Thread: Recent FE390 rebuild. Getting blow back smoke out of exhaust and engine. Pleas help

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Hello friends. Was wondering if I could get some help. Recently had a 68 FE390 in my Fairlane 500 fastback rebuilt. The engine only has about 50 miles on it. I took it up to the local gas station this evening and noticed it is beginning to smoke out the exhaust. When I got home I let the car idle and noticed it was still smoking out the exhaust and when I opened the hood the engine at the intake manifold fill tube/breather as well as the pcv valve when I briefly removed it was putting out smoke as well. My oil pressure was between 60-80psi. Water temp steady at 185. This motor has a high performance cam with solid lifters, Weiand aluminum intake and Edelbrock 650cfm carb. I'm just wondering if I should be giving this engine more time to break in or if there is seriously something wrong going on. I'm not famiiar with Ford FE big blocks and was not sure how to proceed with this. I know the engine was bored .060 over and had new pistons, rings, cam and crank bearings, heads serviced. Thank you so much in advance for any help you kind folks could offer. I'm very worried that the engine needs to come back out and broke down.

If it's black sooty smoke, could be the carb is not setup properly.. I'm not familiar with the cam but how many inches of vacuum are in the intake manifold?

At first we'll have more questions than answers, but this helps isolate the real problem(s).. OH! Welcome Aboard, nice to see you here also.

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Welcome to the forum, and glad you're here.

Good questions above, and better answers will come from knowing the whole story but my quick reply based on what you've said to date is that I would not be concerned until I had more like 500 to 1000 miles on it, preferably with at least one or two spins of 75 to 100 miles at a stretch, varying rpm's as you go to be sure your rings are seated.

Originally Posted by stotzbotz

I know the engine was bored .060 over and had new pistons, rings, cam and crank bearings, heads serviced. Thank you so much in advance for any help you kind folks could offer. I'm very worried that the engine needs to come back out and broke down.

If the motor set for some time, the assembly oil can disapte leaving the rings dry. When a motor has set it is a good idea to prime the oiling system and squirt some oil into the cylinder prior to start to lubricate the motor and rings. While some blow by during the break in period is to be expected while the rings are seating (can take longer depending on the honing method used), I would do a compression test to ensure everything is ok.

Thanks everyone for your opinions. I am getting a reading of about 12 on my vacuum gauge when at about 1000rpm and about 15 when at about 2000rpm. I was told this was close to normal with a race cam but you folks are the experts. I have an older Weiand aluminum intake that came with the car and although I read some less than positive reviews about it I think that it's sealed pretty well. I sprayed carb cleaner all around it the best I could while the engine was running and didn't get any changes that I could notice. I know that I might be jumping the gun a little and maybe should give the engine more time to break in but I want to do anything I can while it's breaking in to make it a smooth and stress free process. I'm thinking that the pcv valve and hose I was sold at the parts store might be a little restrictive so I'm going today to get a larger more open style valve and hose. What do you folks think? Man I love this forum. I really appreciate the responses

blow by - oil blowing out breather/ pvc and oil leak = compression rings . smoke out exhaust = oil rings.
could be valve guides also .
black smoke is too much fuel little air . ( choke hung ) white smoke is water/antifreeze .
blue smoke is oil.
light blue smoke is excessive fuel .

What oil are you running?

Some folk claim that synthetic doesn't allow rings to seat, and break in should be done with dino oil.

There has also been a lot of discussion on this board regarding zinc for the cam break-in. (Just search the threads for zinc, you'll find it - if you're interested)

Ford FE's are infamous for leaking oil into the intake ports if the intake is not installed correctly or if the mating surfaces are not machined to mate exactly. This is also an issue if Print - O - Seal intake gaskets are used. It can also happen if the cork china wall gaskets are used, which can result in the intake standing proud of the head mating surface and not sealing correctly.

If it doesn't clear up, you might want to consider removing the intake manifold, and cleaning all gasket surfaces on the head, intake and block perfectly. Use a feeler gauge with the intake sitting on the engine with no gaskets to check that all surfaces are parallel and true. Then reinstall using good solid intake gaskets, and using "The Right Stuff" on the ends for the block china wall seal.

As you know this is not a easy job due to the FE's unique architecture with the intake actually making up half of what is traditionally the cylinder head, and subsequently the pushrods passing through the intake. It's not terribly difficult, though. Just take your time, then re-adjust your valves when done. Best of luck.

Again I very much appreciate everyone taking the time to try and help me with this issue. I guess the thing that doesn't make sense to me is that this car did not smoke in any way when it was first fired up and during the first 30-45 minutes of break in time. The brief trips around the country didn't yield much if any smoke at all either. Yesterday I started the car and let it do a high idle for a little while and at first no smoke. Suddenly the smoking started up and continued the rest of the time I let it run. Oil pressure was around 40psi at 1000 rpms after the warm up, temp steady at 185. The smoke is the best I can tell a very light blue in color although it was very cloudy and fixing to rain the whole time I was running it. The carb I'm using in an Edelbrock Performer 650cfm and is new. Not much to adjust on it but I did set the mixture screws at about 2 1/2 full turns for a good starting point. The people who did the bore job, installed the cam bearings and serviced the heads build racing engines and have been in business for over 30 years. They also ordered the pistons, rings and crank bearings. My brother has been repairing and building engines since he was 14 and is now 57. He really knows his potatoes about engines so I feel confident everything was installed properly. I'm not sure if a compression test this early on will be an accurate indication of anything but I can see what I'm getting at this point. Maybe I should stop bothering you good folks and just give the motor more time to seat the rings.

Originally Posted by DennyW

Do you have an automatic trans ? It could also be the vacuum modulator allowing trans fluid to enter the vacuum line.

As Denny says above, remove and plug the vacuum line from the carb that is going to the automatic tranny and see if the problem disappears.

Originally Posted by stotzbotz

I'm not sure if a compression test this early on will be an accurate indication of anything but I can see what I'm getting at this point. Maybe I should stop bothering you good folks and just give the motor more time to seat the rings.

The smoke coming out of the PCV port when valve was removed usually is an indication of positive pressure in the crankcase (blow by), usually this condition rules out an internal vacuum leak (leak on the underside of intake manifold) causing the smoke. While some crankcase pressure is normal (especially during break-in), usually the PCV system handles it and by lowering the crankcase pressures aids the seal at the rings and lessens the chance of oil slipping past the oil seals at the valves.
Excessive crankcase pressures that overcome the PCV system are usually caused by piston rings not sealing correctly. While this can occur during break-in, it seldom gets worse as the break-in procedure continues. Extreme crankcase pressures can sometimes be felt at the PCV port by placing your hand over the valve cover port, with the pressures trying to escape around your hand. This extreme condition in a new motor is almost always caused by a serious ring failure (incorrectly clocked or broken rings). And, a compression test will show the low cylinder pressure at the trouble cylinders. If damaged or broken rings exist, continuing to operate the motor will only increase your damages.

keep in mind the pcv is just a smog device. i run the large moon breather to vent. if you run the pcv and a solid cap on the other side it will blow oil out every seal in the motor.

Originally Posted by shine

keep in mind the pcv is just a smog device. i run the large moon breather to vent. if you run the pcv and a solid cap on the other side it will blow oil out every seal in the motor.

When the PCV was originally designed it was a sealed system smog devise and quickly resulted in seal and other motor problems. The addition of a breather to reduce negative pressures solved the problems and the benefits were soon learned and practiced on even race motors. Improvements to the system continued including valve cover splash baffles exc.. A properly operating PCV system will also aid in keeping the internal engine parts cleaner by reducing some of the harmful gases that will cause corrosion.
IMHO, the benefits of a good operating PCV system far out ways any disadvantages and I have PCV on every motor I have.

Certainly not meaning any disrespect or trying to sound like a know it all.
IMHO, a properly installed PCV system will not cause blow by (crankcase positive pressures), as it is a vacuum based system. Not to say an improperly designed PCV system will not result in oil being introduced into the intake causing smoke. Simply, if you have the PCV removed and have excessive crankcase pressure causing extreme oil smoke to come out of the PCV port, you probably have additional conditions adding to the problem.