tapping noise from engine

[BLUE74]

I rebuilt a 350 for the truck i'm driving 74 1/2 ton longbed. NOW it makes a tapping noise. We have tried tracing it down with a stethoscope type of deal. We put in a Edelbrock cam and lifters and thought may be a bad lifter. Replaced 2 lifters, nooo difference. is it the fuel pump pushrod? It is the same rod except i turned it around. Any help?  

[roundedline]

Did you set the valves after installing the cam?

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[BLUE74]

do you mean adjusting them?  i had them adusted to 3/4 turn in after the slack is out but the fellow at the machine shop who rebuilt my heads said i should go with a 1/2 turn in. that is what i'm running at now. they are hydralic lifters

[Lt.Del]

You should be able to diagnose which lifter/valve it is by idling the engine w/ the valve cover off.  It is extremely messy, oil should drip all around and on the exhaust manifold causing smoke, but you should see for the first couple of minutes (while you can still see thru the smoke) find out which valve it is and try tightening that one.

SgtDel

[FULLSPEEDJUNKY]

nice trick SgtDel is right but it can be done without the mess

Summit racing sell oil deflectors that do on the rocker arm and prevent the oil from being flung onto the headers/manifolds. They are about ten bucks and belong in every Chevy mans toolbox

BTW I think that Mr Gasket is the manufacturer

[BLUE74]

well guys, i did replace 2 lifters on no.2 cylinder which was close to where we thought the noise was coming from. we did tighten the valves to see if it would help but it didn't.  the motor runs great no major rough running but the knock is still there. could a reversed connecting rod do it? thanks for replying  i just would like to solve the noise!!!

[ChevyGuy]

Why dont you try to adjust the valves while the motor is running. Loosin up the nut on the rocker until it starts tapping and then tighten down slowly until it goes away and then give it the 1/2 or 3/4 or whatever your preference is and do it to all of them if you are unsure. Also did you replace the timing chain? sounds like the chain may be slapping the cover. Does the noise speed up when applying the throttle and quiet down?

[BLUE74]

yes, i did replace the timing chain and the noise does speed up when you rev the engine. i can't hear it running down the road but just at idle and coming up to a stop sign or slowing down.

Edited by: BLUE74 at: 9/24/05 7:35 pm

[RSBAD454]

Get some old valve covers and cut the middle of the tops off, but only enough to get a valve adjusting tool in there. This is what I did with my big block.....no mess at all.  

Toys are my game

[Lt.Del]

RSBAD454  -- that is a terrific tip about the old valve covers.  I may have to vist the salvage yard and get me a pair, then take my saber saw to it.

SgtDel
www.delbridge.net

 

[TRUCK6DRIVER]

I had 2 small blocks with fuel pump pushrods that knocked. It took me 3 weeks on the first one to find and just a few hours to find the second one. I just replce the pushrod and pump and the knock goes away. This may not work if the cam is shot too. Take a screwdriver and put your ear to with it against the fuel pump and run the engine. It will be too loud to keep the screwdriver to your ear if it is the problem.

RH

[BLUE74]

well guys, i just finished putting on a fuel pump and a pushrod and the noise is still there   i guess i'll just drive it and put up with the noise.  its probably a lifter clattering.....   truck drives fine anyway                thanks

[DnStClr]

Blue, when the timing chain was replaced, it may have been replaced one tooth off. This affects the timing and can cause an engine tapping noise. If the oil pressure hasn't dropped, the bearings are probably ok. A bad crankshaft also causes knocking, but you're saying it's a tapping noise, so most guys look for
1. a bent push rod or one that's short
2. lifter sticking
3. loose valve
4. a flat spot on the cam
5. slapping timing chain

[TailGater]

I had a similer problem with a 327 once and it turned out to be a pushrod, the rod was slightly bent and after it was adjusted it would just bend a little more and start tapping, after re-adjusting the valves several times i noticed one of the pushrods looked a little funny, replaced it with a good one and never had the problem again. Might be something to look at next time you have the valve cover off.

Hope you get it solved.

Chris

[shortbox85]

if its like a knocking sound then u may have a colllapsed lifter, or it could be ur valves r shutting to hard