exhaust crossover and pressure testing

R

revkev6

Senior Member
hey guys, I pulled the 8ba down in my roadster this spring to freshen a few things up... basically all it seems to need is a new gasket set and some paint if the pressure test turns up ok. I found 30" of weld in the pan rails, but it was rebuilt and running for 25 years like this. i have smelled a little coolant in the exhaust so I'm concerned about whether it's the head gaskets or exhaust ports cracked.

when the motor was put together it had the old school copper penny tapped into the exhaust crossover holes trick done to it. well on tear down one was missing and the other looked to be pretty close to falling out as well. This car is only run during warm weather so I don't want heat in my manifold. I don't want problems with boiling the gas on this thing with ethanol....

on a side note... I'm in western mass (springfield/six flags area) can anyone recommend a shop near me that I can bring a complete motor minus heads/intake/water pumps and have them pressure test it?? tried scrounging up a set of testing plates from a retired engine builder I know but every call I get I'm getting pushed out further.
 
You can pressure test it yourself. I made a gasket for head(didn't have a spare head gasket laying around) then put a plumbing plug, the type you tighten, inside the head outlet. Plug the temp sensor holes. Install a good water pump and gasket, and use the same type plug with a small hole for air chuck. attach a gauge and add air.
You can see if it loses pressure, but I like to fill it with water. That way if it leaks, you will see it. You can also spray it with soapy water(with just air). Of course, you have to test each side separately.If you want to get fancy, put some dye in it.
Typical flathead pressure is about four pounds, I put approx 25-30 in.
Not scientific, but it works and it's low cost and you can do it at home.
 
You could consider doing a magnaflux on the deck surfaces.
This will be a preliminary to the pressure test, and cheaper.
Look at the area around the valve seats and cylinder edge.
With a test plate you can see this combustion area.
I would use a test plate, with air pressure- spray water with a bit of soap in it.
Look everywhere, but check pan rails, behind the valve springs, exterior.
Contact me if you wish.

Karl
 
revkev6 said:
I'm in western mass (springfield/six flags area) can anyone recommend a shop near me that I can bring a complete motor minus heads/intake/water pumps and have them pressure test it?? tried scrounging up a set of testing plates from a retired engine builder I know but every call I get I'm getting pushed out further.
Click to expand...
I have used Eastwood machine for crank and balance work.
Don't know if they can provide what service you require but you can give them a call.
http://eastwoodsautomachine.com/contactus.html
 
The test kits run around $250 but when you think about how long it would take to fabricate that stuff the price looks better & better.

One that has had cracks repaired in the past already shows the vulnerability. It must have frozen up somewhere back in its life for sure. The pan rails are the first thing that cracks but who knows where else it might.
 
rotorwrench said:
The test kits run around $250 but when you think about how long it would take to fabricate that stuff the price looks better & better.

One that has had cracks repaired in the past already shows the vulnerability. It must have frozen up somewhere back in its life for sure. The pan rails are the first thing that cracks but who knows where else it might.
Click to expand...

yeah, I work in a machine shop... if I wanted to I could drop a pair of stock heads off to my tooling guy here and he would mill out the cylinder and valve area... probably harder to find a decent rubber gasket than anything. i've heard the water pumps are not good to use as a cap for a pressure test. mine are stock type so if I put too much pressure on them they leak???

as for the pan rails that is the obvious worry. when the rails crack the possibility of the exhaust ports being damaged is very real. The motor is pretty much a stocker with aluminum heads and dual 97's... no real pushing it hard. if it's leak free it's going back in.
 
I'm sure the caps are likely water jet cut pieces of just flat plate with neoprene gasket. If the deck plate part is fabricated thick enough, it could be used as honing plate less the seal.

I've seen a few that had coolant come out the exhaust port as soon it was poured in there. The siamese ones like to crack more than the end ones but who knows?
 
We made ours, but then again we have a 50ton iron worker and punched all the holes. Used a old headgasket to lay it out. Got the neoprene from a local industrial rubber supply. $20 and some time and used what plate that was in the shop.

Same goes for the plates on the water pumps. Used a gasket to lay it out.
 
skidmarks said:
We made ours, but then again we have a 50ton iron worker and punched all the holes. Used a old headgasket to lay it out. Got the neoprene from a local industrial rubber supply. $20 and some time and used what plate that was in the shop.

Same goes for the plates on the water pumps. Used a gasket to lay it out.
Click to expand...

I'll double your money for a set! :D
 
I made something to do preliminary testing. It was a plate the bolted onto the thermostat housing with a tee screwed into it that had a schraeder valve on one leg and a pressure gauge on the other. I made plates for the water pump openings out of 1/4" aluminum, but found no matter what I used for a gasket, they would leak on the one edge. I believe they would have to be 1/2" aluminum or 1/4" steel to hold. Anyway, I ended up using some vinyl caps I got from Amazon to cap the lower water outlets. Unless your water pumps are in excellent shape, you will get leakage around the shafts. I was able to test for leaks however, because I made fittings out of old spark plugs that I put in the plug holes and put a kid's balloon on each one. Believe me, if you put 5 lbs of air pressure on this setup and you have ANY leakage in a cylinder, the balloons will detect it. One of my water pumps would hold pressure and one would slowly leak down, but this was enough for me to determine that there were no water leaks in the block.

Someday, I am going to finish these by making better block off plates, but I haven't gotten around to it yet. I believe that, even with only the vinyl caps, this setup has the advantage of be able to be used in the field, The plate with the gauge, the vinyl cap, and 4 kid's balloons and a portable air supply will allow you to separate the "wheat from the chaff" just about anywhere.
 

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john in illinois said:
Tubman,I like that. Simple tool to do a complex job.

John
Click to expand...

John,

If you want to make your own, I had 10 of the thermostat housing plates made "on the come". The other components are pretty cheap if you get them from Amazon. Say the word and I'll send you a plate and a vinyl cap (I had to buy them 10 at a time, as well). Old spark plugs and balloons are available locally.:)

Tubman
 
Ok guys.. decided to attempt this myself. My brother had some foam rubber sheets so I made a gasket to use with my heads and stock waterpumps. I will put a air chuck regulated in the head.
What psi should I shoot for and does anyone have a recommendation for a solution to spray in the ports to foam up that won't rust up the motor?
 
Use dawn soap and water, you can blow it out with air after you check for leaks.
Spray it in. If it leaks you will see the bubbles. I have found tiny leaks on truck brake systems this way, even ones you cannot hear.
 
Well.. dawn worked well... no worries about getting anything rusty... this thing is junk. number 1 exhaust cracked and leaking at 10psi. Center exhaust on driver side is the same.. time for a new motor... not a happy hot fodder right now.
 
Tried posting pictures.. but they are too big.. oh well maybe tomorrow. Really too bad. Motor runs great and was rebuilt 25 years ago with probably 15k on it in the roadster... easy miles and it shows inside. Except for the cracks!
 
Pins pins and more pins...and then a sleeve or 2...welcome to the wonderful world of flathead overhauling...
If it is a good running engine pinning a couple of cracks is perhaps an option...it takes time so will cost a few bucks though.
 
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