Id this odd engine noise. old problem time to solve it

[mtdave2]

http://s27.photobucket.com/albums/c1...ent=tap3-1.mp4

http://s27.photobucket.com/albums/c1...rrent=tap3.mp4

http://s27.photobucket.com/user/mtda..._0013.mp4.html (about 0:30 in you can hear it well.)


I have been so pissed at this truck, and busy with other things, I have not looked at fixing it several years. so I am not really remembering all the details, but I am going to fix it now. even if I have to swap the motor out.

Anyway, thought I would start and ask all the experts to give me their best guess on what this very odd sound is.

orgnial motor, made into a 383 by very good shop. ( i have lost the details of what was done. 400 crank is all i remember)
rockers
http://www.summitracing.com/parts/SUM-G6935-16/
heads
http://www.summitracing.com/parts/NAL-12558060/
cam/lifters
http://www.summitracing.com/parts/CCA-CL12-234-2/

[mtdave2]

worse when cold, and cold weather, gets better with warm up still hear it though. No dam power, should be double what it has. It does cruise nicely at 70.

I did measure push rods. no evidence of flat cam (measured motion of all rockers while running)

[john]

Dave your photobucket links do not work.

[mtdave2]

working on it! thanks

[cleszkie]

Are you running flat tappet or roller lifter/cam set up? I don't think that measuring the rockers while running would give you a good indication of cam lobe condition since the lifters will be compressing a bit. I would try measuring while manually turning the motor over. I would also consider inspection of your lifters to make sure one or more has not failed. I am not able to listen to your files, but I do have another suggestion based on your description of no power. Sounds like your timing may be impacted somehow. Inspect your distributor for faulty mechanical advance (loose or stuck weights, or broken springs.

[mtdave2]

http://s27.photobucket.com/user/mtda.../tap3.mp4.html
http://s27.photobucket.com/user/mtda..._0013.mp4.html

[hamjet]

I am no expert but it sounds like cam/valve train to me, almost like lifters aren't pumping up..

[Steeveedee]

Sounds like the timing is retarded, but that doesn't address the tapping noise. How did you adjust the lash?

[mtdave2]

well, I have done all of the above. the lash was adjusted and readjusted and checked, while running, and not. the timing has been messed with back and forth and upside down. lol.


when i was messing with all of this, i remember leaving it set thinking like you hamjet, that it was a lifter. though I do remember when we were adjusting the valves that the lifters were responding as you would expect


so I guess the question is this. If you were to pull the truck into your garage just with the info i shared here, what would you do? first. second etc.

i have my finger on the trigger of this
http://www.summitracing.com/parts/edl-2098

but I hate to be a parts changer. this set up should work, and work well. just doesn't right now. I am remembering my frustration trying to chase this down before so I know my patience for this is thin.

[toolboxchev]

I have had HEI ignition modules still work with no power and back firing going on.

The video sound does have an erratic sound going on, yet the quality is quite lacking to make any type of diagnosis from me.

Better quality would help on the video if you have that capability available. Check a friend with a good quality cell phone.

[hamjet]

First, how about some back ground. did you have the shop do it for you or buy it done. did it do it from day 1, gradually, or suddenly. Are they clearing the valve covers? look for wear marks in the covers.

[mtdave2]

shop rebuilt and installed heads and cam. did it from day one, no signs of anything hitting.

3 different hei units. video quality? granted the visuals suck, but there is nothing to see, turn up your speakers.

[toolboxchev]

I had a similar issue traced it down to a oil additive. LUCAS does not contain any antifoam agents. I was pushing oil foam into my lifters.

This still does not address the lack of power. What type of motor oil are you using.

The HYD FLAT TAPPET cams require a oil made for them, check comp cams on that. Those comp cams lifters are noisy, mine did that for a while, and Comp Cams tech guys verified this. The noise is not an issue.

You still have a power issue, that is what I would focus on. Have a professional shop try to diagnosis before you do any 2k purchases, It can be something very simple. Seems to idle ok, with little movement in the block.

[toolboxchev]

Are your pushrods spinning while the engine is running. This should be happening, use a paint pen placing a line on each pushrod right under the rocker arm. You can clean each area with a solvent beforehand with a cold engine.

That test revealed nothing was wrong with the operation of cam and lifters. The lifter spins as it is lifted each pass of the lobe. This will directly in turn make the pushrod turn also.

[mattfranklin]

Not sure what to tell you about the noise (I have heard some strange engine sounds in my time and this one is not that strange [see my build if you're curious].). I almost hear a little dieseling after the 30 second mark. (I'd give it a small probability that timing of one cylinder might be too early -- causing spark knock.)

Or maybe it's an exhaust port leak? I'm not as familiar with that one.

Here are some steps to think about, knowing that you have already checked cam lift.

Half the power it should have is quite a hit...

Here is a list of things to check starting with the easiest.

0) How are the air and fuel filters?

1) Confirm that the firing order is correct and all of the plugs are firing.

2) Check the compression of all cylinders.

3) Confirm your timing marks are correct with a dead stop.

4) Confirm that the cam timing is reasonably close.

If it's making good compression and is getting fuel and correct cam and spark timing that there isn't much left. Is your exhaust in anyway blocked?

[mattfranklin]

Here is kind of a messy suggestion, but an easy one. What oil viscosity are you running? Next oil change can you try something thicker or thinner and see if the noise changes?

[chevyblue72]

fuel pump rod failing/bent?

[toolboxchev]

Could also be piston slap from re using old pistons in the rebuild. Just for a reference point I have 50k on a complete top end rebuild, comp cams cam, lifters, timing chain and gears.

I am starting to wonder about those aluminum rockers.

[mattfranklin]

Originally Posted by toolboxchev

Could also be piston slap from re using old pistons in the rebuild. Just for a reference point I have 50k on a complete top end rebuild, comp cams cam, lifters, timing chain and gears.

I am starting to wonder about those aluminum rockers.

Good thought, but earlier he said the shop converted it from a 350 to a 383. They couldn't reuse pistons in a conversion like that.

[toolboxchev]

383 stroker, with a clearance problem???????? Hmm....

I hope things work out, owner has to be pretty stressed at this point. I would be looking at that shop at this point.

[mattfranklin]

I can see how the Edelbrock kit would be really tempting, but your Vortec heads are supposed to flow pretty well already. -- hey, i just had a thought. They do flow and are supposed to flow with higher lift cams. But the valve guides need to be cut down to handle the higher lift -- there is a recent Car Craft issue where they mess with a Vortec engine rebuild and they mention that. I didn't see the Car Craft article, but several sources say you can't use more than *0.420* valve lift with Vortec heads without cutting down the valve guide height.

Several places site that number. Here's just one example: http://www.superchevy.com/how-to/148...ds-valve-lift/

[chopnchaneled]

What Toolbox said !!!!!!! Would not be the first time.

[mattfranklin]

I think we have an answer: You have incompatible cam and heads. First step would be to change the cam for one with lower lift. Or an easier thing would be to have a machine shop you trust shorten the tops of the valve guides.

I just finished Live Chat with Summit Racing on whether or not Summit did that mod already. Here's a snip of that conversation...

Eric: Hi, my name is Eric. I will be with you in a moment.
Eric: Good afternoon.
MATT FRANKLIN: Hi. I have read that the max allowed valve lift for stock Vortec heads is 0.420". Have these heads been modified to allow for more lift than that?
Eric: No. I find that these heads have not been modified in any way.
MATT FRANKLIN: Ok, thanks.
Eric: Have a great day sir.
Eric has disconnected.

[mattfranklin]

Good article on how to modify the heads yourself, or at least to know how it's done so you can tell the machine shop what you need: http://www.superchevy.com/how-to/148...ds-valve-lift/

[hamjet]

Originally Posted by mattfranklin

I think we have an answer: You have incompatible cam and heads. First step would be to either change the cam for one with lower lift. Or an easier thing would be to have a machine shop you trust shorten the tops of the valve guides.

I just finished Live Chat with Summit Racing on whether or not Summit did that mod already. Here's a snip of that conversation...

Eric: Hi, my name is Eric. I will be with you in a moment.
Eric: Good afternoon.
MATT FRANKLIN: Hi. I have read that the max allowed valve lift for stock Vortec heads is 0.420". Have these heads been modified to allow for more lift than that?
Eric: No. I find that these heads have not been modified in any way.
MATT FRANKLIN: Ok, thanks.
Eric: Have a great day sir.
Eric has disconnected.

If the guides were not cut this makes sense, you may have your answer..