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Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447003
06/04/13 08:10 AM
06/04/13 08:10 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline
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How far are you willing to go on reducing crank pin size to gain stroke? At some point (2.100, 2.00, 1.889,) there is a loss of strength that is too much. My one shot at a 2.100 size to get 4.00 stroke lived quite a while at 600 hp, 2100 bob weight, 6200 rpm. That was an RB with custom aluminum rods. Without having much experience, I would assume it would be application specific.

Last edited by gregsdart; 06/04/13 08:14 AM.
Re: Offset grinding RB crank for a Lowdeck stroker [Re: gregsdart] #1447004
06/04/13 08:29 AM
06/04/13 08:29 AM
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Vermont
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TrWaters Offline
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As Dan will tell you,there are other factors to consider when trying to gain the largest amount of stroke using the smallest diameter journal size.

Re: Offset grinding RB crank for a Lowdeck stroker [Re: TrWaters] #1447005
06/04/13 09:17 AM
06/04/13 09:17 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline
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Yep. The stock oil holes in the rod journals get out to one side a ways! What else? I suppose the internal passege may get too close to the radius, weakening it?


8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
Re: Offset grinding RB crank for a Lowdeck stroker [Re: gregsdart] #1447006
06/04/13 10:17 AM
06/04/13 10:17 AM
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Syracuse,NY
CompWedgeEngines Offline
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Quote:

How far are you willing to go on reducing crank pin size to gain stroke? At some point (2.100, 2.00, 1.889,) there is a loss of strength that is too much. My one shot at a 2.100 size to get 4.00 stroke lived quite a while at 600 hp, 2100 bob weight, 6200 rpm. That was an RB with custom aluminum rods. Without having much experience, I would assume it would be application specific.




I recently saw both a SBC and a SBF circle track motor, that the jouranals were ground down to Honda size, and they broke. These are asphalt speedway deals, and only about 400HP 2 BBL motors.
Whats funny is they are not allowed to do this, so when they broke, some people found out that they were cheating...double whammy,.....


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Re: Offset grinding RB crank for a Lowdeck stroker [Re: CompWedgeEngines] #1447007
06/04/13 10:38 AM
06/04/13 10:38 AM
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Delray beach, Florida
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Quote:

Quote:

How far are you willing to go on reducing crank pin size to gain stroke? At some point (2.100, 2.00, 1.889,) there is a loss of strength that is too much. My one shot at a 2.100 size to get 4.00 stroke lived quite a while at 600 hp, 2100 bob weight, 6200 rpm. That was an RB with custom aluminum rods. Without having much experience, I would assume it would be application specific.





I recently saw both a SBC and a SBF circle track motor, that the jouranals were ground down to Honda size, and they broke. These are asphalt speedway deals, and only about 400HP 2 BBL motors.
Whats funny is they are not allowed to do this, so when they broke, some people found out that they were cheating...double whammy,.....




That doesn't surprise me in the least. Those cranks just don't have enough material to go that far. I bet they learned a valuable lesson.
Even on a BB mopar crank, there are limits on how far I'll move the stroke. Back when I was doing the welded strokers from OEM cranks they were pretty strong and would hold up to 700 HP and 7500 rpm for many years of service. anything above that back in the day IMO really wasn't worth attempting. 3.75 to 4.15 was a real common one to do although I did do some out to 4.25.
With the availability of decent and inexpensive 4340 cranks available now, why bother with that stuff.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447008
06/04/13 10:54 AM
06/04/13 10:54 AM
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Eighty Four, PA
B G Racing Offline
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Dan,how's the cost compare to take a stock(no radiused) and offset grind it to purchasing a budget radius fillit crank and is there a trade off for strength.And are the cut cranks re-hardened after cutting and what method is use?

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447009
06/04/13 11:19 AM
06/04/13 11:19 AM
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westerly, ri. usa
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440lebaron Offline
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just had my 4.15 mopar/scat crank done to 4.25 2.20 chev rod, what are you folks doing about .060/.070 side clearance, some people leave it alone?


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Re: Offset grinding RB crank for a Lowdeck stroker [Re: 440lebaron] #1447010
06/04/13 11:20 AM
06/04/13 11:20 AM
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Posts: 9,672
Lima, Peru
domingo Offline
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Quote:

just had my 4.15 mopar/scat crank done to 4.25 2.20 chev rod, what are you folks doing about .060/.070 side clearance, some people leave it alone?


thats way too much clearance! I think they sell rods with a chevy journal size and mopar width

Re: Offset grinding RB crank for a Lowdeck stroker [Re: domingo] #1447011
06/04/13 11:32 AM
06/04/13 11:32 AM
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Renton Washington
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Triple Threat Offline
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Side clearance isn't an issue as long as you have some. The oil hole in the crank is the restriction.

There are countless engines running around with way more than the factory specified side clearance.


-Dustin
67 Dart, 9 second, 392" G3 Hemi
68 Barracuda 340 F/SA
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Triple Threat] #1447012
06/04/13 11:37 AM
06/04/13 11:37 AM
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Posts: 9,672
Lima, Peru
domingo Offline
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Quote:

Side clearance isn't an issue as long as you have some. The oil hole in the crank is the restriction.

There are countless engines running around with way more than the factory specified side clearance.




.009" to .017" is whats specified from the factory. I would tend too think 0.07" is too much....I bet you would have lots of oil flying around and getting excessive oil on the cilinder walls, leading maybe to oil control issues with the rings, specially if running low tension oil rings????....

Re: Offset grinding RB crank for a Lowdeck stroker [Re: domingo] #1447013
06/04/13 11:51 AM
06/04/13 11:51 AM
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Renton Washington
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Triple Threat Offline
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Quote:

Quote:

Side clearance isn't an issue as long as you have some. The oil hole in the crank is the restriction.

There are countless engines running around with way more than the factory specified side clearance.




.009" to .017" is whats specified from the factory. I would tend too think 0.07" is too much....I bet you would have lots of oil flying around and getting excessive oil on the cilinder walls, leading maybe to oil control issues with the rings, specially if running low tension oil rings????....




Do a search, there are dozens of threads about side clearance with Chevy rods.

https://board.moparts.org/ubbthreads/show...mp;Main=5697177
https://board.moparts.org/ubbthreads/showflat.php?Number=4983215


Trying not to hijack Dan's thread here, as these are some of my favorite posts. I wish there was more of them.

Re: Offset grinding RB crank for a Lowdeck stroker [Re: domingo] #1447014
06/04/13 11:51 AM
06/04/13 11:51 AM
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Bend,OR USA
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Quote:

Quote:

Side clearance isn't an issue as long as you have some. The oil hole in the crank is the restriction.

There are countless engines running around with way more than the factory specified side clearance.




.009" to .017" is whats specified from the factory. I would tend too think 0.07" is too much....I bet you would have lots of oil flying around and getting excessive oil on the cilinder walls, leading maybe to oil control issues with the rings, specially if running low tension oil rings????....


My Duster motor had from .054 to .032 rod side clearances, it also had .0033 to .0035 rod bearing clearances. I never saw smoke, used oil or had any other issues with to much oil on the cylinder walls The rod bearing clearances dictate how much oil gets out of them, not the rod side clearances I did use a crank scraper in that motor to start with The last crankshaft in that motor started out as a six bolt flange forged import that was 4.150 stroke with Mopar rod journal sizes, I had it offset to 4.300 stroke with 2.200 (BB Chevy) rod journal sizes I have three more 4.150 stroke cranks with Mopar rod journal size throws on them that will get offset stroked like that also As far as costs of grinding and reheat treating check with your local shops first before deciding, it may be cheaper to buy the stroke you want to start with , maybe not depending on how much you pay for the cranks to start with


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Offset grinding RB crank for a Lowdeck stroker [Re: RUNCHARGER] #1447015
06/04/13 12:07 PM
06/04/13 12:07 PM
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Charleston
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sixpackgut Offline
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Quote:

How many hours does this take?

Sheldon




19 hours and counting I guess


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Re: Offset grinding RB crank for a Lowdeck stroker [Re: Cab_Burge] #1447016
06/04/13 12:27 PM
06/04/13 12:27 PM
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Lima, Peru
domingo Offline
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Lima, Peru
Quote:

Quote:

Quote:

Side clearance isn't an issue as long as you have some. The oil hole in the crank is the restriction.

There are countless engines running around with way more than the factory specified side clearance.




.009" to .017" is whats specified from the factory. I would tend too think 0.07" is too much....I bet you would have lots of oil flying around and getting excessive oil on the cilinder walls, leading maybe to oil control issues with the rings, specially if running low tension oil rings????....


My Duster motor had from .054 to .032 rod side clearances, it also had .0033 to .0035 rod bearing clearances. I never saw smoke, used oil or had any other issues with to much oil on the cylinder walls The rod bearing clearances dictate how much oil gets out of them, not the rod side clearances I did use a crank scraper in that motor to start with The last crankshaft in that motor started out as a six bolt flange forged import that was 4.150 stroke with Mopar rod journal sizes, I had it offset to 4.300 stroke with 2.200 (BB Chevy) rod journal sizes I have three more 4.150 stroke cranks with Mopar rod journal size throws on them that will get offset stroked like that also As far as costs of grinding and reheat treating check with your local shops first before deciding, it may be cheaper to buy the stroke you want to start with , maybe not depending on how much you pay for the cranks to start with




...and I was worrying because I had like 0.025" side rod clearance on one jouurnal on a stock 383 I just rebuilt... ... well, one less thing to worry about now!!!

Re: Offset grinding RB crank for a Lowdeck stroker [Re: roadhazard] #1447017
06/04/13 12:32 PM
06/04/13 12:32 PM
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Dan, I'm pricing a 1.850 rod stroker Olds smallblock for a '65 Cutlass S that I've owned since 1977. (there aren't any olds stroker cranks that I know of). What would be a ballpark price for you to grind mains to standard undersize and offset grind 2.125" rod journals to 1.850"?
Here, I'm looking at $400 or so. The guy does custom work on an italian crank machine. It sounds pretty fair to me. What to look out for?
Thanks,
R.

Re: Offset grinding RB crank for a Lowdeck stroker [Re: dogdays] #1447018
06/04/13 01:21 PM
06/04/13 01:21 PM
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Delray beach, Florida
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Quote:

Dan, I'm pricing a 1.850 rod stroker Olds smallblock for a '65 Cutlass S that I've owned since 1977. (there aren't any olds stroker cranks that I know of). What would be a ballpark price for you to grind mains to standard undersize and offset grind 2.125" rod journals to 1.850"?
Here, I'm looking at $400 or so. The guy does custom work on an italian crank machine. It sounds pretty fair to me. What to look out for?
Thanks,
R.




$400.00 dollars is a very fair price for quality work IMO. The most important thing is the guy doing the work, Not the machine he's doing the work with unless it's a worn out pile of scrap.
It's real easy to mess up the indexing when your taking a lot off of the journals. On top of that, some cranks will relax and loose their straightness. That's an easy fix if you know what your doing and do things in the right order.
In other words, it's just a little bit more involved than just grinding some metal if you want it done right.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: sixpackgut] #1447019
06/04/13 01:23 PM
06/04/13 01:23 PM
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Posts: 2,091
Delray beach, Florida
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Quote:

Quote:

How many hours does this take?

Sheldon




19 hours and counting I guess




Hey, don't you have some Chevy heads to port or something. Get back to work and pipe down.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: B G Racing] #1447020
06/04/13 01:31 PM
06/04/13 01:31 PM
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Posts: 2,091
Delray beach, Florida
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Quote:

Dan,how's the cost compare to take a stock(no radiused) and offset grind it to purchasing a budget radius fillit crank and is there a trade off for strength.And are the cut cranks re-hardened after cutting and what method is use?




Bob, I would guess the cost difference depends on the cost of the budget crank and what it costs to fix any problems. Some of them are pretty decent pieces and some are just horrible, so it really just depends.
Naturally there is a trade off for strength. The old OEM cranks can't compare to 4340 no-twist forgings.
As far as sending the cranks out to harden them, NO. If someone really felt they needed that done I'd tell them to buy a 4340 crank and make sure you never grind more than .003" off of it because that's about how deep the plasma nitride penetrates. I've never seen any accelerated or unusual wear on a reground crankshaft that is the fault of the crank.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447021
06/04/13 01:53 PM
06/04/13 01:53 PM
Joined: Jan 2003
Posts: 26,816
Rio Linda, CA
John_Kunkel Offline
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I'm curious, when plunge grinding like that how much do you infeed at a time?


The INTERNET, the MISinformation superhighway
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447022
06/04/13 02:28 PM
06/04/13 02:28 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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Romeo MI
I've had only one crank re-nitrided.. with the work and
the nitriding was like $400.. that was one of my
billet cranks.. I havent seen any difference if it
wasnt done

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