Okay I had my valves tightened too much which collapsed the lifters bent the pushrods and wiped out my cam lobes. So I installed a new cam and lifters and pushrods. The new cam has .006" more lift than the old one, so I assumed it wasn't going to change much. I got the same length pushrods. I pumped up the lifters and set the valves with the car off. So I start the car, there is lots of backfiring and running rough. I mess around with the timing and it doesn't really help much. I did drive the car like this for a few days. Today I took off the valve covers to readjust the valves and one of the pushrods was GONE! I found it in the lifter valley just lying there snapped in half. All of the intake pushrods were bent, but none of the exhaust ones. I figured that maybe the valves hit the pistons, so I pulled the heads.

So here are my questions:
1. Can you tell if valves are bent without removing them from the head? They look to be sealed very well and I looked in the intake and exhaust ports and they look straight from what I can see.

2. I don't think the valves are bent, so what is causing the intake pushrods to bend? I know I didn't have the valves too tight this time. Could it be that my heads can't handle the .006" extra lift? They are GM 193 castings with screw-in studs. I don't know if they were ever machined for any extra lift, the old cam had .464" intake and exhaust and it was fine that way.

3. I did not get new valve springs with my new cam. This was a crate motor with maybe 1000 miles on it. Could my new cam need stronger springs? I mean I know obviously it could, but I thought they would be fine with a similar cam as the old one.

4. Could the .006" extra lift cause my pushrod geometry to be off so bad that it bends the intake pushrods? I know I should have gotten an adjustable pushrod and checked, but I don't really understand how you check what length you need, and if the geometry was wrong, wouldn't the exhaust pushrods bend too?

That's everything I think, if you need any more info to help just ask. Sorry for the long post I'm just really confused and don't know what to do. Any help is much appreciated. Thanks.

 

1 bent valves would, or should be stuck

2 you sure it's .006? if it is forget it. there's not enough differance to matter. my guess is you have two differant locating systems for the rockers.

3 you should run springs to match the cam. you should run any spring from gm in a preformace application. if you don't know what springs you have trash them, and the factory rotators.

4 no

 

Springs are Comp Cams 981 Single Outer with Damper

O.D: 1.254
I.D: .820
Seat Load: 105@1.700
Open Load: 295@1.250
Coil Bind: 1.150
Rate: 417 lbs/in

I just looked at the Comp Cams website and these are the recommended springs for the old cam and the new one. The old cam was .464/.464 lift and the new one is .470/.470. I am using guideplates with hardened pushrods meant for use with guideplates.

Any thoughts?

 

u can tell if the valves are bent by turning the head upsidedown put a spark plug in it and fill the combustion chambers with water to see if it leaks past the valves. if u didn't line up the timing marks correctly that could cause the valve timing to be off causing the intake valves to hit the pistons and bend the pushrods. pull the heads off and look at the pistons to see if the valves have hit them. there would be some slight marks in the valve reliefs.

 

Are you using non-self aligning rockers?

Did you open up the pushrod guide holes in the heads (to be safe?)

 

rokn91rs- The heads are already off. I can't see any marks on the pistons that would indicate the pistons hitting the valves. The timing marks are lined up correctly. I will do that test tomorrow to see if the valves are sealing.

8Mike9- I assume I have non self-aligning rockers. They are the rockers that came with the engine and it ran fine with them for a few months, so I don't think that they are the problem. How can I tell if I have self-aligning rockers or not?

I did not open the pushrod guide holes in the heads, but before they were bent, the pushrods slid in easily and did not appear to be binding in any way.

 

What is the installed height of the valve springs? (and don't just quote the height the catalog specs are given at.... get the measurement)

I'd bet you have coil bind.

Also, look VERY CLOSELY at the top of the guides and the bottom of the center of the retainers, to make sure the retainers aren't hitting the guides.

 

Okay I'll measure the height tomorrow. Do I just measure from the top to the bottom or are there special points that I need to use?

If the retainers are hitting the guides, that requires machine work, right?

 

To measure the installed height, you need a valve spring micrometer.

You might not necessarily need machine work... you can get offset keepers, that allow the retainer to sit higher up on the valve stem. That would also increase the installed height, by however much they change the retainer position (.050" usually).

 

Is there any way to tell what's going on without a valve spring micrometer?

If the retainers aren't hitting the guides, does that narrow it down to just needing stronger springs?

 

i use a snap gage and dial caliper. no it doesn't narrow it down to needing stronger springs.

 

Okay I don't have anything to really measure the installed spring height, so I took off a few springs to look at the guides. I noticed that the exhaust springs were harder to compress than the intake springs. I guess I didn't think it mattered, but the exhaust springs have these big circle things on top and the intake ones don't. I'm trying to attach a picture I drew of it, but I don't know if it will work. Would these circle things have anything to do with the exhaust pushrods not bending? The actual spring part is the same height intake and exhaust, but the top piece on the exhaust makes its overall height taller when uncompressed. When compressed they are the same height but the exhaust springs have more tension.



edit: I found this picture on google. This is what the thing on top of the exhaust spring looks like, but mine is deeper. It is called an exhaust seat? What do they do? Why don't I have intake seats?

 

Just looking at these numbers:

Seat Load: 105@1.700
Open Load: 295@1.250
Coil Bind: 1.150

The height difference between the closed and open height is only .450...my lift is .470...is this a problem?

Also I just compressed an intake spring with a press and it seems to be just about binding at 1.25 or so. So do I need a spring that binds at a shorter height?

I called Comp Cams and they told me to check for pistons hitting valves (no), the rocker bottoming out on the stud (I don't think so, the studs all look fine. There are no signs of any strange wear or collisions), or the guides hitting the retainers(I don't know how to check this). My springs don't look like they have retainers on the bottom...the spring just sits in the little indent seat on the head.

I'm really just throwing out ideas here. Any other ideas?

 

You're good for .500 lift with those springs if they are installed at the recommended 1.700" installed height, which is exactly stock installed height spec. Not to say that all heads hit spec exactly or that they're even the same from one valve to the next, but I've put together plenty of heads for stock/mild performance applications that are very similar to what you've got- same springs and all. You SHOULDN'T have a problem with the valve springs or the installed height, but you MUST check at this point.

That metal disc is to take up the space that USED TO BE occupied by the original (thicker) exhaust valve rotator/retainers. I'm going to take a guess and say that you have standard retainers on the exhaust side (same as the intake side), then this disc and then the spring, right? That's how it should be. Personally, I would have just kept using the stock rotator/retainers but how yours is set up is fine for mild performance, too. Stock heads have the exhaust-side spring pockets machined about 1/16" deeper than the intake side. This is because the stock exhaust-side rotator/retainers are about 1/16" thicker than standard retainers which would normally reduce the valve spring's installed height. So the factory just machines the exhaust valve spring pockets deeper by that 1/16" and then they can use the exact same springs on both the intake and exhaust.

You really need to check for retainer-to-guide clearance as well as measuring the spring's installed height. Stock heads often "poop out" around .460-.480" lift when the retainers start to make contact with the guide seals- this is often LONG before you bind up the valve springs. If they used some thick seals it's possible you may have even less room than that. You check by taking out the valve springs and then re-assembling the retainers and locks onto the top of the valve stem. Grab the retainer with 2 fingers and pull the valve closed HARD onto it's seat. With your other hand measure the distance from the top of the guide seal to the bottom of the retainer- the inner collar of the retainer, which sticks down the valve stem at the center of the retainer. A cheap outside distance mic will work fine for this kind of measurement- I use a plastic one I bought at Lowes for $9- it's plenty good to measure in .01" increments. That distance is all you got before the retainer starts to contact the guide seal. If it's .450" and you're lifting the valve .470" you've found your problem. Really you want about .050" EXTRA retainer-to-guide clearance beyond your cam's maximum lift for safety if you float the valves at high RPM.

There is absolutely NO substitute for checking. Also, what length pushrods are you using? I would think stock length would be fine for your application.

 

I am using 7.794" pushrods because that's what the motor came with and I assumed (incorrectly maybe?) that the .006" increase in lift would not change the required pushrod length.

I will try to check the installed height of the springs and check the retainer to seal distance.

The intake springs and exhaust springs are identical, but the exhaust one has a slightly different retainer in addition to the spacer that eliminates the stock rotator.

 

On the intake valves, the retainer to seal clearance was only .463 or so. The exhaust valves with the larger retainer was even less than that, about .453.

Why does the exhaust with less clearance never bend the pushrods?

Can I get away with using offset keepers, or do I need to have the heads machined?

edit: This may be a horribly ignorant question, but could I use the offset keepers and maybe trim the tops of the valve seals a little bit? They seem pretty big (though I had never seen them before until today so I don't know if they all look like that). They have two rings going around them to hold them in place. I believe they are the good kind of seal, positive or whatever it's called.

 

Since you have the heads off, machine the bosses. Have the springs set up by a shop, tell them your cam info. No point going through all of this again later.

You can use offset keepers, but to do that you need to check for clearance between the rockers and the spring retainer. If the retainer hits the rocker, you'll have problems again.

I think it's best you use a shop to set up your heads.

Umbrellas are normally used on the exhaust valve. If you look at the bosses, the intakes are flat topped. The exhausts are angled on stock heads. The bosses are normally machined to have positives on both.

Lose the rotater stuff. Use valve seat shims. Lose the oil shields if you kept them too.

You may have measured incorrectly. How did you measure the clearance? Did you measure the lowest point right on the retainer (right on the valve stem) to the valve seal? I find it difficult to believe your exhaust side survived but the intake side died.

 

I definitely measured it correctly, from the bottom of the retainer against the stem to the top of the seal. I guess its time to go to the machine shop. I still don't understand why the exhaust was fine even if I measured it incorrectly. I would have thought it would have been the same as the intake.

What do oil shields look like? I don't think I have them now anyway.

 

I was thinking you measured the bottom of the rotator to the top of the seal, so you may actually have more room than 0.453 on the exhaust side. But since you confirmed you did it right, I don't know. I have no clue why it survived, if you ever find out, do post. It's curious, unless all your exhaust lobes are wiped out, which is unlikely.



Oil shields look like a cup over the top of the valve springs. I forget the thickness. They cover the top of the spring to prevent oil from splashing down the valve stem. Totally useless if you maintain the seals appropriately or have positive seals.

 

First thing I have to ask is why are you using 193 swirlport heads and expecting a performance cam to work for ya?

Is there any chance you installed the valve locks on the second valve stem groove ( oil O ring groove) instead of the top groove. This would drasticly decrease the installed height Therefor the max lift coil bind height and retainer bottom to guide top clearance.

Usually most stock SB heads with stock retianers are good for .480" lift or so. (not all)

 

I'm pretty sure that I had the locks on the right groove. I made sure they were at the same height as the ones on the springs that I haven't taken off yet.

I know the heads are pretty much junk but I had some decent power with the old cam. I was really just hoping to replace the cam and keep the same performance. That's why I chose this cam because it had very similar specs.

 

Did you measure the actual cam lift in the motor? wouldn't be the first time a cam was mislabled.

Is the cam severly over advanced in the motor? This would reduce intake valve to piston clearance.

 

I haven't measured the actual lift of the cam.

I don't think its severly advanced...lined up the dots so...

I don't think the problem is intake valves hitting the pistons. There are no marks or anything on the valves or on the pistons.

 

I have not messed with 193 heads but on typical 305 heads (416) etc, when eliminating the exhaust rotators in favour of normal chevy retainers, a stack of 1x .015" 1x .030" and 1x .060" spring seat shims totaling .105" corrects the difference in the spring seat depth.

measure yours, if its the same you'll know just what to do to set up the installed heights after eliminating the rotators.

 

Thanks for all the input. It looks like we're getting somewhere here. However, I still find it very hard to believe that the engine ran fine with .464 lift and now it bends intake pushrods like crazy with .470 lift. Six thousandths of an inch. I could believe that the difference could cause a slight bend in the pushrods, but to snap one in half and bend the other ones severely...it just doesn't seem to add up. Anyone else think that I have another problem maybe in addition to the retainers hitting the seals? And if the retainers hit the seals, wouldn't the seals get crushed or ruined instead of bending the pushrods?? The seals all look brand new.

Also what is an average price for having the machine work done that I need, if the only problem is the retainer/seal clearance?

 

I'd think it would, yes. You may have other problems, improperly installed springs getting you coil bind at a much higher height. How about setting up the pushrods and set the lash on the rockers and slowly turn the crank by hand? See if you can see what's binding at the valve or pushrods? Leave the intake off and mock install the heads.

The pushrods don't look scored?

No clue, it depends on your area. Different shops have different rates. You can do it yourself with a drill and an attachment, if you pull all the valves out yourself.

 

I have to wait for the tool to turn the engine over by hand to come this week, but that sounds like a very good idea to mock it up with the intake off and see what happens.

The pushrods don't really look scored, just really bent/broken.

What exactly is needed to be done with the machine work? I can easily get all the valves out myself and I have a good drill.

 

I just thought of this:

I have a set of 081 TPI heads from my old 305...would I be better off putting these heads on anyway?

 

ttt...Any ideas for what I can do today?

 

Where would I buy the attachment for the drill to cut down on the guide bosses?

Both the intake and exhaust bosses under the seal appear to be angled.

The seals all have 3013 USA and then another number that is different on each seal. I don't know what brand they are. Anyone know if these seals are bigger than normal or if they are the good kind?

I can't really get a good measurement on the installed spring height, but it is about 1.75".

 

Your favorite speed shop will have them. Comp Cams, Crane Cams, etc. Just about any of those companies have them. Look for a valve guide cutter or call the companies, summit, jegs, etc.

Take it to a shop. I don't want to see a "help! I ****ed up my heads" post. There may be some things you don't know, as you didn't know to check the retainer to seal clearance. Call around, get price quotes. Let them set it up for you, talk to them after they do it, find out what they did and what should be done so you can do it yourself next time, if needed.

Doing it yourself may (and has) cost you more than it would have to take it to the shop. I'd be hard pressed to say cutting the guides would cost more than one hour's labor.

 

The 081 heads make a good starting point if you're willing to home port them and have larger valves installed.

The ports are essentually the same as the 350 TPI heads (083.) And can be vastly improved with complete porting. The combustion chambers are a little smaller. (58cc)
Once the chamber wall is swept out the clear a new larger valve, the chamber will be about the same (64cc).

They have much more performance potential then the 191 or 193 swirlport heads.

If you're willing to do the porting and modifications, they will make good performance heads.

Should have used those to start with.

 

I know the 081s have much better potential, I just don't have the time right now to port them. I read Sitting Bull's thread and apparently it takes a longg time. I'm going to have the 193s machined tomorrow or ASAP and just get the car running. Maybe I'll work on the 081s over the summer.

 

I think that would be a great move. If I had spare heads lying around, I'd give it a go for sure.

 

Please keep in mind that if you replaced the pushrods that originally came in the motor with new ones, and the motor was originally equipped with a factory hyd. roller cam, the pushrods are 7.195 inches NOT 7.795 inches. You will bust studs, pushrods, guides , and springs if this is not checked out..(we're speaking form experience here).. Good luck

 

Thanks som6969 but it is a truck block-not originally equipped with a roller cam.

I got the heads back from the machine shop today. I did a little portwork on the bowls to smooth things up, especially on the intake side. I reassembled the heads. Hopefully I will have them on tonight or tomorrow, then its time to check pushrod length. Thanks for all the help everyone.

 

Don't forget to spin the crank manually. If there's any tension you'd feel it without any damange to the valvetrain.

 

I don't see it in your sig or in this thread.

You got aluminum heads?

Aluminum expands more, you gotta set them sloppy cold, right on racing hot.

 

nahh 193 swirlports no aluminum here!

I got the heads on tonight, so hopefully tomorrow I will have some time to spin it over by hand and see how everything looks.

 

I think my pushrod length is pretty good. I colored the valve stem with a sharpie and turned over the engine a few times. I pumped up the lifters before doing this. I think the mark that it left is close to what it should be. I took a pic but I don't know how to post it. Anyone want to post it for me if I email it to you?

 

I turned it over by hand a bunch of times. Nothing was binding. Put everything together and started her up. It still backfires like crazy, but at least the pushrods don't bend. It doesn't really help that my starter is toast so I only could start it a few times. I think I'm gonna sell it, I need reliable transportation for the summer.

 

If the car wasn't running, how did you pump up the lifters before starting the car and setting the valve lash?

 

with a press

 

HUH? Please excuse my ignorance on this one, but would you mind elaborating just a little bit?

 

I filled a small bucket with oil. Put the lifter in the bucket completely submerged in the oil. Put an old pushrod in a drill press. Bring the pushrod down on the lifter, it squeezes all the air out and fills it with oil when you let the pushrod go back up.

 

AHHHHH!!!!! Now I understand, Thanks for the clarification for this old phart!

 

Lol no problem!

So today I put new plugs in it after fouling the old ones trying to start it. It started with some difficulty but still runs really rough. It's not backfiring, just seems like a steady misfire on all cylinders. The timing probably needs some adjustment.

I took the valve covers off because one of the gaskets was falling down towards the headers, and I noticed that all the rocker arms seemed to be in the same position, like none were open. I thought that was weird since when I cranked it over by hand they all moved up and down. So I had a friend crank the car over with the starter while I watched, and all the valves opened how they should. However, as soon as he stopped cranking, the valves that were open slowly shut. I mean immediately when he stopped cranking, you could see the spring uncompressing. Is this normal?? It's like the lifters are bleeding down really quickly. I've never seen this happen before. Any thoughts?

 

Never heard or seen anything like that. My 383 sure doesn't do that..... how old and what kind are the lifters?

 

They are the lifters that came with the Comp Cams 270H Hydraulic Flat Tappet Cam. Less than a month old.

 

If it were me, I'd be on the phone to the CC Tech Line....