Author Topic: Head gasket decision  (Read 9291 times)

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63.5xl

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Head gasket decision
« on: December 22, 2015, 10:04:29 PM »
So I went to the united engine site and used their calculator with my cam info and come up with all the following head gasket info:
Running 91 Octane, the best we have here, in my 390 Galaxie, What would you go with? These are all with a 12 cc dish. If I go with a flattop it starts out with the .051 gasket at 9.879 static and 8.528 dynamic. These pistons are the 1.759 compression distance.
Changed gears since my last post. 3:70 gears, 29 inch tires, 4 speed

Brand           Compressed Thickness           Gasket Bore          Quench             Static Ratio              Dynamic Ratio
Felpro                        .051                              4.250               .082                    9.255                        7.999

Felpro                        .041                              4.4                  .072                    9.393                        8.116

Cometic                     .040                              4.250               .070                    9.473                        8.184

Cometic                     .040                              4.165               .070                    9.504                        8.210

Edelbrock                  .038                               4.4                  .069                    9.457                        8.171

Mr Gasket                 .038                               4.4                  .069                     9.457                       8.171

Cometic                    .036                               4.4                  .067                     9.501                       8.208

Cometic                    .036                               4.360              .067                     9.516                       8.221

Cometic                    .036                               4.250              .067                     9.553                       8.252

Cometic                    .036                               4.165              .067                     9.584                       8.278

Cometic                    .030                               4.4                  .061                     9.634                       8.321

Cometic                    .030                               4.250              .061                     9.679                       8.359

Cometic                    .030                               4.165              .061                     9.705                       8.381

Cometic                    .027                               4.4                  .058                     9.702                       8.378

Cometic                    .027                               4.250              .058                     9.744                       8.414

Cometic                    .027                               4.165              .058                     9.767                       8.433

Mr Gasket                 .020                               4.420              .051                     9.862                       8.514

Thank you for the help
Carl
« Last Edit: December 22, 2015, 10:46:51 PM by 63.5xl »

My427stang

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Re: Head gasket decision
« Reply #1 on: December 22, 2015, 10:53:38 PM »
What are you using to calculate dynamic?  What are the specs you are using?

Also, are the surfaces freshly cut?  Are the decks square?

I personally like to see the tightest quench I can, but your dynamic numbers look different than what my calculator generally gives, and any calculator is only as good as the history you have with it

Bottom line, if newly cut surfaces, I'd go the tightest MLS gasket or maybe even shim with sealer to stay at .060 or less, although I generally shy away from shims.

If not a fresh surface, I'd likely pick the tightest standard gasket, but I'd like to run your numbers for a real recommendation
---------------------------------
Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

63.5xl

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Re: Head gasket decision
« Reply #2 on: December 23, 2015, 12:27:09 AM »
I had the blocked decked just enough to to square it up, I am using this calculator,

https://www.uempistons.com/index.php?main_page=calculators&type=comp

It is asking for my intaking closing which is 38 degrees and add 15 to it so I am using 53. The .031 deck clearance I measured with the piston, a sealed power h304p that measures 12 cc of dish and I had my head cc'd and it come up to 69cc

My427stang

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Re: Head gasket decision
« Reply #3 on: December 23, 2015, 07:47:32 AM »
I think those of us that use DCR as one in a set of tools often use this one

http://cochise.uia.net/pkelley2/DynamicCR.html

You can download his program at the bottom.

The problem with multiple calculators is that they all do the interface slightly different, like for yours, it forces an assumption of advertised duration.  In any case, once someone has multiple builds using one, then, within reason, they can make assumptions on the next one. Unfortunately I don't have experience with yours, I cannot replicate the static numbers with your data and the DCR numbers it is generating seem too high, if correct it would be especially bad for a loose quench, but my hunch is it's the calculator not the compression

In the end, though, it does sound like the tighter you can make the quench, the better

Guessing at your cam as a 270H with the intake valve closing, calculating .021 below deck with a 10.160 block and the numbers you provided, and using the thinnest MLS with the 4.165 bore, I am getting 9.84 static and an 8.06 DCR with .048 quench, which is a nice street setup.  FYI the quench distance came up using a deck of 10.160, then the stack of 1/2 stroke, plus 6.49, plus your compression height. 

I can check back after work and see what the real cam and deck height is is and see where you are, but assuming the advertised duration is not shorter than 270 @ .006, I'd run the MLS at the bottom.  Compression is power and quench will help more than the compression will hurt

However, don't just use my assumptions, unless I got lucky and they are all right LOL

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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

63.5xl

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Re: Head gasket decision
« Reply #4 on: December 23, 2015, 12:07:46 PM »
The guy who squared the deck on my block only took .005 he said, the piston I M using H304 P has 12cc dish and 1.759 compression, it measures .031 in the hole. The cam is from Scot at Cam Research:
      Hydraulic Camshaft data

Lift                           In 540 Ex 565
Advertised duration In 291 Ex 298
Duration @ .050       In 226. Ex 234
                 Valve Timing
                   Open.           Close
Intake      BTDC     8      ABDC   38
Exhaust.  BBDC   52     ATDC     2
 
Lobe separation       109
Intake centerline.    105

4 degrees advance built in
Install straight up


  Recommended Valve Spring Data
Installed Ht    1.800       Lbs   115
Open Ht         1.200       Lbs   315




« Last Edit: December 23, 2015, 12:22:02 PM by 63.5xl »

jayb

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Re: Head gasket decision
« Reply #5 on: December 23, 2015, 02:22:33 PM »
Hi Carl, like Ross says we need some more specifics.  If you will provide them we can calculate DCR for you, and then make a more informed choice on the head gasket.  I am also suspicious of the DCR numbers you are getting; here's why:

Most DCR calculators, including the one I use, require advertised duration, not duration at .050".  What you are looking for is the point where the intake valve closes completely.  The DCR calculator you are using is estimating that, by having you add 15 degrees to your duration @ .050" number.  This might be pretty close for a cam with a very aggressive ramp, but your cam has fairly gentle ramps.  You have 291 degrees of advertised duration, and 226 @ .050".  This is a difference of 65 degrees.  Half of that is on each side of the .050" lift value, so in your case you should be adding 32.5 degrees to your intake closing point, not 15 degrees.  This is going to give you a completely different number for DCR.  By the way, if you add up the intake opening and closing points from your cam specs (8 + 180 + 38), you will see that this is for the duration @ .050", not seat to seat.  So, at 38 degrees ABDC, you still have .050" of lobe lift, and about 0.085" of valve lift.  Even if you add 15 degrees to this, you are still probably at .025" or so of cam lift, and .045" of valve lift.  Still quite a bit of air leaking by that valve.

Post the following information and I can do a DCR calculation for you:

- Bore
- Stroke (if stock, this is 3.780")
- Rod length (if stock, this is 6.488")
- Pin Diameter (if stock, this is 0.975")
- Combustion chamber volume in cc

You've already provided the rest of the information needed (cam specs, piston dish volume, compression height, etc.)


Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

My427stang

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Re: Head gasket decision
« Reply #6 on: December 23, 2015, 04:18:43 PM »
I'd go with the small bore Cometic on the bottom of the list.  Static is 9.4:1,  DCR is closer to 7.33 with my calculator, it'll run fine, but you are leaving a power on the table compared to something closer to 8:1 DCR.  The shim gasket is good too, but the big bore doesn't help you much, it turns out to be 9.73/7.4

If you haven't assembled yet, you could also go with a more modern piston, cut the deck more to raise compression and tighten up quench, or even cut the heads a little if you wanted a bit more torque.   

In the end, those pistons are hurting you. They are just deep in the hole
---------------------------------
Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

63.5xl

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Re: Head gasket decision
« Reply #7 on: December 24, 2015, 12:08:44 AM »
Bore is 4.110
Stroke 3.78
Rod 6.488
Pin   0.975
Head chamber  69cc
speed pro H304P has 1.759 compression distance and 12 cc and it measure .031 in the hole when I mocked it up.
And Yes the engine is still all apart. Only thing that is done to it is the block bored, block decked square and cam bearings installed.
What about the different piston, what do you guys recommend?  Maybe the L2291 speed with 10cc and a 1.776 compression height?
The flat top speed pro H395p is the same compression height as I have, 1.759, with 6cc.
The Keith Black I found were either Flat step or dish step except for the 1.760 compression height Keith black.
Thanks again for the help.
Carl
« Last Edit: December 24, 2015, 01:23:27 AM by 63.5xl »

ScotiaFE

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Re: Head gasket decision
« Reply #8 on: December 24, 2015, 08:05:43 AM »
If you have the option to put the piston higher than you should.
The closer to the deck the better.
I ran those L2291 for a number of years using 91 pump and they look perfect on the tops
after I pulled the heads. Short block is still together.
One issue you will find is the black coating will make your oil look black.
Not a big issue for me.

My427stang

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Re: Head gasket decision
« Reply #9 on: December 24, 2015, 09:30:23 AM »
My recommendation is a big "it depends"

I'd like to see you with tighter quench and more compression for the cam you are using.  However, if this is just a fun weekend driver, you could get away with what you have and just advance the cam a little, maybe cut the heads, and expect that it won't like a quick advance curve.

With the checkbook open, I'd likely go with the 2291s, they should be about .017 below without a cut, then take .010 off the block. (Although I hate saying what to cut off the block, I'd much rather say square deck at 10.155 or 10.160 or whatever the target is)

Hate to make it sound like I am changing my tune, but engines don't have to be completely optimized if that is not the goal.  Sometimes it's easy to scare someone or spend their money, how hard do you intend to work this car and how will it be used?  Maybe .010 off the heads to get compression up, run the thin gasket, and put the cam at 103?  Cheaper, you lack the quench benefits, but watch the curve and engine temp and they'll run
---------------------------------
Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

jayb

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Re: Head gasket decision
« Reply #10 on: December 24, 2015, 09:51:05 AM »
I get a static compression ratio of 9.5:1 and a dynamic of 7.23:1 with the .041" head gasket, using your numbers.  For sure go with the .027" head gasket that Ross suggested; that bumps the numbers to 9.78:1 and 7.43:1.  It will also decrease your quench to 0.058", assuming your measurement of piston top to deck is accurate.  (Using the other numbers, stock FE deck is 10.170", cut 0.006" is 10.164", then subtract 1.759" compression height plus rod length + 1/2 the stroke is 0.027", so you are certainly close.  Maybe the deck was only cut 0.002"?). 

You would really like to have more like 0.040" quench and probably 7.75:1 or higher dynamic compression ratio.  If you went with the L2291 pistons, assuming you pick up the difference in compression height (0.017"), and the .027" head gasket, your quench would then be 0.041", which is about perfect.  Static CR and DCR would be 10.35:1 and 7.85:1, respectively. 

Either way will work, but the engine will be stronger with the L2291 pistons.
« Last Edit: December 24, 2015, 02:53:07 PM by jayb »
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

63.5xl

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Re: Head gasket decision
« Reply #11 on: December 24, 2015, 10:07:16 AM »
Ok, I think I will get the 2291 pistons then, what about my fresh bore with the 2291 pistons since it was bored for the H304p cast? The good thing is that both pistons take 5/64 in. x 3/32 in. x 3/16 in rings which is what my hasting moly rings are.
Going with the 2291 piston what would be the ideal head gasket?

jayb

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Re: Head gasket decision
« Reply #12 on: December 24, 2015, 10:14:58 AM »
I'd still use the 0.027" Cometic; that would give you the 0.041" quench distance.  On the pistons, find out what skirt clearance the shop honed to for the cast pistons, and see if that will work with the recommended skirt clearance range of the L2291s.  You may have to hone the bore out a few thousandths...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

63.5xl

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Re: Head gasket decision
« Reply #13 on: December 24, 2015, 11:59:31 AM »
What do you have the ratios at now goin with the 2291 and the .027 gasket. Maybe the deck was only cut to .002 as as temporary put the crank, bearing and one piston in after and it measured .031 with the depth mic.
What formula are you using for the compression ratios Jay, so I can figure out myself next time without bothering you?
Thanks again for the help everyone and Merry Christmas!
Carl

My427stang

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Re: Head gasket decision
« Reply #14 on: December 24, 2015, 12:34:42 PM »
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 measured pieces

With the 2291

Stack height = 1/2 stroke + rod + CH = 1.89 + 6.488 + 1.776 = 10.154

If he square decks it, located off the mains so they all have a common reference point, I'd put it somewhere between 10.155 and 10.160, likely 10.160 because the less you cut, the easier things fit

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.

So with the 1020, and .006 below, you end up at .047 quench distance, 10.07 static compression and 7.65:1 dynamic, which is getting better

If you went with the 1020, but cut it to 10.155, or .001 below, you end up at .042 quench, 10.18 static, and 7.73 dynamic, and it's looking even better

You can 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 with the 10.160 deck and 7.86 DCR with the 10.155 deck

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

« Last Edit: December 24, 2015, 12:39:39 PM by My427stang »
---------------------------------
Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch