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Too oval bores?


cygnusx1

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I got the parts today. Everything looks good but I am not sure about the ITM head gasket. Does anyone have any experience with them? The cork pan and valve cover gasket will be tossed, or saved for future spares. Thanks for the advice on that. I hate oil leaks.

 

I don't have a press so I will ask the shop to separate the old pistons. As far as assembling the new wrist pins and pistons to the rods, should I attempt the oven heating of the rods (400deg) and freezing of the pins, for a hand assembly, or do you think I should pay the machine shop to do it? I didn't ask for a quote on that yet. Realistically, how hard is it to get right, or should I say, how much working time do I get when sliding in the pins?

 

I read where TonyD also used Teflon pin buttons, even with the pressed in pins, which is nice peace of mind, but I don't think I'll need that for my relatively tame engine.

Edited by cygnusx1
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The block is ready to go and I am having the shop do my ring end gaps as well. I didn't want to screw around with a hand file or pay $60 for a grinder that I'll only use once before I lose it in my garage. I am having him set top and mid ring gaps to 0.017" (@0.020 overbore). It might be a tad bit wide, but with the heat I am throwing at this motor I would rather be safe than sorry. Now all I need to do is hunt down some gaskets for the turbo, borrow my buddies torque wrench, and begin assembly. I deburred the inside of the block and was surprised to see the amount of casting flash that flaked off by hand :o

Edited by cygnusx1
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I got the parts today. Everything looks good but I am not sure about the ITM head gasket. Does anyone have any experience with them? The cork pan and valve cover gasket will be tossed, or saved for future spares. Thanks for the advice on that. I hate oil leaks.

 

I don't have a press so I will ask the shop to separate the old pistons. As far as assembling the new wrist pins and pistons to the rods, should I attempt the oven heating of the rods (400deg) and freezing of the pins, for a hand assembly, or do you think I should pay the machine shop to do it? I didn't ask for a quote on that yet. Realistically, how hard is it to get right, or should I say, how much working time do I get when sliding in the pins?

 

I read where TonyD also used Teflon pin buttons, even with the pressed in pins, which is nice peace of mind, but I don't think I'll need that for my relatively tame engine.

 

I've used ITM head gaskets, and they are as good as OEM. Get the Felpro oil pan and valve cover gaskets.

 

Just have the shop press old out/new in. Have them check the size of the big end.

 

I have no idea what teflon pin buttons will do for a pressed pin setup. I suppose Tony will chime in though. If the pin is moving in the rod, you got issues. I know they are an option over pin clips in a floating pin setup.

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The shop quoted me the bore and hone, and then I asked them to fit the pistons to the rods and end gap the rings for me. The machinist was really cool and only charged for the block prep. I got the block back this morning, so I fit the main bearings, plastigauged it, and then torqued it down for good. The crank spins nicely. Tomorrow I'll knock in the core plugs, install the rings, pastigauge the rods, and get the pistons all installed. 33-40ft-lbs for the stock main cap bolts seems low to me, but I tend to have gorilla hands. I will be using ARP for the rod bolts and head bolts.

 

Sears had a Craftsman 75ft-lb click wrench on sale for $50 today! My lucky day.

 

 

 

 

042720111767-XL.jpg

 

042720111768-XL.jpg

Edited by cygnusx1
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Nice work!

 

The ARP rod, main, and head studs all torque to 60ft-lbs with their special lube.

 

Since it looks like detonation caused the piston damage, I suggest you pickup a cheap dial indicator and confirm that your timing pointer is accurate while you have the head off. This way when you calibrate the ignition timing in Megatune you will know that it is accurate. While you at it you can measure the deck height and compute the exact CR.

 

I recently went through this with my C production engine I built:

 

P3210007.jpg

 

Pete

Edited by z-ya
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I have a basic question.

 

Piston to cylinder clearance notation.

 

In the FSM they call for 0.0014 "middle of the road" Piston to Cylinder clearance. Is it a misnomer? Technically 0.0014" is the spec for the difference in diameter between the piston and the cylinder from the FSM.

 

Piston to Wall clearance should be ( CylinderdD - PistonD ) / 2

 

It looks like when everyone says Piston/Wall clearance, including the FSM they are really just quoting ( CylinderdD - PistonD).

It seems like this can cause some confusion.

 

???

 

 

 

 

 

 

Regardless, my new pistons are about 0.0028" smaller than my new bores which makes the wall clearance 0.0014"

Edited by cygnusx1
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I have a basic question.

 

Piston to cylinder clearance notation.

 

In the FSM they call for 0.0014 "middle of the road" Piston to Cylinder clearance. Is it a misnomer? Technically 0.0014" is the spec for the difference in diameter between the piston and the cylinder from the FSM.

 

Piston to Wall clearance should be ( CylinderdD - PistonD ) / 2

 

It looks like when everyone says Piston/Wall clearance, including the FSM they are really just quoting ( CylinderdD - PistonD).

It seems like this can cause some confusion.

 

???

 

 

Regardless, my new pistons are about 0.0028" smaller than my new bores which makes the wall clearance 0.0014"

 

 

Piston skirt to wall clearance is what I was told by my machinist. Pistons are tapered, because they expand more near the fire than at the skirt. The piston skirt clearance on my build was 0.006", but this was for forged pistons which expand more than cast.

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My machinist settled on just under 0.003" for my ITM's (cast) which is looser than stock, but then again, I do run 2.5 times the stock boost. Dimensions measured at the skirts, like you said.

 

Maybe I am opening a can of worms, but technically, the difference between the bore and piston should be divided by two. Clearance all the way around. However books only spec the difference between the piston and bore, not really the clearance. Unless you push the piston all the way to one side in the bore.

Edited by cygnusx1
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  • 2 weeks later...

The engine is built and the head is torqued. I will drop it into the car next week and begin the break in. Fingers crossed. It's my first motor so I am second and third guessing myself at every step. The timing marks are dead on, top to bottom. After searching locally for an "A" cam and coming up short, I decided to leave the turbo cam in place. It's probably a good idea to break in the motor with the cam that was used to create the existing tune anyhow.

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Here are the chambers as they came out of the motor. 5000 miles of street, and two track events. No obvious signs of chronic detonation in my inexperienced eye, correct? Could I have an intermittent detonation from something, well.....intermittent?

 

Chamber #4 worse case fire ring burnt, and pushed out to the cooling port:

 

042720111774-XL.jpg

 

Chamber #1 for reference:

 

042720111770-XL.jpg

Edited by cygnusx1
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Boring video of my first engine rebuild having just been fired up. I have the idle up with some feeler gauges under the throttle stop. I was told you don't want the engine to idle too low at any length of time for it's first few runs.

 

Edited by cygnusx1
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Congrats on getting it running. I'm envious of what you've done in a short time. I wish I could make that much progress on my project.

 

When does it go back to the track?

 

John

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Yeah sorry, rod bolts were set to 45 by the sheet that came with the bolts. Head bolts set to 60. Mains are factory. I followed ARP's instructions and used their moly. Good catch!

Edited by cygnusx1
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Hold that thought, cause the ARP rod bolts I have on my L28ET say to torque to 44 ft/lbs with their moly (blue packet)lube.

 

I forgot that I used 3/8" ARP rod bolts with Carillo rods. These also torque to 60ft-lbs. 9mm ARP bolts for the stock rods should be torqued to 44ft-lbs.

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