Well I completed the vortec head swap on the 327 and installed new LT1/Z28 springs from Competition products. I machined the heads for the 454/480 lift cam. I fired it up and set the total timing at 32 BTDC without the vacuum advance and took it for a drive. I had a lot of valve rattle under part load so I backed the total timing back to 28-29 BTDC and took another spin. That solved the part load valve rattle but now it rattles at idle when it goes over 190F. Not tapping like the valves were out of adjustment, just a lot of low level valve train noise. Shut it off and let it cool down and valve rattle is gone. Heat her up and its back. I know that I set the valve adjustment right but I'm not sure that I'm running enough preload. I set the preload at 1/4 turn because that is where it was with the stock springs. I brought it back to the house, pulled the covers and added another 1/8 turn and it still makes a lot of valve train noise when it goes above 190F.

Does the spring rate change make that much difference on the amount of preload? Should I run 3/4 - 1 turn of preload with a performance spring? The lifters are new federal mogal stock lifters. They worked perfectly with the old heads and stock springs. Oil pressure is 35-40 psi at idle.

What do ya think?

Valves don't 'rattle' due to timing. That's pre-ignition or detonation you hear, not the valves. This noise is caused by heat and the change in combustion chamber design that you have induced by changing the heads. The fact that its better when cold only verifies this. Either run better gas, use less timing, change your timing curve, lower your compression or richen the mixture. All the valve adjustments in the world won't fix what you describe.

Those vortecs have small chambers, even with flattops w/4 valve reliefs,my son HAS to run 93 octane to keep it from pinging.

Agreed. It's detonation. If you don't take care of it, you're gonna destroy your engine in short order.

What's the duration on that 454/480 lift cam? Increasing the duration a bit with a healthier cam might help bleed down some cylinder pressure.

Is your cam a Crane PowerMax H 272-2??

As for your compression, I think I read here that Vortec's are very close to 62 cc's which should put your 327 depending on it's actual bore, down in the hole and headgasket thickness right at 10 to 1 CR...

Yes, your motor is rattling at about 10 to 1 just like the guy's are telling you...

pdq67

My SCR is about 9.7:1 and my DCR is about 7.8:1 and I'm running 93 octane. My quench is better now than it was with the old heads but it still sucks as it is about 0.060" due to a 0.045 deck heighth. SCR and DCR are almost identical to the old settup as i had 58cc heads before and changed to a thinner gasket to compensate for the new 62 cc heads. The cam is a Lunati 06109 which is a 216/228 at 0.050. I checked the plugs and found some very minute specs but they were so small that i could not see them well without a magnifying glass, almost undetectible. The specs are also not purple but a medium brown color.

I took care of the detonation under load with about 3 degrees less timing but the noise at idle when hot did not go away when i retarded the time. I even retarded it another 4 degrees at idle and still the noise is there.

Ok, so I'm running the same SCR and DCR, I have a better quench and head design and I'm running the same gas and i'm running about 7 degree less total timing but now i have pre-ignition, i don't understand. Do you think i would do any good with an adjustable vac advance or just drop it altogether and run initial and mechanical only. I have about 8 initial, 20-22 mechanical and 10 degrees vac right now , all in by 3000 rpm.

Signed,

Frustrated, Aggrivated and confused

I disconnected the vacuum advance on my sons truck, doesnt get mileage like it should,but no detonation with good gas....adjustable vacuum advance might help??

Originally posted by Clyde_Maston:
I took care of the detonation under load with about 3 degrees less timing but the noise at idle when hot did not go away when i retarded the time. I even retarded it another 4 degrees at idle and still the noise is there.

Ok, so I'm running the same SCR and DCR, I have a better quench and head design and I'm running the same gas and i'm running about 7 degree less total timing but now i have pre-ignition, i don't understand. Do you think i would do any good with an adjustable vac advance or just drop it altogether and run initial and mechanical only. I have about 8 initial, 20-22 mechanical and 10 degrees vac right now , all in by 3000 rpm.

Signed,

Frustrated, Aggrivated and confused Clyde,

If it is rattling at idle, it is NOT detonation/preignition. Cylinder pressures are very low at idle.

Mike

What rocker arms are you using?

I think the Vortecs need self alighning rocker arms. If you used your old non vortec rocker arms than that could be the problem.

Also the design of the Vortecs combustion chamber is supposed to be more forgiving with high compression ratios. Even with 10:1 on vortec heads with a decent size cam you shouldn't see detonation.

I noticed the same thing with my fresh 383, running a mild hydraulic flat tappet cam. Valvetrain is relatively quiet, even at idle, until the temps come up. at 190-200°F, the amount of noise from under the valve covers increases. Not ticking like a loose rocker arm; just mechanical noise.

BTW I'm running 1.52 magnum roller tip rockers and 1/2 turn preload.

I have some limited experience with the roller tip rockers and have found them to make more noise than stamped rockers in some cases. However, I've heard them on stock-cammed engines and they are whisper quiet.

I wonder if you're on to something with the idea that more spring pressure may contribute to increased mechanical noise?

If quench is .060, you're losing the advantages of the heart shaped combustion chamber and other characterisitics of the Vortec head that help it fight off detonation. I agree with others here, you're pinging it to death.

I don't think it is pinging. I have an even worse quench on my vortec headed 350 (.040 deck height and .041 head gaskets). 9.4-1 355, 14* initial timing, 36* total, 180psi cranking compression with a XE268 cam. The ONLY noise i get out of mine is a bit of valvetrain tick from the XE cam. I run 89 octane with no problems at all, in a heavier vehicle...even when towing. You must use some sort of self aligning rocker arm with vortecs unless they are machined for screw in studs and guideplates. How are you adjusting your rockers? Try doing it with the engine running...back each one off until you get a noticeable clacking, then slowly tighten it until the clacking just goes away, then another 1/2 turn should be good. It is messy, but it works. You can take an old valve cover and cut a section out of the top to help keep the oil slinging down. Even an old style valve cover will work.

Engines don't detonate at idle, unless something is seriously, seriously wrong. Visually check all your valvesprings and make sure one is not broken...sometimes this will do what you are describing.

I'm running the stamped vortec self aligning rockers. They are brand new. However, I used the rocker balls and nuts off of a standard head. I compared them to the few vortec ones I had and they looked exactly the same. If that was the cause, i think they would rattle all the time, not just when it gets hot. Its not just one cylinder either, its all of them ticking but it seems worse as you go towards the back of each side of the engine. However, that may be because the sound is bouncing off the firewall and hood and just seems worse at the back. Myself, i have never heard of detonation at idle either and the fact that you can back the time off and it doesn't change makes me want to rule it out.

What is the preload i should run on the lifters? Some of you have said 1/2 turn. I tried to use the old cut out valve cover pan from the old heads and it didn't work very well when i tried to adjust them running but i was able to get a couple of them done and when i checked them they were right back where i had set them before so i am pretty sure that they are set correctly. What will it hurt if i set the preload at 1 turn? As long as they don't bottom out, what will it hurt? Is it possible that i am loosing my preload when it gets hot? I only have about 3/8 turn right now.

Clyde

Preload is usually 1/8 to 1/2 turn past 0 lash. I usually run 1/8 of a turn or less as it helps prevent valve float at higher rpms, less room for the lifter to pump up at high rpms. On a nonperformance application I go 1/2 turn past zero lash. I thinks you have a clearance problem somewhere, how does the car perform? or haven't you got on it yet? You may have to pull the covers and check it out with a stethascope, maybe pull a few springs and check for contact marks.

I haven't gotten on it 100% yet. I'd say 80% so far. I have floored it a few times but get out of it pretty fast. I have revved it to 5000 rpm's in park to listen for problems but it sounds really. just the mechanical sound at idle when hot. I'm going to go to 1/2 - 3/4 turn past zero lash to see if this helps.

Clyde

Are you sure it's just not small exhaust leaks? I have a very small one on my car and you can only hear it at idle. Maybe once header gets warm and expands you get a small leak or leaks.

Just something to check.
Steve

What weight oil are you running? Sounds like the lifters may be collapsing slightly when the engine heats up. If the additional preload solves the problem, I suspect the oil is "going thin" at operating temperature, which isn't necessarily a bad thing.

Travis, How in the world are you getting away with that much timing? Are you sure about the numbers? My dish pistoned .058 deck with an XE-256 (170# cranking compression) will not tolerate anything more than 4 initial and 30 total. I had to shorten the HEI vacuum advance and use a very slow advance curve. We only have a very poor 91 oct in Cal maybe thats the problem. Even with the lack of much timing the thing flat goes. Like everyone elses XE series cam my lifters sound more like a solid cam with about .005 lash.

Cj,

You may be right, I was running 10W40. I was going to try more preload but I think i will go back to 10W40 first. I was sure that I had bought 10W40 but i checked the jug in the garage and what do ya know, 10W30! Boy i hope its that simple.

Its definitely not an exhaust leak because it is all around the engine when it happens.

Clyde

Originally posted by Mike Feudo:
Travis, How in the world are you getting away with that much timing? Are you sure about the numbers? My dish pistoned .058 deck with an XE-256 (170# cranking compression) will not tolerate anything more than 4 initial and 30 total. I had to shorten the HEI vacuum advance and use a very slow advance curve. We only have a very poor 91 oct in Cal maybe thats the problem. Even with the lack of much timing the thing flat goes. Like everyone elses XE series cam my lifters sound more like a solid cam with about .005 lash. Positive on the numbers. This engine is fairly sensitive to timing. Anything less than 10* initial and it is a pig. I did a lot of trial and error setting up the current advance curve for best all around performance. Anything over 36* total and it loses top end power dramatically. I think one thing in my favor though is that my engine runs very cool...too cool really. This engine is in my '78 1/2 ton and I am using a 4 core heavy duty radiator...it rarely ever gets up to 160* even in the summer. The carb is also just a touch fat when the weather warms up...I think this helps also. I am also running a fairly slow advance curve. If I bring full advance in under 3K or so it bogs in the midrange (too much advance too early I guess).

non-race hydraulic lifters are designed to run between 0.020" and 0.040" preload. With 1.5 ratio rockers on a small block with standard rocker studs, 1/2 turn = 0.030" preload. 1/4 turn would provide 0.015" and 3/4 turn would provide 0.045". I can't say I've noticed any difference in valve train noise between 1/4 turn and 3/4 turn. However, engines with 1/4 turn will typically have a few noisy rockers until the oil pressure comes up at startup. 3/4 turn will typically alleviate this problem.

I notice the same thing as Mr. Matson. The noise appears to be more noticable at the back of the valve covers.

Originally posted by Mike Feudo:
Travis, How in the world are you getting away with that much timing? Are you sure about the numbers? My dish pistoned .058 deck with an XE-256 (170# cranking compression) will not tolerate anything more than 4 initial and 30 total. I had to shorten the HEI vacuum advance and use a very slow advance curve. We only have a very poor 91 oct in Cal maybe thats the problem. I have 2 vortec headed combo's. One was ran as a 10:1 385 with a 214* cam on 91octane and a MSD 6a, the other is ran stock with 9.4:1 compression, a 198/204 or so cam, adjustable vaccum can, and 87octane when its 110* outside. The stock vortec motor likes 12 initial and 32* total.

when the heads were machined for the cam lift, was the guide boss diamter reduced for the damper in the z/28 springs?

The inner damper will ride on top of the guide boss and actually coil bind the inner spring long before the outte spring gets to max lift. It'll coil bind at ~.250-300 lift... So stock cam will coil bind with Z springs unless the guide boss is cut down.

Well i changed the oil tonight to 10W40 and it sounds like the lifters are still noisy when the temp goes up around 200 F. Its definitely not a tap but i'm guessing it has something to do with the lifters collapsing as cj guessed. They are new stock lifters with the Z28 springs. They worked great with the stock springs Is it possible that they are too weak to handle these springs? Is anyone else running stock lifters with these Z28 springs.

I also checked the plugs for color and to look for detonation specs. No specs but the plugs are snow white. They look like brand new. I think I'm running lean. Could a lean condition make the temp rise about 20 F. I also added a new shroud and it still gets hot at idle and at speed. The more load that I pull the hotter she gets. I'm going to jet up from 68 to 70 jets on the qjet. i jetted up fron 64 to 68's when i changed the heads but i also epoxied the plugs on the fuel bowls at that time. I'm betting that those were leaking which was causing it to run rich before and now it is lean. I'm going to check for intake leaks tomorrow. What will the exhaust smell like when it is running very lean?

White plugs=lean. Richen it up before you lose the engine.

Also, if you decide to change lifters, although that isn't too likely the problem, put Speed-Pro 817R lifters in (817 without the "R" are standard lifters). These are sold under a number of other brand names and most use the same number. Comp sells them as their Pro Magnum lifters for about $50 more. They are an anti-pump up lifter that can, if you desire, be run with lash instead of preload. Running them with lash does require periodic adjustment.

Originally posted by Clyde_Maston:

I also checked the plugs for color and to look for detonation specs. No specs but the plugs are snow white. They look like brand new. I think I'm running lean. Could a lean condition make the temp rise about 20 F. I also added a new shroud and it still gets hot at idle and at speed. The more load that I pull the hotter she gets. I'm going to jet up from 68 to 70 jets on the qjet. i jetted up fron 64 to 68's when i changed the heads but i also epoxied the plugs on the fuel bowls at that time. I'm betting that those were leaking which was causing it to run rich before and now it is lean. I'm going to check for intake leaks tomorrow. What will the exhaust smell like when it is running very lean? Careful here. It's been my experience that with the new fuels, plugs really don't color when the engine is driven at part throttle.

From 64 to 68 on a Qj is a huge jump on a percentage basis. What size primary rod are you using?

If you are too lean, the engine will feel a little bit lazy as you try to gradually accelerate. If it's much too lean it will stumble and buck.

Mike

Bob,
While I agree with you, that is a HUGE jump, 64's are super super tiny jets for that thing. I don't recall, was it pinging under WOT, part throttle, or both? As Bob has led on, if it is part throttle you will probably end up changing main rods. In my suburban with a warmed over 350 it has responded best to 70 :eek: jets up front!! I also had to change primary rods, and it enjoyed some richer secondary rods as well.
Best of luck!!

Originally posted by 70mousejob:
Bob,
While I agree with you, that is a HUGE jump, 64's are super super tiny jets for that thing. I don't recall, was it pinging under WOT, part throttle, or both? As Bob has led on, if it is part throttle you will probably end up changing main rods. In my suburban with a warmed over 350 it has responded best to 70 :eek: jets up front!!
Yes, but it all depends on what this Qj came with from the factory. If it came with .064" jets, then it probably had a .037" or smaller primary rod. When they come with .070" jets they typically have a .041", or .042" rod. Based on that, if you have the .037" primary rod and drop in a pair of .070" jets you are going to be running very, very rich.

Really?!?! I didn't know the tip of the rod was still in the jet under WOT, but did wonder from time to time. Now that you mention it, I don't see how it wouldnt be, Thanks!!

The qjet came stock with 40B primary rods and 64 jets. I believe it came off of a 78 chevy pickup with a 350. As for the rattle, it was at part throttle and it shutters if you ease into it. You don't hear the shutter but you can feel it in the gas pedal as i run a solid linkage to the carb. It ran much better when the secondaries kicked in.

I jetted up to 70 primaries today but didn't get to start it. I also noticed that my secondaries weren't kicking in fast enough so i checked the vacuum secondary lockout and it wasn't open fully until the vacuum dropped to 1.5 inches and it took about 2-3 seconds for it to go fully open so i just took it off all together so i can try it without the lockout.

Jakeshoe - the guides were machined down to 0.770" and i believe the springs are 0.880" inside. Do you think that the dampers and springs could be loosing contact with one another when the heads heat up? I talked to an engine builder today and he said that it sounded like I was describing "spring noise" like when you run a spring without a damper.

Clyde,
Reason I mentioned it is because I built a vortec headed 355 circle track motor for a guy before they were really even known about.
I used a solid lifter cam and Z springs and at that time had to remove the damper spring because of the guide boss.
My book shows .870 or .880 depending on PN used for the Z or LT1 spring.

So of you are machined to .770" diamter al the way to the seat you should be good.

I ran that motor to ~6500 rpm with no damper springs no problems.

Just a thought.

I've gotts to chime in here.

I have a .30 over 350, with flat tops and an EDelbrock Performer RPM cam, the heads are GMPP Bowtie Phase 1 cast Iron with Edelbrock Springs and Alluminum Roller rockers.

My motor does the same thing, after it warms up to operating temps, it ticks. Sounds like a loose lifter but its not, they have been adjusted both EOIC and running.

I have changed, rockers, valvesprings, and fuel pump and pushrod, with no change in this hot engine ticking. Also went from synthetic to regular oil with not change as well.

I have adjusted my timing all over the place with not changes as well.

I have also checked for header leaks with a stethescope and that not it either.

I'm glad to hear I'm not the only one with this problem, but lets find a cure.

anyone?...Buler...Anyone?

Well, I don't know what the sound was but it is gone. It was definitely heat related. I switched from 10W30 to 10W40 and still had the noise above 200 F, so i bit the bullet and bought a new 3 core radiator. Now the car runs about 170 F at idle and on the road (165 thermostat. The sound went away. I also set my total time back to 32 degrees and no more detonation. Its amazing what 30 F more degrees will do. The plugs were still snow white after installing the 68 jets so I went up to 70 jets and went for a drive. The car sounded better and didn't shutter but i didn't do any wide open runs. I'm still feeling my way through this change. I pulled the plugs tonight and about half are showing just the slightest hint of a light tan color, the others are still snow white. Could this thing still be lean or as some have said before, you can't read the new plugs like you could the old ones. I'm running autolite platinum 605's. They definitely have a long heat path.

shuttering? you had the pinging blues going on! jet it up man! look for light brown