Just changed my oil and filter and now I've got a fast knocking noise in the engine bay that wasn't there before. Did no other work on the car except this job. Kept car running for a few minutes to get it up to operating temp., but noise is still there.

What could it be and will it disappear after the new oil has circulated for a few days. Am I geting concerned over nothing?

btw - oil used was Kendall GT1 20w50

 

phil
if it a rod knock it won't go away. Are you good at describing engine sounds?
pull each plug wire one at a time to isolate noise

 

If you are running with hydraulic(sp?) cam,it will knock a little.Mine did just the same when i changed in to 20 50 ...And it disapperad after a little spin on low rpms.. :cheers:

 

Thanks BB. Not sure if my Cam is Hydraulic or not. I'm assuming it's the stock one that came with 1978 L48 engine.

If it is, then I feel a better knowing that the knocking will hopefully soon disappear once the oil has circulated a bit more.

I've started the car a few more times since my initial posting and the knocking doesn't seem quite so bad as it was earlier.

Here's hoping :cheers:

Matt - I'll get practicing my engine impressions for the next time I need to describe a noise. :D

 

That oil is pretty thick, for high-heat conditions. Did you happen to use 5W or 10W-30 before?

 

"High Heat Conditions" - what are they? We dont get any of them here in England. :lol: :lol: :lol:

I've only had the car a few months and I wasn't sure what was in it before, so rather than risking mixing oils I decided to drain it and start from scratch.

An American parts dealer near my home recommended I use the 20w 50.

 

Did you fill the filter with oil before you installed it? If not then things were probably knocking as the filter filled. How is your oil pressure? It's most likely a lifter or something that should go away once the engine warms up.

 

I hope that's a dealer in America parts rather than an American who is dealing in parts. But whichever it is, I think he's full of sh##. The clearances in your engine were set up for 10W30. Admittedly, as the engine ages, wear occurs and the clearances increase, and switching to a higher viscosity oil is a band-aid for that. But it sounds to me like that's not your problem.

Switch back to 10W30 and see if that doesn't cure the knock.

 

I used to run a heavier oil in my older engines, but I have re-thought that
whole deal.
Here is my theory: The thicker oil is simply harder for the pump
to push through the passages. Thinner oils flow through easier. Since I
live in a cooler region of the country, I never require anything heavier than 10w30. In fact, I have since switched to using 5w20 and 5w30 year round.
No more lifter tapping like I had with 20w50.

Just my experience. Your results may differ.

 

Yep, 10W-30W or just 30W is all you require in a 'normal' climate. 20W-50W is too heavy and could do what you describe unless it gets very warm over there.

 

I have never see GM recommend 20W-50 for any of its passenger vehicles. Go back to 10W-30 and I suspect your problem will be solved.

 

i noticed erratic psi at high rpm with 10w30. Super Chevy did a dyno test and had the same problem.
Cured with 20w50 :cool:

 

I didn't think to fill the filter up first :crazy: - I just followed the instructions in my Haynes manual and somewhat suprisingly they don't mention that part. :rolleyes:

Oil pressure is bang on 40 psi and I'm glad to report that the knocking has disappeared now that I have been out for a few runs.
:cheers:

 

Hi Phil

If its any consolation, I've used Kendall 20-50 for years in my 78..... But, interestingly, it has lately developed a bit of a "knock". Varioius friends and "gurus" have more or less agreed that it may be a lifter, but that it is not something to worry about unduly :confused:

Now of course I'll have to do a quick poll of Kent Corvetters to see what they are running oil wise!

Oh, and I don't fill the filter before hand either.... I can see a lot of rolling eyes from our friends across the pond on this one ;)

Any chance you'll make the Damn Yankees "bash" at North Weald on the weekend?? We could compare noises :D


[Modified by Stephen Irons, 12:21 AM 7/23/2002]

 

Hi Steve, I feel a bit better knowing there are others running 20w 50. I wasn't keen on doing another oil change so soon.

I'd love to, but already got plans this weekend :( .

How did you get on at Goodwood? The weather couldn't have better for you. Saw bits of it on the TV at the weekend. Apparantly, they had a few dragsters there for the first time this year including a 'vette which could do a 1/4 mile in 8 seconds. :crazy: .

btw. from my previous post - I used a fuel hose as a temporary fix until the real tranny hose arrived from the US - worked a treat. Spent the weekend cruising round the Cotswolds. What a grin it is taking the 'vette round all those country roads :D - the high sides of the lanes just made the sound from my duel exhausts bounce straight back into the car - awesome noise.

 

Steve,

I would appreciate any info on the show, I`m always looking for something to do at weekends.

Thanks in advance.
J.

Phil,

Hope your vette is ok I have been using Valvoline 15/50 recently in my cars, readily available from just about any motor factors at about £7 a gallon.

 

Phil

Glad to hear that the trans hose swap was OK in the end.... Fun little job isn't it! ;)

Goodwood was great. Weather on Friday was a bit grim, turned everything into a mud bath by the evening and for first thing Saturday. Did we feel smug that we had got the Suzuki "Jeep" back on the road or what :D But perfect during Saturday and Sunday! There was a good little selection of dragsters, including the Vette. Star of the day was Micheal Megram, one of the Scandinavians, who came over with his Camaro Pro Stock car. Got the "burnout record" with no problem! Also had the Le Mans Class Winning C5R there, along with Oliver Gavin and Gary Pratt. Big crowd favourite, as Ollie was enjoying himself! Also one of the Greenwood Corvettes from '74 there. It may feature on the TV programe, as we watched the girl (can't remeber her name, but she does the show with Simon Taylor) doing a bit of filming in it. Biggest legends in attendance probably Emerson Fittipaldi, and my hero Jacky Ickx.

Re the oil, intersting that "J" from Hartlepool is using Valvoline. Given the high cost of Kendal since the sad passing of Tony Dickson I was thinking of going over to that, as I have a "contact" for it. Maybe next time and I'll compare. You no doubt know all the advice that we should use an "American oil" in our Vettes..... I think Valvoline fits the bill....

Pity about the weeknd, we're going to do Sparkford on Saturday, (Haynes Museum) then hope to fuit enough for North Weald! Had you thought of the Beauliea run in September?

'later.....

 

J

This event is the Damnn Yankees Summer Slam. Its at North Weald Aerodrome, Essex. Its just off the M11, junction 7 I think. Last year it was pretty huge, and they had some demos of dragsters, a "legend" car and a few other things. Good selection of cars on show, from classics to customs. And , as I said, there was big turnout from CCCUK, so plenty of "real cars" :D Its held on the runways, so it's a good idea to bring chairs!

Your car looks nice, so I'd be intersted to see it. But isn't this a bit far for the weekend? If youfancy a good run, we'll see you there, anytime after about 10.00am I think.

Regards.

 

I was told by the head service guy at the local GM dealer that certain oil filters might cause a knocking in the engine. Just a thought. Good luck.

 

Hey, we're currently at 72F - that's cooking! :lol:
I was told by a Vette specialist to run 20W/40 oil in mine. The manual also specifies 20W/40 for our balmy weather, but I've never seen the stuff, so I'm running mine on 15W40 & it seems fine. Hope you don't hear that knock again.

Stephen: Hi, thanks for the North Weald reminder :) If the Vette passes it's MOT then we'll c u there (test booked for Thurs, went to check it over last night & found that the fuel tank has sprung a leak :( ).
:cheers: