Diamond forged 3400 pistons now available

[Lilchief]

So what would the recomended cr for a 3.4 with 3500 heads running on 91 octane ?

[geldartb]

Its about 5hp difference from 10.8:1 and 11.5:1 on your setup according to dynomation. I don't know that 5 crank hp would be enough to make me want to keep stock cast pistons over a forged of these quality.

cool thanks Ben.
yeah i would definitely be using these over the old rwd pistons.

these will be this years winter time mod.

[ForcedFirebird]

So what would the recomended cr for a 3.4 with 3500 heads running on 91 octane ?

Ben has a client that is running 12.6:1 (is that right Ben?), we've both had several that are running 11.5:1.

[SappySE107]

12.4:1 is what Eric is running on premium. I would go with the 11.5:1 (10.8:1 with 3500 heads). 91 octane could be midgrade or premium, depending on your elevation. Either way, 10.8:1 should be no problem.

[dimentd]

wouldnt that hi of compression ratios be kind of radical on the street? just thinking in v8 terms i guess but 11.5 and up cr just seem hi for pump gas in a daily driver, could be wrong, first time on this build with a 3.4 rwd and interested in the 3500 swap.

[SappySE107]

With aluminum heads, 11.5:1 is pump gas. I built a 12.4:1 that runs on pump gas for that matter.

[Superdave]

I ran 10.4:1 last year with 89 octane E-10 and had no problems.

[IsaacHayes]

LS1 runs 11:1 stock don't they? There's your high compression V8 streetable comparison right there.

[mfuller]

LS1 runs 11:1 stock don't they? There's your high compression V8 streetable comparison right there.

I don't think they are quite that high out-of-the-box; just checked and the 350HP crate motor is 10.25:1. Just had a friend stuff a LS3 in his 2001 F-body and it was spec'd at 10.7:1 on the compression.

[IsaacHayes]

Might have been LS6 or something. I recall one of them being that high. Oh well maybe not, but 10.7 is up there.

[ForcedFirebird]

Well seeing the "typical" high compression iron head Gen1 V8 can run about 10.5-11:1 and aluminum head can generally run a point higher, even going by what's been done on a regular basis 11.5:1 is really not THAT high, specially when you are talking about super efficient fast burn chambers

[geldartb]

the highest LS motor compression id the LS7 at 11.1.1. then theres the c5r race car with the highest

LS1: A319 T5, 107#
Displacement = 5.7 L. / 346 CID
Bore x Stroke = 99mm x 92mm / 3.90" x 3.62"
Compression Ratio = 10.1:1
Horsepower = 345/350 HP @ 5,200 RPM
Torque = 350/375 #-Ft. @ 4,400 RPM
Redline = 6,000 RPM
Fuel Cut OFF = 6,200 RPM

All engine Generic Data:
Firing Order = 1-8-7-2-6-5-4-3
Spark Plug Type = 41-931
Spark Plug Gap = 1.524mm / 0.06"
Oil Type = Mobil 1 (E) 5W-30 Synthetic or Equivalent
Oil Capacity = 6.5 Quarts / 5.7 L. (With oil filter change)
Oil Pressure (Minimum - Hot):
1,000 RPM = 41 kPa / 6 psig
2,000 RPM = 124 kPa / 18 psig
4,000 RPM = 165 KPa / 24 psig
Length = 519mm / 20.43"
Width = 460mm / 18.11"
Cylinder Bank Offset = 24.10 mm / 0.949"
Bank Angle = 45 degrees
Deck Height = 234.7 mm /

LS6:
Displacement = 5.7 L. / 346 CID
Bore x Stroke = 99mm x 92mm / 3.90" x 3.62"
Compression Ratio = 10.5:1
Horsepower = 385/405 HP @ 6,000 RPM
Torque = 385/400 #-Ft. @ 4,800 RPM
RedLine = 6,500 RPM
Fuel Cut OFF = 6,600 RPM

C5R: A356 T7
Displacement = 7.0 L. 427 CID
Bore x Stroke = 4.160" x
Compression Ratio = 12.5:1
Horsepower = 650 @
Torque = 525 @
RedLine = 7,500 RPM

LS2:
Displacement =
Bore x Stroke =
Compression Ratio =10.9:1
Horsepower =
Torque =
RedLine =
Fuel Cut OFF =

LS7:
Displacement = 7.0 L. / 427 CID
Bore x Stroke =
Compression Ratio = 11.1:1
Horsepower = 500 HP @ 6,200 RPM
Torque = 475 #-Ft. @ 4,800 RPM
RedLine = 7,000 RPM
Fuel Cut OFF = 7,100 RPM
Dry Sump

[robertisaar]

that was informative... and when it mentions bank angle and says 45, it does mean each bank is 45* from the centerline, yes?

[ForcedFirebird]

that was informative... and when it mentions bank angle and says 45, it does mean each bank is 45* from the centerline, yes?

Yes. 90* inclusive (or included) would be the common term used when talking about bank angle - side to side.

[robertisaar]

makes more sense, i couldn't imagine why anybody would make a 45* V8...