Timing a SBC after installing a PCV Question

OK, I've done a ton of searches but still have one question.

I've got a SBC with a front fill tube/breather. I installed a PCV valve on the back of the manifold (just short of the dizzy) since I have finned valve covers that I didn't want to hack. Question is this: Do I need to plug the breather/fill tube as well as the vacuum advance when trying to time the motor?
I'm asking because when I was trying to re-set the timing I was having a hard time matching everything up (timing groove will only "show" at around 90 degrees) . A friend said I need to plug the breather because that's now a vacuum leak...I couldn't find anything on this...

Thanks,
Aaron

 

I think if you have the PCV valve mounted correctly, you shouldn't have to plug the breather. I've never heard of plugging a breather to do a tune up.

You do have to pull the vacuum advance line and plug that up to set the timing though. I always set the timing with the centrifugal advance all the way on, which is up around 3000 rpm. I set the timing like that so the timing is about 34 or 35 degrees advance with the engine up at around 3000 rpm. You'll probably need a timing tape on the balancer or a timing light with a dial on the back.

If you have a totally stock engine with a totally stock cam, you can use the factory timing specs at idle. Anything other than stock and you'll probably need more advance and what matters the most is how it is timed when the centrifugal advance is fully on.

 

Ya, I had never heard of that either. I have been pulling the vacuum advance and plugging that. This all started because of the timing being way off now. I'm thinking the first thing I need to do is re-calibrate the carb since I've got the PCV hooked up and go from there.

 

Check to be sure that the outter ring on your balancer has not moved and that the tdc mark on the balancer and the tdc/o mark on the timing tab are actually true tdc. Also, insteading of disconnecting and plugging the vacuum advance, just clamp some needle nose vice grips on the line.

 

The reason you pull the hose or pinch it off , on the vacuume advance is so the advance is not active when you do the timing. Don't want to remove or pinch any other lines. Now if the motor runs poorly with the new PCV it could be the wrong one is installed if it leaks too much. Maybe other HAMB's can chime in with their favorite PCV to use.

 

The motor is a '02 Goodwrench crate (possibly w/cam, bought it used). I used a PCV for a '90 Camaro with a 350...should be fine. I really don't think it's the valve. The more I think about it I'm thinking I just need to adjust the carb and go from there. I'm also going to take the advance and move it from ported vacuum to manifold vacuum as that seems to be the general consensus.

 

Have you set the timing on this previously without any trouble? It sounds like you might have a late timing cover and early balancer or vice versus.
I have run into this a couple of times. Usualy guys by a new balancer for their engine and install it. The motor is fine because nothing has really changed except for the timing marks are now about 90 degrees off.

In cases like this, I typically will set the timing by engine vacuum. adjust the timing to give you the highest vacuum reading, then turn back a few degrees. Test drive and make sure there is no detonation.
This is not the ideal way to do things but works ok for most applications. I would not want to gamble on a full race engine however.

 

I'm a little fuzzy on how you installed everything.

When you say you installed the PCV valve on the back of the manifold, just short of the distributor: Did you drill a hole in the manifold and add a port, or are you using the vacuum port that is often found on one of the runners?

Did you then run a line to the carb base?

Is your oil fill tube an open-type breather, or is it a sealed cap?

PCV valves are directional. Is yours going the right direction?

-Brad

 

No, it's not in a runner. As I mentioned I did search

I took the manifold off and drilled it. The valve I have has a metal end on one side (grommet) and a 90 angle plastic tube with ribs on the other side(pretty sure this is for the hose, no?) And the fill tube is an "open" breather. I'll try and post some pics when I get home.

The balancer has been on the motor for some time and yes, I have set the timing with ZERO problems before...

 

Ok, let's make things more confusing. I'm pulling 20" of vacuum at idle and the only way I can get the balancer groove to line up is to set my digital advance at 90 degrees....now I'm really confused.

 

do you need the pvc?if not, why use one..

 

Yes. I tried running without it and it would build up enough pressure in the crankcase and valve covers to push the gaskets and blow oil everywhere.

At this point it purrs once started, pulls plenty of vacuum and sounds great...I'm thinking my fancy timing light is screwed up. The ****py thing is I can't go driving around as I've got all the lights, bumpers and grill removed so I can paint.

 

Do your valve covers have breathers or provision for a port to the PVC?

Your 350 does not have a breather built into the rear of the block like the early SBC's had that used the intake with the oil fill tube in the front. The crank case needs an "in" and an "out" to vent properly.

Those early SBC's with a PVC used a hose from the breather hole in the rear of the block to the air cleaner as an "in" and the PVC in a tube from the base of the carb to the oil fill tube. The oil fill tube was capped with a lid that sealed tight.

Those early ones w/o a PVC used a "road tube" at the rear of the block and one of those steel wool filled, oil soaked breather caps on the oil fill tube.

You CAN run the early style manifold with the later blocks, but you will need to run at least one valve cover that has a hole for a tube that goes from the valve cover to the PVC and on to the intake. The oil fill tube can have one of those breather caps (or visa versa).

In any case, make sure the PVC is installed in the right direction or it is useless.


On your original problem...it's easy to mix up vibration dampners and timing marks from different vintage SBC's. If so, you will see pretty much what you are seeing with your light.

 

Like I mentioned, I did a search...I know how a PCV system works. I do not have provisions in my valve covers as they are finned Edelbrocks and I didn't want to hack them up. I DO have a fill tube up front with a breather. I installed the PCV valve in the back of the motor (PCV= side to side or front to back).

I guess I should just try and clarify my question: Will a SBC even run AND produce 22" of vacuum at idle if it was advanced 90 degrees??? I think the answer is no and my timing light or balancer is somehow out of wack.

 

It almost sounds like you've got the lead on the wrong plug wire...

I dunno. The air should be coming in the fill tube, down the lifter valley and out the back of the intake at the PCV, into the base of the carb (from the description of what you have installed). That sounds right to me. You shouldn't have a vacuum leak. Plus, if you had a true vacuum leak, it'd run like hell. (I screwed up and hooked the hose on the air cleaner base to the runner port on the manifold once. You know when your PCV system is a direct vacuum leak!)

If all else checks out, time to check the balancer.

Did you pull the distributor when you did the PCV valve? It might be off too. (I drove a slant 6 from LA to Georgia with the distributor off a tooth. It ran fine at the right mph, but sounded like a vacuum leak at idle. You could have something similar happening.)
-Brad

 

Motor in question:

 

I keep thinking about the plug wire, but it's kind of hard to mix up 1 cylinder...at least when I'm sober.

Yeah, I did have to pull the distributor. This might sound dumb, but I thought given the oil pump drive they would only go on one of two ways...can I really have got it in the groove and somehow got the gears off???

 

My bad.

When you said you drilled the intake, I thought you meant to pick up vacuum. Sounds like you did it in an area to access only the valley (crank case). That should work fine.

 

No worries. Went ahead and shot some images. Sorry they're fuzzy...can't use a flash with all the polish and chrome.

 

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Yeah, I did have to pull the distributor. This might sound dumb, but I thought given the oil pump drive they would only go on one of two ways...can I really have got it in the groove and somehow got the gears off???[/quote]

The SBC distributer can be put in every tooth of the cam. You need to determine the correct position of the distributer then turn the oil pump drive to the necessary position and drop in the distributer.
Put #1 cylinder(driver's front) to top dead center compression.You can put your thumb over the plug hole while turning the engine with a ratchet...when it starts building pressure stop. Put a small screw driver in the hole and carefuly continue rotating until the piston is at top dead center.This should be very close to what your timing tab is indicating as 0TDC.....If it is significantly off then you have a slipped ring on your balancer or the wrong balancer/cover match.I always put a paint mark on the balancer when I install them from center to outer ring to visualy tell if it moves overtime.
Now that you are at TDC compression..........I make a small mark at the base of the dist. in perfect alignment with number 1 terminal position of the cap. Now align the rotor with that mark and insert the ***embly into the engine. Remeber you need to compensate for the twist the gears give you as it drops. If needed to drop all the way down....you will have to turn the oil pump drive to mate to the dist. Once the distributer is in fully you should be able to rotate the distributer to align the mark on the base(made earlier) to the rotor. This must also position so you have ample room to rotate the distributer(advance) to time it as this is only 0 degrees. Now you are ready to run.
NOTE:I usualy do the above distributer setup but set the crank/balancer position to 8 degrees instead of 0.....this gives an excellent startup as you have 8 degrees built in.

 

I know you said you read the theory of pcv operation. Remember that modern engines pull air in one side valve cover and up and out the other. This air movement travels in one head down into the crankcase and up the other by design. But anyform of ventilation/vacuum is better tham sealing it off.
And no you should not have to mess with the breather/PCV system for timing or carb tuning.

 

With the way it is mounted I hope it don't **** up any oil, I don't think you put a shield over the valve to keep oil away.

 

Good point Rodhotz made on picking up oil from the valley if you don't have a good baffle.

A good test for this is; once you get the car running ok, run the highway at about 3000 rpm for a bit - watch your speed and use a lower gear if necessary - then romp on the throttle and see if you get an oil cloud behind you.
You can also run through the gears at full throttle and see if your car looks like a low flying cropduster.


Fwiw



Are you running an ignition amplifier box like MSD etc.?

Combining an MSD with a dial-back light will give you erroneous timing readings with some timing lights.

If you have a conventional timing light, give it a try and see what you get.

 

Bingo. You will have to adjust the idle mixture screws in the carb because you are adding air to the air fuel mixture after it leaves the carb. Richen up the idle mixture to compensate for the extra air that you are adding after you once set the mixture and never look back.

Remember you are setting the "initial" timing when using a light. You remove the manifold vacuum when adjusting the timing using a light so that you are reading only the initial timing. When you hook the manifold vacuum back up, the light will jump up off the timing tag. If it doesn't then you have it connected to the wrong port or something else is wrong. Who cares what it is reading then. The initial timing was set correctly. The split second that you step on the gas the vacuum drops and the timing is back where it should be under a load. Try reving the engine with the light still hooked up. You can see how instantaneously the timing reverts to the desired setting. It really is not important where the light is at idle with the vacuum hooked up. Once the initial timing is set, the weights in the dizzy and the vacuum advance take over and move the timing around depending on the loads on the engine just like the engineers designed it.

Long story short...adjust the idle mixture and set the initial timing and rest ***ured all is well.

 

Update:

Got the idle mixture in good by turning all the way in and backing out to (approx. 1.5 turns) for the highest RPM (800) at idle. Physically picked up TDC and matched it to the distributor...walla...the outer ring on the balancer had "rotated" a few inches, hence the bad reading. Made a new mark at 0 and fired it up. Set it to 10 degrees advanced and it purrs. Still pulls 20" of Vacuum and fires right up.

Thanks guys!

 

No MSD box, just a standard points type cap but with a Pertronix module.

And yes, I was stupid and didn't baffle the underside of the manifold. Will have to take off and do that. In the meantime I think I'm going to try a fuel filter between the PCV valve and the carb...hopefully that will reduce the amount of oil getting to the motor.

 

I wouldn't get too excited about a baffle under the pcv valve right now. I don't think that there is any more oil hitting the bottom of the intake than there is bouncing around in most Small Block valve covers. The draft tube setups/early pcv valve setups actually pulled the fumes from the lifter galley but did have the baffle because it laid on the bottom of the galley just above the cam. The main thing is that you have air flow in and out through the carb/intake to reduce the pressure build up in the crankcase.

As far as the timing, I think you did pretty much the same thing that I did a few weeks ago and got the distributor a tooth or two off where it should be.

I'd suggest doing this.
Pull #1 plug (and the coil wire) and get a helper to bump the engine over with the starter to get #1 up on compression. you have to hole your finger against the plug hole and it will blow against the finger when it comes up on compression on #1.
Then I would take a breaker bar or long handle ratchet and the proper socket and rock the crank back and forth to get the piston exactly on tdc. On that engine you can probably look in the plug hole and watch the top if the piston as it sits right now. otherwise you can use a phillips screw driver or length of welding rod to check the movement of the piston.
When you are sure that it is on TDC check the mark on the damper against the mark on the pointer. The whole project will probably take less time than it took me to write it.
Once you are sure your mark is lined up and the engine is on tdc you can reset the distributor to the right tooth on the cam and retime the engine.

 

Not that it makes that much difference, but the simplest way to install a PCV is to use a carb spacer plate with a vacuum fitting, or some 4 bbl carbs have vacuum fittings for PCV valves. This puts the vacuum right o;ver the plenum where it mixes better. I would use ported vacuum for your distributor, because using manifold vacuum will pull in all vacuum advance at idle making the engine idle too fast and too advanced and will cause incomplete combustion increasing unburnt hydrocarbons and CO ***uming you have to p*** a smog test, but in any case, would like to have your idle at 650-700 RPM. With ported vacuum and the throttle ****erflies in correct idle position, there will be no vacuum at the distributor port. Setting timing is what we call static timing. There is usually 10-12 degrees of vacuum advance (for cruise at light load) and 28 degrees of centrifugal advance. Centrifugal advance plus static advance is for full throttle high load and should be 38-40 degrees at over 3000 RPM. Thus, the static advance at sea level should be about 10 degrees. Vacuum advance is for light load conditions above idle and helps gas mileage at cruise. When you load the engine, detonation would occur with that much (centrifugal plus static plus vacuum) advance, but vacuum drops, so vacuum advance drops. The only reason timing adjustments are necessary are when centrifugal advance is increased or the centrifugal springs are changed, bringing in the centrifugal advance at a lower RPM, and also when operating at a higher al***ude which with less oxygen in the mixture, requires more advance. Many are under the impression that increasing the initial advance will give them more power, but as any performance tuner can tell you, total advance (no vacuum advance) is the key. The advance curve can help with acceleration, by increasing advance at lower RPM. This is why the springs are lightened in the centrifugal advance mechanism. Sometimes, to widen the window of advance, the centrifugal weights are changed or are modified to raise the centrifugal advance limit, so that initial advance can stay at a low amount while total advance is raised. This makes for smoother idle and more total power.

Regards,

Alansres

 

I'd say maybe on the oil running around in the valley.

The SBC probably does better than do the big Buicks.
If remember right, the Chevys don't have very big drainback holes whereas the Buicks have a big drainback system and you could probably toss a Lone Star can through them into the crank area.

With the crankcase exposed to the valley lots of oil-laden air to get ****ed into the PCV system.

I understand Mr. Gasket makes a baffle for PCV's and I think you may not have to yank the intake manifold off when installing one of these.

 

Thanks, I'll look into it. Believe it or not your posts were the ones I did most of my searching on before I tackled this. I had every intention of adding the baffle, but it was around midnight and I was half awake and got the intake all torqued down when I looked over on my bench and noticed the sheetmetal and screws still sitting there... I guess it had been a long day.

Any input on the filter Idea? I was thinking that or adding the baffle externally (at the grommet), and placing the valve in-line somehow...