Listen to this!

[fasterdamitt]

I have been having a little problem with two new 331 short blocks now. I built the first one and thought I had a loose piston. So I bought this one. They both have a knock at idle and low rpm. This time I replaced everything except the heads, springs and rockers. Here's a sound clip, hopefuly someone may recognize the sound. The clip is taken just at the pan and block area.
http://s129.photobucket.com/albums/p211/FASTERDAMITT/?action=view&current=347012.flv

A pic of the cut open oil filter after brake in: http://i129.photobucket.com/albums/p211/FASTERDAMITT/347011.jpg

Thanks in advance,
Tom

 

[samickguy15]

That sounds bad...very bad...Did you check bearings and piston clearances? Maybe you're smacking pistons into valves just slightly, although I doubt it b/c that seems like a smooth idle, so probably a stock cam...

 

[dcurtis]

Are the blocks notched for the 331, some people don't have to but some do. Just my guess
For the second 331 shortblock did you buy it or build it?

 

[PUNISHER RACING]

The 347 in the red car just started to do that when the weather chilled off got me baffled. It sounds like piston noise to me.

 

[samickguy15]

Maybe somebody bought pistons after they had the block bored? Piston manufactures have tight tolerances for piston to block clearance. Maybe it's too big and you're slapping. Either that or maybe the change in temp has shortened your deck height just enough for the piston to hit it?

No matter what I think you'll be taking them both apart for a sort of blueprint check.

 

[PUNISHER RACING]

Oh no it will come apart when it removes itself from the inside of the block ... more spray anyone?

 

[408gt91]

fordged pistons usually knock a little till there warmed up and expand ,but that seems a little excessive.

 

[fasterdamitt]

Thanks for all the replys. This is the second engine doing the same noise. Upon teardown of the first one, I looked for evidence of valve to piston and rod to block clearance issues. Nothing found. This time I had one built by M&R engines. They have been helpful in trying to identify this.

Update I pulled the intake and found the roller cam looks worn on a couple lobes. This is a brand new cam. While in there I replaced the lifters on those lobes just for kicks. There was no damage to the lifters I took out. What can cause a roller cam to get scuffed? I used standard 30w oil for breakin. Prepped the cam lobes and lifters with same oil at installation.

[/IMG]

 

[302RollinHard]

if your valvetrain isn't set up correctly, it can scuff them a little (ie incorrect springs for the cam, improper pre-load or incorrect length pushrods). Or if for some reason you didn't use dog bones. Good luck.

 

[fasterdamitt]

I'm wondering if the springs are too strong. I bought a on head measuring tool from Jeggs. The opening pressure I got was about 165-170. That seems alot to me for a street vehicle that revs to 5600.

 

[Fast63]

that is very low opening pressure. You should have 300# or more open and at least 130# at installed height with a roller cam.

 

[fasterdamitt]

This is what I'm getting from Comp Cams catalog for my cam:
part# 986 Seat [email protected] open [email protected]
I'm at seat 170 installed, but I don't have at the actual hight. I will have to pull a spring to check the open pressure.

 

[Cal40]

Uhhh that sound clip sounded horrible

 

[fasterdamitt]

I'm going to do a head on block piston to valve clearance check when I get the tools I ordered form Jegs. If that's not it, then I could have the piston hitting the head due to multiple deck surfacing.