Figuring out how much heads have been cut?

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72Duster440

72Duster440

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I picked up a new Performer RPM intake and when I tried to install it, the bolts holes were all off 1/2 a hole in height. The M1 that came with the engine ended up going back on, which was also a challenge to get the bolts started, but eventually they all fit.

I am assuming since the new intake didn't fit, that either my heads were milled or the block was decked at some point over the years and the mating surface on the heads weren't adjusted to match.

Is there a good (easy) way to grab some measurements with the engine assembled to determine how much metal has been removed? I thought I read somewhere that the outer head bolt flange surface was 1" thick and that can be measured to see how much was milled off.

Is that correct and is there a similar measurement to take on the block?

It's a '69 440 block with 915 heads.
 
72Duster440 said:
I picked up a new Performer RPM intake and when I tried to install it, the bolts holes were all off 1/2 a hole in height. The M1 that came with the engine ended up going back on, which was also a challenge to get the bolts started, but eventually they all fit.

I am assuming since the new intake didn't fit, that either my heads were milled or the block was decked at some point over the years and the mating surface on the heads weren't adjusted to match.

Is there a good (easy) way to grab some measurements with the engine assembled to determine how much metal has been removed? I thought I read somewhere that the outer head bolt flange surface was 1" thick and that can be measured to see how much was milled off.

Is that correct and is there a similar measurement to take on the block?

It's a '69 440 block with 915 heads.
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The easiest way would be to cc the heads combustion chambers and the reverse the measurements. I think it's roughly about .005- .006 per cc on the small chamber.
I have an example to go off of.
My trick flow heads were 78 CC's and are now 65 CC's. I took off .080 so it came out close to .0055 per cc.
If I remember correctly I had to take .240 off of the intake flanges. I will double check that.
 
The outer row of head bolts bosses on a BB are nominally 1.00” thick.

Measure several of then and average the numbers.
However much thinner they are than 1” will be very close to how much has been cut.

Gonna be a challenge to do with heads installed & in the car.

What you’re experiencing is why it’s a good idea to cut the intake side of the heads the appropriate amount when the decks are cut.
 
PRH said:
The outer row of head bolts bosses on a BB are nominally 1.00” thick.

Measure several of then and average the numbers.
However much thinner they are than 1” will be very close to how much has been cut.

Gonna be a challenge to do with heads installed & in the car.

What you’re experiencing is why it’s a good idea to cut the intake side of the heads the appropriate amount when the decks are cut.
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Well that's much easier than the way I would have gone about it lol
 
PRH said:
The outer row of head bolts bosses on a BB are nominally 1.00” thick.

Measure several of then and average the numbers.
However much thinner they are than 1” will be very close to how much has been cut.

Gonna be a challenge to do with heads installed & in the car.

What you’re experiencing is why it’s a good idea to cut the intake side of the heads the appropriate amount when the decks are cut.
Click to expand...
That's the way I always check bbm heads.
No way to know how much the block has been decked while in the car, that I know of.
If the heads were off, and IF you knew the compression height of the pistons, actual deck height could be compared to calculated dh.
 
33IMP said:
That's the way I always check bbm heads.
No way to know how much the block has been decked while in the car, that I know of.
If the heads were off, and IF you knew the compression height of the pistons, actual deck height could be compared to calculated dh.
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Thanks. I wasn't sure if there was a certain feature X distance from the deck surface that could be used as reference. I can check the head at least. The pistons are a good bit further in the hole than they should be for a stock bottom end, so I have no idea what the bottom end is.



Attached is the bottom of a piston, it shows the only identifying mark on it, the other pic shows how far down in the hole it is. Don't mind the carbon on top. Lol

20240128_123352.jpg


received_1556904371752089.jpeg
 
Actually, looking at that pic, either the piston isn't sitting parallel to the deck, or I have a ton of carbon on that one side! Might run some Seafoam through this once its back together and running!
 
72Duster440 said:
Actually, looking at that pic, either the piston isn't sitting parallel to the deck, or I have a ton of carbon on that one side! Might run some Seafoam through this once its back together and running!
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Is that a quench dome ?
 
Somebody might have milled the crap out of the 915s, trying to get some compression.
A 69 motor shouldn't have what looks like 1/8" deck. If it's got 8 to 1 replacement pistons in it, it would explain the swap to 915s for a little grunt.
From the bottom, they look like cast replacement pistons.
 
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Was 8 to 1 even an option in 69? When I was looking before, I thought 80 thou was the furthest down they would be with a stock piston.

I have no idea on the bottom end details other than it's a 69 block, forged crank and LY rods. It runs great and pulls hard so I never worried about it. Previous owner said it ran mid 12s or so, but I never tried.
 
72Duster440 said:
Was 8 to 1 even an option in 69? When I was looking before, I thought 80 thou was the furthest down they would be with a stock piston.

I have no idea on the bottom end details other than it's a 69 block, forged crank and LY rods. It runs great and pulls hard so I never worried about it. Previous owner said it ran mid 12s or so, but I never tried.
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I have seen 8.7 for the 70 2 barrel. I'm not having any luck finding a chart to compare though.
 
I can't find it now, but I believe I read so.ething that said stock pistons on the base 440 were .090 in the hole and the HP 440s were closer to .020 in the hole. It's hard to tell from a borescope picture, but mine do look more than 90 thou down.
 
I'm NOT familiar much with what is available in cast pistons. But in my old trw catalog there were at least four different forged pistons for a 440.
There were the Sixpack replacements that were somewhere around .020 down. There was the domed 2295 (11.5 to one,Hah!) that were about .050 down, another flattop that was about .080 down, and one that was more than an 1/8. (wanna say, .150 or so)
If you have a stock replacement, for a LATER 440, c.r. could be anything from 7.4 up, with 906s,346s, or 452s. I still think somebody tried to crutch a bad piston choice with a heavily milled closed chamber head.
 
72Duster440 said:
Was 8 to 1 even an option in 69? When I was looking before, I thought 80 thou was the furthest down they would be with a stock piston.

I have no idea on the bottom end details other than it's a 69 block, forged crank and LY rods. It runs great and pulls hard so I never worried about it. Previous owner said it ran mid 12s or so, but I never tried.
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Later 440s (76-up?) (Typical motor home 440) had pistons around .150 in the hole. Whatever they might have been claimed to be by Mopar, they were really on either side of 7.5 to one.
 
If it's really 7.5:1, I guess it's time for a turbo!!

I was told they were TRW 10:1 flat tops.

I'm kind of thinking they just tossed whatever parts they had together.

It's a 69 block from a Newport with LY rods, the trans was a 73 727 from a Charger with a 3600 stall converter, the heads are 915s, the water pump housing was a 1964 or 65 one year only version with a M1 intake. The cam was a Crane 312, which is WAY to big for low compression and stock heads and the exhaust is 2 1/8" pro parts, also way to big.

But, whatever, it runs great and sounds even better!


Now it has a 833, and a Comp 274x grind cam. A little more street friendly, which is why I wanted the dual plane intake, that doesn't fit...
 
Again without pulling the heads to actually see, and measure, what you have, there really isn't any way to really KNOW what you have.
As I said above, Trw made 8 to 1, 9 to 1 and 10 to 1 flattops (the ten to one's had valve reliefs, which yours dont) and domed "11.5 " to one.
It MAY have 9 to 1 trw flattops, and got the 915s for a compression boost, probably why it runs good now (9.75? to one?).
I would bet a bit that it isn't 7.5 to one, LOL.
 
72Duster440 said:
Thanks. I wasn't sure if there was a certain feature X distance from the deck surface that could be used as reference. I can check the head at least. The pistons are a good bit further in the hole than they should be for a stock bottom end, so I have no idea what the bottom end is.



Attached is the bottom of a piston, it shows the only identifying mark on it, the other pic shows how far down in the hole it is. Don't mind the carbon on top. Lol

View attachment 1716227197

View attachment 1716227198
Click to expand...
That piston isn’t anywhere near tdc. Kim
 
oldkimmer said:
That piston isn’t anywhere near tdc. Kim
Click to expand...


It sure is, at least in the pic of the combustion chamber. You can even see the carbon buildup on the sides of the cylinder showing the piston doesn't go up any higher.

Like I said, I feel like they built this motor with whatever parts they had laying around.
 
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