When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a Olds Cutlass supreme "sx" fra 1970 with a 455 engine with the E 403686 heads. The top of a intake valve has broken off. Can someone tell me what size the intake valves are? and do you recommend that i change all the valve both intake and exhaust or just the one that is broken?
Your going to have to pull the head anyway. Once you get it off you'll be able to get the remaining portion of the valve out and you'll be able to measure one of the others. What caused the stem to break is the concern.
Your going to have to pull the head anyway. Once you get it off you'll be able to get the remaining portion of the valve out and you'll be able to measure one of the others. What caused the stem to break is the concern.
Okay. Just hoped that someone knew what the org. valve size was on the motor. I have no idea what made the top og the valve brake off. People have told me that is what happens sometime because the valve issent made of one piece but the top is "welded" on and brakes sometimes. Is that not correct?
Last edited by Randrup; May 6th, 2016 at 01:11 AM.
Okay. Just hoped that someone knew what the org. valve size was on the motor. I have no idea what made the top og the valve brake off. People have told me that is what happens sometime because the valve issent made of one piece but the top is "welded" on and brakes sometimes. Is that not correct?
Yes that is possible. You still you need to check for a cause in case damage was done else where in the engine. You may not find a cause but you may find more damage because of this valve failure. Don't assume the rest of the engine is not damaged.
If the top of the valve broke off, wouldn't that mean that the bottom of the valve fell into the combustion chamber?
As Eric and WR say, this is not good, and, unless the circumstances are quite unusual, requires a complete teardown.
Welcome to ClassicOlds.
- Eric
Thanks
No the keepers were still holding on to the valve so the valve is were it should be. It is only the top 4mm that have broken off. I have startet to take it apart so we will se if it has done any extra damage -
Is this a modified engine? Does it have stock or aftermarket rocker arms?
Originally Posted by Randrup
Is there any thing special i have to look for?
You want to look for any evidence that bits of metal have gotten where they should not have, such as into the combustion chambers, between the rings and the cylinder walls, into the oil pump, and into the bearings.
4 MM = 0.4 CM = 0.16 inches = 3/16" I've never seen a broken valve with that little bit broken off the stem. Either way the head needs to come off to replace the valve and measure it or an adjacent one for size.
Is this a modified engine? Does it have stock or aftermarket rocker arms?
You want to look for any evidence that bits of metal have gotten where they should not have, such as into the combustion chambers, between the rings and the cylinder walls, into the oil pump, and into the bearings.
- Eric
No it is not modified. Only a edelbrock Intake manifold. Rocker arms are stock non adjusterble.
Yes i also think that it is strange that it can break off that piece but a guy told me that in the old days the valve had a top "velded" on... a harder top than the rest of the valve. The break is also 100% clean so i think he is right about this. But i dont know if it is true.
4 MM = 0.4 CM = 0.16 inches = 3/16" I've never seen a broken valve with that little bit broken off the stem. Either way the head needs to come off to replace the valve and measure it or an adjacent one for size.
I am going to throw out a possibility Eric. The stem may have had crystallized crack from being dropped many years ago and finally broke off. The missing part is what makes me think damage internal to the engine may have happened. Then again it may be in the oil pan. If it made it's way into the combustion chamber i think the piston will show damage. If it fell into the exhaust chamber then no problem. You can bet this engine didn't run right for sure. Till the op looks deeper it is speculative. I hope he finds no damage.
No the keepers were still holding on to the valve so the valve is were it should be. It is only the top 4mm that have broken off. I have startet to take it apart so we will se if it has done any extra damage -
Is there any thing special i have to look for?
I just can't picture that much valve stem sticking out above the keeper? Can you take some pictures and post?
I didn't think that either at the beginning - but it is missing about 4mm so the rocker hits the retainer and not only the valve. I thought it was the keepers that was broken, but no it is the valve that is missing a part of the top
I didn't think that either at the beginning - but it is missing about 4mm so the rocker hits the retainer and not only the valve. I thought it was the keepers that was broken, but no it is the valve that is missing a part of the top
That is a vague answer. What i am getting at is the missing part causing damage. Did you get a miss right away? Was the motor running fine and then started to miss all of a sudden? In other words did you acquired this engine and discovered this problem?Did you buy this car and discovered the problem after you started the engine? What really matters is it looks like you had a valve stem failure.
That is a vague answer. What i am getting at is the missing part causing damage. Did you get a miss right away? Was the motor running fine and then started to miss all of a sudden? In other words did you acquired this engine and discovered this problem?Did you buy this car and discovered the problem after you started the engine? What really matters is it looks like you had a valve stem failure.
Ahh okay. The car was running fine by my opinion. No missing or anything. Only thing i noticed was a tikking sound.
Many aftermarket valves have a hardened wafer tip that is welded onto the end of the stem. Allows cheaper stem materials to be used as well as oroviding a safety margin for poor valve train geometry. Looks like the tip came off to me.
Many aftermarket valves have a hardened wafer tip that is welded onto the end of the stem. Allows cheaper stem materials to be used as well as oroviding a safety margin for poor valve train geometry. Looks like the tip came off to me.
Yeah i think so to. I just hope that there is no damage somewhere else in the bottom end from the missing tip.
I have decided to change all the Intake Valves and the dealer sent me some edelbrock retainers without the bearings ( see picture ) is this okay to use the new ones? The spring is now sitting higher and are easyer to compress because the new retainers are different is this a problem?
I have decided to change all the Intake Valves and the dealer sent me some edelbrock retainers without the bearings ( see picture ) is this okay to use the new ones? The spring is now sitting higher and are easyer to compress because the new retainers are different is this a problem?
Yes, it is a problem. The installed height of the spring is specified.
You need to shim under the bottom of the spring to make up for the thinner retainer at the top.
You can buy hardened spring shim washers for this purpose. Also, be SURE to set the installed height of the valve stem tip per the Chassis Service Manual or using the gauge tool.
Hmm is it bettet to use the org retainers then? 2 of them have marks on the top from the rocker arms
The original rotators are heavy, which can induce valve float at high RPMs. People tend to replace them with simple retainers and shim the valves for performance builds anyway.
What do you mean by the high of the valve stem tip. The new Valves are the same High as the old ones so do i need to do that and if so how?
How do you know they are the same? And how do you know the old ones were at the correct height anyway. One of your earlier pictures shows aftermarket valve seals, so the heads have been worked on previously. Chevy-centric machine shops frequently do not correctly set the valve tip height on Oldsmobile valves, resulting in incorrect valvetrain geometry and ultimately failure.
Valve stem height can be set in two ways:
Grind tip of valve stem to shorten valve,
Grind valve seat deeper into head to make stem longer.
This means that the depth to which the valve seats are ground is critical, and must be even across all the valves.
Sloppy builders may grind the seats to different depths, creating a situation where a set of valves which are all the same length stand at different heights when installed.
May 5th, 2016, 09:27 AM
