need another opinon with this problem

So, I have been working on my "new" engine for the 52, it seems that whenever the temp starts to get close to 200*F a light seemingly blue smoke begins to come from the driver-side exhaust, after this begins it's only a short period of time before my idle very gradually drops and the engine seems to want to stall.

My coolant level is steady as far as I can tell, though I do have a slow leak at the top plug on my water pump, and I never have to add any oil. The last thing I would think it could be by judging from the smell, is fuel, but usually the exhaust would be black if that was the case.

I recently added a bunch of 4 gauge ground wires to the back of the heads, this made a big improvement and the buzzing noise from my distributor went away. Today I changed out the primary jets from a 65 to a 62, which allowed it to start much easier, but seemed like it only made a very slight difference with how long it would run before having troubles, the next jet I have on hand is a 58 I can try later. Carb float levels are perfect, 5.5psi fuel pressure, and don't see any sign of over-flowing. I also have reinstalled the intake about 4 times thinking I had an intake leak, each time made no difference.

It would also be good to note that when I bought this short-block from the guy it was supposed to have 20,000 miles since the last rebuild, but, ran like crap until I readjusted all the rockers to no farther than zero-lash, and the cyl. 7 (I think it was the exhaust valve) was tightened down waaaayyy too far. The heads on this engine I recently found out ARE crack-prone, but I don't have the paper where I wrote down the cast number at the moment.

I did do a cold compression test and all cylinders were basically even at 120psi +- 10psi. Engine Spec's are as follows:

-Chevy 350,
-Holley 600 CFM with mechanical secondaries 2.5 power valve 62 primary, 72 secondary jets,
-Holley Street Dominator single-plane Aluminum intake,
-Unknown very lopey cam,
-Engine pulls 5-6in vac. @ idle

 

After it gets "hot", do another compression test. A cold leakdown test would be more telling than a cold compression test. Also check your plugs after one of these "hot" cycles. Compare cyl to cyl on the same bank, and compare left bank to right bank plugs...all 8 should be out for the look see. Look for any differences. Blue smoke is oil, plain and simple, and since you say it isn't much smoke, it isn't much oil. Could be a small headgasket leak or a valvestem seal getting bad when it is hot or even an intake leak into the oil gallery, smell your oil, make sure it doesn't have a gas smell to it. It may not be enough to make it smell strong, but it shouldn't smell like gas at all.

 

Ill do my best to do a hot compression test as soon as the weather allows, though it would be difficult to not burn my hands on the manifolds with only 3" of space! Oil smells fine, maybe another thing I could check while i'm in there is if the head bolts are torqued down to spec, a head gasket leak does sound likely. The last time I pulled the plugs all 4 in that bank were wet, but maybe ill take some pic's of them when I go to do a hot compression test, just in case they look different than last time.

Thanks for the ideas Willy.

 

Check location of P.V.C. and if it has some kind of divert-er plate,The oil will be sucked through if it doesn't. tex1935

 

My initial thought was stem seals, but Willy seem to be all over it! Thanks Willy, I learned something too!

Cheers, Matt

 

One thing I forgot to mention, If I pull off a plug on any of the full manifold vacuum ports after it has heated up, the engine will idle back up to normal, but I don't remember if the smoke goes away or not, ill have to test it again and make a note of the results here. Changing jet sizes never really seems to make a difference, though im willing to try anything.

 

If introducing a vacuum leak makes the idle smooth out that makes it sound like you're fighting an over-rich condition when the engine gets fully up to temp. Which at first thought doesn't seem to make a lot of sense. Do you have any sort of spacer or heat dissipater between the carb and the intake?

When the idle is smoother is there no noticeable fuel dripping from the main nozzles? When the engine is hot and the idle gets flakey do you notice any fuel dripping from the main nozzles then? Maybe the fuel in the float bowls is getting hot enough to expand a bit and raise the fuel level? Just trying to make some kind of connection between the increase in temp and the richened mixture.

 

Yup, I got a Holley heat shield under my carb and the bowls barley even get warm to the touch. If it was the carb, then you would think it would be happening on both sides of the engine right? I'm thinking that there might be more than one problem that's going on making it even more confusing. At one point I thought I had it all fixed when I found out that I had a small crack in my PCV line allowing it to draw in air. I will make sure to check the main nozzles like you said.

Im going to be making a to-do list now hahahah.

*Edit* Just a thought, is it possible, that since I did not block off the heat riser passages that maybe the intake is getting too hot? It is aluminum which is very thermally conductive.

 

Assuming dual exhaust and no heat riser you're probably not pushing that much heat thru the crossover. And that should have the most effect for cold start driveability and to preventing icing. How about hooking up a vacuum gauge and seeing if the idle vacuum drops as the engine warms up?

 

I was not sure if that was normal since I don't have another engine as reference, (still learning) but yes, the vacuum does begin to drop when the temp gets just above 190*F. It seems to drop about 2in of vac, which is technically quite a lot since I only start off at somewhere around 6in.

I'm at work now, so ill see what time I get off, hopefully ill be back with more details on that.

 

What heads are on this engine?
Assuming stock or mild aftermarket heads and looking at your engine specs, I can tell a few things:

You should have more vacuum at idle. Even huge cams can provide 8-10 inches of vacuum at idle. The low number power valve will need to be replaced when you correct the vacuum situation. Your lopey cam may not be as lope as you think, but is instead running rough because of a tuning problem. Have you tried adjusting your mixture screws and checked the float level? Have you had the carb apart for a good cleaning? Have you checked for a blown power valve?

I agree with the above. Smoking when hot is typically valve seals.

Your engine would be happier with a dual-plane manifold, like an edelbrock performer.

Your jetting seems off. 62 is pretty small, and typically you don't want to be more than 4 numbers off between primary and secondary. This is to prevent the "rush" you feel when the secondaries open. When tuned correctly, you shouldn't feel any rush, it should be a smooth transition. This "rush" is from a drop in fuel delivery on the primary, being corrected by the secondary. When tuned and jetted properly, you shouldn't feel much of this rush at all. Have you tried reading your plugs running on the primaries and also when on the secondaries?

 

Well now we're getting somewhere! Only now there's a kind of a "chicken and egg" factor thrown into the mix. Is it too rich because the vacuum's so low or is the vacuum low because it's running too rich???

So let's dig a bit deeper. Are the vac readings you're posting with it in neutral or in gear? Do you have a vacuum advance on the distributor and is working right? Is it connected to manifold or ported vacuum? Do you know what your initial timing is set at?

As stated, you may have a power valve problem. But you may also be able to bring up the vacuum at idle buy juggling around some of your tune-up specs.

 

If for whatever reason at 200* be begins introducing oil (FUEL) into the cylinder, that makes perfect sense a induced vacuum leak would raise the idle.
More than likely a bit lean , & hotter to burn the oil better.

 

SWEET! you all had good points, I have a lot of testing to do when I get home. I did consider a power valve problem, I had a 3.5, but reduced it to a 2.5 and made no difference (as far as I could tell). Floats are perfect, and this is a brand new carburetor. I had an old vacuum secondary carb on for a while, but the secondary shaft was worn pretty badly, with that carb I got 8in of vacuum. Ill edit this post with more details when I get to another wireless hotspot.

All of you, thanks for the responses

 

Do the age-old vacuum leak check. Let it idle with the air cleaner off (plug any open vacuum lines) and hold a hand over the carb throat, if the idle picks up, you have a vacuum leak. Try it first cold and then hot and see what happens.

Bob

 

My boss and I were talking about it after work, sounds like the best option at the moment is to double check the torque on the driver side head bolts, and reset the rockers to zero lash. I read on another forum (don't know if this is true) that you need to let the lifters set for an hour with the rockers completely loose before you can adjust them accurately, and last time I did not let them sit. After I'm sure I got that all correct, then Ill definitely do more to the jetting.

Never knew to try that bobss369, ill definitely try that soon.

Rain is coming so I better get out there, wish me luck!

 

LOL! But then we're back to why it seems to be getting a little oil in the cylinder only after it warms up. I'm tempted to forget about that part for a while and lean toward the tune-up side of the story. It might have bad valve guides and/or seals but that's usually only an issue with higher intake vacuum readings. Though if it had the oil drainback holes in the heads plugged it might be holding a quart of oil under the valve covers. That might put some oil past the valve guides or suck up a bit in the PCV system.

It won't hurt to check the torque on things and readjust the lifters but I'm guessing it probably won't make much, if any, difference. If the valves were too loose you'd hear some clatter and if they were too tight you'd probably hear some random popping thru the intake or exhaust. But while you're in there make sure the oil dranback passages are clear.

I'd be more interested in getting the vacuum up at idle, especially in gear. The easiest way to do this is to increase your initial timing a few degrees. Hook up the vac gauge and timing light and watch how the vacuum responds to changes in timing. If you have a vacuum advance distributor, make sure the advance is working. If it's hooked up to ported vacuum switch it over to full manifold vacuum, at least temporarily. Just remember that if you advance the initial timing by 5 degrees you're also advancing the TOTAL timing by a like amount. Which may still be okay or it may give you some pinging under a load. The distributor may have to be reworked to take a little mechanical advance out if you end up adding enough initial timing.

Also if the timing is a bit retarded the engine will tend to run hotter. Getting the timing to advance properly will help things run cooler.

 

Ok, so I got a bit more info now. I loosened all the rockers, let them sit for an hour before setting them back. Cyl. 7 was far too loose, don't know how that happened, and cyl. 3 was tightened down a tad too far. Torque on all the bolts seemed good except for one which tightened just a slight bit.

Spark plugs looked much better than the last time I pulled them out a couple months ago, electrodes are nice and dry, just got oil on the threads, though the electrode is pretty dark and has a very slight smell of fuel, so I'm thinking it still has to be running too rich. Plugs on both sides look the same, and I noticed I do have an exhaust leak on the driver side...

I got the cast number off the heads: 462624, and right now Im running an HEI distributor, and I have the vac. advance disconnected at the moment. Never knew advancing the timing could make it run cooler! Ill remember that. Seems like the extra ground wires did the biggest help so far, ill use my timing light to also check each wire to make sure they are all firing correctly.

Well, maybe tomorrow after the RTV dries ill find out even more with a vacuum gauge, I feel better about the rocker adjustment this time, just hope I don't have to go back in again, I'm running out of RTV lol

 

Oh man, this is going to be fun! Wish I was within driving distance so I could see the results if you try this!

If you haven't already, don't change anything on the tune-up. Hook up the timing light and vacuum gauge. Make sure that the distr. vacuum advance is working and will hold vacuum. Now get a length of vac hose and connect the vacuum advance to a source of full manifold vacuum. Find a port either on the intake manifold or on the carburetor somewhere below the throttle plates that will provide full vacuum at idle. Then fire that mother up!

If your initial and total timing are close to right the additional vacuum advance at idle should make a world of difference. More vacuum, better idle and the power valves shouldn't be opening up when they aren't supposed to. Work back and forth between the idle speed and mixture adjustments to get a stable idle and the highest vacuum. Odds are that it's likely to drive like a completely different car! And run cooler and use less fuel.

Once you get the idle sorted out then you can work with the rest of the tune-up and figure out the optimum timing specs.

 

Crap... we got one more problem lol I should have left the rockers alone but noooo I just had to get my hands into it

So, I got back from work knowing the RTV would be dry, fired her up and it sounded like hell and thought to my self... "I tightened them past zero-lash again didn't I..." pulled the valve cover off, started readjusting the rockers one at a time, sure enough I had them farther than zero-lash. Got it all back together, fired up again and I heard a repetitive flat pop, walked over to the engine and heard a tap-tap-tap-tap... "awwww it's too loose..." Pulled the valve cover off AGAIN, readjusted the valves trying to be as precise as I can... put it all back together, fired up again, sounded much better, walk over to the engine... tap-tap-tap-tap... by this time It was getting dark so I just let everything warm up to 180 so I wont have condensation buildup, and just packed up and went into the house lol.

Well, I know what ill be doing tomorrow... the idle did seem a bit better so it might have been part of my problem, but I don't know why I have to be soooo dead on zero-lash, and it seems no matter how hard I try to get them perfect, they always seem to come loose or just get too tight after starting. I'm starting to think that maybe I don't have hydraulic lifters, but it would just seem too odd, I guess ill look it all up, if I set them the way you would need to if you had solid lifters and everything works great, then I know.

 

Have you ever tried adjusting them while its running ?
Need an old valve cover cut in half length wise, a set of little clips , sold at summit, jegs, speedway that go over the rockers to keep the oil from going everywhere.
An other thing is the adjusting nuts, do you have poly-locks with a set screw, or at least new nylocks, or are you running your old nylock nuts?

Are you using a feeler gauge under the rocker to valve stem ? Or guessing at zero by twisting the pushrod ? I have never heard of this "wait an hour" thing either.

A cold motor and warm motor and running motor will all have different measurements and adjusting requirements. Do it running and there is no guessing.

 

Waiting an hour.. must be bro-science. Definitely while warmed up and running. I go down one bank, back it off until it clacks, tighten 'til it gets quiet, let the lifter pump up, it'll run smoother. Then go 1/4 turn, again let it settle down and go another 1/4 turn, let it settle again. Go to the next valve and so on.

The 1/2 turn past zero-lash works well for used motors. I've used this method for years. Barring a bum lifter, it should work for you.

Bob

 

Don't know if anyone talked about re-torque the intake, How far off are you from factory jetting and power valve?

 

Ha ha Bro-Science, one of the many forms of BS.

 

Just to throw a wrench in things, anyone else thinking flat lobe on the cam? If the lash adjustment seems to be all over the place and he mentioned a rocker that was loose when he checked it . . . .

I would say the initial timing is the biggest issue, sounds like a too big cam in there making little vacuum.

 

It may not help with your idle, but have you completely ruled out the chance you have a leaking head gasket or a cracked head that opens up with heat?

 

I was thinking that or a collapsed lifter. That's something you find out in the valve-adjusting process. Use a vacuum gauge in case he needs a tie breaker.

Bob

 

Maybe nylocks, they look stock. So the good news is, I finally got it all set. The tip about cutting an old valve cover and adjust rockers while running, that's probably something I should do soon to be 100% sure they are perfect. I did try out using a feeler gauge, but they just seemed too loose afterwards. So, the good news, idle is just a bit smoother, maybe my imagination, but the temp seems to stay steady at 195*F I had to cut it off since I'm starting to get low on fuel, so it might have rose to 200 again if I just let it run even longer.

The first time I tried setting the valves I would spin the push rod till I felt just a bit of friction, this did not work. The only way I could get it all set was by moving the rocker side to side and tightened till they would only move by a few millimeters.

My carb came stock with a 66 jet front, 72 jet rear, and a 6.5 power valve, I now have it set: 62 jet front, 72 jet rear, and a 2.5 power valve. I want to set the rear to a 70 and see what happens, I believe (correct me if I'm wrong) that the secondaries are cracked open at idle just a bit on Holleys.

ajmopar mentioned a lobe going flat... that would explain if I cant seem to get the jetting right, and who knows if the last guy broke the cam in correctly.

[Edits are below here]

Nope, I have not COMPLETELY ruled it out, and my heads are the crack-prone 462624's, ill get that leak stopped soon enough and then we will know for sure

YES! that would be freakin awesome, someone more experienced than I might get it all up and going, or at least find the problem within a day.

I hooked up my vacuum gauge just now, to tune the idle screws, to my surprise the vacuum gauge needle was very steady, it used to flick a bit, but I thought that was just from the cam, guess it was a badly adjusted valve. I think I might have a few misfires, not in a pattern like it would be on the same cylinder, ill see if it clears up as I do more tuning to the carb. Turning the idle screws does not seem to have much affect it's very possible the power valve could be open.

I want to pull the cam out to get the cast number which would clear up a bunch of questions, but I simply don't have a place clean enough that's not over dirt ground...

Once again, thanks for all the tips, it helps a ton when making decisions!

 

I recently installed a 350 in my FED, didn't sound bad but wasn't quite as smooth as normal. When I installed zoomies, I saw oil mist, not smoke coming only from #5. A leakdown test showed a huge leak. Pulled the head and had a bent valve, which had cracked the boss around the guide, allowing oil to be scavenged from around the valve spring and into the exhaust port. Replaced all valve springs and 3 valves. Welded the crack under the valve spring (GM aluminum head) problem solved.

 

:O wonder how long it took you to figure that problem out?

Well, anyways, just wanted to tell everyone I'm still working on this issue, just did not make any progress since I had to resolve some other automotive issues with our newer cars, but ill be back at it shortly with more news.

Idle SEEMS to be ok now, if not, it's a whole hell of a lot better than it was, but I still got smoke coming out of the driver side exhaust, so were about 1/2 way there!

I just looked up how to tell the difference between hydraulic and solid lifters without removing them, so ill be pulling the valve covers one last time to take a look and do some final adjustments if I feel it's needed. Then ill report back!