Rocker Arm Adjustment

Hi, new to this site and a rookie gear head, so pardon my ingnorance as I may be asking some very basic questions to most of you.

I have a 1974 Pontiac Ventura Custom with a SB chevy 350.  It is gear driven with an hydraulic cam and roller rockers.

I was getting some "Popping" out of the exhaust when I accelerated quickly and discovered that when I pulled the #3 cylinder spark plug that the gap had closed on it some how.  I changed the plug and tried it again...still got the popping, pulled the #3 plug again and the gap again had closed and the plug was wet.  I also found the compression was 40 lbs less in this cylinder.  So obviousely something is hitting the plug inside the cylinder, and causing it to lose compression.  I took the car into a shop and they pulled the valve cover off and told me that the roller rockers had been installed backwards by who ever built this engine (not me...I bought it as is), IE: intake on the exhaust and exhaust on the intake, I didn't realize that there was a difference??  Any thoughts on this?  Also, there was engraved on every other rocker arm the number "1.6", what does this mean?

So I have switched the rocker arms around and now I need to adjust them , so what is the best way to do this?  All the research I have done has the engine out of the vehicle and they talk about turning the fly wheel to get the valves in cetain positions to adjust them.  My engine (A small block chevy 350) is still on the car so is there a way I can adjust the rocker arms like this?  Are there torque specs I need to know about?  Special tools to accomplish the task? (I have heard of something called a click-adjust).

I may be putting the cart before the horse by doing this before finding out what is hitting my spark plug, but I just picked a starting point.  

I suppose I should check for broken springs or broken valves too, so is there an easy way to do this just by removing the valve cover or will I have to pull the head too?  If I can remove the valve spring from up top, is there a special tool to remove the valve spring as I want to take the springs off of that cylinder to check for a broken spring/valve, or does some one out there have a trick to do this with out a special tool?

Any help you can provide me with is very much appreciated and my thanks in advance to every one who responds!!

Craig B.  

Craig,
The issue with the rockers is a bit of a concern, typically SBC builders tend to run 1.6:1 ratio rockers on the exhaust valves to compensate for Chevy's slightly weak exhaust port, effectively this acts like a larger cam on the exhaust only. Usually, they will run a 1.5 or 1.52 ratio on the intake side. On SBC's, the valve arrangement from front to back is E I I E E I I E, same on both sides. Even if the long ratio rockers are on the wrong valve, it won't cause the spark plug electrode gap to close up. Something is hitting the plug, pure and simple. Either something has found it's way into the cylinder, such as a washer or nut, or the piston is hitting the electrode. Another possibility is the spark plug itself, is it the right plug for the application or has someone used on plug different with a longer reach. The only plugs I use for SBC's are AC Delco R43TS,R44TS or R45TS depending on the heat range required in taper seat heads, and R43, R44,R45 in gasket applications. I don't believe in trick of the month split fire, V groove or platinum plugs, I've never seen any improvement using anything other than delco.
It's possible that due to the cam lift plus extra rocker ratio, a valve hit a piston and bent, causing it ti hit the plug. When all your rocker arms are off, check the height of all the valve stems, they should be roughly equal when you lay a straight edge on them, any shorter ones will indicate a bent valve which isn't fully closed.
When you do get the problem figured out, we'll talk about the rocker adjustment.
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

Hi Steve,Thanks so much that is a great explanation and makes things a whole lot clearer.  Now I know what the 1.6 menas that was engraved on the rocker arms.  I switched the rockers all around and put the 1.6 ratio's on the intake valves.  I agree that some thing is hitting the plug in the #3 cylinder.  The plugs i am useing are the NGK UR4 V power, and I agree that I did not notice any diference when I switched from the standard UR4's.  The length is good, as I have been running these for 2 summers now and Ihave not had any problems untill now.  As an experiment I put a shorter reach plug to see if there was any difference and I still got "something" hitting that plug.  I am going to switch to AC Delco once I have things back together on your reccomendation, but I admit that I do not understand the whole heat range thing so I am not sure which of the three plugs to use that you reccommended (taper seat).But the good news is that I took off the Valve cover yesterday, and found out that the #3 exhaust spring has broke, so i have found one of the problems.  I also took a straight edge to the valves and on the drivers side there were a couple of valves that I was able to stick a 35 thou feeler gage between with room to spare.  I compared that with the other side and there is a difference, so I am thinking I may just pick up a rebuild kit from Summit.  What do you think?  Can I do this without pulling the engine?  Other tips n tricks??  If the piston hit the plug do you think there could be internal damage?  I did not see a piece of the spring any where, could this have made it's way into the #3 cylinder?  Thanks again for your help!!!

Craig  

Craig, the spark plugs I mentioned are basically the three heat ranges of the same plug design, with 43 being the coldest and 45 being the hottest. Most SBC's from the 70's thru the 80's used R45TS plugs from the factory. The hotter the heat range, the less likely the plug is to foul from oil or carbon deposits because it self-cleans, however the colder plugs tend to run cooler and shed heat so they don't become a hot spot in the chamber causing preignition in high cylinder pressure applications (ie: high performance). The down side is they will tend to foul more readily in cold weather. From the picture of your car, I'd say cold weather isn't a factor  to be concerned with.
As for your valve stem heights, ideally we'd like to see them all the same height, but in a non-racing engine, likely the shop that did the work didn't bother to get that picky and treated them like a stock rebuild. I would remove the intake manifold, distributor and header from the driver's side (this can be done in the car if you are careful and protect the paint) and find out what is hitting the plug, you won't find the valve spring piece in there, it's impossible to get in the cylinder from under the valve cover. Likely it is in the bottom of the oil pan, if there is no other reason to pull the pan and it doesn't come out when you drain the oil, leave it there. It's heavy enough to stay on the bottom out of harm's way.
Was any work done on the intake recently? A carb swap maybe? I've been there and lost a 5/16" bolt and flat washer years ago ( I switched from a Holley to a Q-Jet and didn't miss the bolt because the carbs used different bolts). I was able to suck the washer out with a thin magnet thru the plug hole after it got folded in 1/2 between the piston and head but I hade to pull the head to get the bolt after it bent the intake valve on that cylinder.
How was the compression on the other cylinders? If you have a bent valve and broken spring on #3, that can explain the lost compression and you likely only need to repair that head. Keep me posted on what you find and I'll try to help you along the way.
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

Steve,
Thanks for the spark plug info, I think what i will do is experiment and try the hotter plugs first and then move to cooler ones if there is a problem with pre-ignition.

I have already began the process of taking the head off on the drivers side so I will let you now when I get it completly apart and what I find.  It is a spare time thing so it might be several day s before I am there, but we will see how anxiouse I get to get it fixed.  I am already going through withdrawl to drive it...lol!

I did swap carbs this spring from a Holly 600 race carb to a Holly 770 street avenger.  I am sure I did not lose anything down the intake as I was very carefull, but you never know.  When I drain the oil, I will run a magnet through it and see what I pick up.

If I may take a detour for a bit, speaking about my carb.  There is an adapter plate under the carb and the adapter has one side  of the "inlet area" that is tapered.  When I removed the adapter,  I noticed this tapered side was face down, and while I was watching the holly installation video they put an adapter plate on and it appeared tat the tapered side was facing up.  Can you advise me on this please? (It seems that this engine was built rather sloppy).

Back to the valves...When I put things back I would like to make sure that the valves are all the same height, so perhaps you could advise me if this is simple to do and how to ensure they are the same.

As far as the compression goes, only one other cylinder was checked and I believe it was 170, and the #3 cylinder was 130 (I don't know what the ratio is).  If I only need to repair that valve and spring that will save me quite a bit of money, but I am wondering if it would be better to just replace all of the valves and springs so that each cylinder is exactly the same, or will it not make any difference if I just replace the one as opposed to all eight?

Craig  

Steve,

In addition to my previouse post, I was just thinking about my predicament and perhaps an easy and inexpensive way out of it.  

My neighbour happened to have a valve spring removal tool....the type that is like a gear puller.  What if I were to make sure that the piston is at TDC, so that the valve won't fall through and then remove and replace the broken spring only. I am thinking that replacing one spring will not probably make any difference in continuity of the strength of the springs. I have been thinking further about your comments in regards to shops not being picky and getting the valves aligned.  Seeing as I have two valves that are a little lower, the chances of bending two valves are pretty slim.  Especialy since this problem just happened when I started the car.  it was not like I was driving hard (which I just don't do any ways) to cause a spring to break and/or valve(s) to bend.

I should be able to remove the spring once the valve is fully up, put the new one in place with new keepers.  Re-assemble, and then Bob's my uncle!  At least this is my theory.  If there is still a problem, then I will find out very quickly and will the have to go back to the drawing board.

The unfortunate thing is that I have already undone all of the bolts that I need to for this, but the good news is that I have not actualy pulled the intake or head off yet and disturbed the gaskets.

So what do you think about my idea?  

Craig  

Craig, if the only problem was a broken valve spring I would say go with your plan to replace the spring. You are correct about the procedure to replace the spring. The problem is that the valve would have to be severely bent or broken to be hitting the plug. Since you've already loosened all the bolts, I would go ahead and pull the head and intake. I believe you will find your answer inside. When you get the head off look for any sign of contact between the piston/valves/plug and take some pics to email me if possible.
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

I agree with barney you should pull the head.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Sounds good guys, consider  it done....I will get some pictures for you and post them here for you to see.  

One more question.....on the cylinder head are there 8 bolts on the side in line with the plug holes that need to come out?  And when I remove them is it normal to have coolent leak out? ( I just did one and stopped when the coolent began to come out).  

Yes coolant will leak out that is why I drain the cooling system when removing the heads on any engine there is a block drain plug on the side of the block that you can pull to drain that side of the block.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks PM8!!  

No problem.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Ok I have run into a small snag....

The very last bolt at the back of the head is directly under the centre of the exhaust manifold.  I placed a floor jack under the exhaust pipe and was able to jack it up just enough to move it up and give me a little more clearance, but I still can not get a socket on it even with a universal joint.  Do you have any tricks of the trade I could try?  

How about a boxed end wrench.
If not you may have to unbolt the exhaust pipe from the manifold which will most likely be what needs to be done.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races