I have a few questions I would like to ask them so I can better understand the brainstorming going on here if no one minds...

What'* a pressed in pin or a floating wrist pin? What are the benefits. What'* a knife edge job?

Press fit wrist pins are pressed into either the rod or piston. Floating wrist pins have clearances in both the connecting rod and piston. Full floating wrist pins have less friction than press fit wrist pins. I could be wrong on that, but that'* my understanding.

Knife edging is machining the crank shaft throws to an edge to reduce weight, air resistance, and any oil it may hit.

an email from 95naSTA, this thread by MyLittleBlackBird, and the LN3 piston thread by clm2112 (HERE), along with wilwren'* incessant search for power gains , have combined to make me think that people may actually be realizing that there are gains to be had by improving rotating assembly geometry...

ya'll know that I’m the nut working on a hybrid of the tall deck SI (EV6) block with the much better symmetrical port heads of the SII (Ecotec) bolted on (I am also looking at several improvements’ to the oiling system/windage as well as more involved roller cam bearings...)

So maybe I can lend a hand...


first off I don’t have all the info (I'm kind of half done with a REALLLY long write-up of my work thus far) of the GN and LN3 and EV6 blocks, but I don’t mind finding out more info! (I already have 3 3800'* in my garage, and i would love to have an LG3 and LN3 along with the SI and SII L67 for comparison purposes... but I’m not sure I have the room )

as Wilwren stated in the thread by clm2112 the SI (EV6 or earlier even the GN) loses all power potential at a fairly low rpm, this is sad because the tall deck long rod rotating assembly makes for a good mid/high rpm Tq curve and breathing (aka more HP as well) the problem is simple...poor head design that doesn’t flow well

the SII engines have the opposite problem, a head that flows extremely well but on a short rod bottom end that lacks the geometry for better induction at high rpm but is very good for low rpm grunt, which also seems to make our FWD trannies cringe

I saw this first hand looking at the flow charts of a seriously worked over set of EV6 (aussie SII which is our SI) heads with spread guides for larger valves and serious port and seat work, which were still out flowed by a set of mildly ported SII heads on the aussie forums...

my thoughts are that for the eventual development of max effort racing 3800'* the best of both worlds needs to be utilized, that said, lets get to work.

The SI (EV6) NA specs
Connecting Rod Bore B/E = 60.295mm - 60.312mm or (2.3738" - 2.3745")

Length Center to Center = 162.052mm - 162.154mm or (6.3800" - 6.3840")

Piston Pin Diameter = 22.995mm - 23.000mm or (0.9053" - 0.9055") Pin to Rod fit = 0.018mm - 0.043mm Interference or (0.0007" - 0.0017")

I do not have the info pertaining to the SC SI L67'* specs or the LG3/LN3 GN engine readily available...

The SII (Ecotec) has some interesting differences...
The connecting rods will fit the crank (SI EV6 or SII Ecotec cranks) as the n/a & */c conrods have the same size connecting rod big end bore of = 60.295mm - 60.312mm or (2.3738" - 2.3745")

Now for the differences

*/C con rod length center to center = 143.256mm or (5.640")

N/A con rod length center to center = 145.80mm - 145.90mm or (5.740" - 5.744")

*/C piston pin Diameter = 22.981mm - 23.002mm or (0.9048" - 0.9056")

N/A piston pin Diameter = 21.995mm - 22.000mm or (0.8659" - 0.8661")

this means that there are differences in the piston compression height as well, particularly because of the ring package spacing due to the differences in the dished area of the piston as well as ring land strength requirements.

now on to my thoughts (which I Knooowww that 95nasta is interested in...lol)
unfortunately there isn’t much that can be done to the SII NA (L36) piston compression height that will allow for a longer rod other than maybe a dykes ring setup or a radial gas ported 2 ring design, but this would call for very good oil control to keep from overtaxing the oil scrapper and keep oil out of the chamber (a good bet would be a Variable displacement AC compressor utilized as a "on demand" vacuum pump to improve this)
however...
Utilizing a EV6 tall deck block (really...who wouldn’t love an extra inch? ) and ditching the tall compression height SI pistons and running a set of aftermarket (and fairly cheap I might add compared to custom jobs, though I hate standard dishes and would prefer a chamber mirror dish design for maximum quench characteristics) forged L36 pistons would let you run a rod that is a full inch longer than the L36 rod,
6.740 > 5.740 as well as being almost 3/8ths of an inch longer than the factory SI rod.

a side by side pic of a 93 EV6 L27 rod and piston next to a 98 SII L36 rod and piston:

L36 on the left 93 EV6 on the right (note the differences in dishes on both NA engines this relates to the difference in combustion chamber volume as well)


Now for my question...

this REALLLY interested me.. the C to C is 6.658 inches correct?
so this rod (given proper big and small end sizing) would work well with a set of SII L67 pistons with the crown cut down .018 inches which increases the quench area a bit as well as lowers the dished area'* volume while having a negligible effect on top ring land strength (the additional material removal required by radial gas porting is minor as well)
what application are those sourced for?
I have looked into the Eagle rods but have focused on the Pauter rods more windage efficient x beam rods $$$ (very close to a diamond shaped beam) since I have been looking at the whole engine design from a max effort point of view...
while it may not me the longest rod you can fit in there it may prove to be a good compromise with a non stroked 3800...

Can you give me more info on that rod?

Regards, James

It'* a cheap 4340 "ultra light" H-beam for the Ford 5.4L engines. I think the wrist pin is .896" bronze bushed for floating pins.... I'm sure it could be fixed up to work. Anything will work if you put enough time into it. Set of 8 ran me about $400 shipped.

*edit* duh, I just re-read your post and noticed you asked what appication it was for, so you are aware already it'* not a GM rod. I can try to dig up the ebay vendor that I got it from when I get home later.

Don’t worry about it...it'* not suitable, too much reworking
This is the rod I have been looking at
Chrysler "RB" 413/426/440 6.760" Eagle "ESP" 3-D H Beam Connecting Rods - .990" Pin
http://www.cnc-motorsports.com/produ...107&CtgID=1003
it'* .020 too long to use with the L36 pistons, however the big end size is identical though the big end width is 1 inch and has to be cut down, it can be narrowed to the correct dimensions without much effort and it wont impinge on the rod bolt area.
the small end while being a bit big .990 vs .904-.905 can be rebushed and offset honed to the c to c distance of 6.740
I can easily hone the L36 gudgeon bore larger the .040 required to use the stronger L67 pin and given enough crown thickness (ala flatop L36 forging, without the dish machined) relieved in a mirror image of the SII combustion chambers.

thank you for getting back to me on that...

Regards, James

As far as custom pistons go, a guy from abbott racing heads got custom L36 forged flat tops from CP. Hes making 271 whp too.

Making 271whp on an NA L36?

Yep.
http://www.abbottracingheads.com/gm3800.html
I had brought this up before and it listed nitrous somwhere but this is actually without nitrous.
The weird part about it are the times. (pretty high)

You saying his 13.3 is pretty high? Considering he did that in 4500ft. density altitude, I don't think it'* too bad. Would you have expected 12s?