Valley Pan pushed up

[moper]

You need some real air pressure to have the gages read correctly - at least 100cfm. But a lot is still a lot. The issue that caused the test was the pushed up valley pan - so it's not the gages or the 90psi. The 400 will be a good platform, and IMO the stage VIs should outflow the stealth if the Stealth were not ported. But - the MP heads are well known to have some issues out of the box. I would be nervous about them if they were never actually run on an engine. I would have them checked by a shop familiar with them before I ran them.

 

[PRHeads]

As I said, if you want to “directly read” the percentage of leakage off the leak down gauge, the inlet gauge MUST BE AT 100psi.

That’s why there is a regulator on it, so it can be adjusted to exactly 100psi while the test is being performed.

As for the stage 6’s, they look hand ported to me.

The best(least problematic) version were cast by the Zeus foundry, and have the name Zeus cast into the top of the heads.

If they aren’t Zeus castings, I’d have them checked out thoroughly before putting them into service.

They have more potential than the stealths....... a lot will depend on which heads are more developed.

 

[Garys1969RR]

Well I just returned the Pittsburgh gauges. Every time I tried to adjust pressure, the right gauge would continue to slowly drop down for a few minutes. Made it very difficult to get an accurate reading . But there certainly is a Lot of leakdown, just not sure of the percentage. If the pressure gauge shows 100, and the leak down side shows 90, then you have ten % leakage, right? The pressure control would only make the right gauge move. And I couldn't get the compressor pressure adjusted to 100. It was about 85.

 

[Garys1969RR]

Far as the heads go, I'll look for the Zeus logo on there.

 

[PRHeads]

The tester in your picture has the face of leak down gauge reading the “percent of leakage”, but only when the inlet pressure is set at 100psi.
With the gauge all the way clockwise it’s “0%” leakage,with it all the way counter-clockwise it’s “100%” leakage.

If you have the inlet pressure at around 85psi, the leakdown gauge is probably showing around 15% leakage before you even attach the hose to the engine.

You hook up the hose, let the gauges stabilize......... adjust the regulator so the inlet pressure gauge is sitting at 100psi, then whatever the leakdown gauge reads, is the leakage.
If the needle is pointing towards 90%, you have 90% leakage.

If you can’t get the inlet pressure to 100psi, the leak down gauge will read low(high percentage of leakage).

On the older type that has two identical gauges you can use pretty much any pressure you want, and do the math.
Years ago the inlet pressure used was typically 80psi, so if the second gauge read 72, you had 10% leakage.

I just went and read through the instructions on my old gauge set(about 25 years old) that has the two identical gauges, and they’re recommendation is to use a test pressure at least 10psi less than the supply pressure.
Since many home shop style compressors run at about 90psi, that’s probably how 80psi got to be used as the std leak down test pressure.

 

[MOPOWER871]

Hi Gary, just curious , what where your spark plugs read ? Any signs of detonation? Just my two cents ,I've done leak downs before and I remember having a problem getting a consistent reading when checking each cylinder. Though it was the tester, turns out the crank was spinning a little when compressed air was introduced into the cylinder, had to put a braker bar on the damper bolt to keep the crank from moving . Then I got consistent reading when repeating test. Good luck

 

[Garys1969RR]

Thanks! Well, as I said, adjusting the regulator on the gauges only made the right hand gauge move. The inlet one stayed at 85. Then once the right one was at zero, then you hook the hose from the gauge up to the cylinder for leakage %, according to the instructions. And then it would always go into the moderate range. I'm going to get the dual gauge set up like you have, PR. So much for buying a tool like that from Harbor Freight! LOL. All the other tools from there have worked fine.

 

[Garys1969RR]

Hi Gary, just curious , what where your spark plugs read ? Any signs of detonation? Just my two cents ,I've done leak downs before and I remember having a problem getting a consistent reading when checking each cylinder. Though it was the tester, turns out the crank was spinning a little when compressed air was introduced into the cylinder, had to put a braker bar on the damper bolt to keep the crank from moving . Then I got consistent reading when repeating test. Good luck

Spark plugs have a nice tan color, no sign of detonation. I set #1 piston at TDC, then went 1/4 turn to check each cylinder in the firing order. My damper is marked at 90 degree intervals. At no time did the crank try to move while pressurizing the cylinder. If the piston is at exactly TDC, then the crank won't move when you apply pressure to the cylinder. I even rotated away from TDC, and at no time would the crank turn on it's own. That's how poorly the rings are sealing. Leakdown actually improved, as the piston moved away from TDC.

 

[PRHeads]

Have you tried doing a regular compression test?


My guess is that gauge set you had would have worked fine if you had more pressure coming from the compressor.

If you can believe the pictures to be correct representations of what you’ll receive........ looks like several places still offer the testers with twin 0-100psi gauges.

 

[Garys1969RR]

On a compression test, seems we had around 160, which isn't bad for this altitude. Unless the C Ratio is up around 13 to 1. My 451 was getting 210 to 220 PSI on the test. It was a 13 to 1 motor, with a 509 cam. I suppose there are too many unknowns here. That's another reason I want to tear it down this winter. Find out exactly what I have, address an oil leak, and at the very least re ring it. Plus I may try out the Stage VI heads. Which by the way , don't have any ZEUS logo on them, but the date built is July 1995.

 

[PRHeads]

The first three things to check on the stage 6’s before going too far are:
-valve seat depth/valve drop.
Typically they will have .040-.060 valve depth variance between two heads.
The best I’ve ever seen for ootb heads is about .030.

-rocker stand to valve tip length.
I know of a couple where the stands were way too far away from the valves.

-be sure to mock up the heads, rockers, pushrods and check for interference around the intake pushrod tunnels.
Usually you can just eyeball the tunnels from the top and see they aren’t all in the same relationship to the v/c rail or intake port.

-cc the chambers...... all of them.
They are often all over the place....... and almost never 78cc’s ootb(the Zeus were pretty close as I recall).

-check the head gaskets/chambers for overhang problems.
Not usually an issue with the ones that didn’t have the cnc’d chambers, but worth checking early on in the process.

-it’s also a good idea to check for parallelism between the dowel pin holes and the intake flange, and also make sure the dowel holes are the correct distance apart.

Last set I did:
http://board.moparts.org/ubbthreads/ubbthreads.php/topics/2426472/1.html