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Old 10-30-2019, 06:04 AM
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A vergin head from those years could have .090" whacked off of it as I and many others have done for high comp race use without a issue.

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Old 11-05-2019, 06:41 PM
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When you take 060 or larger do you run into problems with intake mating to the water pump?


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Old 11-06-2019, 07:45 AM
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That passage way between the Intake and the rear of the timing cover is not even needed and you can plug it if the alignment gets too far off, but a .060" mill should not make for that issue .

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Two pairs of brown leather flip flops, never seen more then 2 mph.

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  #24  
Old 11-06-2019, 06:03 PM
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Quote:
Originally Posted by footjoy View Post
When you take 060 or larger do you run into problems with intake mating to the water pump?
Not a issue. Had heads milled .060 for years.


Last edited by Stuart; 11-22-2019 at 07:29 PM.
  #25  
Old 11-23-2019, 12:08 AM
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I just got the heads ccd and they unfortunately were 90 ccs

looking at .040 at least to get to 82ccs

This a street car. will heat be a problem for 40-50 thousands

Thanks

Greg

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Old 11-23-2019, 07:28 AM
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As I posted I have wacked .090" off iron heads and run 14 to 1 compression and had no head gasket issues!
Every .005" milled off will reduce the open chamber type head volume by 1 CC.

If the stem of the valves in the high ware area of the big valves in your 16 heads show that they are not worn by more then .001" and the guides in the 15's are good then I would get a valve job done on the 15s to stuff in those bigger valves and then CC the head again to now find out how much you need to wack off of them.

I would shoot for 75 to 76 CC's.

For example , if need to mill .055" of the deck then mill .035" off the Intake flange and all will bolt up fine and take a little less out of your wallet!

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
  #27  
Old 11-23-2019, 08:08 AM
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I've always read, as was mentioned here, that you should always have the same amount taken off the chamber surface & the intake surface of the head.

Some blocks also have quite a bit taken off the deck, to achieve zero deck height. Therefore, to maintain intake fit, without having to whack any off of it, or enlarge the bolt holes, should you take equal amounts off the block deck & intake surface of the head.

To say it another way: If you remove .020 from the deck, should you also remove .020 from the intake surface of the head.

Using this method, the numbers might look like this: Deck - Remove .020, Chamber surface of head - Remove .060, Intake surface of head - Remove .080, Intake manifold - Remove none.

So, if any is removed from the deck, since it's a 90° block, wouldn't you need to remove exactly the same amount from the intake surface of the head, in order to maintain the same intake to head alignment ?

This makes sense to me. But I've never read of anybody removing more from the intake surface of the head, than from the chamber surface of the head.

Is this a common practice ? If not, why not ? If my math is wrong, please explain it to me.


Last edited by ponyakr; 11-23-2019 at 08:15 AM.
  #28  
Old 11-23-2019, 01:37 PM
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The change in distance from one bank to the other @ 10.2" and 10.145" (Cut of 0.055") . You would need to remove half of the difference from each head.

► (10.2 ^ 2 + 10.2 ^ 2) ^ .5 = 14.42498"

► ((10.145 ^ 2 + 10.145 ^ 2)) ^ .5 = 14.3472"

► 14.42498 - 14.3472 = 0.07778"

► 0.07778 / 2 = 0.03889"

Stan

PS- he change in distance from one bank to the other @ 10.2" and 9.65"(Cut of 0.55"). If you wanted to make it a short deck block.

► (10.2 ^ 2 + 10.2 ^ 2) ^ .5 = 14.42498"

► (9.65 ^ 2 + 9.65 ^ 2) ^ .5 = 13.64716"

► 14.42498 - 13.64716 = 0.77782"

► 0.77782 / 2 = 0.38891"

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  #29  
Old 11-23-2019, 02:49 PM
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Sorry, but I'm not an engine machinist or an engine builder, & I'm not that good at math, so that post means absolutely nothing to me.

Here's what I(think) understand.

(1) It is desirable to have the piston tops be even with the deck, at TDC. This is called having "zero deck height".

(2) It has been posted that many Pontiac engines came with the piston tops "in the hole" at least .020, or more.

(3) Therefore, unless the replacement pistons have a pin location which will place the piston tops at zero deck height, some material must be removed from the block, in order to achieve zero deck height.
(This is assuming the same crank stroke and rod length as original.)

(4) Now, removing material from the chamber surface of the head will lower the head, toward the pistons, by the exact amount removed from the head.

(5) It's my understanding that if you remove material from the block deck, that will ALSO lower the head, toward the pistons, by the exact amount removed from the block. To me that means that if you cut .020 off the head, & .020 off the block, the head is lowered by a total of .040.

(6) Therefore, my simple deduction is that in order to maintain exact intake bolt hole to head alignment, you'd need to cut .040 off the intake surface of the head, in order to offset the .020 cut off the deck + the .020 cut off the head(or whatever the total amount of the 2 cuts happens to be).

There is still some online info suggesting that the intake manifold be cut, rather than the intake surface of the HEAD. But, I think most engine builders who post here, think that it's best to cut the heads. That way the intake can be used on other engines.

I understand that some engines require angle cutting the intake surface of the head, in order to maintain intake to head alignment. But, as was mentioned, it has been long reported that because the Pontiac V8 is of a 90° design, no angle cutting is needed. Therefore, I assume that the amount cut off the block, + the amount cut off the head is the amount that must be cut off the intake surface of the head, in order to maintain the exact same intake to head alignment that existed BEFORE any material was removed from any part. (This is assuming that the head gasket used has exactly the same crush thickness as the factory gasket.)

If you had an .045 thick gasket, & switched to an .027 thick Cometic gasket, that would lower the head by the same amount as removing .018 from either the head or the block, or a combination of the two.

If any of this ain't so, then somebody please try to explain it to me, in simple terms that a non-math-expert can understand. Thanks !

"...Some of Pontiac’s best flowing and most capable D-port cylinder heads were produced during the 1970s. They are low compression castings, however, and have rather larger combustion chambers. Your machinist can mill the deck surface to reduce chamber volume. Because the Pontiac V-8 is a 90-degree design, the intake flange must be milled an equal amount for proper port alignment..."

https://www.cartechbooks.com/techtip...c-v-8-engines/


Last edited by ponyakr; 11-23-2019 at 03:12 PM.
  #30  
Old 11-23-2019, 04:43 PM
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While (6) may seem logical to you it is not correct. The math shows the difference. The math I posted above uses the Pythagorean theorem.Where the sum of the square of each side of a right triangle is equal to the square of the hypotenuse.

Stan

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Old 11-23-2019, 07:03 PM
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Back to the OP's question...

If you mill more than .020 off the deck you should mill the intake surface as well. When you start getting past the .040 mark the deck on a Pontiac starts getting a thin and are prone to crack between cylinders. As for the 15's with small valves... I would bring the valves out to 2.11 and you will virtually have 64's minus a couple CC's, but still too big for a 400. Go to a 12, 13, 48 or even 62's( 62's having slightly larger chamber).

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Old 11-23-2019, 07:47 PM
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Quote:
Originally Posted by Stan Weiss View Post
While (6) may seem logical to you it is not correct. The math shows the difference. The math I posted above uses the Pythagorean theorem.Where the sum of the square of each side of a right triangle is equal to the square of the hypotenuse.

Stan
RIGHT ! There may be hundreds of guys here who understand exactly what you are saying. That's great. But I'm not one of 'em.

I can understand when the Pontiac book says remove equal amounts off both head surfaces. But, if that is false info, then I have no idea how to figure what it actually should be.

Just curious tho, do most all Pontiac engine builders, including those who post here, actually determine exactly how much to cut off the head's intake surface, using your mathematical method ? If not, exactly how do they make that call ?

  #33  
Old 11-23-2019, 10:47 PM
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Quote:
Originally Posted by ponyakr View Post
RIGHT ! There may be hundreds of guys here who understand exactly what you are saying. That's great. But I'm not one of 'em.

I can understand when the Pontiac book says remove equal amounts off both head surfaces. But, if that is false info, then I have no idea how to figure what it actually should be.

Just curious tho, do most all Pontiac engine builders, including those who post here, actually determine exactly how much to cut off the head's intake surface, using your mathematical method ? If not, exactly how do they make that call ?
I when over to Jeff's site to double check my math and based on his site I am wrong. For a Pontiac it is the same on the intake side.

http://victorylibrary.com/mopar/intake-mill-c.htm

But how much is take off of the intake side does vary from engine type to engine type and is based on the intake side angle which I had wrong.

Stan

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  #34  
Old 11-24-2019, 03:03 AM
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Quote:
Originally Posted by FrankieT/A View Post
Back to the OP's question...

If you mill more than .020 off the deck you should mill the intake surface as well. When you start getting past the .040 mark the deck on a Pontiac starts getting a thin and are prone to crack between cylinders. As for the 15's with small valves... I would bring the valves out to 2.11 and you will virtually have 64's minus a couple CC's, but still too big for a 400. Go to a 12, 13, 48 or even 62's( 62's having slightly larger chamber).
I have .060 milled heads, did not have to elongate bolt holes or mill any intake. Not prone to cracking. 64 heads work great on street 400s as do the 71 96 heads with a little milling. Its not hard to get 9-1 CR with those heads on a 400 and you don't really want anything much past 9.5 CR anyway. Big difference between a 13 and 48.
A 400 with 9-1 CR and iron heads is a great combo. 87ccs is not too big for that.

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Old 11-24-2019, 07:36 AM
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In terms of near virgin pontiac heads ( only ever a .003" clean up cut is virgin to me) then the only castings I would shy away from milling .060" or more off of would be the early mid 70s heads just do to the heat they have been exposed to from trying to pump Exh out thru converters.

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Two pairs of brown leather flip flops, never seen more then 2 mph.

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  #36  
Old 11-24-2019, 09:15 AM
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Quote:
Originally Posted by Dragncar View Post
I have .060 milled heads, did not have to elongate bolt holes or mill any intake. Not prone to cracking. 64 heads work great on street 400s as do the 71 96 heads with a little milling. Its not hard to get 9-1 CR with those heads on a 400 and you don't really want anything much past 9.5 CR anyway. Big difference between a 13 and 48.
A 400 with 9-1 CR and iron heads is a great combo. 87ccs is not too big for that.

I need to mill .050 off of these #15 heads to get what I want 9.4:1. At what point do you know if you have to mill intake after assembly or after milling the head you take some kind of measurement. I saw The formula but I have read where guys say they didn't have to do anything.

Greg

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Old 11-24-2019, 09:26 AM
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You probably need to trial fit the heads on the block with the intake to see how much to take off the intake side?

The block could have been decked also which would need to be accounted for.

The intake on the heads/block, the port alignment up/down would show how far off it is? Possibly the bolt hole alignment would be off.
(as Scott70 said basically)


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  #38  
Old 11-24-2019, 09:47 AM
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Default Are the small valves good enough for snappy street driving

My 15s have small valves It will be spirited street driving and alot of hiway driving. Is there any real need to go with big valves? It won't go over 5,000 rpms ever.

What would bigger valves actually do for the engine? I have to admit that is probably a lot of money I dont want to spend.

Thanks

Greg

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Old 11-24-2019, 10:16 AM
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Quote:
Originally Posted by footjoy View Post
My 15s have small valves It will be spirited street driving and alot of hiway driving. Is there any real need to go with big valves? It won't go over 5,000 rpms ever.

What would bigger valves actually do for the engine? I have to admit that is probably a lot of money I dont want to spend.

Thanks

Greg
Some here seem to want to make max power on every build. Don't wanna leave any power "on the table".

But, if you're gonna spend most all your time well below 5000 rpm, why build for max hp at or above 5000 ?

Makes a LOT more common sense to build for low to mid range torque, where the engine will spend most of it's time. Small valve, unported heads are just fine for that, IMO.

In fact, you may wanna consider cutting less off the heads, running a little less CR, & using a small Voodoo cam. I suppose there are several ways to build it, to do what you want.


Last edited by ponyakr; 11-24-2019 at 10:52 AM.
  #40  
Old 11-24-2019, 10:47 AM
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Why the fixation on 9.4 comp if it’s just a fun driver?


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