ENGINE EXPERTS, I NEED YOUR HELP!

crushnut · Jul 18, 2004

Ok here it goes......

I have had a pretty loud knocking sound coming from my engine for a while, so i decided to tear it all apart to try and find the cause of the noise. While it was my original thought that i had a loose wrist pin on the #4 cylinder, i come to find out that isnt the case. So now im kinda stumpted on what was causing the god awful noise. Im taking the pistons and rods to a local machine shop to have them checked out, but i am in need of someone who knows more about engines, and this kinda thing. Please help me if you can, and thank you.

D.Hearne · Jul 18, 2004

I'd need to see the parts to tell you for sure what was causing the knock. Small blocks used to get a knock from the fuel pump lever under certain conditions.

crushnut · Jul 18, 2004

D.Hearne said:
I'd need to see the parts to tell you for sure what was causing the knock. Small blocks used to get a knock from the fuel pump lever under certain conditions.

Thats what my mechanic said about the fuel pump lever, and he advised me to take out the fuel pump and run the engine on the fuel in the carb, which i did and the knock/noise was still there.

golf4283 · Jul 18, 2004

there could have possibly been a small leak from the axuahst. My exhaust manifolds were junk and air came out of them making a horrible tick. It sounds as if you ruled it out though but I figured I would throw in my 2 cents. good luck figuring it out man.

crushnut · Jul 18, 2004

golf4283 said:
there could have possibly been a small leak from the axuahst. My exhaust manifolds were junk and air came out of them making a horrible tick. It sounds as if you ruled it out though but I figured I would throw in my 2 cents. good luck figuring it out man.

Its more than a slight ticking, more like a loud awful knocking and clattering noise, similar to a diesel truck

6Stang7 · Jul 18, 2004

Did you check you rod bearings?

crushnut · Jul 18, 2004

6Stang7 said:
Did you check you rod bearings?

Yes, they are all within specs and look good.

7DMACH1 · Jul 18, 2004

Could be a piston slap. Bore and piston get worn and the piston slaps back and forth. Does the engine have a lot of miles on it?

crushnut · Jul 18, 2004

7DMACH1 said:
Could be a piston slap. Bore and piston get worn and the piston slaps back and forth. Does the engine have a lot of miles on it?

Not sure, but most likely.

7DMACH1 · Jul 18, 2004

That is what was wrong with my 130k 351c. The pistons and bores were worn and the pistons were slapping.

crushnut · Jul 18, 2004

7DMACH1 said:
That is what was wrong with my 130k 351c. The pistons and bores were worn and the pistons were slapping.

Have you fixed it already? If so did you have the cylinders bored out and oversized pistons fitted in?

7DMACH1 · Jul 18, 2004

Yes, I had the entire engine rebuit, bored, new pistons and stroked to 408cid.

crushnut · Jul 18, 2004

7DMACH1 said:
Yes, I had the entire engine rebuit, bored, new pistons and stroked to 408cid.

Do you mind telling me how much it cost you to get it bored and new pistons?
I just wanna have an idea of how much it may cost me, on average.

Thanks

7DMACH1 · Jul 18, 2004

I had n all out racing engine built for $6700.00 I would think you should be able to get a standard rebuild with new pistons for $1500.00-2000.00.

crushnut · Jul 19, 2004

Im taking the pistons and rods to a local machine shop on Monday to get them check out, do you think they could tell piston slap by just looking at the pistons i bring into them? How much do you think it would cost to just get the cylinders bored out to the next oversize, if i do all the rest of the installation myself

D.Hearne · Jul 19, 2004

With any rebuild involving boring the block and new pistons, figure on spending at least $1000. What motor do you have anyway, Crushnut?

69PaleHorse · Jul 19, 2004

What transmission do you have? If you have an automatic, you may want to check the condition of your flywheel. They can sometimes make a loud metal to metal knocking/clanging noise when they crack...

crushnut · Jul 19, 2004

D.Hearne said:
With any rebuild involving boring the block and new pistons, figure on spending at least $1000. What motor do you have anyway, Crushnut?

302

crushnut · Jul 19, 2004

69PaleHorse said:
What transmission do you have? If you have an automatic, you may want to check the condition of your flywheel. They can sometimes make a loud metal to metal knocking/clanging noise when they crack...

Yes i have a C4, i did check the bolts too see if they had come loose and while doing that i didnt see any cracks. I wish that was the case

crushnut · Jul 19, 2004

UPDATE!

I took the pistons and rods to the machine shop to have them looked over, and guess what? They showed me 6 or 7 hairline cracks in the piston skirts and at least 1 or 2 that had serious cracks in them. (so much you could grab it and flex the crack! ) Both my dad and i looked over the pistons and we didnt even see them, but the guy saw it within 5 seconds of picking up the first piston. I guess i just dont have the trained eye for that kind of thing like they do

Looks like it is time for a complete rebuild

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