Big block valve train clatter

Looking for ideas if anyone has one. I have a 402 that has a moderate valve clatter or knock on initial takeoff. It doesn't occur at idle and when crusing. I've noticed it after a moderately heavy foot just after take off when the oil pressure is the lowest. The pressure is good over all and the springs are good but I can't figure it out. I've heard that some big blocks had oiling issues to the cam, and Ive seen a kit installed which basically was a copper tube installed in the lifter galley drilled and tapped into the cam lube passage to increase the volume. I can't seem to find it now though and not sure that would fix it. Anyone know what I'm talking about? I can romp on it all day long with no troubles as long as it's not off idle. Help!

Try setting the valves. I know a lot of guys try fudging the setting by not turning them down the last 1/4 turn or so, trying to delay "pump up" of the hydraulic lifters. Then, of course, they tap a bit at low speeds. Set 'em to manufacturer's specs and they usually work, unless they are Rhodes or some other freaky setup.

have you tried retarding the timing or premium fuel?

after ruling that out
perhaps a higher volume oil pump?

yeah, are you hearing the valve train rattling, detonation, or some exhaust leaks??? All of which can make the noise in a fashion you describe....

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Originally Posted by R Pope

Try setting the valves. I know a lot of guys try fudging the setting by not turning them down the last 1/4 turn or so, trying to delay "pump up" of the hydraulic lifters. Then, of course, they tap a bit at low speeds. Set 'em to manufacturer's specs and they usually work, unless they are Rhodes or some other freaky setup.

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Setting the valves was the first thing I thought since the valve covers were leaking a bit any way that would be a good time to do it, this is when I noticed two rockers hitting the falve covers. The book calls for 1 full turn after lash but I've always went 1/4, but this time I went half and that took care of the rockers. I had it idleing and running great! I worked it a bit yesterday and if it were a rod it would definitly puked it out. I'm getting to the point I want' it to fail so I can find it, just can't afford an expensive fix.
Thanks to all with ideas, I know I'll narrow it down soon with the help of this forum! Keep em' coming!!!

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Originally Posted by t0oL

have you tried retarding the timing or premium fuel?

after ruling that out
perhaps a higher volume oil pump?

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I did retard it 2 degrees and it made no difference, although I would (probably will) try higher octain fuel, at this point I'll try anything! It doesn't really sound like ping though, I picture the sound like a lifter slapping or something. But it makes no sense. No knock at idle, knock begins about 1000rpm, then goes away under load, now comes back at any speed off load (coasting) and goes away on deceleration. I'm afraid to try a higher volume pump (may already have one) the pressure pegs the stock pressure guage until it warms up and then stays fairly high.

Thanks for the ideas!

Thanks for all the help everyone! I'm still wondering if it's possible I'm losing pressure to the cam an lifters at certain points. I wish I could remember where I found the article years ago mentioning older big blocks having cam oiling issues, anyone aware or heard anything about this? Thanks all! Keep the ideas rolling as I'm in dire need before it becomes catastrophic!

bbc never had a upper end oil issues they did oil thru the rear cam with a groove in the cam journal older blocks 65/66 and not in the block under the cam bearing like the 67up that lets oil to the lifters with no groove in rear cam for upper end oil .now if some one put upper end oil restrictors that cut alot of oil down they can go in the 1/4 plugs in the back of the block or they tap the main upper oil thru the rear groove of the block. you tap the block and go under the cam bearing if a old race block it could have them if it was a soild lifter cam or soild roller cam. if that checks out then you could have bad valve train parts .you did not say much on what you have for parts ? if you have roller rockers they make some clatter if shot alot more .the steel stamp rockers get marks worn in to them for valve stems they will work in and out of lash rocker balls could be bad and pushrods worn.wrong size guide plate?? they made 5/16 .3/8 .7/16. now if you had 7/16guide plates with a 5/16 push rods ? will make upper end clatter lifter s could have junk in them ? now if you had low oil psi there could be no front plug s in front of block

clattering---low oil supply

high oil pressure/pegged guage---oil not getting somewhere

have you pulled any plug wires one at a time to see if there is any difference????

402 pretty old engine---if its wrong application cam you could get your symtons

Worn lifters/ bosses---oil leaks out of galley and takes a bit of time to pump up--chev added vent holes to front galley plugs to bleed air from lifter gallies

hitting valve covers??? why was that? what do you have for rockers/ valve covers???

Dist where it passes thru lifter galley blocking oil flow or leaking it down???

the welded sheet metal valve covers can hit the rockers arms ? some rocker are wide body and will hit valve covers you need to round the rocker body with a belt sander and wash the rocker very good it s the intake rocker . if rollers they have a alum lip that hang under the rocker pushrod side of rocker. the dripper if m/t valve covers hit if you use roller rockers .i drill the front plugs but that helps to but if it clatting that bad could be more then air .i seen a bbc did the same thing the oil pump cover was falling off. i pre all the block for the O rings from msd that keep oil from moving past to dist hole in block never seen much more for the spray shot for dist gear oil

Not sure I follow you Pat, about drilling the plugs in the front and what keeps oil from moving past to the dist hole?

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Originally Posted by bigred1957

Not sure I follow you Pat, about drilling the plugs in the front and what keeps oil from moving past to the dist hole?

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well they are small under 060 see them on this sbc i built? the dist is part of the oil galley if the bock hole is big or dist is small some oil will pass like jerry said .MSD grooves there dist for Orings to help some and helps put oil on dist gear they drill a small hole that sprays oil on the gear with the Orings on that make s the oil shot circuit work that MSD use

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Originally Posted by pat mccarthy

well they are small under 060 see them on this sbc i built? the dist is part of the oil galley if the bock hole is big or dist is small some oil will pass like jerry said .MSD grooves there dist for Orings to help some and helps put oil on dist gear they drill a small hole that sprays oil on the gear with the Orings on that make s the oil shot circuit work that MSD use

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I see, so by what your saying, my distributor could be the next place to look? It is aftermarket but I haven't looked into it yet. I need to look for or add o-rings to complete the passage efficiently. Is there any difference between bb and sb dist's that could cause this problem?

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Originally Posted by bigred1957

I see, so by what your saying, my distributor could be the next place to look? It is aftermarket but I haven't looked into it yet. I need to look for or add o-rings to complete the passage efficiently. Is there any difference between bb and sb dist's that could cause this problem?

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well what i am saying is with MSD they have o rings nice to have .i roll the cast on the bore hole on the block so they do not cut O rings going in . i have never seen this so bad that you would get low oil psi or nothing but it would not hurt to check ...there allways a first time.... so check the dist for size next to another one stock GM one or one out of a running engine.if not i can get you a size if you need it . if it a cheaper china one could be off .i used the MSD and MALLORYS AND ACCELS AND others never had a lost of oil psi from this.but you need to start some place .look what Jerry has posted and what i did as well as others .make a list and check every thing we posted on this.here s is a photo of how close the rockers can get to the upper boss of the valve coves can rub if you look on number 8 and 1 intake rocker by the upper valve cover bolt

I understand about the o-rings, I do have an old stock distributor to compare with. I'll definitely dig through the posts for info, everythings been helpful so far. Thanks alot for your help Pat, If I run across something wierd I'll fill you in.