Destroked 318

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SS Lancer

SS Lancer

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Hello - thanks to all who have helped me figure this Gasser motor out over the last month or so.
Ok I just purchased a 3.20 Stroke NOS
Bob Glidden crank and its on the way to GA .
Im planning on a 60 overbore or 3.97
Bore and crank accepts standard LA rods which I have a box of new H Beams so im going to have custom pistons made unless someone can come up with a formula for me on this issue .
Still running 340 Rpm heads so I have the 60ths area in chambers I can have that milled out or use it to accommodate a dome piston after all I want atleast 11.5.1 compression or and even up to 13.1 compression if I can achieve it
Thanks Chris
PS yes weight per CI class Im running with.
 
Take it out to .090 and use common 4.00 360 pistons with 6.250 Chevy rods. Would need crank rod bearings turned to Chevy size.or and spacers? You'll need a pretty tall piston using stock rods.
 
or 400 stroker pistons and an even longer rod
how do the weights change
did you check on AL rods?
 
Wyrmrider said:
or 400 stroker pistons and an even longer rod
how do the weights change
did you check on AL rods?
Click to expand...
Still gathering info I can buy other rods if needed I just have new Scat H Beam rods stock 6.123 lenth but they are heavy.
 
They are heavy and they would require a heavy piston
not the high , quick reeving solution-
save them for a stroker
 
tons of cheap light Chevy 2.250 rods as well as 4.00 chevy pistons. Just a supply and demand consequence.
 
pishta said:
tons of cheap light Chevy 2.250 rods as well as 4.00 chevy pistons. Just a supply and demand consequence.
Click to expand...
Ten 4 thank you looks like thats the best alternative im taking several blocks to machine shop to have them checked to see if they can handle a 4.0 bore and get deck height verified then I will need some advice on what to buy
 
before you pull the trigger, check on spacers to allow a chevy rod to ride on a smaller Mopar bearing.
 
You need aluminum rods. I'd turn the rod journals to 2.100 or even 2.000 if you don't move the oil holes too far off.

The smaller journal means a lighter big end, lighter bearing, less friction. And the aluminum rods are much easier on the already questionable strength block.
 
yellow rose said:
You need aluminum rods. I'd turn the rod journals to 2.100 or even 2.000 if you don't move the oil holes too far off.

The smaller journal means a lighter big end, lighter bearing, less friction. And the aluminum rods are much easier on the already questionable strength block.
Click to expand...
Taking it all in thank you
 
old school would just run another bearing as a spacer. You could also get some shim stock and bend it up and notch it if possible or just pin the rod. These look like you'll need to turn down the crank .025 for the smaller big ends of the Chevy.
Eagle SIR rod comparison, very close specs 6.123 and 6.250 compared:


6.123 rods
Approximate Connecting Rod Weight (g):605

Rod Journal Diameter (in):2.125 in.

Big End Bore Diameter (in):2.2500 in.

Pin End Bore Diameter:0.984 in.

Big End Width (in):0.925 in.

Pin End Width (in):1.060 in.

6.250 rods
Approximate Connecting Rod Weight (g):615

Rod Journal Diameter (in):2.100 in.

Big End Bore Diameter (in):2.2250 in.

Pin End Bore Diameter:0.927 in.

Big End Width (in):0.940 in.

Pin End Width (in):1.060 in.
 
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There are some good tips in the articles referenced in the poly thread, read through them
some articles have additional links
 
lets see
chevy rods 2" and 2.1 BBC 2.2
SBM 2.1245
how do we figure chevy rods are bigger and require spacers?
maybe I'm just tired
I did see where one of the Engine Master builds used .060 os bearings as spacers (spacers machined from
one used a 3.4 rod other interesting Poly combinations with 4.1 and 4.2 strokes
 
Wyrmrider said:
lets see
chevy rods 2" and 2.1 BBC 2.2
SBM 2.1245
how do we figure chevy rods are bigger and require spacers?
maybe I'm just tired
I did see where one of the Engine Master builds used .060 os bearings as spacers (spacers machined from
one used a 3.4 rod other interesting Poly combinations with 4.1 and 4.2 strokes
Click to expand...


You don't for the rods. You just turn the journal down and run a Chevy rod and bearing. And it really isn't a "Chevy" rod. It's just a connections rod made to specs GM made up decades ago.
 
yellow rose said:
You don't for the rods. You just turn the journal down and run a Chevy rod and bearing. And it really isn't a "Chevy" rod. It's just a connections rod made to specs GM made up decades ago.
Click to expand...
It looks like the Chebby rods and pistons for a 4.0 bore is my CHEAPEST solution otherwise I will have to run a 6.123 Mopar rods with custom pistons
& just do a 60 over or 3.97 bore on my 318 block .
 
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yellow rose said:
Yup
Click to expand...
Thank you - Hoss
Mongo should have this project going very soon.

FB_IMG_1511270055523.jpg
 
Wyrmrider said:
..
how do we figure chevy rods are bigger and require spacers?
...
Click to expand...
Thats what I originally thought when I was thinking back of the poly build then I looked at the SIR rod data and added the latter part saying these are smaller and you'll need to cut the crank.
 
Ooops... no longer full. PM away!

And just FWIW, the OP and I had discussed the Chevy pistons... eyebrow location was aquestion. Some Icon 351W 4.000" ones looked better, as the eyebrows look to be closer to where the SBM eyebrows are. But the pin bosses need honing out .015" for .927" Chevy pins.

One other thing that came up with the Icon forged pistons was to keep an eye on the distance from the top ring to the deck. One combo that we discussed put the top of the top ring about .160" from the deck... which I think should be usable, especially for racing, but would probably require the use of a better top ring, like a ductile iron one.
 
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Ok sorry been gone a while working on home to sale but got some news today from guy who sold me this crank small change to the specs he said this crank is machined for the 2.00 Chevy rods so that will change a little bit but its on the way .
 
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