Calculating Compression Ratio 390FE
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
Calculating Compression Ratio 390FE
I'm trying to use this calculator to calculate my compression ratio on the Summit website:
http://www.summitracing.com/popup/ca...ion-calculator
I'm shooting for somewhere around 9.5:1, which is what my Silvolite 1130's are rated at. I just want to check it with this calculator. But, I'm having trouble coming up with the exact numbers that the calculator is asking for.
Bore: 4.352 (.30 over)
Stroke: 3.784
Cylinder Head Volume: 66 cc (D2FE stock heads, is this correct?)
Effective Dome Volume: (does anyone know for 1130's at .030 over?)
Deck Clearance: Can't get this number yet? It is a stock D4TE block.
Compressed Gasket Thickness: .037 (This is what the machine shop says for the Victor gasket set they sold me)
The numbers I'm not sure of is the Cylinder Head Volume, Dome Volume and Deck Clearance. Anyone know what these numbers would be? I know I won't be able to get exact Deck Clearance til I install the Crank and Pistons.
Thanks
Byron
http://www.summitracing.com/popup/ca...ion-calculator
I'm shooting for somewhere around 9.5:1, which is what my Silvolite 1130's are rated at. I just want to check it with this calculator. But, I'm having trouble coming up with the exact numbers that the calculator is asking for.
Bore: 4.352 (.30 over)
Stroke: 3.784
Cylinder Head Volume: 66 cc (D2FE stock heads, is this correct?)
Effective Dome Volume: (does anyone know for 1130's at .030 over?)
Deck Clearance: Can't get this number yet? It is a stock D4TE block.
Compressed Gasket Thickness: .037 (This is what the machine shop says for the Victor gasket set they sold me)
The numbers I'm not sure of is the Cylinder Head Volume, Dome Volume and Deck Clearance. Anyone know what these numbers would be? I know I won't be able to get exact Deck Clearance til I install the Crank and Pistons.
Thanks
Byron
Super Moderator
Joined: Apr 2004
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Deck height - compression height - rod length - 1/2 stroke will give your your piston to deck.
Deck on stock FE is 10.17".
"30 over" is .030, not .30. Your bore of 4.352 is too large for the block.
Your "30 over" bore will be 4.080.
10.17 - 1.760 - 6.486* - 1.892 = .032
* rods are said to be between 6.486 and 6.490
As oem in cars, these are said to be between .010 and .030 for piston to deck clearance, so says:
FE Series Engine Specification Chart
Missing is the dish volume.
"3.000 inch diameter, 0.147 inch deep recessed piston head"
Calculate that volume and convert to cc's, then plug it in to the calculator you posted. I gotta run or I would have done it.
Without the dish, you are a tick over 11, so my guess is you are close to 10 with the dish.
Deck on stock FE is 10.17".
"30 over" is .030, not .30. Your bore of 4.352 is too large for the block.
Your "30 over" bore will be 4.080.
10.17 - 1.760 - 6.486* - 1.892 = .032
* rods are said to be between 6.486 and 6.490
As oem in cars, these are said to be between .010 and .030 for piston to deck clearance, so says:
FE Series Engine Specification Chart
Missing is the dish volume.
"3.000 inch diameter, 0.147 inch deep recessed piston head"
Calculate that volume and convert to cc's, then plug it in to the calculator you posted. I gotta run or I would have done it.
Without the dish, you are a tick over 11, so my guess is you are close to 10 with the dish.
Thread Starter
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
Thanks for the correction on the Bore.
With 3 inch by 0.147 dish on the piston, I'm coming up with 17.034cc on the Piston Dome Volume. Does that sound right?
If so, this gives me about 9.29:1 compression. Might have to consider some thinner head gaskets.
With 3 inch by 0.147 dish on the piston, I'm coming up with 17.034cc on the Piston Dome Volume. Does that sound right?
If so, this gives me about 9.29:1 compression. Might have to consider some thinner head gaskets.
Thread Starter
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
XE262H Comp cam grind
Dur at .050 218 (int) 224(exh)
Lift .513 (int) .520 (exh)
Lobe Separation 110 degrees
Apparently, not actually a Comp cam. But, a custom grind to match, from Delta Camshaft.
Here's a prior post on that:
https://www.ford-trucks.com/forums/1...d-pistons.html
Dur at .050 218 (int) 224(exh)
Lift .513 (int) .520 (exh)
Lobe Separation 110 degrees
Apparently, not actually a Comp cam. But, a custom grind to match, from Delta Camshaft.
Here's a prior post on that:
https://www.ford-trucks.com/forums/1...d-pistons.html
Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
or use the silvolite 1131s
like mentioned in this previous thread
https://www.ford-trucks.com/forums/3...or-1131-a.html
like mentioned in this previous thread
https://www.ford-trucks.com/forums/3...or-1131-a.html
Thread Starter
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
Yeah, I definitely considered the 1131's but didn't go with those because I didn't want to have to run Premium fuel. I am definitely considering the thinner metal gaskets (.014) to bring it to 9.73:1. Do you have to run premium fuel with 10.1:1?
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Logistics Pro
Joined: Jan 2011
Posts: 4,762
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From: Antelope Valley ,CA
I run mid grade with no ping , true CR is like 9.91:1 I don't use my truck to tow or haul anything heavy either
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From: south louisiana
I came up with 9.5 to 1 also, same as Silvolite advertises. I would not use thinner gaskets, if you're talking about steel shims. They don't tolerate overheating well. I've run two 10 to 1 390's on 87-89 octane. It's all in the cam. Last one had a Crane 272* Energizer, it was fine with 89 octane. The one before that had a Cam Dynamics grind (no longer around, this was in the early 80's) with specs of .516 lift, 290 something advertised duration, it ran on anything you fed it.
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
A mechanic told me that I have 78cc head volume. That puts my compression ratio around 8.5:1. That kind of bums me out, cause I was thinking around 9.25:1 with 66cc. The engine is already assembled and back in the truck (haven't hook everything up and started it yet.) Is there any way to get the exact cc for these heads? They are D2TEAA.
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D2s are supposed to be around 68 stock. How did he get them to 78? Did work on them a bit, and remove material from the chamber?
If they are 78 and you have the dished pistons, you are at 8.3 or so. If they were 68 you would have about 9.1.
If they are 78 and you have the dished pistons, you are at 8.3 or so. If they were 68 you would have about 9.1.
Thread Starter
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
He didn't actually work on the heads. He just looked it up in a book he had, but the part numbers weren't exact. He's a friend of a friend just trying to do a favor. So, I'm hoping he's wrong about that. I like 68cc much better. He did seem pretty knowledgeable about these engines and these trucks as he has worked on many.
Other than that, I just hand lapped the valves. New exhaust valves. Guides weren't in terrible shape and I didn't want to put another grand into the rebuild. There was slight play which will mostly go away when there's oil on them. When I have extra money, I'll redo the heads down the road. I'm already about $3k into this motor, for a truck that I paid $1900 for. But, I'll have a pretty nice truck when I'm done.
Thanks for the feedback.
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