225 Build for the A100

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Jim Kueneman

Jim Kueneman

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Now the A100 is painted my buddy is feeling the pressure..

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.... he has been dreading doing this setup but it is now done so the block can start through the process.. He almost destroyed his line honing stones on my first 225 when he realized there is a small step at the back of he block that has no apparent use. He now machines off that lip so he can line hone the block without destroying his equipment on the Bridgeport.
This will be getting 0.080 off the block, 0.050 off the head, oversized valves, port cleanup, Oregon Cam 819 with a custom 106 LCA and rebuilt rocker assy by Rocker Arms Unlimited. Topped off with Aussie Lynx intake and Hi-Tech exhaust.

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What's your program say about dynamic compression?
 
Jim Kueneman said:
static should be around 9:1 and dynamic a touch under 8.0ish.

Someone has mapped out how many cc per .010” off the head you get. Do you recall?
Click to expand...
I believe the formula is .0067 = 1cc.
 
Jim Kueneman said:
static should be around 9:1 and dynamic a touch under 8.0ish.

Someone has mapped out how many cc per .010” off the head you get. Do you recall?
Click to expand...
I think you're gonna be higher than that. In fact, I'd be looking at that dynamic.
 
Also, if he was on the lip the red arrow is pointing

REAR LIP.jpeg


to that IS the rear main seal lip.
 
I took 0.030 off the block, 70 thou off the head, have the o/s valves and with 0.020-overbore, and rebuilder grade pistons, 0.050 (compressed) Aussie head gasket mine cc'd out dead nuts 8.4:1. Still 0.180 in the hole even with that 0.030 block shave. I used a 70s peanut style '447 head and with 0.070 head shave, my chambers came out at 49-50cc each. (4 were 49 and 2 measured out 50)
I have the same 819 cam, but no "special" LCA. 819 "as listed" by Oregon cams.
I have run mine in but have yet to drive it.
I'm in a "which trans am I gonna run" condundrum.
amongst 3 choices on hand.
 
RustyRatRod said:
Also, if he was on the lip the red arrow is pointing

View attachment 1716183783

to that IS the rear main seal lip.
Click to expand...

Correct, my mistake. It needs to come down to the diameter of the journal. They seem to be about 0.010 smaller diameter than the journals so you can’t line bore them. Unknown how the factory line bored the block like this.
 
RustyRatRod said:
I think you're gonna be higher than that. In fact, I'd be looking at that dynamic.
Click to expand...

I am assuming they are 0.180 in the hole stock and will be 0.100 down when done.

0.050 off the head gives me about 7.5cc and the last head we cc’ed were 58 so say 50cc?

Agree with those numbers?
 
Jim Kueneman said:
I am assuming they are 0.180 in the hole stock and will be 0.100 down when done.

0.050 off the head gives me about 7.5cc and the last head we cc’ed were 58 so say 50cc?

Agree with those numbers?
Click to expand...
Perhaps good guesses, but you didn't measure? What are you using to figure dynamic?
 
By the time Dave gets done with everything any measurements took at disassembly would not be right.

Performance Trends.

Relooking.
 
So I can base CCs on the last head he did that we measured and that was 58 CC with .010 off the head.

I’m getting about 9.5 static (not accounting for the second order effects that take it down some) and Performance Trends says 7.85 dynamic with 198 cranking pressure. That is getting up there.

I may kick back on the head a little. Thanks for questioning this.
 
volaredon said:
I took 0.030 off the block, 70 thou off the head, have the o/s valves and with 0.020-overbore, and rebuilder grade pistons, 0.050 (compressed) Aussie head gasket mine cc'd out dead nuts 8.4:1. Still 0.180 in the hole even with that 0.030 block shave. I used a 70s peanut style '447 head and with 0.070 head shave, my chambers came out at 49-50cc each. (4 were 49 and 2 measured out 50)
I have the same 819 cam, but no "special" LCA. 819 "as listed" by Oregon cams.
I have run mine in but have yet to drive it.
I'm in a "which trans am I gonna run" condundrum.
amongst 3 choices on hand.
Click to expand...

WOW.... what pistons did you use? Just the common Sealed Power? That would have been WAY down in the hole without the decking.... you sure you didn't have 170 rods installed from the factory!
 
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Yup. Sealed power.
And I've heard of others with similar dismal "down in the hole" numbers using those pistons, the build of the 67 dart motor by that community college in PA amongst them, and there was a magazine writeup across a few issues of a 66 dart that they had done upgrades on in each issue that told of the same issue. With no deck machining both told of 0.210"ish in the hole numbers at TDC on their engines.
 
Teaser... I am not going that big on the cam (220 vs 245 duration) which means I need to go to lower compression. Mine should have more torque on the low end but start dying off around 5000 RPM.

 
If I remember correctly, Sealed Power made two different piston configurations. One was the "standard" replacement piston, and the other was a "low compression export" piston. You have to check the specs to get the piston with the correct compression distance.
 
Charrlie_S said:
If I remember correctly, Sealed Power made two different piston configurations. One was the "standard" replacement piston, and the other was a "low compression export" piston. You have to check the specs to get the piston with the correct compression distance.
Click to expand...

What is that number? 1.74"?
 
Mine weren't the "low comp" versions.
I remember @my68barracuda talking about this very subject back when I was building my last engine. Something due to emissions BS where the piston makers intentionally make them with compression height less than original because with an overbore, no matter how slight, they don't want "any chance" of increased compression as would happen if the replacement pistons were the same height as own were ... An overbored cylinder is by nature bigger than original si if the piston is the same height, with all else equal, your cr would ever so slightly increase.
That doesn't take into consideration that the additional thickness of any commonly available head gaskets compared to OEM shim style as these engines used would more than take care of that "issue" solely by itself.
 
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