440Source math problem?

Posted By: Stanton

440Source math problem? - 04/06/10 02:31 AM

Got a 440Source stroker kit for an RB ...

4.375 stroke crank
7.1 rods
1.423 comp. height pistons
.009 deck height (down the hole)
10.725 stock 440 deck height

so...
4.375/2 = 2.1875
+ 7.1
+ 1.423
+ .009
= 10.7195 ??? What gives ... where's the .0055 gone ???

This is critical stuff !!!

Posted By: 446acuda

Re: 440Source math problem? - 04/06/10 02:38 AM

Any chance that's a typo from 440source on the compression height?

Posted By: CompWedgeEngines

Re: 440Source math problem? - 04/06/10 02:49 AM

Thats very typical. Many combos are figured for 10.720 as to allow for a -.005 clean up cut off the decks to provide a square , clean deck surface as most old blocks need it, and to be honest, most new blocks deck surface finish is pretty poor. If you need to use Cometics or any other MLS gasket, that .005 will give you enough room to correct the RA for proper finish.

Posted By: Skeptic

Re: 440Source math problem? - 04/06/10 02:55 AM

I'd contact Brandon( before yet another

inflammatory

440 source post) and let him know....If you really spent money with him and aren't just trolling about a math error on his website. The difference could be taken up with a cleanup deck.... Ma Mopar wasn't that careful with deck heights. Good Luck with that.

BTW I checked a few other combos listed on his site, funny thing, that's the only one with a deck height error

Posted By: Stanton

Re: 440Source math problem? - 04/06/10 04:03 AM

Oh, I spent the money all right !! The block's in being machined and we want to zero-deck it based on the numbers but we need to know if they're correct first.

I'll likely make the phone call tomorrow.

Posted By: jamesc

Re: 440Source math problem? - 04/06/10 04:10 AM

Quote:

What gives ... where's the .0055 gone ???

hopefully onto the table of the mill that squaring the block to where it should be. stock deck heights are all over the place. better to have is stack up a little short for clean up room then have it too tall. as mentioned i would consider this common practice not a math error.

Posted By: 1_WILD_RT

Re: 440Source math problem? - 04/06/10 04:38 AM

What it likely is is a typo on the in the hole dimension.. Allot are calculated @.014 in the hole.. This one probably winds up .0145 in the hole.. & I'd be decking the block to 10.710

FWIW I originally decked my current build at 10.720 being conservative & since have shaved another .010 off...

Posted By: AndyF

Re: 440Source math problem? - 04/06/10 04:50 AM

What exactly is the problem? You deck the block to match the rotating assembly.

All the piston vendors assume the deck is shorter than blueprint because they are selling parts for 40 year old engines.

Posted By: Moparteacher

Re: 440Source math problem? - 04/06/10 06:07 AM

I agree. I decked my 383 .050" to get the piston where I wanted it.

Now just hope the crank and rods are as advertised.

Posted By: DaytonaTurbo

Re: 440Source math problem? - 04/06/10 07:42 AM

Quote:

What exactly is the problem? You deck the block to match the rotating assembly.

You do a mock up assembely and measure how far each piston is in the hole so you can square it and mill correctly. I would sooner do that than go off of advertised lengths.

Posted By: POS Dakota

Re: 440Source math problem? - 04/06/10 09:47 AM

Quote:

Quote:

What exactly is the problem? You deck the block to match the rotating assembly.

You do a mock up assembely and measure how far each piston is in the hole so you can square it and mill correctly. I would sooner do that than go off of advertised lengths.

I have friends who think I was crazy to have the bores done first so i could fit the oversized pistons and do a mockup assembly in order to find the true deck height I needed afterwards.

IMO taking your time and getting things right is worth the extra trip to the machine shop.

Id rather do that, than end up with the compression all wrong, or a problem I can't correct afterwards because i put my head in the sand.

Posted By: Dodgem

Re: 440Source math problem? - 04/06/10 11:07 AM

It's only .0055 thou the decks are more often 10.720 than 10.725 and they like to leave a little to square the decks and resurface them. .0055 is not much and would make less than .2 compression difference you would never notice it. My stroker (RIP) needed .015 to square and surface the 40 year old flaws out of the deck. when machinist said they were stock (i did not hear that he wanted .015 to square and resurface) I ordered my custom pistons to be 10.720 0 deck and when we actually started the machining I had to have my pistons cut down .010 or my piston to head clearance would have been .028

Posted By: Jimi_Vignogna

Re: 440Source math problem? - 04/06/10 12:04 PM

Quote:

Got a 440Source stroker kit for an RB ...

4.375 stroke crank
7.1 rods
1.423 comp. height pistons
.009 deck height (down the hole)
10.725 stock 440 deck height

so...
4.375/2 = 2.1875

nominal deck on an rb is 10.720, if it was mine i would make the deck 10.700 and if the pistons are above deeck buy custom cometics in the thickness you need to make the required deck ht. square deck the block first then bore it not vice versa!!!!
+ 7.1
+ 1.423
+ .009
= 10.7195 ??? What gives ... where's the .0055 gone ???

This is critical stuff !!!

Posted By: BobR

Re: 440Source math problem? - 04/06/10 01:50 PM

Quote:

Got a 440Source stroker kit for an RB ...

4.375 stroke crank
7.1 rods
1.423 comp. height pistons
.009 deck height (down the hole)
10.725 stock 440 deck height

so...
4.375/2 = 2.1875
+ 7.1
+ 1.423
+ .009
= 10.7195 ??? What gives ... where's the .0055 gone ???

This is critical stuff !!!

IMO. Not that critical.

Posted By: B G Racing

Re: 440Source math problem? - 04/06/10 02:25 PM

If you want the real(correct) math,you should install the crank,rods and pistons at all 4 corners,then make your measurments and do the machine work if necessary base on the actual numbers or if you have an accurate way of measuring the block at crank center.

Posted By: maximum entropy

Re: 440Source math problem? - 04/06/10 03:19 PM

Quote:

Got a 440Source stroker kit for an RB ...

4.375 stroke crank
7.1 rods
1.423 comp. height pistons
.009 deck height (down the hole)
10.725 stock 440 deck height

so...
4.375/2 = 2.1875
+ 7.1
+ 1.423
+ .009
= 10.7195 ??? What gives ... where's the .0055 gone ???

This is critical stuff !!!

easy there, chief! take a deep breath- there. that's better. is this your first engine? suppliers NEVER sell combos that are zero deck in an unmachined "nominal deck height" block. AND, as an added bonus, they'll give you compression ratios and deck heights based on a number they've pulled out of a hat! some will give you deck height based on -.010 deck ht, some -.015, and so on. ALWAYS mock up and measure YOUR deck height before machining, to avoid "nasty surprises". ALWAYS. if it's off, it's your fault. sorry.

Posted By: Cab_Burge

Re: 440Source math problem? - 04/07/10 04:27 AM

Quote:

If you want the real(correct) math,you should install the crank,rods and pistons at all 4 corners,then make your measurments and do the machine work if necessary base on the actual numbers or if you have an accurate way of measuring the block at crank center.

I use one piston(no rings on it) and rod on all four corners, mark all the measurments down. Don't be suprised on a stock OEM motor to have taper front to back(or visea -versa) as well as a different deck hieght on one side versus the other side. OEM machine work was not even close to blueprint specs on al the Mopar motors I have blueprinted

Posted By: SomeCarGuy

Re: 440Source math problem? - 04/07/10 04:36 AM

Get the deck height correct, then order parts to fit that spec. Or cut it down to what a shelf kit needs.

Sounds like you are in the latter.

Posted By: n_bogie1984

Re: 440Source math problem? - 04/07/10 11:03 AM

ya same way i did mine had it ruff bored, fitted pistons in every cyl to check deck height and rod clearance, then sent it back for final decking and hone. ive learned the hard way to do it right the first time

Posted By: B G Racing

Re: 440Source math problem? - 04/07/10 11:51 AM

Quote:

Quote:

If you want the real(correct) math,you should install the crank,rods and pistons at all 4 corners,then make your measurments and do the machine work if necessary base on the actual numbers or if you have an accurate way of measuring the block at crank center.

I use one piston(no rings on it) and rod on all four corners, mark all the measurments down. Don't be suprised on a stock OEM motor to have taper front to back(or visea -versa) as well as a different deck hieght on one side versus the other side. OEM machine work was not even close to blueprint specs on al the Mopar motors I have blueprinted

We usually install the oil ring to make sure the piston is centered in the bore and not cocked,if not it can be off the amount of the wall clearence usually .005

Posted By: HardcoreB

Re: 440Source math problem? - 04/07/10 12:18 PM

Quote:

What gives ... where's the .0055 gone ???

This is critical stuff !!!

This is typical engine building stuff. Designed to allow for correcting machining errors...you should be thankful! You seem stressed-out over this? If it bothers you too much contract a good engine builder and relax. But your complaint is not justifiable. Now someone, if not many, will read your post and in ignorance (IMO) will be upset over an inherently good dimensional stack-up. Besides all this, did you purchase the best stuff money could buy while expecting a stack-up to be spot-on? Let's say you reach YOUR targeted piston to deck and after running the pistons touch the head. Who's fault would that be now, in your opinion? Again this all boils down to fundamental engine building IMO. Either do it and ask questions where needed, then be thankful for input, or contract it out.