[DeTomaso] stroker kit????

[hoppe1]

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" <daniel.c.jones2 at gmail.com>
To: <detomaso at realbig.com>
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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