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Re: Please help me ID my compression ratio and choose a piston. [Re: fast68plymouth] #2717566
11/19/19 03:12 PM
11/19/19 03:12 PM
Joined: Aug 2006
Posts: 2,000
junction city oregon
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viperblue72 Offline
top fuel
viperblue72  Offline
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Joined: Aug 2006
Posts: 2,000
junction city oregon
I have the 2.05 pro tru pistons and only ended up at 9.7 to 1 with a 80cc head.
The speed pro 2295 hasn’t been mentioned. If it were my engine I’d leave the short block and run the 75cc budget Edelbrock Head.

Re: Please help me ID my compression ratio and choose a piston. [Re: viperblue72] #2717618
11/19/19 05:48 PM
11/19/19 05:48 PM
Joined: Jan 2003
Posts: 12,980
So. Burlington, Vt.
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fast68plymouth Offline
I Live Here
fast68plymouth  Offline
I Live Here
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Joined: Jan 2003
Posts: 12,980
So. Burlington, Vt.
I don’t believe they’re available any longer.

Besides, there are plenty of better options nowadays.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Please help me ID my compression ratio and choose a piston. [Re: Twostick] #2717661
11/19/19 08:15 PM
11/19/19 08:15 PM
Joined: Nov 2006
Posts: 1,373
oklahoma
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forphorty Offline
pro stock
forphorty  Offline
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Joined: Nov 2006
Posts: 1,373
oklahoma
Originally Posted by Twostick
Originally Posted by A34
So, assuming a stock cam, how is the horsepower and torque affected by running 9.6:1 instead of 10:1? 50HP? 10HP?


If the old rule of thumb about 1 point of compression = 10% has any validity, I'd say 10ish.

Kevin
I would have to completely disagree with this. You are not going to get a 10% increase in power with a one point increase in compression. More like 3 to 4 percent maybe, with the gains being greatest on really low compression engines. The difference between 9.6 and 10.0 on a stock 440? Wild azz guess,5 hp. Maybe. Or less. You will never know the difference.

Re: Please help me ID my compression ratio and choose a piston. [Re: forphorty] #2717674
11/19/19 08:54 PM
11/19/19 08:54 PM
Joined: Jan 2003
Posts: 12,980
So. Burlington, Vt.
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fast68plymouth Offline
I Live Here
fast68plymouth  Offline
I Live Here
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Joined: Jan 2003
Posts: 12,980
So. Burlington, Vt.
You could see just about a 3% increase in power going from 9:1 up to 10:1.

So, on a 350hp motor....... about 10hp.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Please help me ID my compression ratio and choose a piston. [Re: fast68plymouth] #2717777
11/20/19 09:25 AM
11/20/19 09:25 AM
Joined: Feb 2005
Posts: 2,090
God's Country - Etowah, TN.
A34 Offline OP
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A34  Offline OP
top fuel

Joined: Feb 2005
Posts: 2,090
God's Country - Etowah, TN.
Originally Posted by fast68plymouth
The question has been answered.

One of the 3 flat top pistons I listed, deck block/mill heads/gasket thickness to arrive at 10:1...... done.

If you don’t want to mill anything....... you’ll need to have custom pistons made.


Yes, thank you! I am looking at those now.

I appreciate everyone trying to help and was answering clarifying questions by others.

Whichever I choose, I will get the block decked to make up any difference.


God Bless America, Our Troops and Their Families !

DEO VINDICE
Re: Please help me ID my compression ratio and choose a piston. [Re: A34] #2717794
11/20/19 10:26 AM
11/20/19 10:26 AM
Joined: Jun 2008
Posts: 3,190
usa
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lewtot184 Offline
master
lewtot184  Offline
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Joined: Jun 2008
Posts: 3,190
usa
a simple solution if all the OP wants is a 10:1 factory type 440. just mill .030" off the heads and use a .020" steel shim gasket and your there. keeping in mind the only difference between a factory 10:1 engine and what's there is the location of the top of the piston. the top of the piston is the floor of the combustion chamber but it's expensive to move the "floor". just simply move the "roof" of the chamber down and the relationship between the two will be near identical to a factory 10:1 engine. if the 10:1 thing is what I wanted; then this is the easy way there. of course we need to keep in mind that the10:1 engines were never a true 10:1 compression and these engines are not pump gas friendly.

as far as timing goes the service manual gives specs. 5 degrees BTDC for initial with an automatic trans an zero for manual and 35 degrees total (staged with a light spring and heavy spring). duplicating a factory curve will depend on having the correct springs and plate.

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