Comp Ratio for 408

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ddart74

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I'm piecing together my 408 and I'm looking at stroker kits. What compression ratio would be best for using magnum heads? I think all the kits come with KB hypereutectics and steel I-beams. It should be all motor for now, would like to give it a 100 shot somewhere down the road. Heres what I was looking at.

http://www.cnc-motorsports.com/category.asp?CtgID=20601
 
Thats similar to what I'm looking at, the I-beams are supposedly good up to 500hp, not sure if a 408 with a 100 shot would be too much.

Off topic, does my post count reset if I haven't logged on in awhile? I'm guessing yes 8)
 
use the newer scat I beam 4340 pro comp rods....believe the are good up to more hp then the eagle 5140 I beam rods...
 
70aarcuda said:
use the newer scat I beam 4340 pro comp rods....believe the are good up to more hp then the eagle 5140 I beam rods...
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This is true. They cost more but are worth more. The standard Eagle I-beams also aren't bushed for floating pins and the SCAT's are. 4340 steel is quite a bit stronger than 5140 and a little lighter.

As far as compression goes that needs to be set up as a whole with the rest of the build. 10.3 to 1 is fine with closed chamber style heads but you need to be running a cam with at least 225 degrees duration @ .050".... If you go too small on the cam with high compression it may not run on 93 octane fuel due to the cylinder pressure being so high.
 
scats i beams are selling for 269.00 on ebay....
 
Magnum heads are closed I believe? Also, this is the cam I'm shoving in there; CRN-693801. I'm shooting for 400hp or high 12's on motor, w/e comes first. I'll be using 4.10 gears and I'm still looking for a set of large valve R/T heads. Kinda stumped as to where to look for a decent set of rebuild able used ones (p5007141 w/2.020/1.625 valves). I'm trying to keep the compression decent so I have the option to easily spray it a little later on, trying to figure out the rotating assembly at the moment.
 
The standard Eagle I-beams also aren't bushed for floating pins
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The ones i have are..if your only going to be making 400 h.p. the Eagles should be fine..anything more then that buy a quality rod,i found out the hard way on that one when the stroker goes back together it'll be getting a much better set of rods...
 
I'd check with ohio crankshaft on a kit, I bought their $950 kit that came with a nodular crank and h beams -floating pins- w/KB 9.7 and speed pro moly rings then spent a little extra on having it internally balanced.

The eagle cast steel cranks are a crap shoot, I'm hearing about a lot of failures at right about 500hp.

With 93 octane If your gonna run a cam thats around 248*.050+duration I would go for 10.8-11.1 compression open chamber or not which would take some 'piston reworking' and decking of both block and heads.
 
Just checked out Ohio Crank, 408 kit runs about $1,200, but doesn't specify the CR on the pistons. Whats the difference with the nodular crank compared to the others?

Also, found this. Says its good up to 700, 1000 w/ARP hardware.
Second to last one on bottom of page.
http://www.gofaststuff.com/kits.html
 
A nodular iron crank is stronger than the cast steel eagle crank.
When it comes to 'steel cranks' the 'forged steel crank' is the one you want.

The cast ohio kit comes with KB356 if you go to KB's site you can look it up and then play with the compression calculator, If I saw the right kit I believe the ohio kit is cheaper.
 
fishy68 said:
This is true. They cost more but are worth more. The standard Eagle I-beams also aren't bushed for floating pins and the SCAT's are. 4340 steel is quite a bit stronger than 5140 and a little lighter.
Click to expand...

The Eagle SIR rods I got from Mancini for $220 have floating pins and are held together with ARP series 2000 cap screws (not bolts). I see pictures of the SIRs that use bolts, mine had the 12 point cap screws like the H-beams.
 
dgc333 said:
The Eagle SIR rods I got from Mancini for $220 have floating pins and are held together with ARP series 2000 cap screws (not bolts). I see pictures of the SIRs that use bolts, mine had the 12 point cap screws like the H-beams.
Click to expand...

Was that lately? I looked everywhere I could find last spring and the cheapest I could find the floating style Eagles was $280. That's why I went with the SCAT's. It's been awhile since I read what capscrews SCAT's use but I believe their also the ARP 2000 series. Eagle's are very good rods also. I just felt the SCAT was better deal at the time I shopped. JMO
 
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