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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
383/400 stroker - 3.90, 3.91 or 3.92 crank?
      #7379940 - Sat Sep 15 2012 06:43 AM

For a low deck stroker running 6.700" rods and pistons with a 1.320 CH (Diamond flat tops) - what should the crank be ground to for final stroke?

I've seen both 3.91 and 3.90 used a fair bit, but if I'm doing the math right (and there's a good chance I'm not)

With 3.90 stroke:

1/2 stroke: 1.95"
plus rod: 6.70"
plus piston: 1.32"

Gives 9.97" against a 9.98" deck height, so all things being equal, the pistons will be .010 down in the hole

With 3.91 it goes to .005 down in the hole and 3.92 should be zero deck

So without going into major block work/measurement, which is the best choice to keep both compression up but also a margin of safety for stretch/expansion of the reciprocating assembly?

Heads will be open chamber - worked 346s

Thanks in advance



gives


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CompWedgeEngines
master


Reged: Nov 03 2004
Loc: Syracuse,NY
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7379945 - Sat Sep 15 2012 06:49 AM

You have no intentions of decking or correcting the block deck?

--------------------
Your work is a reflection of yourself, autograph it with quality.


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sr4440
member


Reged: Feb 06 2008
Loc: Central TEXAS!!!!
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: CompWedgeEngines]
      #7379954 - Sat Sep 15 2012 07:04 AM

Without all the info, how do you expect to make an informed decision? Get the block corrected, then you will have your answer.


Joe

--------------------


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gregsdart
master


Reged: Jan 21 2003
Loc: Frostbite falls, Mn ( Home of ...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: sr4440]
      #7379980 - Sat Sep 15 2012 07:36 AM

Quote:

Without all the info, how do you expect to make an informed decision? Get the block corrected, then you will have your answer.


Joe



If you are expecting a good level of performance and anti knock resistance from this build, measuring and doing it right is the only way.
If you are running flt top pistons and will not have any quench, then you can figure compression with a deck of 9.98 and your compression should be close or less than calculated and if you chose you can live with what you get. If it is still a little high you can band aid it with a thicker gasket. There are large bore gaskets in .040 and .051.

--------------------
GREG
Educated at SHK U
Measure with yardstick
mark with chalk
cut with torch!



528 cubic inch alky injected 440-1 wedge, 3055 race weight.
8.779 at 153.16 mph. 1.289 60 ft. density altitude 1617 feet. Best 60 ft 1.25


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67_Satellite
super street


Reged: Jan 20 2003
Loc: Andrews,In. U.S.of A.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7380002 - Sat Sep 15 2012 08:01 AM

Since you're asking "what the crank should be ground at", I'll assume you're using a factory crank. When I had mine done,due to the indexing of the factory crank I started with, 3.908 was all the machinist could get without going to a .010" U.S. B.B.C. bearing. Could have gotten more stroke with an undersize bearing,but I thought material left for future machining/freshening was more important than a few thou, extra stroke.Your particular crank may allow more or less depending on what it was originally ground at. Whatever stroke you end up with, machine the block to set the deck height to the desired level after a mock-up and measure session. The factory didn't always hold the decks equal side to side or end to end back in the day.

Edited by 67_Satellite (Sat Sep 15 2012 08:05 AM)


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MR_P_BODY
Master


Reged: Jun 13 2003
Loc: Romeo MI
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7380069 - Sat Sep 15 2012 08:56 AM

Have a shop check the deck first... that will give
you a idea what you have and the decision will be
alot easier... you would be suprized how bad some
of the decks are


--------------------

W-9 9.08 @ 149.6 NOW ON E-85
Mike "Raff"...(180)Watching over us
CAR IS FOR SALE


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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: MR_P_BODY]
      #7380159 - Sat Sep 15 2012 10:22 AM

Thanks everyone for the input

The goal was to tread the line between budget stroker vs full-on build and see what's involved

Crank is a new MP 3.75" stroke for B engines

Scenario 1 would be to low-budget - keep the 3.75 stroke, use a reconditioned set of LY rods bushed for the .990 pins and just screw it all together and hope for the best

Scenario 2 is to maximize stroke with the same crank, turn down to 2.200 rod journals and go through the rest with a fine toothed comb. Which appears to be at least a few K more

--------------------
2013 Plum Crazy/white stripe Challenger SRT8 - 6.4 6-speed
...and a 13 second hybrid...


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Thumperdart
Breakin The Law!!


Reged: Jul 12 2004
Loc: High Desert Ca.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7380199 - Sat Sep 15 2012 10:45 AM

I must be the only guy running a 3.900 stroke w/a 413 crank and 6.385 rods. Can`t tell ya any more as far as pin height etc. but almost 13 years later and all`s good.

--------------------

Street driven 3200lbs. n/a 1.39 60ft.6.21 at 110.40 1/8th 9.797 at 135.5........You can`t move foreward when your livin in the past..........


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jafr
member


Reged: Dec 31 2009
Loc: Southern IL.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: MR_P_BODY]
      #7380235 - Sat Sep 15 2012 11:19 AM

More than lkely you will end up with a deck less than 9.98 I have seen blocks that need .020 or more cut to square things up. You need to square deck the block. The deck heights from the factory are all over the place. Decking it will get rid of alot of the chamfer on top of the deck, give you a nice flat surface for the gasket to seal and equalize the height of all your pistons for quench. I have a 470 on the stand for a backup and it runs very well for for it's size.
My opinion is to run the quench as tight as you safely can, this will make more power and reduce the chance of detonation. On a big bore like a 4.375 I think .040 is safe and on a small block I think you can tighten it up to .035 without seeing witness marks on the pistons or heads.


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JohnRR



Reged: Jan 20 2003
Loc: U.S.S.A.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: CompWedgeEngines]
      #7380245 - Sat Sep 15 2012 11:28 AM

Quote:

You have no intentions of decking or correcting the block deck?




DING DING DING ... WINNER .

Vlad, my crank is 3.895 stroke with that rod and piston CH combo, but that was for other reasons .

Get the block squared first , find out what the deck is and cut the crank to put the piston somewhere between 0 and .005 in the hole .


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Cab_Burge
Too Many Posts


Reged: Aug 23 2003
Loc: Bend,OR USA
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7380953 - Sat Sep 15 2012 10:42 PM

With iron heads and pump gas I would shoot for 9.5 to 1 or less compression ratio With aluminum heads I'll settle for 10.5 or less on pump gas with 10 to 15 % Ethanol The 3.90, 3.910 strokers like to rev, in a B or RB motor, the last one I built had a set of B1-BS heads with CNC porting to M.W. sizes, it made 720 HP at 7000 RPM and was still climbing in HP at 7000 the ciustomer siad to stop the pulls at 7000 RPM because he is a bracket racer and wanted to keep the revs. under 7000 RPM Check your cylinder heads CC and go from there I have another stock Mopar 440 crank offset ground to 3.90 stroke for another 440 mild pump gas street build with a set of large valve ported 452 heads, I'm shooting for 9.5 to 1 on it I'm going to use a 7.100 long BB Chevy type rod with Icon # IC-838 pistons, looking for 9.5 to 1 comp. ratio with decent quench

--------------------
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)


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Belvedere1
super street


Reged: Jan 20 2003
Loc: Phoenix, AZ
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7380966 - Sat Sep 15 2012 10:52 PM

Be prepared to spend some extra $$ on getting that crank to balance and cutting the counterweights for clearance. I hope yours works out better than mine did.

--------------------
[image]http://mywebpage.netscape.com/PlymouthBlv/000_0067.JPG
[/image]


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440Jim
Diamond Jim


Reged: Jan 19 2003
Loc: Southern Maryland
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: Belvedere1]
      #7381275 - Sun Sep 16 2012 09:30 AM Attachment (22 downloads)

Quote:

Be prepared to spend some extra $$ on getting that crank to balance and cutting the counterweights for clearance. I hope yours works out better than mine did.


To get clearance of the counterweights in the low deck block, there are several ways.
1) lathe turn (round) the counterweights to about 7.25" dia, keep bobweight ~2350g
2) put large bevels on the edges of the counterweights
3) grind the clearance in the block and leave the crank about 7.50" dia

The larger the bevels, the larger dia you can leave the counterweights. The front and rear (large) counterweights will fit at a larger dia than the inner (smaller) ones.


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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: 440Jim]
      #7381318 - Sun Sep 16 2012 09:57 AM

At this stage it's a bit of a 'what if' exercise but the point on the block is well taken.

The crank in question should not require further machining to fit the B-block as it was made with smaller counterweights and B-sized main journals for exactly that purpose. Plus an 8-bolt flange.

For turning it down if/when the time comes, being friends with a crank shop does occasionally have its benefits....

Thanks all for the great advice!

--------------------
2013 Plum Crazy/white stripe Challenger SRT8 - 6.4 6-speed
...and a 13 second hybrid...


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Evil Spirit
Scared Of Clowns!!


Reged: Jan 02 2005
Loc: Newport, Mi
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7381670 - Sun Sep 16 2012 02:45 PM

I'm sure this will rattle a few cages - oh well. Setting the block deck height to set your quench/combustion chamber/piston clearance is important, as eliminating mechanical interference and checking compression is again, important. Decking a block solely to square it up? More important to help make the intake seal than anything else - don't waste your time or money if you think there's "magic" power there. There probably isn't 5 HP gained by decking the block just to square it up, since most blocks aren't that far off, usually in the .010 range, and cutting only .010 off a block won't change compression enough for a big power gain. You will get the same power increase by a thinner head gasket. So if you are cutting the block to set piston to deck height - whack away. Otherwise there isn't the gain there by trueing the deck to the mains that lot of people seem to believe. I've heard of a lot of people decking blocks, but not equalizing combustion chamber volumes - HUH - whats the difference? Ones just promoted better I guess.

--------------------
Free advice and worth every penny...
Factory trained Slinky rewinder.........


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ou812
super gas


Reged: Jan 31 2003
Loc: SoCal
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: Evil Spirit]
      #7381694 - Sun Sep 16 2012 03:04 PM

Quote:

I'm sure this will rattle a few cages - oh well. Setting the block deck height to set your quench/combustion chamber/piston clearance is important, as eliminating mechanical interference and checking compression is again, important. Decking a block solely to square it up? More important to help make the intake seal than anything else - don't waste your time or money if you think there's "magic" power there. There probably isn't 5 HP gained by decking the block just to square it up, since most blocks aren't that far off, usually in the .010 range, and cutting only .010 off a block won't change compression enough for a big power gain. You will get the same power increase by a thinner head gasket. So if you are cutting the block to set piston to deck height - whack away. Otherwise there isn't the gain there by trueing the deck to the mains that lot of people seem to believe. I've heard of a lot of people decking blocks, but not equalizing combustion chamber volumes - HUH - whats the difference? Ones just promoted better I guess.




Piston to cylinder head quench is main reason to zero deck... .010 tolerance is unacceptable.

--------------------

BRIAN HAFLIGER


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JohnRR



Reged: Jan 20 2003
Loc: U.S.S.A.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7381715 - Sun Sep 16 2012 03:21 PM

Quote:


The crank in question should not require further machining to fit the B-block as it was made with smaller counterweights and B-sized main journals for exactly that purpose. Plus an 8-bolt flange.






Is the crank in question a crank sold by Mopar performance in/around 2003 ? If it is have you actually tried putting it in the block ?


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RUNCHARGER
I Live Here


Reged: Jan 20 2003
Loc: Kelowna B.C. Canada
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: JohnRR]
      #7381740 - Sun Sep 16 2012 03:42 PM

Maybe I reverse engineer stuff. I would set it up with as much stroke as you can get with that particular crank. I would then mock it up before decking and see where it was at. Then I would decide how much to deck it.

Sheldon


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23T Hemmee
mopar


Reged: Jan 06 2010
Loc: Franklin, TN
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: RUNCHARGER]
      #7381748 - Sun Sep 16 2012 03:49 PM

Quote:

Maybe I reverse engineer stuff. I would set it up with as much stroke as you can get with that particular crank. I would then mock it up before decking and see where it was at. Then I would decide how much to deck it.

Sheldon


BINGO!!! We have a winner.....

--------------------
Ronny
6.789 @ 198.63 .996 60' (Yes, it does hurt my back....lol)
John 14:6


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BSB67
top fuel


Reged: Feb 19 2005
Loc: Prospect, PA
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: RUNCHARGER]
      #7381809 - Sun Sep 16 2012 04:28 PM

Quote:

Maybe I reverse engineer stuff. I would set it up with as much stroke as you can get with that particular crank. I would then mock it up before decking and see where it was at. Then I would decide how much to deck it.

Sheldon




Me too. You'll be able to figure out if the shelving piston height will work and either move the CD around, cut the deck, or gasket it to what you want.

--------------------

500" NA, Eddy head, pump gas, exhaust manifold with 2 1/2 exhaust with tailpipes
4150 lbs with driver, 3.23 gear, stock converter
11.68 @ 120.2 mph


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Belvedere1
super street


Reged: Jan 20 2003
Loc: Phoenix, AZ
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: JohnRR]
      #7381812 - Sun Sep 16 2012 04:31 PM

That is the time frame (2002 IIRC) of when I bought mine. It was a great deal $$wise initially, but......

--------------------
[image]http://mywebpage.netscape.com/PlymouthBlv/000_0067.JPG
[/image]


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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: Belvedere1]
      #7381842 - Sun Sep 16 2012 04:53 PM

But what?...

(and yes it is one of those cranks)

--------------------
2013 Plum Crazy/white stripe Challenger SRT8 - 6.4 6-speed
...and a 13 second hybrid...


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Belvedere1
super street


Reged: Jan 20 2003
Loc: Phoenix, AZ
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7382291 - Sun Sep 16 2012 09:14 PM

After having to do all the extras I ended up with several hundred $$ in a brand new crank that was "supposed" to work in a B block. I think there is 5 pieces of mallory metal which is not cheap and then having the counterweights turned to clear the block, but hey, the mains were the right size at least. Like John RR, said, check it before you get too far along in the process.

--------------------
[image]http://mywebpage.netscape.com/PlymouthBlv/000_0067.JPG
[/image]


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Evil Spirit
Scared Of Clowns!!


Reged: Jan 02 2005
Loc: Newport, Mi
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: ou812]
      #7382332 - Sun Sep 16 2012 09:48 PM

Quote:

Quote:

I'm sure this will rattle a few cages - oh well. Setting the block deck height to set your quench/combustion chamber/piston clearance is important, as eliminating mechanical interference and checking compression is again, important. Decking a block solely to square it up? More important to help make the intake seal than anything else - don't waste your time or money if you think there's "magic" power there. There probably isn't 5 HP gained by decking the block just to square it up, since most blocks aren't that far off, usually in the .010 range, and cutting only .010 off a block won't change compression enough for a big power gain. You will get the same power increase by a thinner head gasket. So if you are cutting the block to set piston to deck height - whack away. Otherwise there isn't the gain there by trueing the deck to the mains that lot of people seem to believe. I've heard of a lot of people decking blocks, but not equalizing combustion chamber volumes - HUH - whats the difference? Ones just promoted better I guess.




Piston to cylinder head quench is main reason to zero deck... .010 tolerance is unacceptable.




Yeah, I covered THAT. But spending $100 to deck a block just because it is .010 off "square" is probably the worst $100 you will spend in a short block, because it does nothing to improve reliability, nothing to improve repeatibility (bracket racing) and is marginal at best on power increase. You would be better off putting that money towards coated bearings, piston coatings, better springs or pushrods, etc., than decking a block just to square it .010.

--------------------
Free advice and worth every penny...
Factory trained Slinky rewinder.........


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JohnRR



Reged: Jan 20 2003
Loc: U.S.S.A.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7382694 - Mon Sep 17 2012 08:59 AM

Quote:

But what?...

(and yes it is one of those cranks)




Have you actually tried fitting it in the block ? The best I could tell the crank was a 1053 material, Hemi 3.75 stroke replacement crank with the mains cut to fit a low deck block, the counterweights are HUGE, close to 7.5 if I remember right. I had my crank cut down to 7.200, balanced nicely after that with no metal added, 3.75 stroke in a 383 using Diamond 1.320 and I can't remember what rod, but it wasn't stock.


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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: JohnRR]
      #7382707 - Mon Sep 17 2012 09:06 AM

Test fitting soon. And yes, the counterweights look huge relative to a stock 383 crank.

Given that budgets can escalate pretty quickly, staying with a 3.75" stroke and possibly the stock rod journal sizes may be the way to go.

Or does one dump the crank and start with a 3.915 stroker crank from 440source and put the money into checking/trueing it?

--------------------
2013 Plum Crazy/white stripe Challenger SRT8 - 6.4 6-speed
...and a 13 second hybrid...


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YYZ
Moving Pictures


Reged: Jan 20 2003
Loc: Crack-smoking mayor country...
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7382713 - Mon Sep 17 2012 09:07 AM

John, on that build did you stay with the stock BB journal size or did you have the crank turned down to use a 2.200 journal?

--------------------
2013 Plum Crazy/white stripe Challenger SRT8 - 6.4 6-speed
...and a 13 second hybrid...


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JohnRR



Reged: Jan 20 2003
Loc: U.S.S.A.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: YYZ]
      #7382766 - Mon Sep 17 2012 09:47 AM

Quote:

John, on that build did you stay with the stock BB journal size or did you have the crank turned down to use a 2.200 journal?




I ended up selling the crank before that project got finished, but it did stay with the stock rod journal size while I owned it.

It may be a wash by the time you are done if the CCJ crank needs to have the rods and mains cut undersize to fix it . the plus is it's 4340 instead of 1053 .

But also make sure the CCJ crank fits the block properly also , watch out for the crank hitting the block before the thrust bearing .


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Thumperdart
Breakin The Law!!


Reged: Jul 12 2004
Loc: High Desert Ca.
Re: 383/400 stroker - 3.90, 3.91 or 3.92 crank? [Re: Belvedere1]
      #7382796 - Mon Sep 17 2012 10:05 AM

Quote:

Be prepared to spend some extra $$ on getting that crank to balance and cutting the counterweights for clearance. I hope yours works out better than mine did.


IIRC my 413 dropped right in my 400 block but had to be lightened for the lighter Chevy rods and pistons but don`t rmember how much and my bob weight was around 2243...........

--------------------

Street driven 3200lbs. n/a 1.39 60ft.6.21 at 110.40 1/8th 9.797 at 135.5........You can`t move foreward when your livin in the past..........


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