Quench

[blykins]

In Brent's defense, my 361 Edsel block was off .018 across the deck and cleaned up at 10.172. It had the same quench as a '58 352 but the heads had no evidence of contact of any sort and would have had a min quench of .038.

But, Ford would NOT have release a engine with a nominal .036 quench if it would not be enough, period. 5 yrs later they built a all aluminum SBF, reliable enough to finish the Indy 500.

Now, if Ross's engine, that had a deck height of 10.155, had been assembled with a nominal .036 quench, It could not have left the assembly line so, it would have never made it to the street.

Last, it is my recollection (please correct me, if I'm wrong) that the the engine that Brent ran .035 quench on, was his JJ, 352 and he had aluminum rods in it (most high strength alum expands at 3 times the rate of steel). It didn't make any noise and didn't hurt anything, either.

Steel rods. Molnars.

Barry has seen the same thing as me.....contact marks at around the .036-.037" mark. 

[1968galaxie]

Quench numbers of 0.036" and factory cast pistons - with cast piston tight clearances and low sub 5000 rpm use certainly might be survivable.
Add RPM, add forged piston clearance, and one just may have a disaster waiting to happen.
Why take a chance?
Like I said - its not my money.

[Barry_R]

I suppose I can add to this - back up what has already been said.
While doing EMC engines I was chasing any possible advantage - and "everybody said that tight quench was "the ticket".

I had one package with .036 piston to head and it ran really well.
On disassembly many of the pistons had zero carbon on the quench and you could clearly see the machining marks from the head deck mirrored on the piston.
Also visible were very small raised burrs inboard of the quench pad - indicating head contact.
In talking to some pro level race folks they said that light contact would upset the rings and you could see it on vacuum - probably cost some small increment of power.

A later effort had me bring the piston well above deck, and using a rather thick and slightly small diameter Cometic gasket to hit an .037 target.
Idea was to bring the ring up as high as I could to the more rigid top of the bore, and reduce crevice volume.
Do not know if it was worth the work, but that one also ran pretty damn well.

A shorter compression distance is more forgiving - shorter roll couple rotating around the pin centerline on turnaround.

BTW - OEM deck heights and chamber volumes are darn near random numbers.
I have observed unmodified engines that were way, way off.

[Jim Comet]

Thank you everyone. It sounds like the consensus is use the .051 gasket and not worry about it. I really appreciate all of your thoughts and experience with this. Jim

[blykins]

Somebody from Nova Scotia owes me an apology for their belligerence.

A big news headline:  Ford's machine work from the 60's was nothing to write home about.  I'm sure they had nice drawings....they just couldn't follow them.  Deck surfaces that are .020" off from end to end, cam tunnels that are not straight, pan rails that are not flat.  Grab several sets of 427 MR heads, TP heads, or HR heads, and pour some chambers.  If two pair of the same kind are within 10cc of each other, I'd be surprised. 

[Tunnelwedge]

This .020" you keep quoting is the high end of the spec.
If you would read the drawing and have an understanding of how the block was machined
you might be more informed.
This prefect parallel main and cam bores was not a spec Ford measured nor could they with 1956 tech.
Robot CNC lasers were not in vouge then.
FE's are thin wall casting and are prone to flexing, sometimes massive flexing.
Heating and cooling cycles will hold the flex as time and creep goes by.
We are lucky Ford did such a great job casting these blocks.
You can make 500 HP with pretty much any FE block.
My geny was cast with super thick walls to stop flexing. Seems to be working.
I owe you nothing. Stop spreading BS.

[WConley]

My untouched Ford cammer block was way off square when I had the shortblock rebuilt.  One deck was 0.026" off, so I believe what Brent is saying. 

I also worked in a Ford engine plant.  The maintenance on the big machines was minimal at best!  Often we had parallel machining lines and when one went down we would scrounge used spare parts from the other one to get running again.

[My427stang]

As far as the quench discussion, glad to see no attempt to make it too tight.  I think for most .040-.050 is plenty for the squish benefit, and I regularly run them proud with a 8554 and some even taller if we are trying to keep intake dimensions on the rare stuff.  Even comparing .045 or so to .036 I'd expect no gain and only added risk.

In terms of the machining, geez Howie, Brent was right, said Ford was all over the place, and then you come back with Ford couldn't hold a spec with their tech at the time, that is EXACTLY the point.   Who cares what the spec is if the machine can't hold it anyway?  Brent didn't say that the machinists were evil or FOMOCO was playing a trick on us.  I'll add that valve centerline, bore centers, cam bore dimensions are all over the place too once you start measuring.

Additionally, no doubt things flex with heat cycles, I am not sure what you mean by massive flexing, I don't agree with that, an FE is pretty forgiving on head gaskets even fewer head bolts than modern engines.  Although anything can move, they don't change .026 from end to end and grow .010 over deck height.  That's a crank centerline or deck machining issue that causes that much variance, and the numbers can tell you which it was.

Square deck a block or two, you'll see things, square deck 20, you can really see the trends.

[blykins]

As far as the quench discussion, glad to see no attempt to make it too tight.  I think for most .040-.050 is plenty for the squish benefit, and I regularly run them proud with a 8554 and some even taller if we are trying to keep intake dimensions on the rare stuff.  Even comparing .045 or so to .036 I'd expect no gain and only added risk.

In terms of the machining, geez Howie, Brent was right, said Ford was all over the place, and then you come back with Ford couldn't hold a spec with their tech at the time, that is EXACTLY the point.   Who cares what the spec is if the machine can't hold it anyway?  Brent didn't say that the machinists were evil or FOMOCO was playing a trick on us.  I'll add that valve centerline, bore centers, cam bore dimensions are all over the place too once you start measuring.

Additionally, no doubt things flex with heat cycles, I am not sure what you mean by massive flexing, I don't agree with that, an FE is pretty forgiving on head gaskets even fewer head bolts than modern engines.  Although anything can move, they don't change .026 from end to end and grow .010 over deck height.  That's a crank centerline or deck machining issue that causes that much variance, and the numbers can tell you which it was.

Square deck a block or two, you'll see things, square deck 20, you can really see the trends.

Howie can't see logic for rage.  It's ok, I got him dead to rights with a simple observation that apparently all of us have seen, except for him.  My favorite part is that he calls bull on my saying that they're out .020", but he agrees that it's the high end of spec and then gets mad at me again.  Poor Howie. 

Oh, and his heating/cooling cycles argument isn't valid either.  I've had some NOS blocks come through that were still in the crate and were still way off. 

[Tunnelwedge]

Massive flexing.
It flexed so much the #2 cam journal cracked and the cam bearing started walking out.
You put enough juice into an FE block and you can pull the guts out of it.
Ford never square decked any FE block. It was not a requirement or a specification.
They all run just fine without it.
Complaining today that they are not square decked is the definition of BS.
Way off what. Your spec. Get real.
It ran off the line that was the spec. That's real.

[My427stang]

That could as easily be a poorly machined hole, the wrong bearing, or a cam bearing driven in too far, bad balance job, or just a weak block pushed too far, I don't buy it one bit as flex in the deck.

Build to 60s standards, you get 60s performance, but today you spend 2024 money to pay for it...very bad advice for customer wallets

One last comment on edit - we don't complain they aren't square, we fix them.  Is there any reason in your mind we shouldn't?

[blykins]

Hey if Ford ran them with a half point of compression difference from front to back, we can too……ROFL

Ford ran rope seals and oil bath air cleaners.  I guess that’s “real” too and what we should all aim for.  I mean they did it that way in the 60’s, why should technology improve on anything?

[frnkeore]

Brent, I went back and read the JJ thread and in it you purchased a set of aluminum rod for JJ and said you were going to install them. That's why I remembered that.

I'm now curious as to the deck height and head gasket you used. When I bought the adapter and TR, I asked you what deck height you used on it (for reference on gasket fit) and if it was your normally std 10.150 DH and you said, yes. Did you also use the 1020 head gasket that you use a lot?

[Falcon67]

BTW - OEM deck heights and chamber volumes are darn near random numbers.
I have observed unmodified engines that were way, way off.

Having measured and paid for machining of several "as Ford built" 351C and 302 blocks and iron cylinder heads from the 60s - yep.  Published specs are "nominal" at best. 

351Cs - "four-barrel upgrades over the two-barrel engines were stainless-steel head gaskets, higher valve lift (an increase of 0.025-inch intake/exhaust), a different combustion chamber with quench area yielding an 11.0:1 compression ratio, and dual exhaust. "  11:1?  Um, not so much.    Measured one of those "11:1" motors before updating - try 9.99:1.  But lets not let data get in the way of a good argument.   

[pbf777]

351Cs - "four-barrel upgrades over the two-barrel engines were stainless-steel head gaskets,.......................

     From the O.E.M. originally?    Do you mean a stainless steel vs a carbon steel core of a composite type gasket, or are you implying a stainless steel shim type gasket?   

     Scott.