure I am talking about is cylinder pressure. Think about it, when you take a pressure test, you'll get readings well above 100 psi. Cylinder pressure when running is considerably more. So 50 psi is nothing compared to what the engine sees.

Ah, makes sense.

[GB SISSON]

Ok, good clarification. I never thought about pressure testing the combustion area,

[Bored&Stroked]

Originally Posted by KiWinUS

Dale do you put the water glass in with the radiator you are going to keep with engine? We found with race cars it would ruin radiator if not rinsed out immediately after draining. The would not remove/ dissipate heat near as good

I only run the ceramic seal during the initial warm-up of the engine on the test stand - usually 15 minutes max. Then I immediately drain the water (when it is hot) and flush the engine/radiator with fresh water. If the block has a repair in it (like we're talking about), then I do this twice.

[Ken/Alabama]

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I pressure tested the block today. Turned the water pump surface up and filled it with water then bolted on the water pump block off plate. Applied air pressure and kept increasing the pressure up to 50 pounds. The water pump block off plate kept wanting to leak as pressure increased but the good news is that the crack repairs didn’t leak a drop.

[petehoovie]

Originally Posted by Ken/Alabama

I pressure tested the block today. Turned the water pump surface up and filled it with water then bolted on the water pump block off plate. Applied air pressure and kept increasing the pressure up to 50 pounds. The water pump block off plate kept wanting to leak as pressure increased but the good news is that the crack repairs didn’t leak a drop.

[Tim Ayers]

Excellent news

[GB SISSON]

That's some excellent results! Tell us about the crack repair kit. Was this the first repair of this type you have done or are you an old hand at it? And now you plan to sleeve the cylinder? Thanks and congratulations on a job well done!

[Ken/Alabama]

Originally Posted by GB SISSON

That's some excellent results! Tell us about the crack repair kit. Was this the first repair of this type you have done or are you an old hand at it? And now you plan to sleeve the cylinder? Thanks and congratulations on a job well done!

It was my first attempt at repairing a cracked block. My long time machinist friend passed away a couple years ago and the machine shop he worked in didn’t want to touch it. And I understand, very shorthanded and no one with experience in doing this plus the fact they would rather spend time doing actual machine work. I had seen my friend repair several over the years using a Lock n Stitch pin kit. I know the owner and he said if I wanted to try it he would loan me the kit. That one cylinder has a pretty deep pit and the crack ran over into the cylinder a little bit so I’ll have a sleeve installed. I have a Kwik Way valve seat pocket cutter and with that I cleaned up the valve seat recess after installing the pins and now to install two new seats.

[Bored&Stroked]

You might think about going a bit oversize on the seats - unless you can perfectly center your cutter mandrel and exactly set the cutter size. Are you using adjustable cutters or fixed ones? Make sure you have your seats "in hand" before doing the seat ring work.

You want about a .005 press fit.

Do you have the good KwikWay pilot that picks up both the lifter bore and guide bore?

[40larry]

Originally Posted by flatjack9

The engine encounters much higher pressures during when running.

If the water is not allowed to boil and a working pressure radiator cap is used the pressure should not exceed the cap pressure. I see no valid reason to pressure test above 10 to 15 psi.


40larry

[Ken/Alabama]

Originally Posted by Bored&Stroked

You might think about going a bit oversize on the seats - unless you can perfectly center your cutter mandrel and exactly set the cutter size. Are you using adjustable cutters or fixed ones? Make sure you have your seats "in hand" before doing the seat ring work.

You want about a .005 press fit.

Do you have the good KwikWay pilot that picks up both the lifter bore and guide bore?

Yes, the pilot centers into the lifter bore and guide bore. My cutters are of the fixed size. I would like to have an adjustable cutter but the ones I’ve found are a little pricey.

[Dan in MI]

A working pressure radiator cap can only sense the pressure where it is located (i.e. top tank). Pressures vary greatly though out the system. From a low pressure area before the water pump inlet, Ever see a collapsed lower hose? Or a spring inside the lower hose to prevent this? Water pump outlet flow is generally higher than flow through down stream restrictions (think thermostat, openings in block, gaskets, heads etc.) This causes high pressure in the block. After it passes the restrictions the pressure drops (now we are at the top tank). Current production engines can see over 100 psi with 30 psi caps.

All that being said the last Ford block testing requirements for water jackets and oil galley I remember were air under water at 30 psi with no more that 8 cc of air leak per minute. At one time it was 20 psi and 12 cc of air leak. This was for aluminum blocks but should carry over for cast iron.

If it's going to leak you will find it at 20-30 psi, no need to go to 50 psi. Also, leak testing with high pressure air can be dangerous. Ever have a cap or plug blow off and fly across the room? Safer to test under water so the water contains the loose object. Or use a liquid, they are not compressible and if something comes loose the energy is dissipated quicker than all that compressed air. We used to pressure test cylinder heads with WD40. A cylinder similar to what is used on a port-a-power works for this.

[Tim Ayers]

What Flatjack was referring to was the compression pressure of a cylinder during the compression stroke. A fresh engine should see over 100 lbs easy. Faults in cracks work both ways.

[flatjack9]

Right on, Tim