rebuilt engine knocking?, engine builder says its normal for big bore 4's? Options

[sean_v8_914]

I dont think my 103s are that loud...maybe Im used to hearing it now 3 seasons later. we had an "issue" at AX this sat so the motor is torn down to the long block. Ill ifre it up and report back in a few days. we do have to run a loose bore to survive as Jake says. cast pistons can be run tighter.

Jake: does stroke affect that knock? we run a 103 x 71. he has a 78mm crank.
steeper rod angles?

[Jake Raby]

Yes, the stroke changes the rod angle, which can impact the "knock" greatly with the large bore.

Thats why its all in the combo.

[narino]

Just talked to the builder and he was more than happy for me to bring the car back by to check it again. As Jake mentioned, he said the engine would be loud because of the clerances until it warmed up. If the noise persisted after warm up then something isn't right.

Capt'n - the builder has been responsive thus far I wouldn't want to post thier name yet until I see how they deal with this issue. I'll post how they folllow up on warranty repairs and such.

Jake - Thank you for dropping in and posting your insight It's much appreciated. I'm pretty sure it's exactly what you mentioned on the cylinder to piston clearances. Yes they were JE forged pistons.

He didn't have notes on the deck height, though he said the cylinder to piston clearance was JE's manufacture specs. The engine was built over a year ago, but had sat uninstalled until 4 months ago. No fault of the builder, my previous mechanic turned out to be a nightmare.

I'm going to try to take the car in this week. I hope it's an easy fix. *crossing fingers.

[Jake Raby]

Good for you to wait till see how things work out before posting names.. Thats the kind of courtesy that I always appreciate when things don't go perfectly with a client/ build. Its only fair to work this way.

I don't really know what the MFR specs would be on the pistons, I've never known JE to have standardized numbers for this.. Plus the total valve/piston clearance is directly impacted by deck height. If the deck height is unknown, then there is no way to know the actual piston/ valve clearance.

But it still sounds normal for a big bore 103 set up

[narino]

Ok bringing this one back. After paying off some car debt and driving the car around it's still too loud for me.

I've talked to the engine builder and he says he'll swap out the forged pistons for cast iron pistons with tighter tolerance. He is not charging for the piston swap and would only charge labor to do the work, which is about $650.

Does this price sound reasonable? Also, are cast iron pistons really more quiet and worth swapping out the forged pistons for a more quiet no-track, non turbo'd engine?

(IMG:style_emoticons/default/beer.gif)

Thanks in advance.

[rick 918-S]

Ok bringing this one back. After paying off some car debt and driving the car around it's still too loud for me.

I've talked to the engine builder and he says he'll swap out the forged pistons for cast iron pistons with tighter tolerance. He is not charging for the piston swap and would only charge labor to do the work, which is about $650.

Does this price sound reasonable? Also, are cast iron pistons really more quiet and worth swapping out the forged pistons for a more quiet no-track, non turbo'd engine?

(IMG:style_emoticons/default/beer.gif)

Thanks in advance.

Is he going to balance the assembly again? Heavier pistons, Not cast iron though... more likely cast aluminum?... (IMG:style_emoticons/default/confused24.gif) Heavier = more stress on the rotating assembly. But the piston expansion rates should be more equal with the cylinder material.

[karlo]

Forging eliminates metal porosity and improves ductility. With the extra strength, forged pistons can be made a little lighter. The improved ductility will allow them to handle knocking a little better.

Whether or not forged is needed depends on compression ratio, max rpm, power output, etc.

Most forged pistons expand more than cast, so need to run greater clearances when cold, and will be noisier on startup.

[VaccaRabite]

$650 is probably a deal to have the work done, considering he is going to have to re-balance, redo deck height and maybe even redo pushrod geometry.

Zach

[Root_Werks]

$650 is probably a deal to have the work done, considering he is going to have to re-balance, redo deck height and maybe even redo pushrod geometry.

Zach

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[narino]

Again, thank you guys for your replies.

Vacca/Root - glad to hear it.

Rick - I'm pretty sure he'd balance the assemlby again. But of course will confirm this with him. My mind assumed iron when he mentioned cast, but honestly I don't know specifically what material it is not that you bring it up. I'll ask about it as well.

Karlo - He did mention what you've posted. The power output was in a lower range for him to not worry about the definite need for forged pistons. As It's not going to be tracked, and my biggest concern was noise he thought this swap would be best for me.

I guess after the swap to cast pistons could I expect a slight performance drop as the pistons would be heavier and wouldn't rev as fast?

[VaccaRabite]

I guess after the swap to cast pistons could I expect a slight performance drop as the pistons would be heavier and wouldn't rev as fast?

If you are not pushing the car, I kind of doubt you will notice it.
But, I've been wrong before.

Zach

[realred914]

if it is too much noise for you ask to hear one of this builders motors with cast pistons first, it may not be that much quieter, intake nad exhasut can make a big noise differenace.

[narino]

Builder says as long as the piston all weigh the same the is need to balance the assembly? Does that sound right?

realred - Good idea ill see if he has an engine I can hear.