72 302 block .60 over 351 heads 270 cam. I had carb issues recently and installed a new holley 600cfm the 1850 model. Ran like a dream for about 30 miles then a knocking on the passenger side valve area. Pulled over and took the valve cover off and no obvious signs of damage. Put it back together and tried again on the hwy. same problem getting louder. The knock in the valve area does fluctuate with rpm change. Why would this pop up right after a carb swap, and what could it be? I'm running 6.5 of fuel pressure and did set the carb with a vacuum gauge. Any ideas? Posted using the Full Custom H.A.M.B. App!
Nothing at all, I even vacuumed out all the ports before putting anything on. It didn't happen until I was 30 miles down the road at a steady 65mph Posted using the Full Custom H.A.M.B. App!
Exhaust leak, they sound just like a bad lifter. Check to see if any of the exhaust manifold bolts are loose or if there is any carbon stains around the manifold.
Remove the plugs on the noisy bank and look on the plug ends and piston tops for signs of foreign material hitting them. It will be obvious. A bright led flashlight and a mirror might be needed. You need to rule this out.
Cut off a 3 ft piece of broom handle, put it to your ear & try & isolate where the noise is coming from
I'm betting on Smog Guy. Sometimes an object gets hung up for a while, before it turns enough to get past a valve. Bring each piston down to hopefully see the whole top if you can. Not sure on that motor, if you can.
Just pulled the plugs out and they are somewhat oily but not bad, I was able to see inside and found no foreign objects. All the springs are tight and no metal shavings anywhere so far. Posted using the Full Custom H.A.M.B. App!
I would use a clean flexible magnet to fish around in the cylinders to be sure. Is there a miss accompanying the knock? I assume you know the difference between knock, tap, tick, etc. Generally, knock is a deeper noise. Experienced techs don't get knocks and other noises confused. Is it really a knock? I'm not being a smart- aleck, just making sure. We use a modified stethoscope with a long metal brake line to pinpoint noises. A long handled screwdriver will work. On older engines valve train taps come and go. I hope it's this scenario instead.
Ok, then describe "knock" ? Is it a "pre-ignition" knock, or a "lean" knock? These would be somewhat random knocks, not really on each cycle of a piston. If it does not sound like those, and is more consistant with each cycle of a piston, it could be something sitting on the piston, or stuck to the head. If it sounds more like a piston hitting, I would remove all plugs, then turn the crank very slowly with a wrench, and you just might "feel" a slight difference as the object hits. If that happens, see which pistons are at top dead center, and look closer on those.
My apologies it is more of a middle tone tick, not a ping. I did have some bad gas awhile back when I carb was dying and the driver side had a normal fuel ping. This is not a deep sound and does not sound like something hitting hard. I did notice that the fuel pressure was slightly dropping when the noise started, still around 40 and drops to 20 when at idle. This is a brand new carb. Just strange that it started after this. I just pulled a few rods and no visible signs of any damage there either. Posted using the Full Custom H.A.M.B. App!
Ford has had the spark plug wire induced ping ( sounds like marbles rolling around) thing since day one. Cylinder 7 wire induces park in cyl 8 way to early. They used to instruct you to seperate certain wires from each other. Cross them, I think. This is way out on a limb but it happens. You coulda disturbed wires messing with carb since dist is out front? Run firing order again to be sure, also. Otherwise, what about that carb change started this? Or was it just coming on? Try running once with vac advance disc...
What octane of fuel are you running? Have you tried going to the highest and running a tank of it to see if the noise vanishes? No expert here, just speculating. Richard E.
Yeah I read that too but this is on the other side from 7 and 8. I will try the vac advance. I swapped carbs cause my junked up and I wanted to run a holley anyway. Posted using the Full Custom H.A.M.B. App!
I thought about that too, I always run supreme but with the ethanol I put in half a tank of 110 racing fuel and actually less than half a tank. I have a 13 gallon tank and put in 6 gallons of 110 and 7 of 93 octane. Posted using the Full Custom H.A.M.B. App!
It could be as simple as adjusting your valves. I doubt it is anything that has fallen onto the piston. If that was the case the noise would probably vary. To find out where the problem is (If it is a bearing problem) you can do this: With the engine running pull one spark plug wire. If the noise does not change reattach that wire and move on to the next wire. when you remove the wire where the problem is when you find the right cylinder the noise will stop as there is no longer a load on that location. Steve
Finally found out I ruined the cam. Pulling it out and got a new 302 roller Posted using the Full Custom H.A.M.B. App!
Roller as in "roller cam"? A roller cam motor would be 1985 and later,a 1980 is a flat tappet cam and a 28 oz balance in late 1981-82 the 302/5.0 went to a 50 oz balance factor if you use the earlier flexplate and harmonic balancer on a later block it will destroy itself in a hurry.
You can use a roller cam in a non-roller engine,it has nothing to do with the two different balancing weights.Check which firing order your cam is ground for,the cam manufacturer will know. ROY.
Are you running a mechanical fuel pump? I had a weird knocking sound in my 302 that disappeared when I switched to an electric pump.
The spring on the fuel pump arm can "fall out" & let the arm flop around & make a noise that sounds like a bad lifter.
I think the guy that built the engine did not lube it properly and I was not running zinc oil. I'm running an electric fuel pump. This new 302 may not work for me I think it's a 50oz and I don't have the spare cash to get new flex plate and balancer. My stuff is all 72 model 28oz Posted using the Full Custom H.A.M.B. App!
How many miles on the engine? Check to see if you have a lifter collapsing.Also check to see if you have a valve working its way through the keeper , making it just touching the top of piston. This can be checked like steven 185 suggested or visually inspect the valve train.
Just wondering how many wide open runs you made after installing that new Holley carb.lol. Thats the kind of stuff that happens to me when I'm checking out the butt dyno after a new mod on the motor. You find the noise. JUst keep playing detective it'll show it's ugly head. yruhot...Doug
The Jalopy Journal
