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Hi! I'm looking for some advice about my engine. I don't know as much as I would like to about this engine, but here is what I do know: it is a 327 out of either a '69 Camaro, or early-mid 60s El Camino. Currently in a '70 El Camino. Sportsman II heads. Definitely not stock cam, but I don't have the cam specs. Built pretty sick, but not perfect: front and rear main leak a bit and oil pressure is low but not too low. Engine had less than 500 miles on it since build when I bought the ute, and I've put nearly 5k before this particular issue.

I was driving on the highway (not agressive, just boring driving) and lost a pushrod and a valve spring. It looks like the valve seal is also shot. I have had people tell me to just pull both heads and replace all pushrods, valve springs, etc. But only one is broken, not the other 15, so I don't think this feels necessary. Also, I only have this next week to do a whole lot of work on it until March. (Senior year of engineering degree and this week is Thanksgiving break. Next free time is spring break).
The options I'm considering are:


1. Replace valve spring, valve seal and pushrod with engine in car, then do compression test to test for valve damage.
-I do not know how I would get a spring to replace the broken one. Can I match it just by measuring installed height, uncompressed height, and dimensions? Can I take it to a machine shop and have them do some magic measurements?


2. Remove that head and replace the broken components.
-Wouldn't have to put rope in cylinder when removing springs. I would need to replace all head bolts, correct?


3. Remove both heads, replace all associated components: rockers, pushrods, valves, springs, etc.
-I see how some may say this is the proper way to do it, but for me at least, money is not free and time is not free (whether it is my own or someone else's time).
 

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The question that begs here is "why" did you lose the spring and pushrod?


Replacing it is the easy part but if it happens again, then what other issue is going on. AND - is the lifter still in the lifter bore? If not that's another issue to deal with not to mention the loss of oil pressure for whatever amount of time it took to get the engine shut off.


Given your student status, I would consult a good engine shop/machine shop this week and plan on replacing the components. I am assuming that the valve didn't drop and got hung up on the seal - thank goodness. Also where is the retainer and locks?
 
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Any chance of coil bind or not enough retainer to guide clearance? Without a cam spec this is difficult to wager a guess at.

How is your valve train geometry? Another question impossible for us to answer. But if you were to remove all of the rocker on the bank with the failure, and attach some pics of your valve stem tips, then they should indicate the wear area/pattern of the rocker on the stem.

Cam deterioration should not have caused this, but I'm always concerned about FT cam wear. To check it will cost you $20 of intake gaskets, a tube of RTV and some time to re-time the motor.

At some point in your near (1-2 yrs) future hopefully you'll graduate and as long as you don't apply your degree to becoming something that pays poorly, such as goat herding, then you'll have the money to treat this motor to a proper retro roller cam and lifter set and never worry again about any of this FT cam scare ever, ever again :):) hehe.

All kidding aside, you should pull all of the rockers and push rods and inspect. You will also be able to inspect the valve seals at the same time - at least for obvious contact or destruction. To recheck this at time of reassembly with the heads still installed you should grab/buy/borrow a set of checker springs, a compression tester and valve spring changing device. The purpose of these would be to confirm that this isn't the 1st of many failures to come and that the remaining parts in your valve train should live for a good while.

Where are you located?

Jim
 

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A cam of unknown dimensions but sounds aggressive, a busted spring and wiped push rod, and Sportsman II heads sounds like a recepie for springs that are not the usual GM production stuff.

The cam lobe figures hard into the spring characteristics. If this is an aftermarket cam then the head more likely than not has performance springs. This means the new spring needs to match that which broke. Lacking any other information to select a new spring will require removal of a good one and test it for free length, then pressure at installed length, then pressure at max lift length. Unfortunately counting coils and wire diameter is not a good way to answer this because these measures do not account for material type and processing methods which have as great to greater effect upon spring forces as do the dimensions.

Broken springs most generally drop the valve far enough to allow the piston to hit it. The safest way to proceed is to pull that head to inspect the valve and piston for contact damage.

I suppose this won't pass as a senior engineering project, but it does become a study in Root Cause Analysis which ought to count for something.

Generally big cam's have an appetite for their springs. Stiff springs run hot and completely depend on top end oiling for cooling which is usually inadaquate at highway speeds while they are put through long hours of running in this condition. Add to that as spring pressures go up the material to get those pressures becomes quirky to the manufacturing processes, basically heat treat manufacturing problems which do not necessarily show in accptence testing do result in early service life failures (so called infant part mortality failures).

Bogie
 

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With an unknown build, who's to say the springs were adequate to begin with? To some rebuilt is a can of spray paint. If the failure is from fatigue the other 15 are not far behind. There are lots of variables and possible secondary damage to just stick a spring on it and hope for the best. To do both heads I would put it on a stand and address the leaking low oil pressure bottom end also. Once and done to have a solid engine will cost far less time and money in the long run.

I get the money's tight and student deal. Save till you can fix it right. It takes some guys years $5 at a time. Any hobby requires a time investment and some sort of funding. The car hobby generally requires lots of both. If you're looking at it from the time is money/my value perspective it's easy to get discouraged.
 

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Go over everything and look for interference or a bind. Pull off a couple of rockers, look them and the push rods over very carefully.
 

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Discussion Starter #8
Thanks for all of the replies! Valuable stuff.

A guess as to why they broke is that the rockers weren't adjusted properly. The remaining, non-broken ones have varying levels of slop. Furthermore, the engine has matching rockers EXCEPT at where the break occurred. Same ratio, but different brand. I'm not sure if this means it has happened before, or that the guy just used what he had around his shop. The retainers and locks are still in place, but the valve moves very easily by hand so I reckon it more likely than not for it to have hit the piston. Also supports the idea of lost valve seal.

While the aftermarket heads likely did have performance springs, I really am not sure if the springs ever did get matched to the cam. If I were to replace all 16 springs would there be value in measuring the cam lift with a caliper or something, or is duration info needed? I'll try, again, to ask the P.O. is he can find the cam specs. He claims they were in the glovebox, but no luck there. Real nice guy who has had countless Chevys in the past.

Oil pressure is 50 when engine is cold, but once warm *barely* meets the 10psi for 1k rpm rule.
 

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If I do pull the head, what level of damage to the piston would be of concern? I imagine a small ding, while may affect compression slightly, would be okay. Or not?
 

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Thanks for all of the replies! Valuable stuff.

A guess as to why they broke is that the rockers weren't adjusted properly. The remaining, non-broken ones have varying levels of slop. Furthermore, the engine has matching rockers EXCEPT at where the break occurred. Same ratio, but different brand. I'm not sure if this means it has happened before, or that the guy just used what he had around his shop. The retainers and locks are still in place, but the valve moves very easily by hand so I reckon it more likely than not for it to have hit the piston. Also supports the idea of lost valve seal.

While the aftermarket heads likely did have performance springs, I really am not sure if the springs ever did get matched to the cam. If I were to replace all 16 springs would there be value in measuring the cam lift with a caliper or something, or is duration info needed? I'll try, again, to ask the P.O. is he can find the cam specs. He claims they were in the glovebox, but no luck there. Real nice guy who has had countless Chevys in the past.

Oil pressure is 50 when engine is cold, but once warm *barely* meets the 10psi for 1k rpm rule.

Yow, sounds like a pig in a poke build. Try and find the cam specs, very important! Take a picture of what is broken and the rest of the rockers as they are. You may as well pull at least the one head for now.
 

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Go over everything and look for interference or a bind. Pull off a couple of rockers, look them and the push rods over very carefully.
In 1965, when the famous Chevrolet 30-30 cam was first introduced, I installed one and soon broke a stock 068 valve spring. The 30-30 cam has .485” valve lift and the stock 068 valve springs, without a damper, stack up and coil bind at .520” valve lift. . That appears to be OK.

With that much margin between coils at fuel valve lift, why did the spring break? The reason is spring surge. The 068 valve springs without a damper allows the coils to bounce off the spring seats and the retainer at high RPM. The coils then slam into each other. The flat damper “dampens” spring surge at high RPM and prevents the coils from beating together.

Chevrolet continued to use the 068 valve springs, without a damper, in all their low performance SB V8 and 4.3L V6 engines from 1965 to 1992. There is no need to use the 068 springs with a damper if the RPM red-line is less than 4,500 RPM.
 

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Real nice guy who has had countless Chevys in the past.

Oil pressure is 50 when engine is cold, but once warm *barely* meets the 10psi for 1k rpm rule.
Doesn't men he knew what he was doing.

I didn't see where you're located, but if it's close to winter, and your description of 10 psi per 1K of rpm's means you have 6-8 pi at idle, then there is no better time than the present to pull the motor and plan on a set of bearings and oil pump at a minimum. That's also a great time to check the cam specs and heads. If you can get by with a set of bearings, oil pump, springs, pushrods and gaskets, then you can easily get out of this for well under $500.

Motor sounds like a timebomb if you keep going. I hate to sound doomy and gloomy, but you might still have something worth saving. Run either a compression or leak down test before disassembling.
 

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If I do pull the head, what level of damage to the piston would be of concern? I imagine a small ding, while may affect compression slightly, would be okay. Or not?
Depending on piston type, either cast or forged, size of damage could make a difference, but a small nick or ding generally doesn't doom a piston...just clean it up with sandpaper or a Dremel and continue on.

One concern is tagging a valve typically bends the valve, rendering it junk.

SBC head bolts are reusable, they are not torque-to-yield 1-time use like newer engines.
As long as they aren't heavily rusted enough to visually see reduced shank thickness or thread damage, re-use them.
If you should need to replace them, $25 at most performance parts houses will get the job done, complete set for both heads.

If a spring broke, simple because it broke, due to a flaw in the material or from use fatigue, then I would replace the entire set.
The hard part for you, is determining what caused the break? Was it a valvetrain clearance problem, an over-rev condition, or a random part failure??

I'm with 64Nailhead, if it isn't your regular driver and just a play car, then pull the engine, check everything else inside before you hurt it mortally....then you can see what the cam is and pick a spring to match at reassembly. This also gives you a chance to affirm or discount the previous owners ability to do things correctly.....which is a factor that often gets way too much trust placed on it.. I've seen guys you'd think would know a lot judged by the vehicles they've owned turn out to not know nearly what they think they do, much of what they think is gospel is old wives tales and falsely repeated word of mouth info, or bad info from 30 year old magazine articles.
 

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If the piston whacked the valve it usually is bent, it cannot make a seal if it is. The piston will have a contact mark. Usually unless the head comes off the valve or the locks fail dropping it into the cylinder, the piston doesn't have much damage.

If the springs are nested with at least a flat wound damper or a second spring, the valve may not have dropped far enough into the bore to have been hit by the piston, same if the failure was near and end of the spring and the valve didn't fall far enough to get hit.

Careful examination of the surface of the spring's failure whether sudden or a building fatigue failure might help pinpoint the failure. A sudden rupture will leave a fairly smooth surface. If a fatigue failure you will see a progression of one or more small tears then a step then another tear and step maybe once possibly repeated up to the final tear. These are called benches and are the trade mark of a failure building over time. This does not address the root cause very much, but gives some indication of whether the strength of the material was suddenly exceeded, or gradually grew from a manufacturing or materials processing error or if from damaged started from a one time event that exceeded the material strength causing a micro crack which the then grew with time and declining zone strength.

As for low oil pressure this mostly speaks to excessive bearing clearances. The pressure is simply the ratio of what the pump delivers against the rate of leakage from the clearances. The engine could have been built with loose clearances which is typical of old fashion competition builds. These rely on thick oils and high volume pumps to keep pressures up. Such an engine would run 15w40 or 20w40 to a straight 40 or 50 weight oil. Or the low pressure could be excess clearance from ignorance about clearance and effect on pressure, or it could be the life is just raced out of the bearings. This is something that can only be found by total disassembly. In the meantime you can play with oil viscosity to see if you get a change. This engine is a 1950's design it from the beginning was never designed for oil less than 10w30 and frankly I only view that oil as a winter grade in the northern states for these gear pump engines. You will note that no modern engine designs use a gear pump and for good reason with modern machining and light weight oils they are both unnecessary and ineffective in these situations. What they do offer is inexpensive to make, as a working engineer you will learn that cost overrules function everytime where there isn't a government body levying requirements or greater customer concern than worry about stockholder return, damn few companies fall into the latter.

Bogie
 

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Thanks for all this great info guys!


I'm thinking what I'll do for now is: pull both heads, replace gaskets, valve seals, valve springs and push-rods. I didn't know that the head bolts were reusable, that's nice to know. I still need to figure out the cam specs before proceeding.



This way the El Camino is drivable, but I won't be driving it much until I pull the engine to check bearings and what not. The reason I am not doing that all at once is that I do not currently have a paved workspace to maneuver an engine hoist on.



When this occurred the El Camino was my daily driver, but I got sick of not having the time to work on the car once it broke so I got a Volvo 244 to get me around.
 

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Thanks for all this great info guys!


I'm thinking what I'll do for now is: pull both heads, replace gaskets, valve seals, valve springs and push-rods. I didn't know that the head bolts were reusable, that's nice to know. I still need to figure out the cam specs before proceeding.



This way the El Camino is drivable, but I won't be driving it much until I pull the engine to check bearings and what not. The reason I am not doing that all at once is that I do not currently have a paved workspace to maneuver an engine hoist on.



When this occurred the El Camino was my daily driver, but I got sick of not having the time to work on the car once it broke so I got a Volvo 244 to get me around.
If you do indeed go with this plan, then at least remove the oil filter and cut it open. Any shiny particles of bronze/brass looking things means pull the engine now. Otherwise what you spend on the top will mostly have to be re-done later.

Bogie mentioned throwing in some heavy weight oil - great idea as long as you aren't already running 20W50 lol.

Maybe a pic of the El Camino ?
 

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If you do indeed go with this plan, then at least remove the oil filter and cut it open. Any shiny particles of bronze/brass looking things means pull the engine now. Otherwise what you spend on the top will mostly have to be re-done later.

Bogie mentioned throwing in some heavy weight oil - great idea as long as you aren't already running 20W50 lol.

Maybe a pic of the El Camino ?

Good call. I will certainly be doing this.

I have tried 10W30 and 20W50 and haven't noticed a huge difference in oil pressure, but that was in the heat of the summer.



As far as the gauge being inaccurate, I have tested with a mechanical gauge too.
 
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