Compression ratio help please

[C Body Bob]

Need a compression ratio calculation please
440 motor home block
True flat tops .145 thousands in the bore with chamfered edge
4.320 bore 3.75 stroke with 4.350 bore head gasket
030 compressed head gasket.
72 cc chamber aluminum head.
I’m thinking 9.0:1
Anybody got a way to work this out

 

[volksworld]

i'm getting 8.856....engine compression ratio calculator- inch calculator....( www.inchcalculator.com ).....dont know about the chamfer....and i think most perma torque style gaskets are .039.....oops edit...8.892 is right...i entered 4.5 as gasket hole (felpro 8519) instead of 4.35 like you stated

 

[C Body Bob]

i'm getting 8.856

How did you get that ?

 

[Trace 300 Hurst]

Makes it easy: https://goodcalculators.com/compression-ratio-calculator/

 

[65Fury440]

When you add in area above the ring and chamfer, it gets even better.... for an EBAY TURBO!!

 

[70bigblockdodge]

Summit has a pretty good one. Just go look up pistons for thisi engine and it is at the bottom of the page.
Nice tight chamber head, and no quench. With barely 8.8, better keep the cam small and the 93 octane in the tank. Time for new pistons Bob or as mentioned eBay turbo

 

[Trace 300 Hurst]

Time for these.......

 

[65Fury440]

My guess is that Bob has a low mileage MH engine he wants to slap together.
That slippery slope of putting pistons in, can end up in an aluminum headed stroker with all the associated accessories.
Which is not a bad thing.

 

[70bigblockdodge]

My guess is that Bob has a low mileage MH engine he wants to slap together.
That slippery slope of putting pistons in, can end up in an aluminum headed stroker with all the associated accessories.
Which is not a bad thing.

Just need pistons from a late 60s 440 they are less than .100 in the hole. Gotta be some money throwing putting a stroker together throwing away all the good parts. I have half a set of .030 cast pistons, it's alot of work to sand that .015 off each side to fit it in a standard bore. They are '70 spec compression distance.

 

[C Body Bob]

Summit has a pretty good one. Just go look up pistons for thisi engine and it is at the bottom of the page.
Nice tight chamber head, and no quench. With barely 8.8, better keep the cam small and the 93 octane in the tank. Time for new pistons Bob or as mentioned eBay turbo

Got a good used 509 purple shaft I was planning on using. Dedicated drag motor

 

[C Body Bob]

Time for these.......

View attachment 384582

No budget on this build.

 

[C Body Bob]

My guess is that Bob has a low mileage MH engine he wants to slap together.
That slippery slope of putting pistons in, can end up in an aluminum headed stroker with all the associated accessories.
Which is not a bad thing.

 

[C Body Bob]

Just need pistons from a late 60s 440 they are less than .100 in the hole. Gotta be some money throwing putting a stroker together throwing away all the good parts. I have half a set of .030 cast pistons, it's alot of work to sand that .015 off each side to fit it in a standard bore. They are '70 spec compression distance.

I stopped by my machinist yesterday & he’s covered up. 2 months back log. So I’ll throw together an Uncle Tony’s special

 

[furious70]

There's been several threads over the years about people running big cams and stalls in low CR engines. They are soft down low but with a big stall they still work.

Or get a turbo

 

[70bigblockdodge]

If you can crank it with starter to get cranking compression. I would advance that cam to get as much cranking compression as you can. I used a 509 cam in a 7.8:1 '77 440 and it had terrible throttle response and unstable vacuum idle. I would advance it at least 4-6°.

 

[C Body Bob]

If you can crank it with starter to get cranking compression. I would advance that cam to get as much cranking compression as you can. I used a 509 cam in a 7.8:1 '77 440 and it had terrible throttle response and unstable vacuum idle. I would advance it at least 4-6°.

Have you read IQ52’s thread over on FABO. He made very good power with a 509 & 850 Holley on stock 440 low comp engine.

 

[70bigblockdodge]

Have you read IQ52’s thread over on FABO. He made very good power with a 509 & 850 Holley on stock 440 low comp engine.

Yeah I read it. While impressive a Dyno is not a drag strip.

 

[C Body Bob]

If you can crank it with starter to get cranking compression. I would advance that cam to get as much cranking compression as you can. I used a 509 cam in a 7.8:1 '77 440 and it had terrible throttle response and unstable vacuum idle. I would advance it at least 4-6°.

Have you tried the cam straight up. I think you’re opening the intake valve too soon on that 4 *

 

[70bigblockdodge]

It was only advance 2° in reality, the keyway is off by 2° retarded. I had it in both ways straight up (2° retarded) and 4° advanced on the timing chain(2° advanced) it was very bitchy. I never had those problems with my ~9:1 engine with a double pumper and a single plane, so maybe you will be fine.
My Challenger took alot of playing to get it drivable and it still will not pull hard out of the hole.