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Sound found

4K views 32 replies 3 participants last post by  toobroketoretire 
#1 ·
I was chasing a knocking sound in my Vett for a while now it’s been tracked down to the Fuel Pump Regulator.

It holds 43 PSI of pressure at Idle But as soon as you turn the engine off it drops to Zero.

It has almost NEW FIC Bosch III 24# injectors and same for the Fuel pump a Walberg 190.

When doing some more reading some are saying the Fuel pump regulator pulse dampener is bad.

That’s fine I ordered one where is it on the car.
 
#3 ·
Youn hear pluse from there.
 
#5 · (Edited)
When I got home from work today my new pulse dampener was at the door

It took about 30 minutes to install it fired the car back up Idove it to work today it seems much better.

I find out more after the car sits and I can start it cold thats when it made the noise the worse.

But so far so good.
 
#6 ·
Did a cold start up this morning much much bettter there still a little noise but unles you were purpose listening for it you never notice it.

I going to order a new FPR diaphragm and see if this will completely get rid of all fuel rail noise.
 
#7 ·
The noise is back.

I am going to delete the 9th injector and see if this helps like I said before it only makes the noise when it is cold start up.
 
#8 ·
Marv, be sure to check the inside of your distributor cap for signs of the rotor is hitting it as mine only made the "tapping" noise when it was cold too. Pull your cap and look right under the #5 terminal as that terminal is directly above the notch in the distributor housing.

After studying the problem I found the aftermarket caps have a slightly taller "indexing peg" than the A/C Delco caps have so the aftermarket caps don't sit down completely flat on the distributor housing.

And have you tried using a 1/2" to 5/8" diameter hose yet? A large hose will quickly find the source or ANY noise no matter how slight it is.
 
#10 ·
I used the rubber hose trick.
 
#11 · (Edited)
I pulled the cap NO hitting at all the rotor seen better days I change that

I also pulled the distributor out and checked the end play it's at .017.

The Composite distributor gear is showing wear about half the teeth are worn though already with 7000 miles on it sounds funny to me also the lower 3/4 of the gear is worn more towarded the top of the gear.

I using the stock 1986 distributor with a composite gear is this my issues.
 
#12 ·
I just ordered a OEM GM melonized distributor gear.

When I built the motor others said the composite gear was the way to go now I reading GM saying for a LT4-Hotcam go with the melonized gear set.

I going to give this a try and see how this gear holds up compaired to the high dollar composite gear.

The OEM is half he price of the composite gear set.

With any luck this where the noise is comming from.
 
#13 ·
When the camshaft turns it's gear holds the distributor gear up against the thrust washer so the amount of end play it has is of no concern. If you have your distributor out clamp it in a vice and set the cap on it and see if the cap is sitting on it dead flat. See if the indexing peg on the cap is bottomed out in the distributor's notch or if it has any clearance. Should have some clearance to ensure it's fully down. And with the cap mounted on it spin it by hand and listen for any noise it might be making.
 
#14 ·
I give that a shot But if did hit why after the motor warms up the noise go's away thats the weird part.

I can feel the distributor index when you spin it when the pickup coil go past the ignition Module.

QUOTE=toobroketoretire;626223]When the camshaft turns it's gear holds the distributor gear up against the thrust washer so the amount of end play it has is of no concern. If you have your distributor out clamp it in a vice and set the cap on it and see if the cap is sitting on it dead flat. See if the indexing peg on the cap is bottomed out in the distributor's notch or if it has any clearance. Should have some clearance to ensure it's fully down. And with the cap mounted on it spin it by hand and listen for any noise it might be making.[/QUOTE]
 
#15 ·
Pulled the distributor apart the center shaft that spins the rotor has galling where the bushing mate the upper bushings are is the worse.

It has worn thought the harden surface.
 
#16 ·
Distributor shafts are made out of ordinary finish-ground cold rolled steel with no "case" hardening. Is the shaft really galled or does it simply have some bushing material stuck to it? If you have any fine emery cloth try polishing the shaft and see if it smooths up. The biggest problem is the bottom bushing gets plenty of oil but the top bushing relies mostly on the oil inside the bushing (which is almost nothing). But at the same time there's virtually no load on the top bushing either. A far as making any noise goes I can't see how it could make enough noise to be heard over the engine running.

As the HEI distributor is magnetically triggered a little slop won't hurt anything so unless the shaft is definitely torn up I'd just lube it with some 30 weight oil and throw it back together.

But you still haven't told me you checked your cap's sitting dead flat on the distributor housing. As you have it torn apart put the cap on and see if it has ANY rock to it because of it's indexing peg being too long for the depth of the notch it indexes into.
 
#17 ·
Rotor's Blade Hitting Inside Of Cap (???)

Look closely for a 1/16" wide groove in the side of the cap right under the #5 terminal. The groove (if there is one) will appear to be a little "scratch" about 3/8" to 1/2" long caused by the rotor's brass blade making contact with the inside of the cap. It won't be very obvious as the groove will be the same black color as the cap.
 
#18 ·
Yes the cap sits flat.

No marks in the cap.
 
#19 ·
Using A Length Of 5/8" Hose To Locate The Source Of A Noise




Thank you for finally confirming that. But now for the "biggie" question. Have you tried using a 4-foot piece of 1/2" to 5/8" hose to locate the source of the noise yet? I learned many years ago a hose is 100% accurate in locating the source of any noise as the hose will block out all of the surrounding noises.
 
#22 ·
Swapped the gear out fired the car up the noise still there.

I dont want to pull the motor again.

I just dont get it.

After the car is good and warm no noise.

I went to McDee's drive though on the way to work this morning you could hear the knocking noise very well as it echoed off the wall next to me.
 
#23 ·
Marv, use a 1/2" to 5/8" hose, plug your other ear, and listen closely. The hose WILL find the source of the noise. Or bring it over to me and I'll find it.

As you're saying the noise goes away as your engine warms up that tells you heat is changing something. Or...........it's entirely possible a lifter is bleeding down during the night and it's taking a long time to get refilled.

And once again will you describe the noise? Is it a "ticking"? A "tapping"? A "thumping"?
 
#24 ·
We have tryed the rubber hose thing when it cold starts out as a Knock as it warms up a tick after driving for 15 minutes no noise at all.

When I first built the motor I thinking it was a lifter my self I put all new GM ls7 lifters in the motor

Checked all the new rockers arm swaped position to see if the noise would move replaced all push rods just in case.

I just dont know I would think if it was the bottemend it would a deep Knocking sound that heard it the pass i heard in other motors the sound of death.

I been wondering if is piston slap after all but it not a double Knocking sound.

I tryed the hose trick on the oil pan just to make sure it was not the bottenend and thats not it.

I wish I had a spare set of heads swap them ut just to see if in the heads some where.

I hate t buy anouther set of heads but I guess that be better taht pull the complete motor and fine out it not the bottemend.

If I do buy a set of heads they will be Profilers and if the ones I have now are good sell them.
 
#25 · (Edited)
Marv, if you're running forged pistons they will make a lot of noise for the first 25-30 minutes as forged pistons require around .005" clearance. I have a set of single-eyebrow TRW's in my '82 and the engine makes a lot of noise until it warms up. Stock-type pistons are set up real tight with clearances of only .0005" to .00075" and start off quiet because of so little clearance. But with almost 10 times as much clearance forged pistons really hammer until they warm up enough to expand and close up the clearance. And as all of the 2.02"/1.60" heads require push rod guide plates because of their wider valve guide spacing they add to the upper-end noise. And for those of us who are running retrofit roller cams (in pre-87 blocks) with the "linked" lifters those lifters also contribute to the noise.

So if you're running forged pistons AND 2.02"/1.60" heads expect to have a lot of noise on start-up. As you're saying the noise goes away after warm up that's all that matters..................
 
#26 · (Edited)
It takes 10 miutes or so then the sound is gone most of the time.

It has Hyperteck KB pistons in it I think stock type rods It a Blueprint short block I checked all bearning cleananes before this motor went in the car they were all good checked all TQ on everything before it went in the car also.

What I can tell you it has pressed in type piston pins never had them apart.

On the 355 motor I had in the car also a Blueprint short block they didn't clean out the oil passage ways out very well the first motor ate it self in 3000 miles grim in the oil passages ways.
They sent me a replacment Short Block.

This 383 I took apart made sure everything was clean before it went in to the car I glad I did it also had grim in the oil passways.
 
#27 ·
As you're now running a roller cam did you remember roller cams require a thrust button or thrust bearing in their nose to prevent "cam walk" against the front timing chain cover? Or are you running a 1987 and later block that has a thrust plate to prevent cam walk?

If your engine does have the KB hyperutectics than they should be clearanced just like the older style cast pistons and shouldn't make any noise.
 
#30 ·
I just traded in my 2001 Ford with a 5.4 engine those are also known for start up knocking I lived with it also.

So if the LS1 are also known for Start up knock I just might have to live with it for now.
 
#32 ·
Question I know the pushrods are a little bit on the long side when rolling the motor over and checking for patter wear on the valve stem tip it not completely center it on more the exhaust side more than center I using the stock length push rods 7.195

Do you think this could be the problem making the noise?
 
#33 ·
I can't see how that could make any noise. How far down are you adjusting the rocker arm nuts? What is the recommended setting for the kind of lifters you're using? If the book calls for one full turn then I'd suggest going one full turn...............

I just had an idea. Try using a hose again but stick it down into the valve cover thru where the PCV valve goes and listen inside the engine.

As the noise is completely going away when it's fully warmed that tells me nothing is wrong with it. You likely have a few lifters bleeding down during the night and creating a little bit of lash. If so then a slightly thicker oil might solve it. Just for the sheer fun of it try running a cheap straight-grade 30 weight and see what it does.
 
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