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Discussion Starter #1
I have a dilemma that needs your help. I have a 1970 camaro with a 307,#1406 edelbrock carb,performer manifold, point distributor,stock coil,headers,TH350 trans.Oops sorry, THAT is not the dilemma-this is:

I have been getting a knocking from the engine when it is under load-for example; if I climb a small grade the engine knocks at 2000-2500 rpms and increases with engine rpm. Another example is if I'm on the freeway and I stab the pedal it knocks right away and gets louder with engine rpm increase. It was overheating until I timed it with a light, but it will overheat if i continue to make it knock. I have the timing set at 7-8 degrees btdc, the carb is dialed in perfectly, the vacuum advance is connected to the vacuum port on the passenger side of the carb(ported). I have replaced everything but the disributor, which I'm about to do today. Is there anything I have overlooked or any ideas why this is occurring? thanks for any help or ideas.
 

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Discussion Starter #3
i thought of that too but it wont knock unless the engine is under load. I can rev it above 3000 rpm when its parked and not hear anything. if it was a bearing it should make noise without the load on the engine. oh well- i'm gonna replace the distributor and see what happens. wish me luck.
 

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before you take it apart,try high-test and some octane booster.just a guess but does it sound like the lifters rattling .(aka: detonation ?)or as it was said knock could be a rod bearing.hard to tell w/o hearing.

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My68Camaro
Doug G.
68 Camaro
406 ci.

[This message has been edited by DOUG G (edited 08-20-2000).]
 

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Discussion Starter #5
well I removed the distributor and sure enough the vacuum advance was not working. problem solved? NO! i'm still getting the knock, just not as severe. I've re-timed it and still a slight knock. So I went back through everything all over again and realized that I have not changed the oil since I got the car running. So off to the parts store I go to buy some really good oil, a really good filter, some Rislone, and some protectant. again- wish me luck!
 

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Buggin', not detonation ( that puts holes in ur pistons) but pre-ignition.

If the mill is older you might have losts of carbon in the chambers. The carbon acts as a hot spot, helping cause the pre-ignition. I've never used it, but I hear good things about a slime called Seafoam, which is poured into the carb while running.

Item second, while you were checking the distributor, did you check to see how the mechanical advance comes in? Check it. It may be happening too soon or in a totally non-linear fashion due to someone moneying with it who shouldn't have.

Item 3, try full mani vacuum to the vacuum advance. ( use ported for emmissions testing though). A simple test and I believe you'll find it helps the pre-ignition problem and might give you more power as well.

When you spin a rod bearing, at least the few unfortunate one I have, it "on" all the time. Not load related. Main bearings are load related and have more of a thump, than a clack. then theres wrist pins, etc.

Pre-ignition sounds like someone playing the "spoons" under the hood.

Good luck man.

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Gene C.
67 Chevelle SS 427/L88

[This message has been edited by 427TRI (edited 08-21-2000).]
 

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427TRI,
thats what i was thinking and i got a brain cramp. old age ain't even here yet.ha ha

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My68Camaro
Doug G.
68 Camaro
406 ci.
 

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Discussion Starter #8
well the gremlin has not been found yet. I changed the disributor, changed the oil, used rislone, added protectant, new filter but stiil get the knock.

one question: when I'm cruising on the frewway I get between 30-40 pounds of oil pressure and it goes as high as 50 pounds when the rpms come up. Is this the proper pressure or could this be a culprit?
 

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Discussion Starter #10
well I'll try replacing the plugs-(I haven't done that yet)wish me luck!
 

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Buggin, yeah the oil pressure should go up with rpms.

You need to describe the sonic quality of the knock to us. I know its a bear in words on the net, but...

Doug, I sometimes use the words interchangibly, but want to set the youngin' straight!

Buggin, is is like the "spoon player" under the hood, or is it a louder sound?

If the 307 is tired, it very well may be hot spots in the combustion chambers. You'll need to get some of that Seafoam or similar product you dump down the carb to clear out the chambers/valves.

Oh yes and BTW, have you adjusted the valves recently??



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Gene C.
67 Chevelle SS 427/L88
 

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Discussion Starter #13
THANKS FOR ALL THE LEADS. I'LL TRY TO BE MORE DESCRIPTIVE:

WHEN THE ENGINE IS WARMED UP THE OIL PRESSURE IS BETWEEN 30-40 LBS. I CAN REV THE ENGINE TO ANY RPM WHILE THE VEHICLE IS IN PARK WITHOUT HEARING THE KNOCK.WHEN I DRIVE THE CAR I WONT HEAR THE KNOCK UNLESS I CRUISE AT 2300-2600 RPM AND GIVE IT AN IMMEDIATE PUNCH OF THE THROTTLE. THE SOUND WOULD BE DESCRIBED AS A "PLAYING SPOONS" SOUND.(MOST OF YOU HAVE HEARD THIS SOUND WHEN YOU ARE SETTING THE TIMING AND YOU ROTATE THE DISTRIBUTOR TOO FAR)THE ENGINE WILL MAKE THE KNOCK IN LOWER RPM LEVELS IF I AM CLIMBING A GRADE OR HAVE A LOAD ON THE ENGINE.THE STRANGEST THING ABOUT THIS SCENARIO IS I'VE BEEN TOLD IF IT IS AN INTERNAL ASSEMBLY PROBLEM(IE: BEARING,PISTON SKIRT,WRIST PIN, ETC....)THE NOISE SHOULD BE OCCURING WITHOUT A LOAD ON THE ENGINE OR AT LEAST AT A LOWER RPM LEVEL. ONE OTHER STRANGE THING IS THE KNOCK IS NOT AUDIBLE AFTER 3000 RPM.

I'M STILL LEANING TOWARDS SOME TYPE OF FIRING PROBLEM.(THE CHEAPER SOLUTION) BUT IF ANYONE CAN THINK OF ANYTHING ELSE I WOULD GREATLY APPRECIATE THE HELP.

P.S. WOULD THE CARBON BUILDUP SUGGESTION STILL EXIST SINCE WE HAVE DROVE THE CAR EVERY DAY FOR THE PAST 2 WEEKS(700 MILES)?
I HAVENT TRIED A TREATMENT YET OR THE COLDER SPARK PLUGS. WILL BE TRYING IT ANYWAYZ ON FRIDAY.
 
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ok i,am gonna throw this out there and you can do as you please with it.alot of times if i,am thinking rod bearing i will pull one plug wire at a time and have located what cyl i was needing to give attention to.i,am wondering could you drive it a short way with one plug wire off and if problem still there,stop put it on and pull another and etc.alot of time and trouble,but hey that,s what this business is all about.if it was easy everybody would be doing it.BUT i really think you have a timing problem.

IT COST TO GO FAST
HOW DAM* FAST DO YOU WANT TO GO
 

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are you using the Lead Additives? , if this is your orig motor with nothing done, then you dont have hardended valve seats , you needs to have leaded gasoline. high test and lead additves. advance the timing a little and your problem should disapate. the spoons sound may or may not be pre ignition happening, but usually when you have pre ignition you will also have the famous konking when you shut it off, it continues to run off the hot carbon for a few seconds /minutes...

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Discussion Starter #18
I DIDNT GET TO TRY THE SPARK PLUGS YET(WILL TRY TODAY). BUT NOW I'M HAVING MY DOUBTS. I NEVER REALLY PAID ATTENTION TO THE OIL PRESSURE LEVEL AT IDLE UNTIL ONE OF THE GUYS WHO REPLIED TO ME SAID A ROD BEARING MAY SHOW ITS UGLY FACE IN LOW OIL PRESSURE AT IDLE. GUESS WHAT? 10-15 LBS. AT IDLE. I WILL PROBABLY BE DROPPING THE PAN TO CHECK THE RODS.

SO NOW I NEED SOME MORE ADVISE- WHAT AM I LOOKING FOR WHEN I DROP THE PAN? I WILL DEFINETLY BUY A NEW HIGH VOLUME PUMP JUST IN CASE NOTHING IS WRONG SO I CAN BE SURE THAT END IS COVERED. BUT THE ADVISE I NEED NOW IS HOW DO I DETERMINE IF THESE BEARINGS ARE BAD?

LOOKING FORWARD TO MORE INSIGHTFUL RESPONSES SOON. THANK YOU. WISH ME LUCK!
 

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That was probably me and I'm sorry to hear that. After you drop the pan pull the rod caps one at a time; keep them on the same rods and facing the same way. If there is a spun rod bearing or bad enough to knock you'll see it when you get to it. It will be wiped out; very rough and lots of copper showing through. You'll probably notice that even the ones that were okay are probably gouged up good due to the metal from the bad bearing going through the rest of them. At that point you need to repair/replace the crank and bearings at a minimum; you'll probably be better off rebuilding the engine. Possibly look into a crate motor also. It all depends on your budget and how many miles are on the engine.

Hopefully the bearings are fine but I've never seen an engine with 10 psi of oil pressure at idle that the bearings were okay.

Jody
 
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