Mkos1980

iTrader: (8)

I have about 2300 miles on my professionally built 383 shortblock. I had everything done and the lower end consists of Eagle Crank, H beams, and speed pro pistons with clevite bearings. Mains were studded.

Now today I go to start the car and I get this tap tap noise like in the middle of the engine. It ONLY does this between 650-750 RPM's every few seconds. Antyhing above that and I hear absolutely nothing. I drove about 40 miles and no noise unless I get into that low RPM area. Oil pressure never goes under 30, even hot at idle. It sounds as if a screwdriver is tapping my y pipe. Any idea what else to look for?

What does rod knock sound like?

ede

injectors, exhaust leak, pull the belts and see if it stops

Mkos1980

iTrader: (8)

I'll check but its coming from the back of the motor / pan area

Mkos1980

iTrader: (8)

I take back my taping. Sounds like smebody is beating my ypipe with a hammer.

ede

maybe your Y pipe IS hitting something

KrisW

iTrader: (5)

I had a similar condition about a month after the engine install. All of my torque converter to flexplate bolts had come loose and the thing would bang at a certain rpm only. Check everything in that area before you condemn a bearing........

mystikkal_69

iTrader: (2)

also check the engine block to transmission bolts. i had my buddies car make a knocking noise and this was the problem. the were loose. make sure they are all tight. if the were loose, that could lead to the next thing to check, your flywheel. it may have cracked. if the bolts were tight and the flexplate was new, this could be unlikely, but not impossible.

another thing that it could be is a worn trans front pump bushing.

lastly the other thing that could cause this type of noise is a bad convertor.

be sure to check these things out and let us know what it was. good luck.

Mkos1980

iTrader: (8)

Will do. Its so weird it does this ONLY at 650-750 RPM. I started it ice cold today and went up to 1500 nicely and came down slowley then when it gets to the 700 range, bang bang bang bang and when I give it a tad of gas to 850-900 ish nothing. I did a few revs to 5K and nothing. drove it and got on it good to 5K nothing. Oil pressure is perfect. If it were rod knock would I hear it with more rpm?

mystikkal_69

iTrader: (2)

yes it would. if it's loud at idle and not right off idle then it's not rod knock. usually with rod knock the osund gets louder and progressively faster when engine speed increases. rod knock sounds like a ball peen hammer hitting a cement floor.

Mkos1980

iTrader: (8)

NO knock above idle. Lower the RPM louder it gets. Like if the fans come on at idle or since it has a cam it gets a bit lopey and idle goes to 550 and th emotor gets jumpy and comes back to 650 it'll get louder. but 800ish and up nadda.

Mkos1980

iTrader: (8)

2 loose converter bolts and another half off. Tightened them all and super quiet. Thanks guys

KrisW

iTrader: (5)

The best thing about this site is that its like having thousands of big brothers! They chide you about decisions that you make that they don't agree with, but you still get to benefit from all of the mistakes that they made before you!

Glad to hear it turned out okay. Now maybe you will be a follower of the loctite philosophy, like the others of us who had old bolts fall out even after everything was checked 100 times!!

Rick King

to avoid this put some red lock tit on the threads of the bolts--this is a must to keep them tight

later

and

GB

rick