I had a few other threads started regarding my Corvette Oddesey but thought this deserves a new one.

Here is my story...I just obtained an '87 convertible a few short weeks ago in a trade for a '69 Lincoln Continental coupe (for those that like details).

The prior owner was up front about the car having a problem and not running right. I checked the car out and figured worst case scenario it would need a new engine and I could theoretically still be money ahead on the deal when I went to sell it.

Ultimately, I discovered that a valve spring had broken for reasons not then known. I tried the easy way out by just replacing the broken spring on the one cylinder. As fortune would have it the rope I used to keep the valve from dropping into the cylinder got stuck and I had to pull the head off. Good thing I did as it turns out the valve with the broken spring was bent.

I brought the head to the machine shop yesterday to have them replace the bent valve and be done with it. Keep in mind this is a budget project and I was just trying to get it running correctly before I sold or traded it for something else. At this point considering myself fortunate that it would not need a new engine.

The machine shop called me today and was concerned because all of the valve stem seals were chewed up. As it turns out there is a set of aftermarket roller rocker arms in there and Pete at the machine shop surmised that the ratio on the rocker arms was too great and not in keeping with the spring height and the other bits and pieces in there. I will check to see if the rocker arms are stamped with a ratio tonight.

Pete wants me to pull the other head so he can check that one and re-surface at the same time as the first one.

I do not know if the car has a different cam from the original or not but it appears fairly clear that someone was in there messing around before.

I am thinking of just going back to the stock rocker arms which I would have to get. I want the car to run right and do not want to pass on a trouble maker to anyone else.

I do not really wish to pour a ton of money into the car and buy new trick heads etc. But I do not want to be penny wise and pound foolish...meaning if I cheap out and just go back to stock rocker arms am I missing out on some other reasonable cost alternative from stock to make the car that much better?

It seems like at least a possibility that the rockers arms may have led to the valve spring failure.

Anyone care to share their innermost thoughts and feelings on the subject. Getting this deep into the mechanics of things is a bit new to me.

Thanks as always,

Craig

 

Pics of the rockers would help to determine if they are worth keeping. Just because it's been upgraded doesn't mean it broke or it will again, the guy could have over revved it or it could be ebay china junk rockers. Also inspect the pushrod for that spring/rocker as well. If you really want to go back to stock I have a almost new set of stock self aligning gm rockers. I bought them for some vortec heads I ran awhile back briefly on another car and keep forgetting I have them, pretty sure they are the same. If your interested pm and I'll get you a part number and a pic. I don't think they cost much new and I wouldn't want much. Still I've seen plenty of people sell you parts you don't need and then steal that persons good parts. So think about it before you maybe downgrade.

edit: Wait I think 87 was 128 heads and normal rockers with guideplates. Inspect your guideplate also if so.

 

Would it be possible to contact the prior owner to see if he knows what cam is in it? If not, you may want to measure how much lift it has and go from there. Does sound like too much lift for the valves & springs.
If it had just 1.6 rockers in it, most likely the stock valve train would handle it.

 

Pull the other head, get all the guides and springs replaced, make sure both heads are going to be the same and freshened up,
you have to buy a pair of head gaskets so you might as well use them both,

Like the other guys have said, you need to determine exactly what the rockers are, 1.6 isnt too much on its own, but if its got a bigger cam in there with the stock heads, they might be, if you post a picture here someone will know exactly what you have.

If you still have the pushrods and rockers hooked up on the other head you can turn the motor slowly and measure the lift (if you have a dial gauge) and watch how much compression is on the valve springs when they are fully compressed. If you get valve bind this is probably what caused a broken spring and bent valve in the first place.

 

The prior owner had no knowledge of any modification made, he took the car sight unseen on a trade for a Harley and when he got it, it wasn't running right at that time.

I took a look at the rockers and was not able to find any numbers stamped on them. I will post a picture tomorrow. They are blue anodized aluminum if that means anything.

too late to check the lift on the cam I already pulled most everything apart to get the head off. There is a pesky little hose clamp holding some tube to the flange for the header I was not able to get to. Took me awhile to realize this was preventing me from pulling out the header. Should be able to finish up getting the head off tomorrow.

I have dealt with this machine shop before and I believe them to be reputable so I am fairly certain they will not try to sell me something I dont need.

the push rod on the bent valve was also bent.

Thats all I have at the moment.

thanks for the input!

craig

 

Blue unmarked could be a few old brands or cheap china rockers. Got a set of those mystery rockers myself.

 

I guess the stock ratio is 1.5 and the consensus seems to be that a 1.6 ratio should work fine with stock components. Are there ratios greater than 1.6?

I would think the odds are in my favor that I have either 1.5 or 1.6 ratio rockers and can simply re-use them.

What could go wrong...

 

Are the rockers self aligning? That could cause a problem when used with a guideplate, you use one or the other.

There are greater ratio rockers, but I think you run into clearance issues.

 

I do not know if they are self aligning...how could I tell?

There is a guide plate present.

I will get pictures of the rockers up when I get home.

I did not want to use a greater ratio was just curious if there were others beyond 1.5 and 1.6.

 

Hi Greg I'm new here, I only find valve springs break when fatigued, like binding. Seems like having the shop do both heads is good idea.
Other considerations, I have run 1.6:1 rockers they have some performance advantages and some considerations. They have more leverage against your anchor post, seen em pull them out, combined with a bigger cam, spring binding is never good. Sure you know all this
BUT......
CAUTION, many times through the years on broken valve springs or timing belts, when the valve has hit the piston, serious distortion to the piston can have occurred that is not readily visible. This can be in a couple ways either widening the piston top and causing to score with the bore, or more often a slight crush to the ring land binding the ring, again causing a score to the bore.
Many early failures I have seen because this was undetected. My own personal was a 460 I had balanced, cammed, valve spring broke, took off head valve wasn't even bent, ran great at first but got like it was struggling, before I reopened (about a year), it threw a rod, this was due to that same cylinder with the broken spring and the thrown rod, had aluminum bonded to the cylinder walls similar to how an old school 2 stroke dirt bike would, my conclusion was I did not detect the expanded piston.
Just check it.... hope its nothing more than some new springs, I would replace them all myself.

 

Google self-aligning roller rockers and you should be able to find a pic. Looks like they have washers on the side of the roller tip that hold them on top of the valve tip. Some have tabs but those are steel body and you said yours were alum.

 

Could measure cam lift off of an exhaust lifter if you have a dial indicator. Going to need to know the amount of lift the cam is going to give you to know how much valve travel/spring rates you're going to need on the head.

I'm assuming the heads that were on it are the original aluminum heads? Anyone know what the stock aluminum's were good for? (lift wise)

.

 

I do not have one in front of my to compare but I think they are self aligning based on the pictures I see of others.

So I should ditch the guideplates?

I am reluctant to spin the crank as I have the distributor out and I marked it for easy re-assembly.

I had a helluva time getting the passenger side head off, took me awhile to figure out there was a torx fastener on the front of the A/C compressor as it was obscured by crud. I damaged the pulley on the compressor to boot. The A/C was not working anyway, I was going to ditch the A/C in favor of another pulley, that will clear up a lot of space and make re-assembly easier too. Plus who need A/C in N/W Washington in a convertible?

I dropped the second head at the machine shop this morning. It is clear that someone had messed with these heads before as there were some welds and someone attempted to do some porting on them.

 

36 Volt you may be right, I see an extra depression in the top of the piston where the valve hit and looks like some minor scratching of the bore.

I think I will chance it for now. Put it all back together and see what happens....