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 Post subject: Another path to 408
PostPosted: Fri May 03, 2019 6:37 am 
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Joined: Tue Oct 30, 2012 4:50 am
Posts: 53
I have a set of 1.250 CH 393 piston sitting around and then I saw an EBAY ad for 5.950 SBC rods....
It dawned on me that maybe I should do some math....
Huh...you can do a 4" stroke with that combo.....
Interesting


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 Post subject: Re: Another path to 408
PostPosted: Fri May 03, 2019 7:54 am 
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Joined: Mon Oct 29, 2012 9:05 am
Posts: 2585
Yes, if the pistons will clear the counterweights. If not, then you have to do some lathe cam grinding and depending on how much you take off, the balance bill could go up considerably.

Sometimes it’s cool to try new combos but sometimes you end up costing yourself a lot more money.

I’d be more inclined to use those pistons with the correct 6” rod, then using a thick head gasket to get the correct quench. Nothing at all wrong with having the pistons hang out a ways....

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 Post subject: Re: Another path to 408
PostPosted: Fri May 03, 2019 10:29 am 
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Joined: Tue Oct 30, 2012 4:50 am
Posts: 53
yeah, its just a thought.
How thick of a gasket can you go? Anyone ever measured the CW clearance with a probe piston on a 4.00 stroke (lets say SCAT crank)with a 6" rod?


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 Post subject: Re: Another path to 408
PostPosted: Fri May 03, 2019 11:00 am 
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Joined: Mon Oct 29, 2012 1:52 pm
Posts: 585
Mpcoluv wrote:
yeah, its just a thought.
How thick of a gasket can you go? Anyone ever measured the CW clearance with a probe piston on a 4.00 stroke (lets say SCAT crank)with a 6" rod?


Places like Cometic will make just about any thickness gasket that you could want something like an .080 is no problem. I used some on a 454 small block Chevy that I built in a production block so that I could "cheat" and use a piston with a 1 inch compression ht popping about .040 above the block. This worked fine and the engine is still running years later.

There are some differences in the counterweights on the Scat 4 inch stroke cranks. I've had a couple that came with round counter weights that took several slugs of heavy metal so you'd just have to measure. I'd think though that its about .100 clearance at BDC with most pistons. One thing that's for certain is that their 6.200 minimum rod 4in crank takes some effort to make work with a 6 inch rod. I tried that one time hoping I could be conservative when cutting down the counterweights and this would allow me to balance it without heavy metal, not so... It ended up about the same as other builds.


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