Anyone here ever have their pistons machined?

Posted By: Kern Dog

Anyone here ever have their pistons machined? - 09/29/13 09:26 AM

Still dealing with detonation with the 440/493. I'm considering many things to stop it.
I spoke with Dwayne Porter awhile back and he suggested milling my pistons .040 on the chamber side to reduce compression.
Has anyone here had this done before? Any ideas on the cost?

Posted By: B G Racing

Re: Anyone here ever have their pistons machined? - 09/29/13 02:51 PM

Increase the head gasket thickness would be the easy and cheaper way of decreasing compression.What is your piston to head clearence or piston to deck height now?

Posted By: BSB67

Re: Anyone here ever have their pistons machined? - 09/29/13 03:08 PM

Guess you did not like my previous suggestion to get quench and lower CR all in one. Don't even need to pull the motor.

Posted By: Leon441

Re: Anyone here ever have their pistons machined? - 09/29/13 05:39 PM

A thicker head gasket will lower compression, true. Don't know how much piston to head clearance you have. If you have a good PTH clearance like .050" or less. The easiest simple way is head gasket.

I never go the easy route as it usually does not give the most benefit. To cut a dish in your piston you need to have the material to do so and still have enough thickness. If you do have enough material that is the way to go but, be aware this will change your balance numbers.

If your head is open chamber design then the thicker gasket will be the way to go.

Leon

Posted By: Kern Dog

Re: Anyone here ever have their pistons machined? - 09/29/13 06:22 PM

Quote:

Guess you did not like my previous suggestion to get quench and lower CR all in one. Don't even need to pull the motor.

I don't want to appear ungrateful to anyones suggestions, it just worries me to go higher in compression to gain quench.

Posted By: dvw

Re: Anyone here ever have their pistons machined? - 09/29/13 06:25 PM

I don't know your combo. That being said if you now have .035-.045" quench currently, adding head gasket thickness to reduce compression may make detonation worse. If you have no quench now I would definitely go with a thicker gasket.
Doug

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 09/29/13 07:20 PM

Quote:

I don't know your combo. That being said if you now have .035-.045" quench currently, adding head gasket thickness to reduce compression may make detonation worse. If you have no quench now I would definitely go with a thicker gasket.
Doug

The problem is he doesn't have good quench and wanted to make it worse with yet a thicker gasket to lower compression.

Posted By: forphorty

Re: Anyone here ever have their pistons machined? - 09/29/13 07:44 PM

Has any chamber work been done? You could add a few ccs by blending and unshrouding. Something i would do anyway .

Posted By: BSB67

Re: Anyone here ever have their pistons machined? - 09/29/13 08:23 PM

Quote:

Quote:

Guess you did not like my previous suggestion to get quench and lower CR all in one. Don't even need to pull the motor.

I don't want to appear ungrateful to anyones suggestions, it just worries me to go higher in compression to gain quench.

That is not what I said.

This is what I said:
"Take the heads off and have someone with a cnc program (like MCH) cut the chambers to the desired cc's, and put it back together with the 0.027 gaskets."

You want 88 cc, they will cut the chamber to 88 cc., not mill the head.

Posted By: dvw

Re: Anyone here ever have their pistons machined? - 09/29/13 11:14 PM

Quote:

Quote:

I don't know your combo. That being said if you now have .035-.045" quench currently, adding head gasket thickness to reduce compression may make detonation worse. If you have no quench now I would definitely go with a thicker gasket.
Doug

The problem is he doesn't have good quench and wanted to make it worse with yet a thicker gasket to lower compression.

If the quench is poor already adding head gasket thickness won't hurt it. Am I correct in assuming this is an open chamber style head?
Doug

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 09/30/13 05:19 AM

Quote:

Quote:

Quote:

I don't know your combo. That being said if you now have .035-.045" quench currently, adding head gasket thickness to reduce compression may make detonation worse. If you have no quench now I would definitely go with a thicker gasket.
Doug

The problem is he doesn't have good quench and wanted to make it worse with yet a thicker gasket to lower compression.

If the quench is poor already adding head gasket thickness won't hurt it. Am I correct in assuming this is an open chamber style head?
Doug

No it's closed chamber wit hthe piston not at zero . He already put in a thicker gasket , I think .051, so he has .070ish no quench , and changed the cam ... still pings ...

Posted By: dvw

Re: Anyone here ever have their pistons machined? - 09/30/13 11:25 AM

So closed chamber with piston in the hole approximately .020". Using a .020" gasket ( how thick are the thinnest shim availible ?) would give .040" quench. Iron or aluminum head? I've had small blocks have less detonation with quench at 12-1 than w/o at 10.5-1. Would it work in this case? it would only cost the gasket set.
Doug

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 09/30/13 11:57 AM

Quote:

So closed chamber with piston in the hole approximately .020". Using a .020" gasket ( how thick are the thinnest shim availible ?) would give .040" quench. Iron or aluminum head? I've had small blocks have less detonation with quench at 12-1 than w/o at 10.5-1. Would it work in this case? it would only cost the gasket set.
Doug

Doug he has numerous threads on this over the past year or so, I didn't keep a scorecard

. Pretty sure the original combo had the .020 piston depth and .021 shim gasket with .509 MP cam and it pinged , it has spiraled out of control since ...

Posted By: B G Racing

Re: Anyone here ever have their pistons machined? - 09/30/13 12:56 PM

Quote:

Quote:

So closed chamber with piston in the hole approximately .020". Using a .020" gasket ( how thick are the thinnest shim availible ?) would give .040" quench. Iron or aluminum head? I've had small blocks have less detonation with quench at 12-1 than w/o at 10.5-1. Would it work in this case? it would only cost the gasket set.
Doug

Doug he has numerous threads on this over the past year or so, I didn't keep a scorecard . Pretty sure the original combo had the .020 piston depth and .021 shim gasket with .509 MP cam and it pinged , it has spiraled out of control since ...

Maybe he should look for other issues:
Timing not accurate,bad marks,box, dist and etc.
Too hot of plug.
poor fuel or lean condition
Cylinder head temperture
Oil detonating in cylinder..
If some of the information mentioned is correct with his clearences correct timing should cure the issue provided he doesn't have other issues.

Posted By: dogdays

Re: Anyone here ever have their pistons machined? - 09/30/13 03:10 PM

This subject has been beaten to death on the Q&A page.

R.

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 09/30/13 09:01 PM

Quote:

This subject has been beaten to death on the Q&A page.

R.

which is why it's moved to the race section ???

Posted By: GTX MATT

Re: Anyone here ever have their pistons machined? - 09/30/13 09:43 PM

Put a bigger cam in it

To answer the original question I've never had a set of pistons machined but its been done many times before

Posted By: mickm

Re: Anyone here ever have their pistons machined? - 09/30/13 09:52 PM

Quote:

This subject has been beaten to death on the Q&A page.

R.

yes, but he's looking for answers and now has moved it from a more general thread to a more specific one.

he has done many, many things to try and take care of this problem, and it's still haunting him, so he's just trying to get as much info as possible before making the next decision.

Posted By: Sledge_57

Re: Anyone here ever have their pistons machined? - 10/01/13 02:40 AM

Also it's now the "Unlawfl's Race & Engine Tech" section, so it belongs here.

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 10/01/13 02:41 AM

Quote:

Put a bigger cam in it

To answer the original question I've never had a set of pistons machined but its been done many times before

he did , it didn't make it any better

Posted By: Wedgeman

Re: Anyone here ever have their pistons machined? - 10/01/13 02:44 AM

Quote:

Quote:

Quote:

So closed chamber with piston in the hole approximately .020". Using a .020" gasket ( how thick are the thinnest shim availible ?) would give .040" quench. Iron or aluminum head? I've had small blocks have less detonation with quench at 12-1 than w/o at 10.5-1. Would it work in this case? it would only cost the gasket set.
Doug

Doug he has numerous threads on this over the past year or so, I didn't keep a scorecard . Pretty sure the original combo had the .020 piston depth and .021 shim gasket with .509 MP cam and it pinged , it has spiraled out of control since ...

Maybe he should look for other issues:
Timing not accurate,bad marks,box, dist and etc.
Too hot of plug.
poor fuel or lean condition
Cylinder head temperture
Oil detonating in cylinder..
If some of the information mentioned is correct with his clearences correct timing should cure the issue provided he doesn't have other issues.

I agree...! something Is wrong there....

My next choice would be to put a bigger cam to bleed off compression....if it is too high!

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 10/01/13 02:49 AM

Quote:

Quote:

This subject has been beaten to death on the Q&A page.

R.

yes, but he's looking for answers and now has moved it from a more general thread to a more specific one.

he has done many, many things to try and take care of this problem, and it's still haunting him, so he's just trying to get as much info as possible before making the next decision.

He been given a number of ideas on what to do, there are only so many choices and most/all require disassembly and spending money. He seems to looking for the EASY fix and the failed attempts haven't fixed it , nor were they FREE ...

He needs perfect quench to even get it to work , he won't deck the block and putting thicker head gasket in did lower the compression, but it didn't help.

Ok lets try a cam change , bigger off the shelf cam and no quench ... didn't work , maybe a CUSTOM cam might have worked ??

Have the heads CNC'd to make the chambers bigger , but can they get big enough to lower the compression so he can go back to the thin gasket for quench ... hasn't tried this yet ...

Next is mill the pistons , which mean disassemble and REBALNCE ... $$$$$$

If he is going to do the piston mill he should just call a Diamond WD and get a new piston that is at zero deck and has a D dish big enough to lower the compression ... then he can go back to his .509 cam ...

Posted By: B G Racing

Re: Anyone here ever have their pistons machined? - 10/01/13 11:58 AM

Any question no matter how many times it has been asked deserves an answer,ask enough people enough times you just may get lucky and find a solution.I would start a process of taking the different suggestions and through the process of elimination search for an answer.Start with anything easy and cheap that can be timing related before going the tear down big dollar route.

Posted By: Wedgeman

Re: Anyone here ever have their pistons machined? - 10/01/13 10:29 PM

Quote:

Any question no matter how many times it has been asked deserves an answer,ask enough people enough times you just may get lucky and find a solution.I would start a process of taking the different suggestions and through the process of elimination search for an answer.Start with anything easy and cheap that can be timing related before going the tear down big dollar route.

Most logical steps !

If it hasn't been done before........

Posted By: dOc !

Re: Anyone here ever have their pistons machined? - 10/01/13 10:34 PM

... it should be added ...if any machine work is done AFTER the ring grooves are cut ... SAID MACHINING should be done in very small cuts.

Posted By: Twostick

Re: Anyone here ever have their pistons machined? - 10/02/13 12:54 AM

When I built my 493 Ross didn't make a shelf stocking piston with a big enough reverse dome to keep my CR under 9:1. I asked about just taking the one they had and milling it to the desired size and was told it would seriously weaken the structure of the piston.

Given how light most forgings are now it stands to reason that they are engineered for max strength with minimum material already. I paid the extra charge for a custom piston.

Kevin

Posted By: JohnRR

Re: Anyone here ever have their pistons machined? - 10/02/13 01:32 AM

Quote:

When I built my 493 Ross didn't make a shelf stocking piston with a big enough reverse dome to keep my CR under 9:1. I asked about just taking the one they had and milling it to the desired size and was told it would seriously weaken the structure of the piston.

Given how light most forgings are now it stands to reason that they are engineered for max strength with minimum material already. I paid the extra charge for a custom piston.

Kevin

Ross mills the inside of the pistons to make them light so that is why they couldn't do it .

Posted By: cudadoug

Re: Anyone here ever have their pistons machined? - 10/03/13 01:40 AM

Timing curve, quench, plug heat range, air inlet temp, fuel temp all play a roll as well.

If you want an easy fix...octane boost or a few gallons of race gas splashed in...depending on how much you're driving it. Or...do you have E85 gas up there???

Another thought might be water/meth injection. I doubt the kits are cheap these days, but YEARS ago I made a water injection deal using the washer fluid reservoir/pump, a nozzle from a garden sprayer. Used a small vacuum switch to trigger the pump and viola! I had a zero decked, domed piston, 906 headed, 440 (MP .509 purple cam) on CA pump swill. Drove it everywhere!