[DeTomaso] stroker kit????

[Ken Green]

I was poking around on the CNC motorsports web site and found there forged stroker cranks that may be a good deal:
   
  http://www.cnc-motorsports.com/product.asp?ProdID=17242&CtgID=7154
   
  http://www.cnc-motorsports.com/product.asp?ProdID=17243&CtgID=7154
   
  I think they must be used?  They are internally balanced, it might cost a lot more to have a crank internally balanced than these are selling for.  They sell Eagle H beam rods for $335, so just buy pistons (they will have to be custom and fairly expensive), and for about $1500, you have a pretty decent rotating assembly?
   
  Ken

Jason Eaton <jason.eaton at gmail.com> wrote:
    I just wanted to chime in with my stroker expierence. I have a 408 cid motor with 6" rods and 2" stroke crank. The crank is a Scat crank. As Dan said the ring pack is very compact. I think the compression height on the pistons is only 1.20". The oil ring falls on the wrist pin. I have had no problems with the motor except a lose rocker arm which was my fault. However I didn't break anything. I have bout 15k on the motor which is primarly used for track events and an occasional cruz in the summertime. 
   
  The motor is clevland block motor and the crank is a windsor crank. The mains were turned down to fit cleveland and the rod journals are chevy size. The pistons are Ross postions custom made for my A3 heads triangle shape combustion chamber. 
   
  We dynoed the car at 400 rear wheel hp. I suspect that were doing a little more then that now after adding my QuickFuel carb.
 
  Crank: http://www.jasoneaton.net/pantera/blosxom.pl/2000_11_19.html
  Assembly: http://www.jasoneaton.net/pantera/blosxom.pl/2003_01_27.html
   
  Good Luck.
 
  On 3/2/06, Ken Green <kenn_green at yahoo.com> wrote:   The story I was given about 3 years ago is that all the forged cranks use to come from Japan, but the factory burned down about 10 years ago.  A new factory was built, but the volume for Ford cranks was not high enough to get set up for them.  As a result, the forged Ford cranks all come from China now and are OK as far as metal quality, but the machine work isn't real good.  So the result is that when you buy a SCAT or an Eagle crank, the difference is the machining done here to finish the crank. 

Can anyone verify that?

What breaks in a Cleveland?  I don't recall busted cranks.  I know there are busted pistons, and spun bearings.  It would be useful to put together a spreadsheet for rotating assembly and valve train failures.  I guess block failures too. 

Ken

hoppe1 <hoppe1 at cox.net> wrote:
Just to add more options. I have a Eagle 4340 crank with 3.75 inch throw
that makes 383 CI. I decided on the Eagle because it is suppose to be 
stronger than the Scat.
Rich
----- Original Message -----
From: "Daniel C Jones"
To:
Sent: Thursday, March 02, 2006 11:08 AM
Subject: Re: [DeTomaso] stroker kit????


>> My experience with the three 393 Cleveland Strokers was not good. They 
>> all
>> felt from day one like they were going to grenade....Allot more vibration
>
> Mad Dog, can any of those failures be attributed to the increased stroke?
> As I recall, these engines were built by a different engine builder and 
> the one that had the block I sent you was blamed on a broken camshaft.
> If you felt vibration, there was something wrong from the get go which
> I doubt can be blamed on the 3.85" stroke. I've driven a 4.1" stroke 418
> that was nice and smooth and made 556 HP on the dyno under 6000 RPM.
> The piston speed at 6000 RPM of that engine may be the same as a 3.7"
> stroke
> engine at 6600 RPM so the stress on the rods is similar but the rest of 
> the
> parts (valvetrain in particular) benefit from the reduced RPM.
>
> Rod stress increases in proportion to stroke and by the square of rpm.
> While we often speak of RPM, it's really the piston speed that counts. 
> Increasing stroke means increased piston speed at the same RPM so, all
> other things considered, the maximum RPM the short block can sustain will
> be decreased. A stroker offsets this since you can make power at a lower 
> RPM level which has benefits when it comes to valve train life.
> Short rods increase acceleration near top dead center which is a little
> harder on the rods but helps flow in large port cylinder heads. Longer 
> rods are easier on cylinder walls but the trade-off is in pin location
> and ring pack. Gas loads dominate at low rpm, inertia loads at high rpm.
> Excessively high piston speed will exceed the mechanical limitations of 
> the
> materials. Excessive side loading will create increased friction on the
> bore and the pin/rod and rod pin on the crank. The load on the crank is
> a function of the RPM, the weight of the rods and pistons, the stroke, and 
> the balancing/counterweighting. Reducing RPM, reducing stroke, reducing
> piston and rod weight will all help, as will a stronger crank.
>
> Longevity is dictated by the power the engine makes, the strength 
> of the components, piston speed (a function of RPM and stroke), rod
> to stroke ratio (side wall loading) and rin pack (narrow ring packs
> don't seal as well, tend to rock at TDC) and the RPM you turn, not to 
> mention tuning factors (pinging, additional thermal loads due to running
> lean, etc.).
>
>> If I don't expect to rev 7500 rpm.. and seldom see 5500 rpm.. then I can
>> go with the 393 and make sure of my 4V heads and ITB? :) 
>
> Yes. For lower RPM like that, I'd jump to a 4" stroke for 400+ cubes.
>
>> What type of parts should I be looking for and would it basically fit the
>> 351C without much modification? I just don't want to run into unexpected 
>> issue where the machine shop has to do a bunch of other things to make it
>> all work out...
>
> You gotta do your homework. A number of small issues, no major shopw
> stoppers.
> Most of the inexpensive aftermarket cranks are not true Cleveland
> dimension
> cranks, rather they are listed as "Cleveland style" because they use the
> 351C
> main diameter ut in most other regards are Windsor. They are cranks 
> originally
> designed to go in Ford Motorsport hybrid blocks (or other race block)
> which
> combine the 2.75" Cleveland mains with a Windsor architecture. The
> Cleveland
> snout is longer than the Windsor one. Most aftermarket "Cleveland style" 
> cranks use the Windsor snout. Cleveland cranks have a "snout ring" ahead
> of
> the #1 main, to space the lower sprocket out to clear the journal.
> Windsors
> have a collar on the back of the sprocket and are machined flat ahead of 
> the
> journal. When using a "Cleveland style" crank in a 351C iron block, a
> Ford
> Motorsport spacer (part number M-19009-A341C, required with 351 SVO
> crankshaft
> when used in production iron 351C engine), will fix the problem. The 
> spacer
> is not a press-fit and you can push it on by hand. There are true
> Cleveland
> spec aftermarket cranks but they tend to be custom order. Also, RDI
> stocks a
> hybrid 351W/351C timing set from Dynatech to match the Windsor crank snout 
> in
> a Cleveland block. Some have reported balancer fit issues but Dave
> Williams
> said my Romac balancer fit snugly on my SCAT 4340 crank as did the FRPP
> balancer on a friend's stroker. 
>
> The Cleveland #3 (thrust) main is narrower by approximately 0.009" (as
> measured by Jim Sams). Most aftermarket cranks with 2.75" diameter mains
> use the narrower Cleveland thrust width which allows the use of Cleveland 
> main bearings but ask before ordering. The main bearing spacer kit that
> allows 351W blocks to use 2.75" diameter cranks uses the 351W thrust width
> which requires a special thrust bearing (available from Ford Motorsport). 
> The cast iron 2.75" diameter main Ford Motorsport Sportsman cranks have
> the
> 351W thrust width to match the spacer kit. The 4000 series SCAT
> "Cleveland
> Style" cranks have the Windsor snout but have 2.75" diameter mains and
> take
> 351C bearing, including the thrust bearing.
>
> Most aftermarket cranks use small block Chevy 2.1" diameter rod journals
> and
> 0.940" width rods. However, Ford Sportsman and certain 3.85" SCAT and
> Eagle
> cranks are set up for 2.311" diameter 351W rods.
>
> SCAT offers their cranks in versions to use with 6.000, 6.125, and 6.200
> inch long rods, the difference being in the OD of the counterweights. 
> My engine builder wanted to external balance to 28.2 oz-in and suggested
> ordering the 6.2" version, even though we are using 6.0" rods. That way
> he wouldn't need to use any expensive Mallory metal for balancing (could 
> grind down the counterweights as needed). The tech at SCAT (Brian)
> insisted this was a mistake. He said that the 6.0" version would likely
> need to be lightened. Furthermore, he said the counterweights are cam 
> profiled on a CNC machine and that turning them down on a lathe would ruin
> the balance and not have the desired effect. Dave mentioned he had to
> spend
> a lot of time lightening the crank throws to get the crank into balance. 
>
> Canted valve Cleveland heads require uniquely positioned valve notches
> at the edges of the pistons. The limiting factor for Cleveland stroker
> pistons is often the valve notch in the block and pistons. Cleveland 
> blocks are usually notched at the tops of their bores for valve
> clearance/shrouding which can place a limit on the top ring placement
> (needs to be below the valve notch at TDC plus rod stretch). The depth of 
> the notch varies from block to block but on my Aussie XE block, it was
> about
> 0.27" down from the deck. If running quench heads on pump gas, you'll
> probably want a dished piston for anything over 3.7" stroke. If so, don't
> use a circular dish. A d-dish is better and a mirror image of the
> combustion
> chamber is better yet. Wiseco will do a mirror dish if you send them an
> image. You need a flat pad on the piston where the quench pad is on the 
> head to maximize the quench effect.
>
>> If I believe correctly.. a stroker basically has a longer stroke and
>> that's
>> via a modified or different crank that's larger in diameter... mm longer 
>> rod?...
>
> Stroker math is simple :
>
> rod length + crank stroke/2 + piston pin height = deck height
>
> Of course, you can rearrange the equation anyway you want to solve for a 
> particular variable. The deck height of the block is fixed so you have to
> juggle the other parameters to keep the same stack height. You could
> shorten
> the rod but it's best to increase the rod length with increasing stroke to 
> preserve the rod to stroke ratio. A good rule of thumb from Jon Kaaase is
> to keep the rods 2"+ longer than the stroke. What is usually done is to
> move
> the pin up on the piston to offset the stroke and rod length increases. An 
> example of a 4" stroke, 6" rod, and 4.030" bore for 408 cubes in a 9.2"
> deck height Cleveland block. Assuming zero deck, the stack up works out
> to
> be:
>
> piston pin height = deck height - (rod length + crank stroke/2) 
> = 9.2 - (6.0 + 4.0/2)
> = 1.2 inches
>
> 331 and 347 cubic inch strokers are popular for 5.0L Ford V8's these days.
> 5.0L V8's have a deck height of 8.2", so plugging the pertinent values 
> into
> the formula yields:
>
> deck height - (rod length + stroke/2) = pin height
> 8.2 - (5.4 + 3.4/2 ) = 1.100 inches
> 8.2 - (5.4 + 3.25/2 ) = 1.175 inches
>
> so you can see the 1.2" pin height of a 408C stroker is better than the
> popular 5.0L stroker kits.
>
> Rod to stroke ratio for the 408C is:
> = 6.0/4.0
> = 1.5
>
> A r/s of 1.5 is on the low end of production Detroit V8's (slightly less 
> than a Chevy 454 but slightly more than a Chevy 400), so should be fine
> for
> a hot rod motor.
>
>> Would i need a custom piston or a normal forged 351C piston would be
>> fine? 
>
> Custom pistons will be required due to the pin location.
>
>> And then of course i'll need new main and cam bearings... piston rings...
>> etc for my typical engine rebuild right? :) 
>
> Yes. You have the freedom to specify the ring widths and style with your
> custom pistons. The block or crank may need clearancing to fit a stroked
> reciprocating assembly and you have to verify the cam's not in the way as 
> the
> rods swing around. The 351C bottom end is roomier than a SBC so these are
> not generally big problems.
>
> Dan Jones
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