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What is the cubic inch and compression ratio of this build?

Paul_G

Paul_G

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For the second time, I just picked up my stroker engine from the machine shop. Had a bad failure shortly after start up last year. On the highway a freeze plug came out and toasted the engine. There are other threads on that. The machine shop made good on the engine. Repaired the burn through of the head and put it back together.

He said today the engine compression ratio on this engine is 12.7:1. It is supposed to be 10.6:1 with the kit I have. On Summits site the compression ratio calculator comes out to 10.97:1 and 505 CI.
I will put all the specs I can below.

440 source, 440-512-5060 kit

440 block bored .030 over.
Zero deck.
Pistons, #5060, are -17 dish
Crank is #44042506800-6, 4.250" stroke/7.100" rod
Trick Flow PP240 heads. 78cc
Head gaskets are .036 compressed

So what is it really?
 
I got 10.6. Assumed 4.375 gasket bore, and 2cc for miscellaneous, per wallace.
My guess is your engine builder got the wrong entry for dome/dish in his calculator. Easy to do. Wallace is kinda counter-intuitive for that.
505.3 cu in.
If you delete the "miscellaneous" from the equation, i get 10.96 too.
(Miscellaneous is for not round head gaskets, bore valve reliefs, piston outer edge champher, and bore space above top ring, which is almost never measured)
 
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I used the Diamond Piston Calculator
This is what I put in the boxes

Screen Shot 2021-05-11 at 7.28.56 PM.png


This is what I got for results...

Screen Shot 2021-05-11 at 7.29.14 PM.png


FWIW I put the piston .016 in the hole cause unless the block was decked well short of spec it won't be a true zero deck height....
 
I guess there are some things I'll just never understand ?

Like how can the Machine Shop that just assembled the Engine....then NOT KNOW the Compression Ratio of the Engine they just screwed together ?
However, that said....
the Frost Plug falling out after the first time they screwed it together ? sorta makes perfect sense now ?

From the info provided..... 10.85:1
 
Challenger340 said:
I guess there are some things I'll just never understand ?

Like how can the Machine Shop that just assembled the Engine....then NOT KNOW the Compression Ratio of the Engine they just screwed together ?
However, that said....
the Frost Plug falling out after the first time they screwed it together ? sorta makes perfect sense now ?

From the info provided..... 10.85:1
Click to expand...

There is a lot more to the story. This is now a 1 man machine shop. Ray, runs it mostly alone, with some assistance from Jim, the owner. They have an old reputation as a good engine building shop. The two of them built that reputation together. That old rep is what got me to take my engine there.

2 and 1/2 years ago I take my block to that shop. At that time Ray had been gone for some time for health reasons, Jim was also in poor health and not at the shop much. Jim had a guy, Dave, running it for him. Dave had 3 or 4 young men working in there too. They built my block. They installed the core plugs with no sealant, and they used the cheap short wall core plugs.

When I got the block home from the initial build I noticed the valve reliefs on several pistons were in the wrong places. They had the pistons in the wrong holes. Took it back and they fixed it. If I had only known the guys who built that reputation were not there anymore, and some monkeys were there hammering engines together, I would have chosen another shop.

Last year, Jim, the owner, was going to close the shop up if Ray could not come back. Jim fired the whole crew of Monkeys when Ray returned. Ray went through my block this time, Jim came in to repair the burn in the head. No charge to me at all.

Ray also told me the valve seats were not to good on the heads. Not something he expected with the Trick Flow heads. He said he fixed them all. Telling me the comp ratio is 12.7 just did not sound right.

So, 440 Source calls the comp ratio with my stroker kit, at 10.6. On here, all under 11 to 1. I dont know what Ray was thinking?
 
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Paul_G said:
There is a lot more to the story. This is now a 1 man machine shop. Ray, runs it mostly alone, with some assistance from Jim, the owner. They have an old reputation as a good engine building shop. The two of them built that reputation together. That old rep is what got me to take my engine there.

2 and 1/2 years ago I take my block to that shop. At that time Ray had been gone for some time for health reasons, Jim was also in poor health and not at the shop much. Jim had a guy, Dave, running it for him. Dave had 3 or 4 young men working in there too. They built my block. They installed the core plugs with no sealant, and they used the cheap short wall core plugs.

When I got the block home from the initial build I noticed the valve reliefs on several pistons were in the wrong places. They had the pistons in the wrong holes. Took it back and they fixed it. If I had only known the guys who built that reputation were not there anymore, and some monkeys were there hammering engines together, I would have chosen another shop.

Last year, Jim, the owner, was going to close the shop up if Ray could not come back. Jim fired the whole crew of Monkeys when Ray returned. Ray went through my block this time, Jim came in to repair the burn in the head. No charge to me at all.

Ray also told me the valve seats were not to good on the heads. Not something he expected with the Trick Flow heads. He said he fixed them all. Telling me the comp ratio is 12.7 just did not sound right.

So, 440 Source calls the comp ratio with my stroker kit at 10.6. On here, all under 11 to 1. I dont know what Ray was thinking?
Click to expand...
I said what i think happened. With the calculator i use, if you enter a dished piston as a (-) minus, it regards it as a dome.
A 17cc dome would be around a high 12 c.r.
 
33 IMP said:
I said what i think happened. With the calculator i use, if you enter a dished piston as a (-) minus, it regards it as a dome.
A 17cc dome would be around a high 12 c.r.
Click to expand...

Yup, and 440 Source list the pistons as -17cc which is what they are but compression calculators flip flop the terminology...

Accept a 17cc dome would give 15.5 C/R....

No dish/no dome 0cc flat top would give 12.73

Looks like he forgot to calculate for the dish...
 
505.54 cid, 10.96:1 compression assuming the cylinder head gasket bore is 4.410" and 0.036" thick.
Summit calculation of 10.97 might assume the head gasket bore size is the same as the cylinder bore size?
 
Need the deck clearance and gasket bore for a more accurate number.

Using a block with a deck height of 10.720, and assuming a .040 thick gasket with a 4.410” bore, and calling the area above the top ring 1cc....... it would be 10.47:1.
440source calls it 10.55:1...... they’re not accounting for the area above the rings.

Different deck height, different gasket thickness and/or bore = different results.

This is the compression calculator I use(can be used for other purposes):

BE998E31-C387-430D-80CC-5ECED4E71185.jpeg
 
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I asked Ray if he saw any signs of detonation. He did not. I did not either when I pulled the heads after the burn. I was running 14° initial with 30° of total timing while I had the engine in the car and running, and only ran it about 100 miles before the burn.

We have 91 octane gas here, at about 1200' elevation. If this engine was truly 12.9:1, running 91 octane @ 30°, would you not expect detonation? I listened for it constantly, never heard any pinging. I started running the engine with a conservative amount of timing. Figured I would creep up on timing a little at a time. Besides the clutch was not broken in yet at that time, full throttle at a slow roll would slip the clutch with the conservative tune anyway.

Everyone likes pics, here is one of the burn through. You can see the combustion chambers too. Detonation evidence?
20200905-133514.jpg

20200905-133525.jpg
 
The 78cc head is factory. He cut the head to get rid of the "burn thru" area. Much smaller "CC" now is my guess.
 
If it's on an engine stand put number 1 piston to tdc on firing stroke. Turn engine so number 1 spark plug hole is on top. You'll need a cc tube large enough to fill combustion chamber. What you choose to fill combustion chamber with? I'd use 50w oil. Fill chamber to the bottomplug hole with oil. Then you know what's the volume. Then turn so plug hole is down to drain cylinder.
 
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