Mystery 454 Knock

JC2+2 · Poncho Master!

Mystery 454 Knock

Elroy · Poncho Master!

454's were always bad for piston slap. This was caused by the skirt "cold cupping " but this usually goes away after engine warms up. Old 73-74 454's when new had a bunch of recalls from GM to do with aeration in the lifter galleries. This caused a very annoying lifter rattle (knock) that sounded like a dozen elves with little hammers having their time of fun.This was solved by new updated lifters and restricting the rear oil gallery. They often also had a tight piston in the back holes that ended a lot of those engines at high temp/rpm so later models had looser specs and actually had more slap when cold overall but that was better

Guru

HI check all the liffter bores i had a 396 that had a bad bore it only made a noise at 1500-2000 rpm

4SPEED427 · A Poncho Legend!

I had a 427 do that too. It was easy to find which one it was, but all the adjusting in the world, a new lifter, pushrod and rocker arm and I was no better off. I just had to live with it.

694279 wrote:

HI check all the liffter bores i had a 396 that had a bad bore it only made a noise at 1500-2000 rpm

65post · Poncho Master!

Had a couple BBs with a knock also.1 with a rod knock that would go away after warm up and another one that turned out to be the fuel pump.....

Ghost Post · Poncho Master!

Above info is good also if an auto trans make sure the flex plate doesn't have cracks especially around the area where it mounts to the crank..

~

67Poncho · Uber Guru

Just going to add my 2 pennies here........ The 454 I have in my '70 is out of a '91 Crew Cab that belonged to DND when I was stationed in Goose-Bay, Labrador. (DND being Dept Of National Defence, goverment)

This truck only had 80 odd thousand on it and it too had a knock. Now, with previous knowledge with assistance of a chum of mine, his 427 he has in his '67 Biscayne wagon developed the same knock which was in the top end.

I informed the service manager of the problem, but DND wanted a new engine for it!!! ( I was happy) Got the new, swapped covers, steel stamped for aluminum, and off they went.

I disassembled the engine and it was just a couple of valves sticking. I installed flat tops, different cam, rings, bearings an oil pump and that was it.

So, check the top end seeing a couple of lobes are missing........

-- Edited by 67Poncho on Thursday 7th of October 2010 06:05:41 PM

JC2+2 · Poncho Master!

Thanks for all the input.
Before we pulled the engine I listened to the knock and it seamed loudest about midship
and lower end. It came in at no load light rev off idle and a rapping knock like a rod.
I did check the flexplate and the fuel pump (both OK). Also no evidence of valve hitting
the piston or conrod being bent. And what caused the cam to fail so soon? A good quality cam (Comp Cams Xtreme Energy) and broken in properly. The car wasn't driven much and short runs when it was. The oil was washed with gas so not much for lubrication.
Changed the oil but damage was already done. So out she came.

Thanks again
JC

rabbit64cs · Canadian Poncho Superstar!

are you running a cam thrust button? BBC have a tendency to push the cam forward, and then there not centered up on the lobes, even with a new chain.

I lost 2 cams in the 454 in my coupe? a Crane, and then a jobber. I'm now running a used cam that was pulled and the lifters matched. no problems. I also added roller tip rockers after breaking 3 pushrods repeatedly on #2 intake???

I found a problem with one of the lifter bores, I used a small hone to clean it up. The lifter was sticking/jamming in this bore, that was one of the lobes tht failed.

JC2+2 · Poncho Master!

Hi Again

Just thought I would give an update on the 454. Turns out it's quite common
for cams lobes to wear out prematurily if not broken in properly. There
actually is a TSB put out by Comp Cams. Due to environmental regulations
modern day oils drasticly reduced the anti-wear additives such as zinc and
phosphorous (ZDDP) which help break in and overall life of flat tappet
camshafts. There is a ZDDP additive needed now for break in. And the knock - well I found a stiff rist pin and also a scored lifter bore. After a good cleaning the rist pin freed up. Also gave the lifter bore a hone job and renewed the cylinder crosshatch. Assembled
with new bearings, oil pump, camshaft and lifters. To make a long story short the
engine runs great and no noises. Except on the first run the heater core blew up - weakest link. Allways something.
Thanks for all the input!

JC

67SD396 · Poncho Master!

Great to hear that you solved the knock problem. I am glad this thread came along because there were some great replies and I am pretty sure I learned a thing or two about BB knocks.
Thanks

vicfire · Veteran Member

Hey guys just wanted to bump this thread again because it appears I am having a similar problem.

I put the Beaumont away for the winter, put stabilizer in a full fuel tank, changed the oil and filter, fogged the motor and let her sleep for the winter.

A few days ago I started it up for the first time since the end of October. Started up right away and ran really good. Now after a few more start ups and letting things get up to temp there is a intermittent "knock" or "clunk" coming from the driver's side of the engine. It happens only at dead idle and goes away as soon as I increase the RPM. It isn't consistant and seems to occur randomly but it doesnt sound good when it does happen. I can actually feel it througout the car.

Its a 70's 454 not too many mods. I use Shell Rotella 15-40w oil.

Any thoughts?

Thanks

-- Edited by vicfire on Wednesday 6th of April 2011 10:09:20 PM

4SPEED427 · A Poncho Legend!

Are you familiar with a "carbon knock"?

I had a 396 that had many of those. I cured them with many many applications of GM Cleens.

dualquadpete · Canadian Poncho Superstar!

Vicfire. check out that Rottella your using, I believe the dropped the "zinc" from that last yr. I did use that untill I found out they took it out. Now I use a LUCUS Oil additive for zinc.

unburt · Guru

Yup you are correct Pete the rottela is way down from a few years ago, and the only oils i run now are Brad Penn or Valvoline VR-1.
The zinc additves are many on the markets choose wisely, i just run the good oils now but use additves for break in.
There was a thread couple years back that addresed this problem.
I and a few friends lost cams because of this ,not fun seeing metal dust through your motor and starting from square one.

vicfire · Veteran Member

Thanks guys, I'll look into the Rotella and check into additives or other oil. When I bought the car the prev owner used QS 20-50w in it, I thought that was a little heavy but pressures were always good. I may have messed with a good thing by changing to the lighter weight oil. As for the carbon knock anyone try "seafoam" I used it on an old Toyota truck I had seemed to work pretty well. Although do it somewhere remote because the amount of smoke I made was unreal! I am really puzzled as to why it is so random, it will just "clunk" then idle fine for however many seconds then "clunk" again. Strange. The investigation continues........

JC2+2 · Poncho Master!

vicfire wrote:
Thanks guys, I'll look into the Rotella and check into additives or other oil. When I bought the car the prev owner used QS 20-50w in it, I thought that was a little heavy but pressures were always good. I may have messed with a good thing by changing to the lighter weight oil. As for the carbon knock anyone try "seafoam" I used it on an old Toyota truck I had seemed to work pretty well. Although do it somewhere remote because the amount of smoke I made was unreal! I am really puzzled as to why it is so random, it will just "clunk" then idle fine for however many seconds then "clunk" again. Strange. The investigation continues........

Any updates on your knock? Was the cam OK? Sure sounds like the same issue we had. If it is the same, the intermittent knock would be sticky wrist pin due to cam metal filings floating around in the oil. Sorry to say no easy solution except tear it down. Just curious what you found.

chevy4ever · Addicted!

what gas are you running? I have to run chevron 94 or it will knock. If you build up too much carbon it will sound like a piston rod knock.To fix my problem I had to warm the engine and spray water down the carb at 1500 -2000 rpm for about 5 min. Be aware because the tail pipes will shoot out black mud. should tell you if it is carbon or not.