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FE Power Forums => FE Technical Forum => Topic started by: My427stang on February 15, 2019, 10:44:02 AM

Title: Has anyone gone sub-.040 quench distance?
Post by: My427stang on February 15, 2019, 10:44:02 AM

Cast SCAT crank and I-beam rods, 4032 11 cc dish piston, square decked iron block and heads, 6000 rpm max shift point, no rev limiter. Have not measured how much they rock in the bore, but should be minimal.  Street driven but might take a few runs down the track.

Trying to buy a little compression back, build was planned for a 8554 gasket, but if I go 1020 I can sneak up on compression a little, but quench goes to .036. 

I typically use .040 as a min, but see all kinds of crazy numbers out there, some much tighter than .036, thoughts?

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: KMcCullah on February 15, 2019, 11:08:38 AM

.036 quench is what my 416 has. Silv-O-lites .016 in the hole with .020 steel shim head gaskets. It runs great. But with as much rock as the pistons have, I'd be nervous with less quench.

http://fepower.net/simplemachinesforum/index.php?topic=4509.msg47481#msg47481

Edit: Just a thought here, Ross. I think some cheap compression could be had by getting away from the 1020 gasket. It's got pretty big fire rings. A nice fitting Cometic would be good for half a point I'd bet.

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: C6AE on February 15, 2019, 12:54:33 PM

I can tell you that it's not too bad, it sounds exactly like a rod knock *except it occurs when you let off the gas. 

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: Joe-JDC on February 15, 2019, 01:37:00 PM

I have personally pulled FE apart with .038" quench, and there were witness marks on the tops of the pistons and there was no carbon where the flat portion of the pistons had touched the heads.  Steel rods used to come with a warning to require a minimum of .050" on the clearance.  Aluminum rods required more because they grow more when hot.  Experienced FE racers used to say set the quench at .039", and timing at 41*, and drive it like you stole it.   Joe-JDC

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: Tommy-T on February 16, 2019, 12:11:53 AM

When there's a mirror image ".030" on the quench pad of the head matching the ".030" on the piston top...it's just right. The slugs stay REALLY clean!

Seriously, I've run a Badger rebuilder piston .010 out'a the hole on a long rod (352/360 rod) 390 with normal rebuilder Felpro blue head gaskets. Low rpm deal, no troubles.

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: bluef100fe on February 17, 2019, 03:25:32 PM

I’ve run 0.036 before. Pistons were nice and clean around the quench pad. What skirt clearance are you setting the pistons/block up for? 4032 alloy I believe can be run tighter than the old TrW’s I was using. If that’s the case then you should have less piston rock than I did. I don’t see a problem, I’ve heard of guys running tighter than this with steel rods and tight skirt clearances but 0.036 is as far as I’ve pushed it. Assuming your bore size is in the 4.08ish area... bigger the bore,shorter skirt, and longer the stroke might need a little more room. Good luck with the build.

Title: Re: Has anyone gone sub-.040 quench distance?
Post by: machoneman on February 17, 2019, 06:47:09 PM

If street driven as you say with only a few track runs, stick with .040 or so and sleep well!