Blucuda413
Well-Known Member
What is your experience in using a 4.250 crank in a smallblock. I'm sure clearancing at bottom of cylinder would be required but is there anything else?
Big Inch Smallblock
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33IMP
Well-Known Member
I have zero personal experience with a small block Mopar. I know an acquaintance of mine has built a 471 and a 501 small block.
Are you looking at a crank/rod/piston kit, or piecing something together? I would look for a kit that uses small chevy rod journal sizes, Chevy rods and pistons with Chevy pins. Everything would be lighter than Mopar stuff, have better selection of rod quality and sizes, more room in the lower end of the crankcase, wider bearing selection.
Lighter stuff will stress the block less, considering the big stroke.
Are you looking at a crank/rod/piston kit, or piecing something together? I would look for a kit that uses small chevy rod journal sizes, Chevy rods and pistons with Chevy pins. Everything would be lighter than Mopar stuff, have better selection of rod quality and sizes, more room in the lower end of the crankcase, wider bearing selection.
Lighter stuff will stress the block less, considering the big stroke.
My stoker is at 421ci with a 4.125" crank. I got the forged crank/rods from Ohio Crankshaft. Pistons are from Ross. Chevy journals.
The block was a 91' LA roller. We did not have to clearance the block. With a 4.250" it's possible you may have to touch it. Just make sure whatever oil pan you get will accommodate the stroke. I also learned through dyno testing that the extra cube will eat the cam. I went way too small with my initial cam duration. I'm in the process of swapping that cam for a larger one now.
I did a thread about it if you search my profile
The block was a 91' LA roller. We did not have to clearance the block. With a 4.250" it's possible you may have to touch it. Just make sure whatever oil pan you get will accommodate the stroke. I also learned through dyno testing that the extra cube will eat the cam. I went way too small with my initial cam duration. I'm in the process of swapping that cam for a larger one now.
I did a thread about it if you search my profile
schluney
Well-Known Member
Rod angle can get pretty steep at 4.250 and create side loading issues.
Where do you get a 4-1/4 crank for a small block now? Is that going to be a billet only piece? What's the intended end usage, street and strip or strip only?
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mopardude318
Well-Known Member
I’ve never owned one, but I thought the Hughes 426ci kit had pretty decent parts.
www.hughesengines.com
Hughes Engines :: Mopar Engine Performance Parts & Manufacturing
Hughes Engines is the recognized leader in the aftermarket Mopar engine market, specializing in street, strip and racing components and machine work for both enthusiasts and professional racing teams. We have more than 50 years in the business and we only care about Mopars.
www.hughesengines.com
Blucuda413
Well-Known Member
The big inch LA is long been in my mind. Several years ago I decided to do it but when I called Rod for the crank he had sold his last one 2 days prior. He said he didn't know when he would get more. I think it would be neat to have a 454" SBM. I would go 4.125 X 4.250. Use would be a bracket car which should get well into the 9s. Certainly finding one would be a problem but I'm sure one will show up but it must have 340 size mains. All I need would be crank and pistons I've got a few rod choices all with 2 X .927 config, a good X block which will go to 4.125. I also could go 4.125 X 4.125 for a 440 inch engine. There's a 4.250 crank for sale now but it has 360 mains. Just dreaming but if the right item comes along I'll go for it. It would be fun!!!
B3422w5
Well-Known Member
Personally, past a 4 inch crank, I don’t really see any advantages in going bigger from a performance standpoint.
Most heads available for small blocks aren’t even capable of taking full advantage of a 4 inch arm, much less more.
just shorter piston, more side loading, and worse rod ratio.
I actually think the 3.79 deal might be the most optimal choice out there.
Most heads available for small blocks aren’t even capable of taking full advantage of a 4 inch arm, much less more.
just shorter piston, more side loading, and worse rod ratio.
I actually think the 3.79 deal might be the most optimal choice out there.
schluney
Well-Known Member
Im building a 3.79 now >4.00 and airflow becomes limiting factor for most reasonable / feasible builds. Nothing wrong with a well built 3.58 or 3.79 stroke 340 for most people. @PROSTOCKTOM on here is a good choice for crankshafts and rods.
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mopar65
Well-Known Member
If I remember right the huges kit useI’ve never owned one, but I thought the Hughes 426ci kit had pretty decent parts.
Hughes Engines :: Mopar Engine Performance Parts & Manufacturing
Hughes Engines is the recognized leader in the aftermarket Mopar engine market, specializing in street, strip and racing components and machine work for both enthusiasts and professional racing teams. We have more than 50 years in the business and we only care about Mopars.
If I remember right the huges kit use Molnar crank and rods in there kit. I tried to order the 426 kit from them last year. But they were out of cranks at the time and told me they didn't know when they were going to get more in. I talked to them a few weeks ago and they are just now starting to get some crank kits on. When I get some more money saved up. I am going to buy there 426 kit at 12.1+ compression one, for the 360 magnum. That I am going to put in my 91 dakota sport or I might put it in my 1965 plymouth valiant, but it's going to need lots of work before it's race ready. I am wanting to run low tens or high 9 in the 1/4 . Don't know if I can do it. But I am going to try. LolI’ve never owned one, but I thought the Hughes 426ci kit had pretty decent parts.
Hughes Engines :: Mopar Engine Performance Parts & Manufacturing
Hughes Engines is the recognized leader in the aftermarket Mopar engine market, specializing in street, strip and racing components and machine work for both enthusiasts and professional racing teams. We have more than 50 years in the business and we only care about Mopars.
The exception to this is the W2 and up series full house heads with 350 plus cfm airflow. There are some big inch small blocks turning some high rpm with those setups.
Gonna see how it goes on my build. Never built a serious SB before. 4.125 stroke X 4.175 bore. I'm not overly optimistic, as we've had great success with pumpgas hemi engines. New world for me.
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That's should scream. What intake are you using?
Chevy guys were haulin'-*** at one point with that intake. Lots of NHRA Bowtie cars used them. It'll probably work out better with our own lower, anyways. It'll get lots of welding, milling, and grinding.
I’ve never seen a W2/5 go better than 355.
W-7-8-9 will though.
I’ve seen the Chevy guys use MP intakes before as well as some other stuff. They like to break our balls over us using Chevy karts but we all know it’s a multi way street where using your head is best and sticking with your brand could be a limiting factor.
Whatever works to make your stuff quick is what you use.
B3422w5
Well-Known Member
Never seen a W5 head go remotely close to 355. For one thing, they flat aren’t big enough.
I can say this for sure, even a good W5 head is more than used up with a serious effort 4 inch crank deal. You need go no longer stroke on anything like that. Those heads were designed for stock stroke 340-360 mills. Not 400+ inch stuff.
I can say this for sure, even a good W5 head is more than used up with a serious effort 4 inch crank deal. You need go no longer stroke on anything like that. Those heads were designed for stock stroke 340-360 mills. Not 400+ inch stuff.
Rat Bastid
Dunamis Metron
They will go that high. I was at 340 on mine, but it took a **** ton of work.
I think (THINK) I could get close to 400 out of them, but by the time you did all the work you might as well try and find some W7’s because that’s what you’d have.
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