Re: Preferred rod, compression height combo
[Re: mac56]
#1153577
01/09/12 06:45 PM
01/09/12 06:45 PM
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Joined: Nov 2003
Posts: 6,293
Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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Good question..
My current new engine project is this.. 400 block, 4.15 crank etc..
I have the 6.535 or therebouts rod length. It has the small wrist pin .990, and has the Chevy 2.2 rod journal...
This lightens things up a bit.
Looks like the low deck Chrysler block has a 9.98 deck height.
So we come up with the following..
Compression height would be the deck height minus half the crank stroke, minus the rod length... this would be
9.980
-2.075
-6.535
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1.34 compression height would be zero deck.
This is nice and light, not so short that the wrist pin is in the oil ring pack.. Which is in the 1.3- 1.32 range...
This avoids the oil support rails etc. The 572 Hemi I built 2 years ago had a short piston (Wiesco) 4.5 stroke, 4.5 bore and a 7.1 rod.. Pistons were short 1.32 or so and needed the oil support rail.
[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: Preferred rod, compression height combo
[Re: mac56]
#1153580
01/09/12 08:33 PM
01/09/12 08:33 PM
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Joined: Nov 2007
Posts: 778
Sherwood park, Alberta.
go green
super stock
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super stock
Joined: Nov 2007
Posts: 778
Sherwood park, Alberta.
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Quote:
I have to order a custom piston and will need new rods so that is where the question comes from. I would prefer not to have the pin into the oil ring.
Just run buttons and they support the oil ring . easy
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Re: Preferred rod, compression height combo
[Re: mac56]
#1153582
01/10/12 12:12 AM
01/10/12 12:12 AM
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Joined: Aug 2003
Posts: 43,223
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,223
Bend,OR USA
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Quote:
With a 400 block 4.150 stroke and chev rods which combination do you like?
I like long rods in my 400 block strokers, 6.8 or 6.7, that is with the BB Chevy 2.200 rod journal sizes, BB Chevy type long rods with .990 pins and 2.200 rod sizes   Both my low compression street motor and higher compression bracket motor, 4.300 stroke, 4.375 bore with 6.800 long H beam steel BB Chevy type rods and the new bracket motor, 4.35 bore with 4.250 long stroke with 6.7 long BB Chevy type rods both have the wrist pins on the oil ring, SO WHAT  The pistons sure are light 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Preferred rod, compression height combo
[Re: Al_Alguire]
#1153585
01/10/12 07:24 AM
01/10/12 07:24 AM
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Joined: Oct 2005
Posts: 976
ontario canada
mac56
OP
super stock
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OP
super stock
Joined: Oct 2005
Posts: 976
ontario canada
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Quote:
Well based on your info I would decide on what CD on the piston works best for you and order a rod accordingly. Many variables there like cylinder head choice, for instance a valve relief on a B1 type head on a small bore like that is going to get into the top ring quick. What type and size ring are you going to run, is it a true NA set up or will it be sprayed are all questions that matter. An aluminum rod can be had in any size you like. Best to design the piston to optimize it for it's intended purpose and then get a rod that fits, than try to build a piston based on a rod choice. Just my
Yes Al it is naturally aspirated and will have B1 valve reliefs on 4.380 bore so the rings may end up down a little farther. It will probably have a standard 1/16 ring pack.I was thinking of staying with the 1.48 I use now and a 6.385 rod.
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