Hey guys,

My 440 is getting some blow by and has been since I rebuilt it. I thought it may just need to break in. I haven't driven it a whole lot, so maybe it still does. Oil dipstick pops out a bit, oil leak from bottom, and oil smells like fuel a bit. The setup up I have right now is a PCV valve on one v/c w/ hose to carb, and on the other v/c, an open breather. Everything is new. Cam produces about 8-10 in of vacuum. Any ideas to reduce the blow by? Since the engine produces low vacuum could that be the problem? PCV valve not able to pull because of lower vacuum? Is there a better flowing PCV valve to try? I am going to try and do a compression or leakdown test when I get a chance also.

Thanks!

 

The PVC valve is not working if one side of the VC is open.. When it was rebuilt was it re ringed or re bored ??

 

When I say open, I mean one v/c has a breather with no hose going to the air cleaner and the other v/c has a pcv with a hose running to the carb; an open crankcase vent system.

The engine was bored 30 over and has new pistons and rings.

 

I would take it out on the highway when there is no traffic. Stop and burry your foot it up to maybe 75 or ? Use the trans to stop by downshifting - engine braking see if it helps to seat the rings. How much oil are you running in it ? the deal in the day with the 440 CHP cars (told by a CHP officer) with the windage tray and everything was to run them 1qt low to keep them from burning oil

 

I would try a cylinder leak-down test to check the health of the motor.

 

The old school break in procedure was to drive on an isolated road then in high gear run it at WOT from 30mph to 60mph, and repeat over and over. Aircraft engine manufacturers say fly it full power or as high a power setting as possible (keep temps in green) for an hour. Then 75% for half an hour and 100% for another half hour. You have to work them hard for quick break in...you want it to wear. Some will take longer, and a few wont break in.

Also synthetic oils will retard break in (take longer) because they are slicker. Unless it's blowing oil like a steam engine don't give up on it until you're sure. Taking 5,000 miles is not unheard of, but is a bit long. The leak down test will tell you where the problem is.

 

Vettes and others are delivered from the factory with synthetic. I no longer believe that synthetic can not be run in a new motor. The only caveat would be flat tappet wear, versus, roller tappets. And thats the zinc argument. But as far as rings go, synthetic is no problem.

 

Thanks guys for the replies. I drove it yesterday and "flexed" the engine and will try to do that today to try and break in the rings. I'm not using any oil except for the small leaks that I think are leaking because of the blow by. So that's a good thing!

I did do a compression check and #'s were kind of all over the place like when I checked it before (of course engine wasn't warm either when checked). I'll keep breaking in the engine and do a leakdown test later if I see no change. If my rings are not seating, my compression and leakdown #'s would be off anyway, so I'll just keep trying to break it in.

Thanks

 

Building and Using a Cylinder Leakdown Tester

 

Hey guys, here's an update on the leakdown test. I finally had the time to test it.

#1: 6%, exhaust valve, crankcase
#3: 17%, exhaust valve
#5: 28%, exhaust valve
#7: 15%, exhaust valve

#2: 5%, exhaust valve, crankcase
#4: 20%, exhaust valve
#6: 14%, exhaust valve
#8: 10%, exhaust valve

Interesting to note that they are all exhaust valves leaking, and the adjacent cylinder is close in % leakdown. What I am guessing is the valves got bent because of cam timing being off. The cam timing was off after the rebuild awhile back and had to degree the cam awhile ago.

I set #1 to TDC today and the mark on the balancer lined up to 0, so timing should be good.

Guess I'm gonna have to pull the heads and get the exhaust valves replaced.

As far as blow by goes. I'm still getting some blow by but I'll take a look at the cylinders with the heads off and if good I'll keep driving it and hope fully the blow by will go away.

 

On a good motor, most of that would be through the pcv, or crankcase breather. To see that much drop, and through the valves is a sad thing. I'm proud of you for doing homework, and not just throwing parts at the engine! A leak-down test is very labor intensive, but it is a great gauge of an engines health!

 

When I had a bad leakdown test I made a plate with thick rubber gasket to bolt on top of each cylinder to check the rings to be sure it was only the heads. It proved the heads were the only problem and saved me tearing the short block down.

 

I don't understand your reasoning here. If you mean it was off just a few degrees because of tolerances, that would NEVER be enough to cause valve contact

If you mean it was off "several teeth" on the cam drive, then, yeah.

How much lift you have on this cam?

If you suspect valve contact, instead of timing issues, I'd be looking at stuff like valve float, problems in the valve train with parts that are not compatible, valve contact due to lift/ duration.

There are only two ways I know of to test this, and that is to mock up the engine and either use clay or dial indicators to actually measure.

Valve contact on a "big cam" does NOT happen right at TDC so you need to check "coming up" and "going down" so to speak.

 

Once I got the heads off and inspected them. The valves looked fine and don't look bent. Plus no signs of the valves kissing the piston. Agreed, a few degrees off in timing should not make a big enough difference, tolerance wise, to have the valves come in contact with the piston.

Come to find out I took the heads back to the machine shop I had the work done on to have the seats cut a bit more. They were not cut enough to be sealed properly, and my fault for not checking to make sure they were sealed after the heads were assembled before I put them back on the block.

So, hopefully this will fix the issue!

 

So what you are saying is, THE CYLINDER LEAKDOWN TEST POINTED YOU EXACTLY TO THE PROBLEM!!!!!? Another GREAT EXAMPLE of a man doing his homework [not as fun as throwing parts at it, but much cheaper!] and finding his issue! Great job buddy! Sorry to be on my "soap-box" But as a broke-assed-son-of-a-bitch, I ALWAYS troubleshoot before throwing parts at a problem! And with the internet, there is no excuse! Good for you Dakota!

 

In general I agree, however there are many variables that determine the length of a break in period cylinder fit and finish being the main one. Modern manufacturing better assures a good assembly that will break in soon after start. Unless you choose your shop carefully and pay extra for careful work you don't get a guarantied perfect fit finish. Synthetics will prolong break in under these conditions. Also I don't put $100 in a crankcase I'm gonna drain in 20 min. then another $100 I'll drain in 500 miles.

However I agree synthetics are very good stuff, and I use it...after break in.

 

I agree with you one hunert percent. The thing I noticed was in the very first post, fast dak mentioned (and oil smells like fuel a bit)... Not gonna help break in the rings with diluted oil let alone scrub off the bearings. Bad valves did not cause this.Still need to seat those rings. Being as the heads are off I am hoping I don't have to say change the oil, but just in case "change the oil". Remember oil is cheaper than iron.