Head gasket decision

[jayb]

It can be real difficult to measure deck clearance accurately in the block, it certainly can be and is regularly done, but I think that it would be just as easy to start discussing deck heights and make sure the machinist is machining off crank centerline (as opposed to deck reference) and hitting a target number based on your measurement

Ross, I can't imagine not machining a deck off the crank reference.  All the tooling I've ever seen for deck machining bolts a bar into the main saddle, with a plate that indexes off the bar and the cam bore, and provides flats that are parallel to the deck surfaces.  The block sits on the bar in the machine that cuts the deck, automatically making the deck parallel to the crank centerline.  (There are some pictures of this setup in my low buck 390 article in Car Craft.)  Have you seen decking a block done off a deck reference?  I don't know how you would set that up...

Carl, I previously gave the static and dynamic CR numbers with the 0.027" head gasket; I edited my previous post to make that more clear.  I have a spreadsheet that calculates static and dynamic CR, but it is based off the calculator that Ross referenced earlier, so you should be able to just use that one.

[My427stang]

Ross, I can't imagine not machining a deck off the crank reference.  All the tooling I've ever seen for deck machining bolts a bar into the main saddle, with a plate that indexes off the bar and the cam bore, and provides flats that are parallel to the deck surfaces.  The block sits on the bar in the machine that cuts the deck, automatically making the deck parallel to the crank centerline.  (There are some pictures of this setup in my low buck 390 article in Car Craft.)  Have you seen decking a block done off a deck reference?  I don't know how you would set that up...

I only saw it once, it was in a very old shop where they would mount the block in a cradle, level the deck, then the head would pass across the top. They would unbolt the block and turn it, then level it again for the other side.  It was a good shop in it's day, hopefully people aren't doing it that way anymore.  Maybe not an issue anymore, but when I hear of someone assembling an engine to figure out deck clearance, I always wonder if the machine shop isn't setting up to a standard and squaring the decks and just lopping off the top.

I have also seem many shops, albeit again older ones, bore using a deck reference too.  In fact, I didn't know any better until I was in my 20s as the local shop always did that and we built some very nice, if not modern level high powered engines.  In fact, the shop defended it by saying it took the least amount of cylinder wall away.  Unfortunately who knows where those bores really were when finished if not referenced off the crank.

[63.5xl]

Ok, I am adding things up and to spend that much money I am thinking I need to find another block. A fiend of mine thinks he know where there are a couple of std 390 blocks, so maybe put this money in a std block, if it need bored which it probably will I could do all this on a .030 block instead of a .060 block.
What could I do with what I got. Beside different pistons and more machine work, I could save the 291 cam for the other engine. Would one of comp cams worth with what I got better?

[My427stang]

Run the shim gasket and advance the cam to 103 (assuming you already have a 9 position gear)

If not, just run the shim gasket and run it lined up dot to dot.  It'll run great, just giving up some power.   You will likely want a quicker timing curve if the DCR is low, but it'll run fine.

You could also go with a 268H or 270H comp with the .027 gasket.  It'd be a nice runner but sound a little less rowdy than what you have

[63.5xl]

I had sent the distributor to Faron and he set the distributor  up for 36 total all in by 2900 and run 14 to 16 initial. What about the 270S. I have factory adjustable rockers, just for the old solid sound. With that low of DCR would it run on 89 octane or stick with 91?

[My427stang]

BTW, I ran my first 427 in my Mustang at over .100 below deck, with a 300 adv/250@.050 cam, Portosonic intake, close ratio 4 speed, 3.70s and an 850 double pumper, it wasn't the fastest 427, but it sounded it, was dead nuts reliable and brought me all over CA and NV

So I cant say I'd start with a clean slate and have a ton of quench and too much cam, but it doesn't make them fragile either.  Sometimes just assemble, run it, enjoy the car and plan for the next one.

[My427stang]

The 270S would work well too

With static and DCR that low, it'll likely run on any pump gas assuming it's not too hot or too lean

[63.5xl]

Ross, what would the static and dynamic ratio be with that 270s cam and the .027 gasket with 4.165 bore? I used the Pat Kelly Chart and got 9.764 for the static ratio, but where is the dynamic ratio? I must be doing something wrong with the chart cause he says the dynamic is in green but mine says static.
I used 12 cc for my dish and .031 piston to deck clearance, I used the 61 degree closing on the intake and 270 duration. However Comp list the intake closing at .0006, did I do it right. Where do I figure out the dynamic ratio?
Would you install the 270s cam dot to dot. I do have a 9 keyway crank gear.
Carl

[turbohunter]

Now, 10.160-10.154 gives you .006 deck clearance and then you can use your common Felpro 1020 @ .041, or talk to Marc here on the forum and get an SCE small bore at .041 or wherever it is.  I have some on the shelf, but I don't have the bore size and exact thickness here to calculate.an stop there, what's getting you now is the long intake ramp, both options above are real good, I like the 10.155 option above a smidge more, but you could even make a little more vacuum and torque by advancing the cam to 103 ICL.  That would put you at 7.78 DCR

To be honest, I'd likely go with Marc's stroker gasket and a 10.160 deck with the cam on 103 for a street car, especially if it was a close ratio tranny, mostly let things fit a little better and get a little more low end for the tall first.  If the owner wanted as much part throttle torque as we could, I'd do the 10.155 deck

With Marc's gasket, you'll gain compression to the tune of about a 10th, so still in the ballpark

Thanks for that Ross.

63.5xl here is a link if you want to check out the gasket Ross recommended.
http://scegaskets.com/store/ford/ford-fe/ford-fe-head-gaskets/performance-composite-head-gaskets-for-ford-fe/

BTW
Ryan tells me the big bore tooling is in the schedule for that gasket.
Also said stocking in a couple thicknesses is not a problem.

[My427stang]

Ross, what would the static and dynamic ratio be with that 270s cam and the .027 gasket with 4.165 bore? I used the Pat Kelly Chart and got 9.764 for the static ratio, but where is the dynamic ratio? I must be doing something wrong with the chart cause he says the dynamic is in green but mine says static.
I used 12 cc for my dish and .031 piston to deck clearance, I used the 61 degree closing on the intake and 270 duration. However Comp list the intake closing at .0006, did I do it right. Where do I figure out the dynamic ratio?
Would you install the 270s cam dot to dot. I do have a 9 keyway crank gear.
Carl

Input the info on the main page first (compression info) then hit calculate
Then input the cam info using the .006 data, then hit calculate
Then go to the remaining tab and put in stroke and rod length and hit calculate
Then go back to the compression page and click the box next to stroke and hit calculate, the DCR will be listed where you read SCR

[63.5xl]

Ok Jay and Ross,
I found out today the machine shop I used did not square deck the block, he apparently just made a flat service out of what was there.I decided to check the deck clearance one more time to tell them how much to take off. The last time I checked I just used #1 hole and it measured .031, this time I measured #1, #4, #5 and #8.
#1  = .031
#4  = .022
#5  = .021
#8  = .027
 I did not know at the time either, I remember asking him what the deck was now and he said he had no way of measuring it but he thought he took off about .005. I keep learning these lessons the expensive way.

I guess if I can find a shop around here that can go off the main saddle I think they should be able to cut the big end on each side and daylight out to the small end which I think would be taking off roughly .010 which would put all these dish pistons at .021.

Carl