Rebuilt the ol' 390 in the 63 ½ Galaxie last winter and was really pleased that I got her back in for the Springtime enjoyment. It's been a great springtime ride! The rebuild went through just about everything -- bored (+.040), new pistons (H304P), balanced assembly, all bearings, cam (Comp 268H), C8AE heads w/new valves, guides, etc... Blue Thunder Intake, used my old Holley 4150 650DP, original dual point centrifuge distributor, FPA headers, rah, rah, rah...
Since break-in it's been running very strong and I've been quite satisfied with the performance - meeting my objective of wanting a simple freshened up, but lightly spirited, street motor. If I did it over again I might only bump the bump stick up another notch.
My dilemma is now with just over 500 miles on it, it's still burning oil - a quart+ the first 300 miles, and about another quart in the last 200. Still, a bit of blue smoke comes out of both pipes with more at idle than at higher rpms -- but not so much as to get me turned into the EPA or laughed at. I certainly won't claim to be any sort of professional, and just a shade tree wannabe, but any motor I've ever redone in the past has always seated rings before 500 miles. I would think the rings would have seated by now, and I'm not sure they haven't. Hoping to avoid any major surgery here, but I'm starting to wonder. By the way, I believe these are cast iron rings but I don't know for sure since they machinist was kind enough to install the rotating assembly.
I'm running Valvoline VR1 Racing Oil 20/50 with one bottle of the Red STP Oil treatment. Getting 50 - 75 psi oil pressure. All cylinders are consistently holding ~170 psi on compression tests. Vacuum is a steady 18 at idle. The plugs are definitely showing a rich mixture (not sooted, but dark and almost black in some cases).
Some of my preliminary thoughts:
Perhaps an intake leak - However, if there were a vacuum leak in the valley, it would have shown on the vacuum guage and would likely not have included all cylinders.
Perhaps a head gasket leak - However, I would have expected more smoke and, like the intake, would likely not have included all cylinders.
Perhaps I should have changed out that old Holley and it's running rich enough to wash the cylinders and not let the rings seat completely - However, it seems to run fairly well, other than a little dead spot coming off idle (loading up a little).
I'll be doing a leak down test next, but wanted to also get other guidance from you folks.
Sorry for the long winded post, but I was hoping to provided enough information for you guys to give me better advice and direction.
Any thoughts appreciated, and Thanks in advance!
This message has been edited by 63390 on May 31, 2009 5:35 PM
I agree that cast iron rings usually "seat in" rather quickly, however, do you know what grit the machinist used on your cylinders to finish off the bores? Maybe the wrong hone was used! I guess you checked the valve guides, and valve seals were replaced, you know, the usual service items. Mistakes have been made by installing rings up-side down, causing smoking, but I would think this would also effect the outcome of the compression test. I feel a cylinder leak down test would be next! Do you have restrictors installed in the cylinder heads to limit the quanity of oil inside the valve covers? These are just "Quick thoughts" that come to mind, not knowing a whole lot about the engine. I hope it helps you! Dean
Not sure what grit was used, and I'll be calling this week to find out. However, I did ensure there was a surface in each of the bores before I mounted the heads. Valve guides, seals, etc were all done also.
I hope the rings were installed correctly, but I really don't know. I do know that the machinist is a two man shop and has a solid reputation in this area.
No restrictors in the heads. Also, no pcv system. Trying to stay somewhat vintage, I opted for a breather, using a cobra style breather instead of the draft tube. I have been wondering about whether this might be related to the issues but can't see how.
O.K. now, you say you are using a Cobra type manifold vent at the rear of the intake! Does your intake have an oil fill tube at the passenger front corner, or do you have twist/push-in breathers on either of the valve covers? With no pcv valve, the engine needs to breathe in fresh air into the crankcase as blow-by gasses escape through the road draft tube/Cobra Vent. I guess I'm asking if you have those breathers! If not, blow-by could be occuring, but maybe not strong enough to push oil out the Cobra vent! The only place the oil could be going is past the rings! Again, to be sure, DO THE CYLINDER LEAKAGE TEST! If you have axcess to a borescope, I would use it to examine the condition of the cylinders[amount of oil present or absence of oil]. You could also use it to examine the intake gasket area insde each intake runner to check for gasket slippage or presence of oil entry into the intake runners. Simply remove the carb and fish the borescope into each runner. Oil will discolor wherever it is present. Just a few more thoughts to try, before you start taking it apart! I hope it helps! Dean
Re: Have you been babying it. Run like you stole it, run it up to 3/4,000rpm.........
May 31 2009, 7:47 PM
You raise a good point. Though I have stomped on it a few times, I tend to be easy on it - generally keeping it below 4500. Anytime it has seen above that is only for very short revs...
The other thought you raise is the fact that I am running a 160 deg. thermostat. Was thinking about thining the oil to 10/40 and raising the thermostat to 180/190 - then taking it on a long hard cruise on the back roads. Perhaps a few miles like that will get her attention!
What kind of seals were installed on the guides? Stock umbrellas? teflon. Etc..? Poor valve seals can cause in a lot of oil being burned. Also, search the blog for info. on valve seals. There has been a lot of discussion on the matter. A good procedure for breakin in to get on a lonely road and get up to 60/65 mph.,then floor it for a couple of seconds, get off of it,then floor it. Do this repeatedly for about 20 times. This moves the rings around and helps seat them. Good luck. Hope this helps.
Just had the same problem on the wifes 429. On long trips, 4-500 miles. Go through quarts of oil. Could see some puffs of smoke coming out of pipes went accelerating at speed. Finally checked it out couple wks ago. Removed valve covers to find the umbrella type seals( previous owners build) riding up on the valve shafts. This motor has a a high volume oil pump too so oil was pooling up and going through valve guides.
Purchased some positive valve guide seals from DSC here and put them on. They fit great,stay put and oil consumption problem is gone. This worked for me. On my 390 and 428 earlier I installed some holley restrictors #60 in the heads as well as postive valve guide seals. JMO.
68 Torino GT S code 390 fstbk
70 Torino GT 351cl 4spd
71 Torino Cobra 429 C6
If you used moly rings it should have broke in on the first run
June 1 2009, 10:18 AM
I am betting on it sucking oil into the guides. Check the drainback holes for any blockage, use positive seals at least on the intakes, and use the tongue type baffles that route excess oil to the intake valley. If the guides are submerged in oil it will suck oil at high vacuum. BTDT.
If the rings didn't seat after running it in you have a problem somewhere, like a broken one. Moly rings don't require much at all to seat, nor does iron. Chrome can be tough, but usually if its a ring issue you'll have a lot of blowby, blowing the dipsitk out etc, oil spraying out of the vent. You can get some smoke if you lined the 1st and 2nd rings up, but you will see that on a plug, and again blowby. It won't be general, but on a specific cylinder or maybe two. My 352 is worn completely out, and it doesn't smoke or use oil, it just has a bunch of blowby and blows it out.
Another possibility with rings, is improperly interlocking the scrubber causing it to carry more oil up than the 2nd ring can scrape off. The chances of this happening are slim if the guys knows how to build an engine, but it can happen by accident, again 1 cyl fighting oil. If its general to all 8, I'd look at the guide seals and oil control on top. You want oil on the springs to cool them, but without submerging the guides.
Just for grins and giggles - run a compression check.
June 1 2009, 10:43 AM
I would tend to accept the umbrella seal diagnosis. But - being the pessimist that I am, I would run a compression check to see if the cyloindera are all pretty much the same. With a new build, I tend to worry about broken rings when rings don't 'appear' to seat and the car is still using a lot of oil after a decent break-in period has passd
Seeing blue smoke out of both tail pipes, if you have H-pipe, is not necessarily an indication that the problem is shared by both heads, since there is a common connection between the exhausts..
Blue smoke, far as I know is vaccum sucking oil into the cylinders. Best I can remember, it happens when you let off the gas or decellerate. When it happens during acceleration its rings. There should be deposits on the plugs too.
Like I said, its been a while since I had a problem like this. My trouble shooting skill have withered from disuse. Engines are much cleaner now-a-days.
Usually you will see alot of blowby with broken rings
June 1 2009, 11:25 AM
If the 2nd scraper ring is broke it can pull a little oil up, but generally it will go the other way, positive crankcase pressure with the burned oil coming out of the vent or dipstick tube.
Its good advice to do a compression check, but remember that oil raises compression. Do a leakdown test too. A poorboy way of doing this is to use the cylinder chuck for a compression test and plug 100 PSI of air into it on TDC with both valves closed. If it drops to 90, you have 10% leakdown 80, 20%and you can listen around for where its coming out, if its going to the crankcase you have a ring problem, a port, a valve sealing problem. Pull the dipstick and if you get a real hiss or alot more pressure there on a cylinder then we have problem. Stay clear of the fan though, you can turn the engine. The best way is to lock it down mechanically at TDC for each cyl, but I have never had one turn on me with a cylinder at TDC.
As for testimg intake ports for pulling in oil you'll probably see that during a compression test with oil being deposited on the chuck. Note any sprayers, and wipe it down before moving on. Pull all of your plugs, hold the throttle wide open and crank it. If you have a bad intake gasket leak, you'l probably see it spraying while you are checking the others. BTW put the plugs back in before doing the leakdown test, the other cylinders will keep it from moving.
with Bill's text and am also a big fan of leakdown testing. These tests should eliminate broken rings, lack of ring seal, cracked runners, etc. But, no compression or leakdown test can really determine if it's merely the valve seals that are the cause. The following oldie and moldy suggestions still apply though in diagnosing bad seals.
Heck, have someone drive your ride and follow behind for awhile in another car. Amazing what you may see, especially on heavy deceleration!
Blue smoke is only caused by oil in the wrong places:
Blue smoke while idling and low revs, or a puff if smoke when accelarating from idle means the valve stem seals are shot.
Blue smoke while driving shown the rings are worn, usually harder to detect than in petrols but always linked to higher oil consumption.
Blue smoke on decelleration on long slow downhills, shows valve stem seals are shot.
I knew I could count on you guys to send along some helpful suggestions and good insights, and indeed you did. I'll first be doing the Leakdown Test and then pursuing some of the other suggestions next time I'm under the hood - hopefully this weekend. Will let you know what I find.