I'm wanting to do a leakdown test on the 400, but the instructions say to have the engine at full temp.....but that poses a problem.

I need to pull back both headers to get at the plug holes. Especially in order to screw the hose and fitting in the plug holes!!

They headers would be so hot if I warmed up the engine that I wouldn't be able to touch them for at least two hours!

This is my first time trying this type of test. I did a few cylinders on the 305 which is on a stand now, and they looked good at around 87.3%. And that's a cold engine.

But the 400 I want to test is in the car...So does the engine absolutley need to be fully warmed up?? Or will not doing so not give me accurate readings?



EDIT: BTW, most other instructions that I've read about on the web do not mention having the engine warm.

 

Doesn't have to be raging hot. Fire it up, drive it around a little to warm it up and stir the juices. Bring it home and start taking off the headers (which should cool down considerably in only about 10-15 minutes with the hood open). Do your test. I've never done compression checks on a truly hot engine for the same reason you don't want to- burnt flesh isn't fun. Do the best you can with it. Yes, the results will still be meaningful.

 

Well, maybe I'll let it idle for a few minutes then. If I take it for a drive, fat chance of it cooling down in 10-15 minutes, even with the hood open!

I went ahead and got the results from the 305 even though it's on a stand now....Still seems to be a good engine!!
I rebuilt it myself about maybe 5000 miles ago...

I set the inlet pressure at 90 PSI, and got the following:
#1 cyl. = 3lb drop, 87.3%
#3 = 11lb, 80.1% (worst)
#5 = 7lb, 83.7%
#7 = 5lb, 85.5%
#2 = 8lb, 82.8%
#4 = 7lb, 83.7%
#6 = 2lb, 88.2% (best)
#8 = 6lb, 84.6%

All with no leakage whatsoever through the valves. All rings.

I'd be happy to see these kind of numbers out of the 400 I think, but I somehow doubt they'll be near that good... we'll see....

Anyone have any idea whether the numbers posted above are good? I've read somewhere that anything 20% loss or less is good....

 

Quick update with questions...

So far I've only tested 2 cylinders on the 408, and already it doesn't look good.

#2 cyl. =17lb drop at 90psi, 76%
#4 cyl. =1lb drop at 90psi, 89%

I checked #2 cylinder three times with the same results. The air is blasting past the rings. This engine is a fresh rebuild with 2K on it. I was hoping it would seal up and quit smoking by now, but it doesn't look like that's going to happen.

So - the question part...

Since everything is new inside this engine (crank,rods,pistons,rings), what would cause them to not seal properly? It's supposedly bored to 4.165, so there's no room left really to overbore it again for new pistons/rings, so - if it turns out that the cylinder is screwed up somehow, I'll have big issues with the shop that built it.

And if the cylinders are in decent shape, (which they SHOULD be) - what would need to be done in order to get a set of rings to seal? Will a re-hone and new rings do the trick?

To say this is fustrating is a understatement. I'm p*ssed..

Now I have the pleasure of going roudy-roundy with the shop that put this engine together to see if he'll back up his work. It still means I'll have to pull the engine back out of the car and deliver it to him. And after this, I'm not totally sure I want him to try again....

What a mess.

I'll post up the rest of the results after I get them. I'll also shoot a little oil in the low cylinders to futher prove it's the rings, but I'm 99% sure it is.

 

The reason you do it with the engine warm, is because the parts (pistons, rings, bores) change size and shape with expansion, and the seal may get either better or worse as a result. What matters of course is whether it selas when it's hot.

Why are you doing this in the first place? What makes you think that there's something wrong with the rings?

 

Yes, I know it would probably be better to do this when the engine is hot, but I was hoping these results would at least give me an idea if I have rings blowing-by or if I have valve problems.

There's just no way I'll be able to do this on a hot engine because the headers are in the way. It's hard enough to change plugs on the thing, let alone try to screw a hose in the spark plug hole with hot headers directly in front of them.

What makes me think I have a problem in the first place is that the engine smokes. If I allow the car to sit and idle for like maybe 15 minutes, the smoking will gradually get worse. After the engine is warm, it still smokes slightly. If I am driving around town, it isn't noticeable, but If I downshift to stop at a light, everthing's fine till I go to take off - then I get a small cloud of bluish smoke from the tailpipe.

I've changed plugs twice. Now these plugs are black and oily too. I changed intake gaskets twice also with no difference.

I've expressed my concern about the smoke to the builder after I installed the engine and drove it approx. 1K miles with this problem. He felt that 1K miles wasn't enough to seat the rings, and told me to drive it another 1K and see if it stops. Well, it hasn't even slowed down. You may have read some previous posts I had pertaining to how rough it seems to idle, and everyone that responded seemed to feel that my cam isn't very radical, and it should idle smooth and get decent gas milage.

Well - it still idles fairly rough, eats gas like no tomorrow even though I've leaned out the carb alot by stepping down 7 jet sizes all around. So I'm really thinking it's a power inbalance amoungst the cylinders that's causing the rough idle due to blow-by. Athough the engine doesn't seem to be down on power, and accelerates quite nicely, I know there's more there....

I'm open to any suggestions or things to check, because I really don't want to go through all this - again. But I've checked and tried alot of things before I got to this point.

Sorry this is so long, but I want to give as many details as I can.

 

So is there anything else that could cause the engine to smoke , or were you just curious as to why I'm doing a leakdown test?

 

Yes, just curious. It tells what you're trying to isolate. People don't generally get all excited about leakdown numbers on a brand new motor, unless they suspect something is wrong; it's helpful to know what's driving them to do tests like that in the first place.

2 different parts are responsible for oil control and compression. There are compression rings that deal with sealing gases, which is what you're testing with a leakdown test; and then there's oil scraper rings, which is what controls the oil. Either one can be perfect, while the other is totally dysfunctional. In other words, testing the one thing, tells you nothing whatseover about the other.

The only thing they have in common is the cyl wall itself. In an old engine, a piece of dirt or debris can get lodged in a piston skirt or above the top ring land or wherever, and travel up and down with the piston for a hundred thousand miles, and wear a vertical groove in the cyl wall. Then compression can leak past an otherwise perfect compression ring, and oil can leak past an otherwise perfect oil ring, and a leakdown test will show that there's a problem with compression which can be inferred to involve the oil ring as well. That is just about the only possible malfunction that connects compression and oil control.

In other words, in a brand-new engine, you're largely wasting your time trying to isolate an oil control problem with a leakdown test. About the only thing that could have happened that would cause both poor oil control and compression leaks, is very poor cyl wall prep; out of round, very bad honing, damage during assembly (particularly an oil ring that got a corner folded up or something, and immediately chewed up the cyl wall), etc. Personally I wouldn't expect to find that in your case although it's not impossible; it's just highly improbable.

Furthermore, if the rings or cyl walls were bad enough that you had both an oil ring and a compression ring failure, you'd have so much blowby, that your PCV valve probably wouldn't even stay put in the valve cover. You'd have oil seeping out of every gasket, and oil in the distributor, and oil in the air cleaner running out of the crankcase fresh air inlet filter, and so on. Do you have anything like that? If not, you don't really have a cyl wall issue.

Refresh my memory.... exactly what valve guide seals were used? Also, an excessively rich condition will result in oil consumption; have you cheked the A/F ratio? What does the engine builder say? Have you taken them the car and just said "make it stop smoking" and seen what they have to say?

 

Thanks for the reply RB…

There are two reasons I suspect faulty rings and/or cylinders. The first is the smoke, which appears to have kind of a bluish tint to it, but now that you mention it, it is still running on the fuel rich side also. The second reason is that the engine ate two cam lobes when the builder attempted to break-in and dyno the engine after it was initially rebuilt.

He did have one of those round screens installed between the oil filter and engine when it happened, but that just prevents oil discharged from the pump from carrying debris to the engine. I’m sure there was metal in the pan, which they claimed to have cleaned out when the cam was replaced.

I don’t have the extreme problems you’re referring to with blowby. I don’t find oil in the distributor or air cleaner, engine is not leaking oil due to the crankcase overpressurizing, and it’s not blowing the PCV valve out of the valve cover or anything. So no –I don’t have any of those problems.

Even though I specifically asked to have Teflon seals installed on this engine, it was forgotten somewhere along the line, because the extra machining and parts are not listed on my receipt. So I can only assume that whatever seals that are normally used with a new set of dart heads were installed.

I am intrigued that you think that running fuel rich may be the culprit, and that’s certainly a possibility. I just can’t for the life of me relate this to burning oil. Could you clarify how that happens?? Is it due to the fuel washing down the cylinder walls or what?

I personally have no way to verify where the A/F ratio really is. The only measuring device I have is my Autometer A/F gage I have installed, but it’s accuracy is questionable from what I’ve read about them.

It has however, responded to jet changes I’ve made on the carb, and indicates that the engine is running leaner than what it was. I’m still not in the “Stoich” range yet however. It still reads slightly on the “Rich” side. The shop had huge primary and secondary jets installed initially when I got the engine. They installed 80/94’s in it, and it ran pig rich. I now have 74/80’s installed.

The builders shop is near Davenport IA, and it’s a 3 hour drive to get there, so I have’nt let him look at it. He’s the same guy that recommended I drive it for at least 2K miles to seat the rings, and not to lean it down more than 2 jet sizes due to exhaust temps being too high if I lean it out too much. He considered 1400 degrees to be the limit on exhaust temps. Well, I have no way to measure exhaust temp, but I tried stepping down 2 jet sizes, and it done nothing for the pig rich problem.

Unless I can stop this smoking problem, I may end up doing just what you said…driving the car to him and tell him to make it stop smoking to see what he thinks. BTW, I told him of the smoking problem when I had 1K on the engine, so he should be aware of it.

He also mentioned something about putting steel wool in the PCV hose to cut down on the suction, but I didn’t think that was a solution – just a way to mask another possible problem.

So should I look into leaning out the carb more to see if the smoking stops?? Or should I look into other things? Thanks for any help with this in advance!

 

Well, the question still stands....

How does running a rich A/F ratio increase oil consumption?

 

Also, even if the engine is cold while I do these leakdown, will the results not give me any useable findings?

Is there any way to troubleshoot faulty valve seals other than just replacing them and see what happens?

I guess after reading this, I just don't know what I should be checking first, second, etc... either way - something's not right. If 2K isn't enough miles to seat the rings, then what is?

 

OOps....double post...

 

OK- I called the guy that built the engine, and here’s what he says. I’ll try and keep this short.

He says it sounds to him like the engine is sucking up oil from the PCV valve, and he recommends I disconnect it for awhile and see what happens. Just stick a breather in each valve cover.

He thinks it’s not a valve seal or ring problem because all the plugs are black, not just a couple.

He also stated that if I do intend to run a PCV valve, there are different types that have more heavily weighted valves than others. He even said some of his customers run cheese cloth around their PCV valves to help cut down on oil problems.

He also recommended that I lean out the carb until I get a tannish tint on the plugs.

If this does nothing, then I told him I’ll drive it down to him so he can see first-hand what it’s doing. And I let him know that I expect his cooperation in fixing this. He didn’t seem to disagree with that. – But of course, I will be the one that would have to pull the engine back out and deliver it to him.

So what do you guys think.....is this sound advice??

 

I agree that it may be the PCV valve/system. While reading this thread at about the halfway point I was going to post the same thing.

My engine had an oil burning issue, drove me nuts. At times billows of blue smoke would pour out of the exhaust. Sitting at idle it would also start to smoke. It got to the point where I thoguht the rings would never seat. I tracked it down to having oil pulled through the PCV valve into the intake. Even with the stock baffled valve covers (center bolt).

I checked for oil in the fitting on the TB. The inside of the raised ring on the fitting was oil filled (the raised ring being the bead on the fitting that helps hold the hose on).

To fix/verify the problem I built and installed a separator. This consists of a double height baby-food jar, soldered two pieces of 3/8" copper tubing through the lid with one ending near the bottom of the jar and the other at the top. Filled the jar with pot scrubber stuff (looks like very corse steel wool). Thin piece of foam over that.

The PCV valve end goes to the tube that ends near the bottom of the jar, the tube at the top of the jar goes to the TB (or carb in your case).

Placed the jar on the front area of the intake manifold with a piece of foam under it.

The smoking was gone! Oil consumption dropped. And, after a 30 minute test drive there was a small amount of oil in the bottom of the jar (why I used a clear container).

The separator also reduced the amount of oil pulled through the PCV valve. It does this by dampening the air pulsing or change in manifold vacuum on the PCV valve itself. In my case the PCV valve was acting like a pump.

RBob.

 

Rbob,

I'm impressed. Very ingenious.

My son's 89 TA is smoking quite a bit. We replaced valve seals, but it still smokes. We'll have to give this a try. Of course his engine has 160,000 miles on it so it could be rings but .....

 

RBob,

Thanks for the reply! I was beginning to think I was being "shunned" on the board for some reason!

That idea of using the jar sounds pretty neat!

I'll try running w/o a pcv valve for a couple days and see what happens then. Come to think of it, the breather I have installed in one of the valve covers fell out once, and there was oil all over by the time I got it home. And the pcv valve was hooked up on the other side...

And thats using the cheap chrome valve covers - but they do have baffles.

I have a filter type Moroso breather in one cover already (the one that fell out once), and I have a closed type breather lying around I can stick in the other cover. It has a hose connection for the air cleaner. Do you think I should try running that?? I figure there should be a lot less "pull" on it, so it might not suck up oil, if that's the problem.

I just hate the thought of not running one at all. I've heard not running a pcv can gunk up a engine over time.

 

Give that breather a try. Pull the PCV valve and place that breather in it's place. Won't take long to see if it corrected the smoke issue.

If it does then make a separator. Can use PVC pipe and end caps or a small metal container.

I agree about needing a PCV system. Street cars do require them.

RBob.

 

Update: I'm giving the non-pcv option a try. I have a closed type breather installed in one valve cover that has a hose that goes to the air cleaner on one side, and an open filter type breather in the other.

I drove it today, and it was smoking at idle on initail startup, but I didn't notice any smoke at all after I drove it around for a bit, downshifting to a stop and taking off- no smoke! Then when I parked it after driving 30 minutes, I let it idle for a couple of minutes and no smoke.

Jury's still out though....I still need to drive it for awhile... The tailpipes are still awfully black! It'll take awhile to burn all this out.

 

Well, it didn't work...

I'm down to the last straw. This engine is getting pulled really soon if I can't get this figured out. All 8 plugs are still black.

Still smoking, seems to especially be bad after warmed up and idling. It's just a constant haze coming from the exhaust. With the PCV disconnected and the breather tube hooked up on the other side to the air cleaner, the hose is staying dry inside so I know it's not sucking up oil now. What's killing me is the fact that it's ALL 8 PLUGS that are black, and all have a slight buildup forming on the insulators.....

If ANYONE has any other things I should check, please chime in!! I don't want to pull this thing out just to discover it was something stupid! A brief rundown:

-Plugs are still black, even though the carbs been leaned out.
-Still smokes with PCV disconnected
- Engine completly rebuilt, and new Dart heads maybe 2K miles ago
- Oil pressure is fine, engine temp stays at 220 or below.

ANYONE??

 

I've decided to do a full compression test tomorrow. If the results turn out to be bad cylinders, then I guess I'll have something else to post up in the "Vendor review board"...

Again though - Is there anything else, other than intake gasket, valve seals or rings that could cause an engine to burn oil?

I've done various searches and read somewhere that unsealed rocker arm studs can cause oil burning?? Is that true?

 

Yes, that is true, on some heads; the intake rocker stud is (surpris) right above the intake port, and sometimes it's the same piece of material; and the stud hole just goes all the way from the crankcase to the intake port. So you might want to try some Permatex 300 or PST or something.

 

RB - I know you're familiar with Dart iron eagles....is it a problem on those, cause that's what I have.

 

Yes, the rocker studs in those definitely go directly into the intake ports.

Not having sealer on the threads will also create a "mystery" vacuum leak....

 

ok.. i thought a comperssion test was spouse to be done at 40psi. and y don't you just buy a new pcv. thier spouse to be replaced every 60 thousand miles as a regular matnance item. try a vacum test. see if your snap acceleration is good. and your 2500 is good. just somehtings to try

edit: and it is spouse to be a normalized engien. or your accurcy is absoluty noting. we have a ford 6 banger in my class. and 0 miles on it just idle and revs. the leak down test said it was in horible condtion cold but perfect normaliezd just to show you how it effects your reading

 

Thanks for the great info RB - for the 100th time!!

I wouldn't be a bit suprised if none of them are sealed. Thanks for the tip. I'll def. check it out!

 

Thanks ridecamro - The test I was attempting to try was a cylinder leakdown test. The test kit I have has a conversion chart for 75,90 and 100 PSI.

I wanted to try this test with the engine hot, but with all 8 spark plugs being black.......well, I think I may be "barking up the wrong tree". The possibility of all 8 cylinders having bad rings and valves is pretty remote.

The PCV valve is new, along with everything else on this engine (minus the block). As said above, it's totally removed and still smokes.

Not sure what you mean by "snap acceleration" though....it revs like a banshee better than any other engine I've had....

 

snap accelartion. is going from idle to WOT then quickly off so it's like snaping the throttle. is the black a dull black or a bright black. if it's a dull all it is is your runnign rich. like my car is now. just tune to carb. secondly if it's a bright shiny kinda it's oil. thats what i can say if all your cylenders were in 30% of what is idle then your fine. and then it's just running rich

 

All plugs are shiny black, not dull black (like carbon)....

 

We all know what they say a picture is worth....

This is looking into an intake port of a IE200, with a flashlight pointed at the stud hole.

 

Holy CRAP!! Are they the same on all 8, or is it a casting thing - sparadic??

After seeing that, the valve covers are comin off first thing in the morning! Way my lucks been, I'll find all the studs sealed nicely......

I can plainly see now that studs wicking oil could cause the exact problems I have though. Worth a shot, tried about everything else I can think of.

 

They're all just like that.

Most stock heads, the intake runner is thin and the casting on top of the head is thin, and there's water in between; on these, it's a solid chunk of metal, just drilled right through. For strength holding the stud, and because the intake port itself is so much large on top than stock.

 

Ummmm....

I just saw this post. I replied to your other thread and said something about cylinders 2,4, and 8. Now I see this thread and see the results for cylinders 2,4, and 8. All I can say is it doesnt look good, IMO.

If it was me, I would pull the engine and have the rings end-gaps check. Also have the bores mic'd and have them check to make sure that the bores are CLOSE to the same size. Also have them check for "out-of-round" and "taper". BTW, have this done at a DIFFERENT MACHINE SHOP. Take the numbers you get and show them to the machine shop that did the work. I suspect that either...

- The ring gaps are way too wide
- The cylinders bores are not even close to being the same size
- The bores are out-of-round
- The bores are tapered to all hell

If the ring gaps arent right, the bores arent close is size, severely out of round, or badly tapered, then I would have a serious talk with the machine shop.

I forgot to mention... Have the shop checking everything check the piston-to-wall clearance. They should be close pretty close to each other. If the pistons are all the same size and the bore sizes are not even, then the shop screwed up with their boring/honing. If the bore sizes are pretty even and the piston to wall clearances vary too much from piston to piston, then that could mean they either ordered the wrong pistons, or the supplier supplies crap. And if the bore sizes are pretty even, the piston to wall clearances are pretty even but TOO LOOSE or TOO TIGHT, then the machine shop screwed up BADLY.

I may have made some mistakes in this post but Im just trying to lend a hand. So, please dont flame.

 

Thanks for the reply again JAYDUBB! I don't know what "mistakes" you're referring to that you've made on this post, but I agree with what you're saying.

I'm going to pull a head on the engine initially to check the rocker studs in the heads that RB referred to first, since that would take the least amount of work (and expense). Hopefully I'll find evidence of the studs wicking oil into the intake ports. Since all 8 cylinders have black plugs, I'd think I'd be able to see some kinda evidence. If that's the case, I'll just pull the other head and get it fixed. But with the compression and leakdown tests I've done, I don't know if that'll be it.

Another plus to pulling the head...It will allow me to look at the clylinders for scoring or anything unusual like mentioned above.

If I see that, well...engine get pulled and I continue to get the block checked by an independent shop, and go from there.

Wish me luck! I'll post what I find....since I didn't build it myself I'm not so embarrassed to post it. I'll just be embarassed I bought it in the first place...

 

confuzed, did you ever solve this? what was it? I have a very similar to yours

thanks
john