Quench

[Jim Comet]

Hey guys,  I am putting my 416 back together. After machining, my pistons stick out .008-.009. This is a drag only motor. It is a mirror 105 block, w/RPM steel crank, Molnar rods and Mahle pistons. It has aluminum heads. My head gasket choices are .045 and .051 compressed thickness. Do you think I would be rolling the dice using the .045? I know the .051 is the safest route. Just trying to get the most out of this motor but not blow it up on the first pass!!! I will be turning this motor between 6700-7000rpms thru the traps. Thanks, Jim

[JimNolan]

I ran a .031" quench on a 390 with no problems. I did put a custom cam in it to enable me to run mid-grade gasoline. It had 10.7CR and 81DCR.

[blykins]

I've ran .035" piston/head clearance before and it was starting to knock the soot off the pistons at that distance.

If you're .009" out, a .051" head gasket will be just fine. 

[frnkeore]

How are you gauging the head gasket thickness and what head gaskets will do you have?

[Jim Comet]

I have Edelbrock's with 56cc chambers. I am going to run E85, so running the .045 Cometic MLS head gasket would give me a little more compression. If you suspect I would see piston to head contact with .036-.037 clearance I would just get the .051. I wish they made a .048. Jim

[1968galaxie]

What the heck. Run it tight with the thin gasket.
Rev the hell out of it when back together.
Will be a great experiment (that we don't have to pay for).
If it survives we then know how tight we can run an FE.

All kidding aside - the "increase" in compression ratio with a 0.006" change in quench will not be worth even 1 HP.

Like bearing clearance - a little looser will not hurt. A little too tight will break things.
Your money - you choose.

[frnkeore]

I have Edelbrock's with 56cc chambers. I am going to run E85, so running the .045 Cometic MLS head gasket would give me a little more compression. If you suspect I would see piston to head contact with .036-.037 clearance I would just get the .051. I wish they made a .048. Jim

Actually, I think you will be fine with .036 quench. I was asking because some specs on production head gaskets aren't accurate but, I'm sure the Cometic specs will be accurate.

BTW, Fords spec for the '58 300 hp 352 was .036 (1.875 CH piston and a .031 gasket).

[blykins]

When you get down to that level, you have to measure every piston and make sure that piston rock won't be a factor.  A 1.920" piston will rock enough to touch at .035".  A 1.175" piston will rock enough to touch with more than that.   Just depends on the combo.

Ford had trouble machining a block within .020".  I would venture to say that most of the pistons were not sitting perfectly at .005" in the hole. 

[Tunnelwedge]

Ford had trouble machining a block within .020".

BS

[blykins]

Ford had trouble machining a block within .020".

BS

Well, I've seen quite a few and have no reason to exaggerate.  I've seen factory blocks and aftermarket blocks that were off .020" (and worse) from end to end on one deck. 

Matter of fact, Ross posted on one 428 block the other day that had a high deck height of 10.183" and a low deck height of 10.155".

So sorry, yes I was wrong.......it was more like they couldn't machine a block within .028". 

Nothing like having 10.5:1 compression on one end of the engine and 9.9 on the other........ROFL

[Tunnelwedge]

Ford had trouble machining a block within .020".

BS

Well, I've seen quite a few and have no reason to exaggerate.  I've seen factory blocks and aftermarket blocks that were off .020" (and worse) from end to end on one deck. 

Matter of fact, Ross posted on one 428 block the other day that had a high deck height of 10.183" and a low deck height of 10.155".

So sorry, yes I was wrong.......it was more like they couldn't machine a block within .028". 

Nothing like having 10.5:1 compression on one end of the engine and 9.9 on the other........ROFL

Still BS.

[blykins]

Yeah, I honestly don't really care what you think.   I mean, you offered such a strong counter-argument and everything (obviously, that's sarcasm), but I still just.... don't.... really.... care.   

[My427stang]

Ford had trouble machining a block within .020".

BS

Well, I've seen quite a few and have no reason to exaggerate.  I've seen factory blocks and aftermarket blocks that were off .020" (and worse) from end to end on one deck. 

Matter of fact, Ross posted on one 428 block the other day that had a high deck height of 10.183" and a low deck height of 10.155".

So sorry, yes I was wrong.......it was more like they couldn't machine a block within .028". 

Nothing like having 10.5:1 compression on one end of the engine and 9.9 on the other........ROFL

Still BS.

The only way you'd know before assembly is to accurately measure with a BHJ fixture or scope it on a CnC.  Here is one block I am doing now,  left and right from a CnC scope referenced off crank centerline. 

Hard to call it BS, it's a date coded original standard bore CJ too, had Ford std bearings in it, so not some leftover late industrial run.  Of course some twist could be from a hard life, but not that amount of difference on a front to back run.  This is the kind of stuff we commonly see.  I can dig up a few others

[1968galaxie]

Tunnelwedge must have been born on the moon - or has zero experience with FE blocks.
I have seen several that had end to end and side to side issues - as Brent has mentioned.
And I haven't worked on many - certainly far, far less than Brent has.
FE blocks from Ford were nowhere near parallel or square - and it didn't matter for 8.5:1(9.5:1 LOL 2bbl) and 9.5:1 (10.5:1 LOL 4bbl) FE's.

[frnkeore]

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.