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Max cubic inch out of a 401
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hohner0006 View Drop Down
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    Posted: Oct/20/2021 at 3:13pm
Hey guys, I thought there was a sticky on here that had 401 cubic inch builds using the stock crank and block with resulting ci displacements. . Since I can't locate it, what is the most cubes you can get out of the 401 with a factory block and crank with max bore and offset grinding of the crank? Can you get more cubes running a molnar crank and rod setup in the same block? Thanks in advance!
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Points: 6881 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 4:49pm
This is the max I've seen on a Jeep Forum, no dyno or other specifics:
MC rod journals offset ground to 1.89(honda) from stock using newer style honda journal rods with a 6" length .927 pin.

401 Bore 4.195 (.030 over)Makes a 446.5CI motor

Rods
Eagle #CRS6000HJ
Manley #14344 or #15564
Carillo #H6000SB927C06

1.346 Compression height pistons(for maintaining stock height on a 401 block) 
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I have seen one at exactly 500.0 cubic inches, stock block and crank. It did run, but AFIK was not successful.

I have seen an extremely top notch engine at 463 cubic inches, worked well and went fast for years.

These combo's are not streetable.

For usable multi-purpose engines I like the typical "Detroit" combo 426 with a .030" over 4.195" bore and 3.85" stroke. Large bores are counterproductive for strength and in my opinion lose power, even .030" is pushing it if you intend on abusing the engine. The 3.85" stroke fits very nicely in a stock crank, nice if your grinder indexes the stroke away from the nearest oil feed hole. There have been stock cranks ruined by hitting the oil feed with more aggressive offsets. It also makes for a nice piston with a 1.265" CH when using a 6" rod.

The 4" Molnar crank does work but is a little tighter to fit the rod and piston assembly below the deck. Needs a 1.2" piston with the same rod.
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Points: 2450 		Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 6:36pm
Originally posted by Trader Trader wrote:

This is the max I've seen on a Jeep Forum, no dyno or other specifics:
MC rod journals offset ground to 1.89(honda) from stock using newer style honda journal rods with a 6" length .927 pin.

401 Bore 4.195 (.030 over)Makes a 446.5CI motor

Rods
Eagle #CRS6000HJ
Manley #14344 or #15564
Carillo #H6000SB927C06

1.346 Compression height pistons(for maintaining stock height on a 401 block) 
You are not going to get anywhere near that kind of cubic inches using a 1.346" compression height piston and further more there is no way I would cut a factory crank down to a Honda journal. 2.00" Chevy journal is fine, but that isn't a 4340 crank and Honda journals are used on Pro Stock engine that have around 3.50"- 3.60" strokes.

As far as a large cubic inch engine using stock OEM parts a 426" is about all your going to get using a 2.00" rod journal. Trying for anymore than that is just not the best use of parts.


Tom
Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods

1969 AMC Rambler Rouge Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project
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Trader View Drop Down
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Points: 6881 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 7:06pm
Yes Tom,
I just copied and pasted and did not do the math. Largest stroke with the 1.98" rod journal would be 3.9481". Works out to be about 436.5 CI.
It's likely a typo.
As you and Ken have stated, I also don't believe this would not be a very good build idea.
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Points: 140 		Post Options Post Options   Thanks (0) Thanks(0)   Quote PAGAENT Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 7:11pm
Here's a consequence of the oil hole being to close to the journal fillet.
Pat Gary
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote hohner0006 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 7:16pm
Thanks guys! I appreciate your input!
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Points: 311 		Post Options Post Options   Thanks (0) Thanks(0)   Quote rgsauger Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 9:48pm
Good luck

Edited by rgsauger - Oct/20/2021 at 9:50pm
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Points: 311 		Post Options Post Options   Thanks (1) Thanks(1)   Quote rgsauger Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2021 at 9:51pm
Originally posted by PAGAENT PAGAENT wrote:

Here's a consequence of the oil hole being to close to the journal fillet.

Ouch!!!
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Originally posted by hohner0006 hohner0006 wrote:

Thanks guys! I appreciate your input!

Just an FYI: I am a Molnar dealer and have supplied rods to a great many of our members here on the forum. I am also lower priced than anyone on the internet. So if you're looking to build an engine I am the guy to see about rods and yes I can get Honda rod journals too, but I really would not recommend them.

Tom
Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods

1969 AMC Rambler Rouge Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project
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