End Of Season Testing on the New Engine
Below is not a good photograph:
Both heads and the intake are now off for some re-work. It could be worse. The problems are not serious and reparable. Also, the bottom of the engine appears to be fine.
The new engine has about 1300 miles on it. About 100 miles of that is blasting about an autocross course.
Testing included Direct Observation, Blow By, Compression, and Leak Down. I also have sent out an oil sample. I will write that up when it comes back.
I the next step will be to put the Procharger on it (along with a larger radiator). I have even gone to get pricing from a local speed shop (Beyond Redline Performance) here in Green Bay. But I want things to be all well, right & good in there before I put the additional power through it (“But First Syndrome”).
Here is the story on why I just took apart the top of a new engine.
Blow By Testing
This is not a common test. But it is useful and fairly easy. It answers the question – How are the rings doing? A Blow By test directly measures the volume of exhaust gasses passing around the rings into the crankcase in real time with the engine running. This engine has new rings, gapped and installed by me. I am no master engine builder. Needs to be checked… really...
Normally this is done by sealing up the crank case (rocker covers, etc.) and venting one rocker cover (or other port) through a hose with a fixed orifice. With the engine running measure the back pressure behind the orifice with a gauge. A table that comes with the tool gives you the flow through the orifice and that is the blow by getting past the rings. Normal flow rates are 5 to 20 Cubic Feet per Minute (CFM). If it is fluctuating you probably have a problem with one cylinder. If it is high but steady your rings are probably all worn out.
I did not like the orifice method. I am sure it works just fine but it just seems too indirect. So, like any rebel engineer I made my own that directly measures the air velocity from a fixed diameter tube. From there it is easy to calculate the CFM. The photo below is just the “Proof Of Concept” set up with some loose parts cobbled together. It worked better than I thought it would.
I will make a better rig that will give more repeatable results later this year and put together a write up for it. Basically the blow by gasses are straightened to laminar flow and routed through a Dwyer Wind Anemometer ($16). It is remarkably sensitive. I got readings of 5 CFM which is near perfect. Rings are good!
Compression Test
This engine was set up with a 9.5:1 compression ratio in preparation for supercharging. That should come to about 140 to 150 psi on a compression test. My results were 140 to 145 psig on all cylinders except #6. #6 was 138 psig.
Hmm… By itself that is nothing to be alarmed about…
Leak Down Test
The first leak down test was done with the engine cold. I know you are not supposed to do that but It is winter and things get cold quickly. Results were good with 5% to 7% on all cylinders except #6. This one had 12%. These numbers are great. They say your engine is not worn out until you get to around 30%.
Except for one little thing – I heard air leaking from the intake manifold when testing #6. Intake valve is leaking. That is probably why compression is lower on #6 also. This is also why leak down tests are so useful although they can be a bit of a pain to do.
I put things back together, warmed up the engine and tested again. Same results (Damit!).
Direct Observation
I pulled the left rocker cover off and ran the engine with little oil plugs on the rockers to keep oil from going all over. My friend Bill Schirtzinger put me on to these plugs (he has been using them since the ‘70s). They don’t keep the oil in if you rev it but they work great at idle. $16 at Summit.
With the engine idling I sounded each rocker stem with a stethoscope. #6 intake was louder than the others. Perhaps it is misadjusted and being held open? With the engine running I adjusted it. It was fine but no matter what I did it was louder than the others. Something was wrong with that valve. Follow up - Further inspection later in the summer showed it was slightly misaligned - side to side.
Using my boroscope I poked around in the spark plug hole and intake. Could not see anything interesting.
I pulled the head. #6 intake valve guide was very worn and ovaled. The valve stem has bits of guide welded to it. Not sure how this happened. This caused the seat to wear from uncontrolled valve movement as detected by the leak down test.
All the others looked fine with no significant wobble.
The valve tips all looked great – almost new. You have to get the light right on them to see any burnishing from the rollers.
Typical valve tip:
#6 Seat - You can see damage at about 7 o'clock:
#6 Intake Valve stem
Other observations: #6 intake valve is not bent. All of the pushrods look good and are not bent.
But one new issue: All the valve keeper grooves are mushroomed. Hammered. The keepers/locks appear worn on the outside as do the cones in the retainer caps. All of them. All the same.
I checked the valve grooves other head. All the same.
I pulled the other head. All twelve valves have perfect tips and seats (except #6 Intake). But all have exactly the same damage to the grooves.
Valves are strictly off Mistress’s diet! I don’t like the crunchy noises they make when she eats them.
Three Working Theories on the Keepers:
1- Keepers not fitting tightly to the valve stems. I used new Ford keepers. Perhaps they do not fit quite right with these valves. Perhaps the valve manufacturer has their own version of three groove keepers that should have been used (I believe it is supposed to be stock configuration but I am checking). Perhaps I should go with a different groove design.
I think lubrication is ok. In the video you can see oil dripping down all over on each valve.
2 – Last year I re-used the spring retainer caps thinking they were not a wear item. This may have been a mistake for two reasons: 1- They might be worn and thus not seating the keepers properly. 2 - They might be a different angle from the Ford keepers (7 degrees). I believe they are from CompCams and are also 7 degrees but I am checking on that.
3-Springs a little too soft for this cam? These are the recommended springs from CompCam for this cam. As noted during the rebuild I tested them all last winter and they met the specs so I reused them. The fact that the groove damage is very consistent with all 12 valves and only on the top edge of each groove leads me to think the valves are not riding down the backside of the cam and are slamming closed. Not enough, perhaps, to bring on valve float symptoms during a run but enough to slowly hammer the crap out of the grooves.
I am working with Super Six and my machine shop to figure it out. Any thoughts form the GRM family will be welcome.
The heads will go down to Manitowoc Motor Machine this week for a new guide, re-dressing and valves, etc. In the mean time I will start work on the suspension, brakes and long list of other things that are needed.
I am a little disappointed. This was not an expense I was planning on and fixing things is not as much fun as modifying them. But it is something to do on cold winter nights here in the Great White North…