408 Crankshaft with 6.125 rod

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Starting to look at engine options and have been considering a 408C stroker for a while now to wake up my slug Aussie 302C

There are some kits available however there is a sale on at one of our major performance warehouses and they have a crank and rods on special I can't resist but not 100% they will do the job without requiring custom or special pistons, balancer, timing set etc.

As an example 408 forged kit dished pistons $3300 AUD - crank/rods $1385 which leaves nearly $2K for pistons, rings & bearings

The crank is a Scat 4340 standard weight forged 2.750 main journal 2.100 big end journal however the required rod length is 6.125 which is unusual. Scat part number is 4-351C-4000-6125 or 4351C48 which is no longer in their current catalogue. I found it in an old 2009 catalogue online and they are listed for 351W with 351C mains (use narrow bearings?)

From what little info I can find many of the Scat stroker cranks are a hybrid of some sort and can be used between 351W & 351C providing you use the correct balancer and timing chain set which shouldn't be too hard to find.

The con rods on sale are Scat part no 6612521QLSA which are ultra lite h-beam stroker rods (Chev type) which will suit the crank but my main worry is getting the right piston being as this crank must have been phased out.

Anyways would appreciate if anyone has experience with these different set ups. I might even email Scat themselves to see what they can tell me but the sale ends soon so I need an answer soon.

 
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If you build a stroker with a Scat crank, do yourself a favor and have the block milled for a 1 piece rear main seal. The Scat crank design does away with the oil slinger and 2 piece seals tend to leak with the strokers. Sorry I do not know more about your particular set up.

 
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Starting to look at engine options and have been considering a 408C stroker for a while now to wake up my slug Aussie 302C

There are some kits available however there is a sale on at one of our major performance warehouses and they have a crank and rods on special I can't resist but not 100% they will do the job without requiring custom or special pistons, balancer, timing set etc.

As an example 408 forged kit dished pistons $3300 AUD - crank/rods $1385 which leaves nearly $2K for pistons, rings & bearings

The crank is a Scat 4340 standard weight forged 2.750 main journal 2.100 big end journal however the required rod length is 6.125 which is unusual. Scat part number is 4-351C-4000-6125 or 4351C48 which is no longer in their current catalogue. I found it in an old 2009 catalogue online and they are listed for 351W with 351C mains (use narrow bearings?)

From what little info I can find many of the Scat stroker cranks are a hybrid of some sort and can be used between 351W & 351C providing you use the correct balancer and timing chain set which shouldn't be too hard to find.

The con rods on sale are Scat part no 6612521QLSA which are ultra lite h-beam stroker rods (Chev type) which will suit the crank but my main worry is getting the right piston being as this crank must have been phased out.

Anyways would appreciate if anyone has experience with these different set ups. I might even email Scat themselves to see what they can tell me but the sale ends soon so I need an answer soon.
Assuming a zero deck height, that combination would yield a compression distance of 1.075 which is shorter than most piston manufacturers minimum for a shelf or quasi custom piston. I'm not saying it can't be done but it would require, even a thin ring package, to be moved higher up on the piston exposing the top ring to more heat, which may or may not be OK depending on application. It may also require a reduced pin diameter. Moving the ring package higher also limits the depth of any required valve relief fly-cuts. My 2 cents are, "Just because something can be done doesn't mean it should be done." I'd use a 6.000" rod with a 4.000" stroke crank in a 9.2000 deck block.

 As a side note, many after market cranks have the flywheel bolt holes drilled through the crank flange. This exposes the flywheel bolts to crankcase oil. If an effective method to seal this connection is not used, the crank/flywheel mating surface will seep oil and appear to be a rear main seal leak. Ask me how I know ;) . Chuck

 
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Thanks and from reading other posts i will definitely do the 1 piece seal.

Chuck thanks for the advice and i was thinking that could be the case.

As it turns out the crank/rods have already sold so I've purchased my second option - which was my original plan

Bought the 9000 series cast crank which should be fine for my mild stroker - 4.000 stroke 6.000 inch rod

For the rods they didn't have I-beams so I upgraded to H-beams part no 6600021SA

Should be easier to find pistons for this setup but will be a while before i start this build just buying bits when they are on sale

They had Probe dished pistons at a good price but only .040 and i'm not keen on boring a clevo block more than .030

Haven't even taken the heads off yet so hopefully my bores aren't too bad!

 
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