Timing.....Is this what almost killed my engine

[BigBlockMonte]

Hey all. In another post I told you all I had a noise, thought it was ignition break-up. Well it turned out to be a broken valvespring. All fixed and running now.

 

I'm hearing from the guys around me that my timing is what probably killed the spring and the others will follow unless i do something about it.

 

Here's how I do my timing, Please correct me if I'm wrong.

 

Quick Run Down on set-up

468

Je Pistons(forged)

Eagle Rods

Forged Crank

10.2 compression

Aluminum Heads 320(intake) 2.25/1.88 valves

Eddy air gap intake w/ holley 850 vaccum secondary carb

XE284 camshaft 574/578 lift 240/246 @.50 110 lobe seperation

Profrom HEI

Autolite 5224 plugs gapped at .45

Belden Racing wires 8mm

Hooker Full Length Headers

3" exhuast w/flowmasters mufflers

 

Need anything else just ask

 

okay. I get the car warmed up, I take the vacuum line from the carb to the dist and block it off. I set the timing with a light at idle. It's at 17 degrees. I then rev the engine until I see it not advancing anymore, I'm outside the car so I'm pretty sure I'm goin to 3k or more. I check what it says there. It's at 35degrees. Okay I'm done. I put the vacuum line back on and drive the car listening for any pinging when goin up hills or whatever, if I here none I'm done.

 

Well they guys are asking me, what is the timing with the vacuum line on at 3k. I checked it and it's around 50 degrees. They said that's way too much amd thats why the engine broke a spring.

 

Are they correct? Am I goin about this all wrong? Please help. Thanks so much everyone.

[Heckeng]

Mariano, I think that is completely fine. When there is no load on an engine, you want more timing. This is how you get good fuel mileage. Some engines like up to 54 degrees w/vacuum advance all in even. It sounds like a lot but most people don't use vacuum so they never talk in terms of also using vac advance. For performance, you don't need vac advance because when you floor it, you lose all of your vacuum advance anyway, so under load, you go back down to 35 degrees advance. Your setup seems to be about perfect actually. Your engine may want a degree or two more or less at different points, but you should definitely be in the ball park!

 

I'm not sure how ignition timing would destroy valve springs either. Ask them how that happens next time you talk to them. You can not force a valve shut by poor combustion timing, and you can't force it open from bad timing without having a massive backfire through the carb which you are not experiencing either. Your springs may just need a check-up. How old are they? Are they sized appropriately for the cam? Are they near coil bind? Or maybe it was just bad luck on that one spring.

 

Here is a really good thread about this from the chevelle site: Ignition 101

[Heckeng]

If your advance was a problem, your rod bearings and pistons would more than likely be what gave out first.

[wallaby]

10-12 degrees brought in by the vacuum advance is about ideal, and yes, that gets added to the 35 degree mechanical "total" that you have. The problem here is the terminology; the word "total" is misleading. They should have a term like "corrected total", or "full total" to describe the mechanical advance + vacuum advance situation.

Your setup is ok, and it's not going to infuence your valvesprings.

[Winston Wolf]

I would tell the "guys around you" they don't know what they are talking about.

 

50 deg at low load will not wreck your engine. In fact that sounds just about right to me. You have relatively low compression and aluminum heads. If you were't getting any detonation, you should have been perfectly fine.

 

You set your timing exactly how you should have. If you would have had any pinging at low load, then you should dial back the vacuum advance only. (adjustable canister, etc) Total timing at low vaccum (WOT) should be set to provide maximum power without detonation.

 

Watch this video, it will show you the combustion process in an engine and you will see that the valves aren't even close to being open when it occurs. I don't see how detonation could even hurt a spring??? Doesn't make sense to me.

 

 

 

Sometimes stuff just breaks. Replace the spring (or all the springs)and move on with life.

[kc8oye]

THAT is cool video

[Andy's Auto]

Wolfie, how did you get yourself and a vid camera in a combustion chamber? Did it singe your hair? Was it like hot in there.

 

Sorry duder, feeling like a man. Spent all day dialing in the Malibu. That my friend is a car. I just hope I can at least match CrazyOnes 10.27. But I am feeling a 9.50 on spray. I really am.

 

And Big Block Monte, kill the people telling you timing caused a valvespring to break. It can't. Coil bind, poor geometry, defective springs, and poor installation can cause a spring to snap, but never timing.

 

Timing kills starters, rod bearings, pistons and so on.

[Mike 57]

I really have to agree, I doubt that it was timing. If I remember you said that you were shifting at 6500, and you had single springs. That could be an issue.

[kc8oye]

I would question why you would have single springs at all on any kind of a rebuild except a BONE STOCK family grocery getter engine, let alone a decent performance build like you have.. but that's from my small block world.. maybe big blocks are different..

 

 

[CrazyDavey]

he bought a complete engine, I think that's what was on it....

[kc8oye]

davey.. yeah I don't mean to say HE put them in there.. but why a builder would only use single springs on a performance build is beyond me.

 

even my $100 head improver kit that had all 16 SS valves, springs, retainers, keepers, et. al. had springs with a damper in them.

[Jared Richey]

Thats a very neat video for sure.

 

And no, Timing don't break valve springs.

[wallaby]

That video is pretty cool; I just wish it ran a bit longer so we could see the the completion of the exhaust stroke. There is a period there when the exhaust valve is closing and the intake is opening, and the piston is traveling toward them at the top of its stroke. Thats when things get close.

[wallaby]

As a footnote, I discovered that the springs I was running had a harmonic problem at 3000 rpm. The spring would reach its harmonic frequency at that speed and cause the coils to vibrate and "sing" like a bell; or like the way a wine glass will sing as you run your finger along the edge at the right speed.

As fate would have it, my car cruises on the highway at right about 3000, so it was the worst possible thing for the spring to maintain that harmonic for long periods, and it prematurely failed because of it. I imagine that's what dampner springs are for.

Of course I had no idea any of this was happening inside my motor until I had several spring failures and did some research.

[Heckeng]

There is a difference between dual springs and a single spring with a damper though. Dual springs are used when lift is higher than a single spring can comfortably be made to handle, or when the ramp rate is aggressive enough that more spring pressure is needed to keep the lifter on the cam. I don't think the damper really does much as far as adding spring pressure, but like Mark was discussing, their job is to keep harmonics from forming.

 

Since his cam is a flat tappet cam, you don't want to arbitrarily run too high of spring pressure because you will wipe the lobe off. If it were a roller, I would expect a double spring for sure, but I would guess the builder had this reasoning in mind. As long as the springs were rated for the ramp rate and lift of that cam, even if they were single, they would be the right choice in my opinion.

 

I am guessing that this was just bad luck. Or, maybe the builder had some extra springs laying around that he used and they weren't the right springs to use with this cam.

 

Do you have any idea on the part number for the springs?

[wallaby]

There are also a lot of cylinder heads that come assembled, and the springs are really an unknown. The literature might say: "comes assembled with .680 springs". You figure that should be plenty for your .510 cam, so you throw them on.

[kc8oye]

There are also a lot of cylinder heads that come assembled, and the springs are really an unknown. The literature might say: "comes assembled with .680 springs". You figure that should be plenty for your .510 cam, so you throw them on.

 

yeah that's true, I didn't think about it that way.

 

I just threw some better then stock parts at my stock heads, since at the time, I believed it was a stock exhaust valve that failed..

 

it sucks to open your engine up and find this:

[BigBlockMonte]

Hey thanks for the comments. The springs in the head are unknown. Supposed to good to a .600 lift cam. I have a .578 lift, so I didn't question it. Now I know. Comp cam recommends the 924-16 springs for my cam. So I'm goin to loacte a spring compressor locally if I can and swap them all out for the comp cam springs.

 

On another post I started someone directed me to go to summit, saying they have one that will compress dual valve springs. The compressor I have now will only do one spring.

 

On another note. I was reading the timing 101 post as mentioned earlier in this thread, and it says to run the vacuum advance from the distributor to (Full) manifold vacuum not the (Ported) vacuum on the carb.

 

I have mine on the (ported) source from the carb, will placing the line to a full vacuum source be alot better for the idle, and driveablity.

 

Thanks

[Heckeng]

The two different types of vacuum ports available basically do the opposite things. One is ported to the venturi of the carb which would be low vacuum at idle but the higher the engine was revving, the higher the vacuum would get. That is NOT the one you want.

 

The other vacuum port, and the one you want to use, is open to the intake plenum, which will give you high vacuum when the throttle blades are closed, but vacuum will go down as you start to lay into the carb. This is the one you want because the more you open the throttle blades, the higher the load on the engine, and the less advance you want.

 

Your idle should get much better on the port that is open to the manifold. This should increase your mileage too.

[BowtieThunder]

Hey thanks for the comments. The springs in the head are unknown. Supposed to good to a .600 lift cam. I have a .578 lift, so I didn't question it. Now I know. Comp cam recommends the 924-16 springs for my cam. So I'm goin to loacte a spring compressor locally if I can and swap them all out for the comp cam springs.

 

On another post I started someone directed me to go to summit, saying they have one that will compress dual valve springs. The compressor I have now will only do one spring.

 

 

 

On another note. I was reading the timing 101 post as mentioned earlier in this thread, and it says to run the vacuum advance from the distributor to (Full) manifold vacuum not the (Ported) vacuum on the carb.

 

I have mine on the (ported) source from the carb, will placing the line to a full vacuum source be alot better for the idle, and driveablity.

 

Thanks

 

I would wonder if the springs are being maxed out....Not sure I would be happy with springs that are rated to .600 lift and I am running .578 lift...I know if I had a .780 lift cam I am not sure I would use a spring only good for .800

 

 

I agree with everyone above timing will not hurt the Valve springs

[Mike 57]

Mariano,

If you want to come to New Castle you can borrow my spring compressor, it will get it done.

I think Paul is right about the .600 lift springs. I also have a valve spring height micrometer if you want to shim them all to the same height.

[BigBlockMonte]

I haven't changed the springs as of yet, but I did put the vacuum advance on full vaccum instead of ported, I also changed out the distributor springs to a lighter spring.

 

It runs alot better, it's alot more driveable on the street now. That really made a difference. I Thank you all for suggesting I do that.

 

Now to find or buy a spring compressor and change out the springs to the comp 924-16