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Minimum/maximum quench #2180552
10/22/16 10:40 PM
10/22/16 10:40 PM
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Interceptor72 Offline OP
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What do you guys recommend as the minimum allowable quench distance for a 440 (505 stroker)to avoid contact between the piston and head? Steel rods and probably a 5500rpm redline (but I'd like to be able to turn 6000 safely just in case.)

My problem is this: Got my assembled block back from the machine shop and they didn't zero deck it, even after I told them I wanted to know how far the pistons were in the hole before they finished it up...so that I could determine whether it needed to be zero decked or not. I guess I should have just told them to zero deck it no matter what.

Anyway, measured where the pistons are and they are all 0.011 and 0.012 except for one at 0.008 and one at 0.016 (kinda weird...must be a screwy crank?)

That puts me in a zone where there are no head gaskets available to get to the usually recommended 0.040 quench unless I buy a $175 set of Cometic gaskets...

Last edited by Interceptor72; 10/22/16 10:42 PM.
Re: Minimum/maximum quench [Re: Interceptor72] #2180563
10/22/16 10:53 PM
10/22/16 10:53 PM
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I believe .035 to an absolute max of .040 is very good quench & people have gone lower (tighter) especially with steel rods like you have with reasonable RPM limits like you plan. I have found gasket compressed stated distances to be inaccurate & to me it is worth it to waste a gasket to find out for sure. also a piston can rock some depending on piston to wall clearance. I would confirm your measurements & milling some of the pistons and milling the deck is an option.


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Re: Minimum/maximum quench [Re: Interceptor72] #2180569
10/22/16 11:12 PM
10/22/16 11:12 PM
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Are you using aluminum heads? If so then you want the Cometic gaskets anyway.

Re: Minimum/maximum quench [Re: Interceptor72] #2180616
10/23/16 12:27 AM
10/23/16 12:27 AM
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Piston to wall clearance and material play a big part in how tight you can run it. Cometic has a .027, .030 and a .036 compressed thickness. I'd recommend the .036 for your application. I'd rather have 040, but you'll have to cut the block and cut 7 of the pistons. Though you might try switching rods on the 008 and 016 cylinders to try and get them closer.
I know it's a lot more work, but I would rather have it the way I want it than assemble it as is and not be happy. Though you could run 030 gaskets if switching rods gets the two odd balls back in the same range.

Re: Minimum/maximum quench [Re: Interceptor72] #2180622
10/23/16 12:34 AM
10/23/16 12:34 AM
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Are the two weird deck height pistons on the same rod journal(throw), IE 1&2,3&4 and so on? If it is it may be the stroke on that journal, if they are not on the same rod throw then it is probably the rods being two different lengths shruggy I see that more than I like on new rods whiney
As far as the minimum quench I would shoot for .035 at the edge of the pistons and rock the piston over to each side of the cylinder walls and measure the deck height out there at the cam and outside block sides on every piston at the highest point scope I would try to have a max of .050 at the highest point also thumbs

Last edited by Cab_Burge; 10/23/16 12:39 AM.

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Re: Minimum/maximum quench [Re: AndyF] #2180630
10/23/16 12:47 AM
10/23/16 12:47 AM
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Originally Posted By AndyF
Are you using aluminum heads? If so then you want the Cometic gaskets anyway.


Yes, aluminum heads.
To be honest, i've used steel shims with aluminum heads (even though they say not to) and never had a problem.
But steel shims are out of the question now anyway, since they will put me under .030. In the past I've always used them to get my compression up on stock blocks.
I have a pair of the MOPAR shim gaskets and they are actually 0.017...I wonder how much the copper spray adds to the thickness? wink

Re: Minimum/maximum quench [Re: Interceptor72] #2180634
10/23/16 12:53 AM
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Maybe .0010 to .0030 confused Not enough to count on, buy the good ones now once and make sure your block and deck surfaces are smooth enough(50RA or smoother) to work with Cometics thumbs twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Minimum/maximum quench [Re: Cab_Burge] #2180640
10/23/16 12:59 AM
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Originally Posted By Cab_Burge
Are the two weird deck height pistons on the same rod journal(throw), IE 1&2,3&4 and so on? If it is it may be the stroke on that journal


yes...7 and 8. It's a K1 Technologies crankshaft...

I know this sounds cheesy, but for the 0.008 piston, I wonder if only a few seconds of sanding with a sanding block and some fine sandpaper would take off a few thousandths. We all sand on the combustion chamber of the heads, so why not the piston? ANd it could still be polished up shinier than new. It would stay flat and I bet that would make a few thousands disappear in no time.

If I get that one to .012 like most of the others, then the one at .016 is really no big deal... just slightly lower compression and no clearance issues. It's the .008 piston that's killing me in that getting quench right for that one compromises ALL the others...

Re: Minimum/maximum quench [Re: Cab_Burge] #2180643
10/23/16 01:04 AM
10/23/16 01:04 AM
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Originally Posted By Cab_Burge
Maybe .0010 to .0030 confused Not enough to count on, buy the good ones now once and make sure your block and deck surfaces are smooth enough(50RA or smoother) to work with Cometics thumbs twocents


Yeah, I think I really have no choice but to spend $$$ on the cometics at this point. ANything else will put me in the low .030s (shims) or over .050 (composites.) I guess I shouldn't be so cheap after all the other money I've spent so far. It's just that almost $200 for head gaskets (in a very mild street motor) hurts my sensibilities just a little...lol!

Re: Minimum/maximum quench [Re: dodgeboy11] #2180650
10/23/16 01:19 AM
10/23/16 01:19 AM
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Originally Posted By dodgeboy11
Piston to wall clearance and material play a big part in how tight you can run it. Cometic has a .027, .030 and a .036 compressed thickness. I'd recommend the .036 for your application. I'd rather have 040, but you'll have to cut the block and cut 7 of the pistons. Though you might try switching rods on the 008 and 016 cylinders to try and get them closer.
I know it's a lot more work, but I would rather have it the way I want it than assemble it as is and not be happy. Though you could run 030 gaskets if switching rods gets the two odd balls back in the same range.


I'll definitely swap the pitons/rods around on those two to see if I get an improvement, but I suspect the crankshaft.

1=0.011
3=0.012
5=0.012
7=0.016

2=0.012
4=0.011
6=0.011
8=0.008

They are Icon pistons and Scat rods.

Re: Minimum/maximum quench [Re: Interceptor72] #2180705
10/23/16 04:59 AM
10/23/16 04:59 AM
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I would definitely swap #7 and #8 to see if it is the rods, pistons or crankshaft stroke work
Let us know what you find thumbs


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Re: Minimum/maximum quench [Re: Interceptor72] #2180834
10/23/16 02:11 PM
10/23/16 02:11 PM
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It isn't stroke due to the oddballs being on the same journal, and you can't swap pistons due to valve notch arrangements, but switching rods might tell you a story.

Re: Minimum/maximum quench [Re: dodgeboy11] #2180841
10/23/16 02:25 PM
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as far as sanding if I did it I would put the sandpaper on a pane of glass then lightly move the upside down piston in a figure 8 pattern being careful to keep it held square to the work (wet the SP with solvent). I would confirm measurements then order Cometics that would give me .040 at the very very max for the widest one & no less than .030 on the on the tightest one (sand as needed). #1 #1 precision measuring. Holler how it turns out. EDIT use some very very fine grit paper

Last edited by RapidRobert; 10/23/16 02:26 PM.

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Re: Minimum/maximum quench [Re: Interceptor72] #2180847
10/23/16 02:37 PM
10/23/16 02:37 PM
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If you have not done so, double, or even triple check all of your measurements. I doubt that it is the pistons. Although it is certainly possible it is hard to believe an 0.008" difference between rods. That would be a little disappointing.

Re: Minimum/maximum quench [Re: dodgeboy11] #2180855
10/23/16 02:54 PM
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Originally Posted By dodgeboy11
It isn't stroke due to the oddballs being on the same journal, and you can't swap pistons due to valve notch arrangements, but switching rods might tell you a story.


Thanks for the heads up on those two points. I don't build engines (obviously) so I didn't think of that.
I'll just have to compare the rods.

You know, just looking at the numbers, it looks as though the block decks do slope downward towards the .008 piston and upwards toward the 0.016 piston. It's just the sudden difference at the last pistons...so maybe a slight slope in the deck compounded by some slightly different rods makes for such a big difference...error stacking.

Re: Minimum/maximum quench [Re: Interceptor72] #2180865
10/23/16 03:01 PM
10/23/16 03:01 PM
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Quote:
My problem is this: Got my assembled block back from the machine shop and they didn't zero deck it, even after I told them I wanted to know how far the pistons were in the hole before they finished it up...so that I could determine whether it needed to be zero decked or not.
You might consider having another shop remeasure everything, You need (& want) to know where the error is then you can make a practical plan to resolve it. You NEED the short block to be dead on then all the peripherals you add on and your fine tuning will give you a spot on eng with nothing left on the table. Any carpenter will tell you that the foundation is the most important part & when the house is built or even halfway built it is too late to correct things. You are in a perfect position to correct things NOW


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Re: Minimum/maximum quench [Re: RapidRobert] #2180866
10/23/16 03:01 PM
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yeah, I was definitely going to get something very flat and hard, and sand at right angles. That will keep it flat enough. I this is a deep dish piston...the guench area on the piston is actually quite small and only on one side.
If I was talking about a sealing surface or something that makes contact like that, I'd never try to sand it. But honestly, especially since I'm talking about removing a few thousandths...it would be difficult to do anything that would be very detrimental. Epecially compared to letting the piston slap the head...

Re: Minimum/maximum quench [Re: BSB67] #2180870
10/23/16 03:06 PM
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Originally Posted By BSB67
If you have not done so, double, or even triple check all of your measurements. I doubt that it is the pistons. Although it is certainly possible it is hard to believe an 0.008" difference between rods. That would be a little disappointing.


I did check everything twice and wrote it down, but just looking at my numbers today, I realize I didn't write down two numbers for the .016 piston. So I will double check that one today.
As for the .008 piston, got that same number twice. ALl the others I checked, got the same number or one within .001 the second time. SO I think I did it right...or at least consistently.

Re: Minimum/maximum quench [Re: RapidRobert] #2180871
10/23/16 03:13 PM
10/23/16 03:13 PM
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Originally Posted By RapidRobert
Quote:
My problem is this: Got my assembled block back from the machine shop and they didn't zero deck it, even after I told them I wanted to know how far the pistons were in the hole before they finished it up...so that I could determine whether it needed to be zero decked or not.
You might consider having another shop remeasure everything, You need (& want) to know where the error is then you can make a practical plan to resolve it. You NEED the short block to be dead on then all the peripherals you add on and your fine tuning will give you a spot on eng with nothing left on the table. Any carpenter will tell you that the foundation is the most important part & when the house is built or even halfway built it is too late to correct things. You are in a perfect position to correct things NOW


At the very least I am going to pull those two pistons and take them to another machine shop and have them double check the pistons, rods and bearings to make sure it's not them...or if there are any small differences, I can try to even things out a little.

Re: Minimum/maximum quench [Re: Interceptor72] #2180924
10/23/16 05:32 PM
10/23/16 05:32 PM
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I have ran as little as 28.. and it only touched when going over 8200 RPM.. this was a steel rod motor.. at 4.185 bore..


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