451 stroker, cut the crank or block?

-
ramenth

ramenth

Gratis persona
Joined
Apr 27, 2009
Messages
19,241
Reaction score
6,598
Location
Prattsburgh, NY
Asked this question in the another thread and never got an answer, so I'm reposting. I have a 400 from my old Ramcharger and a forged 440 crank. This combo is going together for a stroker engine in my bro's '81 D150. I've heard compelling arguments on both sides of cutting the crank to fit the block or cutting the block to fit the crank.
Personally, I was thinking of cutting the block and going with crossbolt mains since it will have to be aligned anyway. The crank -and I'm still thinking on this one - may get knife edged for lightening it up and reducing windage. Stroker kits aren't gonna happen, not for the price, as the machining would still have to be done on the block and I already have the necessary components to assemble the bottom end, minus the mains.
 
IMO, I would keep as much strength in the block as you can, so I would cut the crank. You already said that you were going to do work to the crank so when they have it setup in the crank grinding machine have them turn the mains down and you need to cut the counter weights 3/16 for clearence anyways. This way the block could still be used as a 400 at a later date. If need be.
 
Like I've said, I've heard compelling arguments for both. I know cutting the crank lightens it, was just wondering if crank flex came into play, but I suppose if I have the counter weights knife edged at the same time as they get cut down for clearance then that issue doesn't come into play. Thanks, guys, always nice to have the insight.
 
The weak spot is the block. So I would cut the crank. You mention not having money for the stroker kit... The stroker crank itself may be cheaper (Brandon's anyway) than the machining on the factory one. Especially if you are knife edging and adding big radii and lightening. The new crank in a better material is $600 plus shipping. The last crank I had done without kinfe edging or lightening, but having it indexed and corrected, plus the turn and polish went $350. I havent had a forged crank that needed to have the counterwieghts cut down to fit a B block, but I've heard of a few that did. Also, dont go too light or you'll be adding metal to balance, for more money... If it was me I'd just have teh mains and rods cut, then test fit it to make sure the counterweights are ok. Run it that way. You wont break it...
 
After a few weeks and a trip to TN by my folks I got a quote from the machinist I trust to handle this job. He's quoting the job I asked him to quote: bore, align bore, installing crossbolt mains (my option depending, although for street use he thought it might be unnecessary) cutting the crank, balancing, as well as knife edging. Let's just say, I'm very pleased with the price.
 
I can appreciate sweeping up all the parts one has lying around to make something useful, but why build a 451 when a .040" over 440 (448CI) is basically the same thing? Plus you get a better rod/stroke ratio. The added expense of fitting the crank and getting custom rods and pistons doesn't seem worth it to me. Maybe the short rod and smaller piston is a bit lighter but you can get some pretty nice light weight pistons for a 440, and since you are going to rebuild it anyway.... For a 6-6500 RPM street/strip engine a basic 440 should be good enough.

Anyway, for the 451 build I would think you would want to cut the block rather than the crank to preserve the journal overlap, plus I thought there is plenty of material in the block (.062" per side to be removed) unless the block casting won't allow it for some reason. I also know there are plenty of 451's running with cut down cranks without issues so I guess it doesn't matter. Just my thoughts.
 
TheGreenSlime said:
I can appreciate sweeping up all the parts one has lying around to make something useful, but why build a 451 when a .040" over 440 (448CI) is basically the same thing? Plus you get a better rod/stroke ratio. The added expense of fitting the crank and getting custom rods and pistons doesn't seem worth it to me. Maybe the short rod and smaller piston is a bit lighter but you can get some pretty nice light weight pistons for a 440, and since you are going to rebuild it anyway.... For a 6-6500 RPM street/strip engine a basic 440 should be good enough.

Anyway, for the 451 build I would think you would want to cut the block rather than the crank to preserve the journal overlap, plus I thought there is plenty of material in the block (.062" per side to be removed) unless the block casting won't allow it for some reason. I also know there are plenty of 451's running with cut down cranks without issues so I guess it doesn't matter. Just my thoughts.
Click to expand...

If you use the 440 rod it has the same rod ratio as a 440 plus revs quicker from less rotating mass and it's all in a shorter more ridged block giving you more room in the engine compartment.

Just cut the crank.
 
1wild&crazyguy said:
If you use the 440 rod it has the same rod ratio as a 440 plus revs quicker from less rotating mass and it's all in a shorter more ridged block giving you more room in the engine compartment.

Just cut the crank.
Click to expand...

block, rods, crank are all things that I have here on hand, with just bearings and pistons needing to be bought. Since my machinist has done this build before, on several occasions and knew exactly what to do, it'll be going to him. He is advising, since it'll be a street engines, that crossbolt mains may be a bit overkill, but added that the extra strength never really hurts and he'll do it if I want the added expense. Still thinking on that one, but since I had him quoting the job, figured I might as well get a quote for the whole thing and go from there.
 
No need to cross bolt unless you plan on reving it 7500+RPM all the time.
I would have oil mods done waaay before cross bolting it.jmo

Girdle might be cheaper....maybe.
 
1wild&crazyguy said:
No need to cross bolt unless you plan on reving it 7500+RPM all the time.
I would have oil mods done waaay before cross bolting it.jmo

Girdle might be cheaper....maybe.
Click to expand...

Yeah, that's what he said about the crossbolts, so figuring that money will be spent elsewhere on the truck. And oil mods are done on every rebuild aren't they? :-D
 
I'm not one to argue with physics, and I have to admit I've thought about the combo my self, but it's definitely not the cheap and easy way out. I imagine a reliable 7000 RPM shift point motor based on a low block and 3.75" stroke using mostly factory parts is very doable.
 
No oil mods are part of a typical rebuild. Only some of the performance shops I know of do anything either. The mopar oiling system is pretty good on it's own in terms of volume and delivery. At least until you get into higher sustained rpms. Like over 6K. With proper clearances even a stock oil system can keep things together at 6500.
 
moper said:
No oil mods are part of a typical rebuild. Only some of the performance shops I know of do anything either. The mopar oiling system is pretty good on it's own in terms of volume and delivery. At least until you get into higher sustained rpms. Like over 6K. With proper clearances even a stock oil system can keep things together at 6500.
Click to expand...


This has been my experience. 70# spring and go-go-go.
 
You must log in or register to reply here.
-

Back
Top