Vet65te

I was heading down to my friends shop where 56 Nomad is now, in order to retrieve the tailgate hinges, chrome bars, opening mechanism and other such stuff so I figured I'd take the 66 Coupe.

I got about a block away from the house and started to hear this knocking sound. Not exactly a knock but close enough. What the hell, the oil was changed out maybe a thousand miles ago which was done three years ago. The car ran fine but kept making the sounds. Got it home and did an oil change plus filter and adjusted the valves but both sides were fine, somewhere between 3/4 and a full turn down after the clacking goes away.

Got them all readjusted, even if they didn't really need it. This was a good sign, or so I thought because if the cam was going away, one or more of the valves would have been loose as the cam lobes get rounded.

Took it out for a test drive and it still sounds the same. Back in my driveway, I got out a wooden stick (maybe 1/2-inch by 1 inch and about 18 inches long). Stuck it on the valve covers, intake, water pump, back of the block, front of the block, thermo housing, etc and nothing coming through. Then...I stuck it on top of the fuel pump and I could definitely feel the knocking. Weird stuff here.

Have any of you 'ever' heard of a fuel pump making noises like this?
Probably not but the fuel pump will be the first thing to be removed and inspected.

A little (and long) background info. My Mosport 66 Coupe has the original 327/350 horse, 4 speed and 3:70s rear gears. Back in the early 90's my Dad and I put the car up on jackstands and dropped everything out of it in order to freshen it up. The engine got detuned a little bit and has 10 to 1 pistons and a Performer cam that's listed for the 400 smallblock that has 214/214 duration instead of the 222/222 L79 cam. The original heads were both cracked so I substituted a set of '68 #291 2.02 heads I had from a '68 L79 out of a Chevelle (325 Horse rating due to exhaust differences). All oil changes were done with the early SG/SH rated oil until that stash ran out and the last two oil changes I've used Rotella T 15-40.
It has the stock 2-inch exhaust manifolds and factory side exhaust.
This engine was broken in back in the early 90's and has less than 4K miles on it now. Mostly street driving and a few runs down the strip. Not much traction with the 215-65's but it runs mid 14's at 97 mph.

It's obvious that something is screwed up and the fuel pump removal will be the first stab. If nothing comes from that, it's looking like the engine will need to come out. Just swell.

Mike T.

SupremeDeluxe

Don't be alarmed just yet....

I had the exact same issue with my 66 L-79 and it turned out to be the fuel pump.

Go to Sears and get an automotive stethoscope. This will be a great assistance in helping you to isolate the source of the noise

Vet65te

I'm dying to know...what was the actual cause of your knocking sound at the fuel pump? The hardened end of the pushrod let loose, the activating arm of the fuel pump got worn down? The engine runs fine, nothing out of the ordinary other than that annoying knocking sound.
Mike T.

mikem350

Give the pump (and the mounting bolts!!) a good inspection, as well as the pump rod, my .02

Lee H

I have had the same sound for about 15+ years on my 1965 327/365. Guess I could change the pump and rod but with only a few thousand miles a year...........If the pump goes out I'll change both.

Kerrmudgeon

What scares me about this noise is your hearing not only the fuel pump but what evers happening at the front of the motor deep in it's belly, aka main bearing, rod bearing, or wrist pin at the bottom of the stroke. Try to localize the noise more, those stethascopes for motors are 100 times better than the 'stick'. Hope I'm totally wrong, good luck.

Vet65te

The 'stick', crude as it is, was readily available and has roughly indicated that it's either the fuel pump or as you mention something else connected with it up front. I'll start with the fuel pump first but if nothing comes of it, the search will continue no matter what has to be taken apart. Start with the easy stuff and go from there.
Mike T.

robert miller

My motor had less than 200 miles on it and #1 rod went out on it. I dont see how it happen with that miles on the motor. Also # one rod bearing was bad. But the #1 crank & rod bearing was totally shot.Crank was eating into with bearing also. Motor down ad out of the car over this last weekend.

Kerrmudgeon

Bob Miller, somebody must have dropped that crank after the machining, and made the front bend slightly. Nice of them to check it out before installing.......!!

verle

In April I found a fuel pump on a 59 that failed by way of the pump arm pin working almost completely out of the pump body. It was sticking out the front, not visible from above. With the pin out the pump arm proceeded to damage the body of the pump. Pump was about one year old.

narlee

Did you say you had about 1000 miles on your oil but it was 3 years old? You should change it more even if it doesn't get a lot of miles.

robert miller

I agree something is not right with it with someone work on it.

rich5962

Mike,

I think I know what your problem may be.........don't pull the engine yet.

I am willing to bet it is exactly the problem I had on our 63 coupe, and I've seen many times. It sounded like the inside of the engine was coming apart. Check your crankshaft pulleys. Loosen your belts and grab the crank pulley and try rocking it. If the bolts can be wrenched a bit tighter, chances are the mount holes in the pulley(s) are a bit egg shaped from being loose, and rocking back and forth causing the loud knocking sound.The fuel pump is close by and the sound could be traveling from the front of the crank up through the pump push rod.

This is what was causing it on the 63. I hope it's that simple for you
Rich

Frankie the Fink

Rich beat me too it but I was going to suggest a loose harmonic balancer.

Some balancers have a rubber piece in between the two halves that can wear and allow slippage too and possibly make noise.

However, those fuel pumps can do strange things if the rubber pieces and/or pinned together parts start going South. Its a 15 minute replacement with a NAPA unit and you'll know for sure. I wouldn't get too spun up before you check the minor things out first.

robert miller

100% Check all th small stuff 1st, befor pulling or going to the inside.

capevettes

When I've had fuel pumps making noise it sounds more like a noisy lifter tapping than the knock you are describing. Definitely start with the crank pulley/balancer as a potential source of your problem. I hope that's all it is. Good luck

Vet65te

Verle - I had a similar issue with the 'first' pump on this L79, it was a generic replacement that had an exposed pivot pin and one day at work (about 65 miles from home) I happened to see the pin had partly worked it's way out. Borrowed a vise grip, clamped the 'wandering' pin back in place and made it home with no problems (sort of a McGiver fix).
I'm guessing that the first pump was on there for around a thousand miles and after double checking my notes, see that I have a total of 5K miles on the 66 since we did all the work in the early 90's so the current pump has about 4K miles on it.

Rich/Frankie/Robert/CapeVettes - A friends '79 454 half-ton pickup had a similar knocking sound a few years ago and a loose crank pulley wound up being the culprit. I just checked my Coupe with a mirror and a flashlight and can see that the three crank pulley bolts are snug on their lockwashers and I can't budge the pulley when I try to move it by hand so later on I'll see if I can tighten them a bit more with a ratchet but they do look like they are cinched down already.

What I'm calling a 'knocking' sound might be a bit misleading. Let's say it's somewhere between a knock and a tap. When I was backing off the rockers for the readjustment, that resulting tapping, or clacking, of the now-loose rockers is a bit crisper than the sound I hear from the front of the engine.

First thing this morning, I'll get the fan/clutch out of the way so I can check the crank pulley bolts. If they wind up being tight, I'll head to the NAPA store for a new fuel pump.

Thanks for the help,
Mike T.

jim lockwood

Mike,

Decades ago a buddy of mine had a 409 that made a knocking sound that, eventually, turned out to be from the fuel pump. My memory of the sound is that it wasn't quite synchronized with engine speed. That is, it proceeded at its own, almost constant rate even if engine speed increased. I really don't remember the cause but my aging brain cells are trying to make me believe it was a broken spring on the pump lever.

In any event, the answer to your question, after all these words, is "yes".

Good luck tracking down the source of the noise from your engine,

Jim

Vet65te

Jim, I'm hoping that all you guys who feel the fuel pump is the cause, are correct. For those who believe it could be something internal meaning an engine pull is in order...well, I've been trying to 'Delete' your entries but for some reason, it's not working. Just kidding

So here's the update. Got the fan and clutch unit off the water pump pulley and got a better look at the crank pulley. The fasteners all look good so I pulled them out, one at a time since the PS is still hooked up, and no elongated holes to be seen. Drat, that would have been nice to find since it's an easy fix.

After finding the crank pulley to be well secured, I went out to the NAPA store and another large parts house and as expected neither had a GM# 6415325/Delco #40083 (or aftermarket equivalent) fuel pump sitting around. What was a surprise was to hear it could take as much as 7 to 10 days to order one. I made sure the guy understood I said 'Corvette' and not 'Packard'. Figured I'd call the local Chevy dept and order one there but due to the downturn in the economy they're no longer open on Saturday mornings.

I see the Forum Vendors have them in their catalogs so with the Holiday weekend upon us, it won't get ordered until Tuesday. Swell.

62Jeff

Mike,
So does that mean you found the fuel pump to be the problem?

That sure would be easier than pulling a motor!

Jeff