Please check my math
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Senior User
Joined: Nov 2007
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Please check my math
I'm picking up my rebuilt 400 this week and was hoping to get my CR math checked.
Deck height is 10.282
TMI's piston for open chamber head 1.71 CH with 14CC relief
Deck clearance -0.008
Head volume ~78 CC since 0.005-0.007 was removed
gasket thickness is 0.041 with 4.1 opening
cylinder is 4.03
using DEH 265 cam that has 58 deg close ABDC
I'm getting a SC of 9.432 and DC of 7.918. Just want to be sure this is right so I can tell the distributer shop.
I would also like to know the final HP and torque numbers. I will be running a holley street dominator with EGR, an Edelbrock 1406 carb, Hooker 1 3/4 long tube headers, and dual mandrel bent 2 1/4 exhausts.
Deck height is 10.282
TMI's piston for open chamber head 1.71 CH with 14CC relief
Deck clearance -0.008
Head volume ~78 CC since 0.005-0.007 was removed
gasket thickness is 0.041 with 4.1 opening
cylinder is 4.03
using DEH 265 cam that has 58 deg close ABDC
I'm getting a SC of 9.432 and DC of 7.918. Just want to be sure this is right so I can tell the distributer shop.
I would also like to know the final HP and torque numbers. I will be running a holley street dominator with EGR, an Edelbrock 1406 carb, Hooker 1 3/4 long tube headers, and dual mandrel bent 2 1/4 exhausts.
Tuned
Joined: Jul 2003
Posts: 455
Likes: 3
From: Berkeley
looks like someone did their homework. nice build.
"Head volume ~78 CC since 0.005-0.007 was removed "
don't guess at the head chamber cc. have 'em measured or do it yourself.
if the scr is too high to get the dcr you need with that cam, polish the chambers
some more (if not already) to get it down.
open chamber heads won't give you any quench, so if you need to, you could use thicker gasket to lower scr also.
danlee will probably be along soon to tell you if that'll be necessary, depending on the octane of fuel you care to run. :-)
"Head volume ~78 CC since 0.005-0.007 was removed "
don't guess at the head chamber cc. have 'em measured or do it yourself.
if the scr is too high to get the dcr you need with that cam, polish the chambers
some more (if not already) to get it down.
open chamber heads won't give you any quench, so if you need to, you could use thicker gasket to lower scr also.
danlee will probably be along soon to tell you if that'll be necessary, depending on the octane of fuel you care to run. :-)
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Senior User
Joined: Nov 2007
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packlet,
I did CC the heads before polishing the chambers and I was getting about 78.5. I was just using a piece of plexiglass and 60CC syringe, so it was accurate enough to see if I had the 78.4 heads instead of the 74.6( I think that was the other size), but I didn't really trust it to be very accurate. I figured after polishing I had ~79CC and the decking brought me down to about 78.
I have already accepted the fact that I will be running premium (only 91 octane in the PNW), so I am hoping that the DCR will be low enough for this. They ended up needing to remove more from the deck than I wanted to square it up, but I want it done right. I also got the thickest head gasket my shop offered. I am hoping not to have detonation issues and have read that 91 octane has a range of 7.5 to 8.5 DCR. I know the large bore and open chamber does not help matters, but the EGR should help things a bit.
I did CC the heads before polishing the chambers and I was getting about 78.5. I was just using a piece of plexiglass and 60CC syringe, so it was accurate enough to see if I had the 78.4 heads instead of the 74.6( I think that was the other size), but I didn't really trust it to be very accurate. I figured after polishing I had ~79CC and the decking brought me down to about 78.
I have already accepted the fact that I will be running premium (only 91 octane in the PNW), so I am hoping that the DCR will be low enough for this. They ended up needing to remove more from the deck than I wanted to square it up, but I want it done right. I also got the thickest head gasket my shop offered. I am hoping not to have detonation issues and have read that 91 octane has a range of 7.5 to 8.5 DCR. I know the large bore and open chamber does not help matters, but the EGR should help things a bit.
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Senior User
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Originally Posted by hollenjoe
how thick was the gasket you got?
on 91 octane you will be lucky to go all the way to 8.0 dcr.....
on 91 octane you will be lucky to go all the way to 8.0 dcr.....
Posting Guru
Joined: Jul 2007
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chek out this wbe page, it can do the math for you , tell you your dcr and gide you on octane.... http://www.edyno.com/Eng_spec.html
im scared with my engine having a dcr of 7.6 and trying 91 octane....
im scared with my engine having a dcr of 7.6 and trying 91 octane....
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Thread Starter
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Senior User
Joined: Nov 2007
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Originally Posted by hollenjoe
chek out this wbe page, it can do the math for you , tell you your dcr and gide you on octane.... http://www.edyno.com/Eng_spec.html
im scared with my engine having a dcr of 7.6 and trying 91 octane....
im scared with my engine having a dcr of 7.6 and trying 91 octane....
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Laughing Gas
Joined: Jan 2006
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From: New-brunswick,Canada
kb-silvolite piston 15.5cc dich. I must make a mistake somewhere in the calculation ? .092 piston to deck clearance, comp.height 1.63 , combustion chamber volume 62cc.When i used Kelly hotrod compression/displacement calcs it's give me a static comp 9.29, 408.2 ci , 6.7L.
Laughing Gas
Joined: Jan 2006
Posts: 883
Likes: 7
From: New-brunswick,Canada
made a mistake. My static 8.70 and dcr 7.1 89 octane or better.Should not have a problem. I recently deck my block .004 just to straight up everything so my number could go up a bit. Not touch the aussie head now but gona be shave a few .001.