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  1. #1
    Crazy SVT Poster
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    03-04 cobra short blocks?

    i have a 99 cobra with a pro charger spun a bearing in my motor..So now im going to build my motor I want to keep my block since its an aluminum teskid block..what you guys think is best way to go? getting a used 03-04 rods pistons and cranks? since they come already from the factory forged and also getting my heads redone and throwing my heads on it? or buying a rotating assembly an get machine work done ? im on a budget here just looking for opinions and good info would help

  2. #2
    Insane SVT Poster
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    I have an '01 shortblock with only 5k miles. Forged Diamond pistons.


    http://www.svtperformance.com/forums...hortblock.html
    A few different Cobras

  3. #3
    Jaded olgreydog7's Avatar
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    You need to go at least .020 over on pistons, so no don't get a used set of pistons. The rods would work though.
    99 Cobra, Black, H/C/I, exhaust, T-56, 4.30s, lots of suspension
    322 ci of aluminum mod motor broken in, but not dyno'd

  4. #4
    SVT God shurur's Avatar
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    I'd rebuild the short-block with a forged stoker kit and later look into cams that work with your procharger.

    Not sure how much head work is worth for you; since you are FI.
    I do suspect there are cams that will help and should be decided upon as you choose your piston's dish options...i.e your CR before boost.

    PM NA SVT.
    Last edited by shurur; 08-09-2013 at 10:49 AM.

  5. #5
    Crazy SVT Poster
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    Should I just get a diamond pistons .20 dish with a set of 03-04 cobra rods? An possibly reuse my crank if its on good condition and reuse my block?

  6. #6
    Authorized Vendor Modular Racing's Avatar
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    A rotating assembly would be suggested and a .020 overbore should clean your block up. We have a $2399 forged rebuild special if you wanted to send in your block and crank (gets you Manley forged H beam rods, Manley Forged 2618 alloy pistons, new clevite bearings and total seal rings with all machine work and digital balancing) or we can set you up with a Fully forged Manley/Kellogg stroker kit for $1799. We also have a few sets of 03/04 Cobra Rods, we get $350 set for them.

    Let us know how we can help!

    Modular Motorsports Racing
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    Last edited by Modular Racing; 08-09-2013 at 02:41 PM.
    www.modularmotorsportsracing.com 1-877-MOD-POWR
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  7. #7
    SVT God shurur's Avatar
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    Quote Originally Posted by 2001SilvrGT View Post
    Should I just get a diamond pistons .20 dish with a set of 03-04 cobra rods? An possibly reuse my crank if its on good condition and reuse my block?
    I'm not an engine builder..but Yes keep what you can for money savings.
    as the block, heads, cams and crank are all great on our cars.

    I was just thinking you could scrape up enough cash to get a 3.75 crank that would be great...it may not be an issue because you are FI...

    Some builders hopefully will show.

    On the side:
    Q: What was your PSI with your procharger?
    And did you have it dyno'd?

  8. #8
    Crazy SVT Poster
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    I think I might buy a mmr rotating assembly kit but I was running 7.5 lbs of boost an car made 410rwhp an 367rwtq

  9. #9
    SVT God SlowSVT's Avatar
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    Quote Originally Posted by shurur View Post
    I'm not an engine builder..but Yes keep what you can for money savings.
    as the block, heads, cams and crank are all great on our cars.

    I was just thinking you could scrape up enough cash to get a 3.75 crank that would be great...it may not be an issue because you are FI...

    Some builders hopefully will show.

    On the side:
    Q: What was your PSI with your procharger?
    And did you have it dyno'd?
    There are downsides to stroking a 4.6 and they are all related to mechanics and physics. For me not worth the added cubes especially on an FI motor. If I wanted the more cubes I would spend the $1700 on a Boss 5.0 block. This engine already has too much stroke and not enough bore

  10. #10
    The Shocker IUP99snake's Avatar
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    Quote Originally Posted by SlowSVT View Post
    There are downsides to stroking a 4.6 and they are all related to mechanics and physics. For me not worth the added cubes especially on an FI motor. If I wanted the more cubes I would spend the $1700 on a Boss 5.0 block. This engine already has too much stroke and not enough bore
    True, but it's still less stroke than a 5.4.
    Lincoln Aviator Longblock (NOW BUILT @ 10.5:1) | P1-SC Procharger | Front-Mount Intercooler | BBK Twin 65MM Throttle Body | gReddy Blowoff Valve | 42LB Injectors | Lightning 90MM Blow-Thru MAF | Morpheus 4" Powerpipe | Morpheus Blower-Brace | BBK O/R X Pipe | Mac Cat-Back | Y2K 00R Rims | Tremec 6-Speed | Pro-5.0 T-56 Shifter with 5-speed knob | Aluminum Driveshaft | Fidanza 11" aluminum flywheel | SPEC III clutch | Kauffmann Motorsports Tune | AEM Failsafe Wideband Gauge | Auto-Meter Triple A-Pillar Fuel PSI/Boost/Oil PSI gauges |

  11. #11
    Authorized Vendor Modular Racing's Avatar
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    Quote Originally Posted by SlowSVT View Post
    There are downsides to stroking a 4.6 and they are all related to mechanics and physics. For me not worth the added cubes especially on an FI motor. If I wanted the more cubes I would spend the $1700 on a Boss 5.0 block. This engine already has too much stroke and not enough bore

    Not true, in fact Ford proved it with the coyote by increasing the stroke to 3.650" (from 3.543" of the 4.6) , the engines share the same deck height and bore spacing. Stroking engines has been around as long as engines have been around. OE manufacturers (saleen)have used the 3.800 stroker for years. The bottom line is if they are properly engineered and assembled they are reliable and make great power.

  12. #12
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    Quote Originally Posted by Modular Racing View Post
    Not true, in fact Ford proved it with the coyote by increasing the stroke to 3.650" (from 3.543" of the 4.6) , the engines share the same deck height and bore spacing..
    WELL that is how the 5.0L displacement was achieved...

  13. #13
    SVT God SlowSVT's Avatar
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    Quote Originally Posted by Modular Racing View Post
    Not true, in fact Ford proved it with the coyote by increasing the stroke to 3.650" (from 3.543" of the 4.6) , the engines share the same deck height and bore spacing. Stroking engines has been around as long as engines have been around. OE manufacturers (saleen)have used the 3.800 stroker for years. The bottom line is if they are properly engineered and assembled they are reliable and make great power.
    Any engine builder who understands bottom end geometry (including yourself) knows that stroking an engines especially a 4.6 only makes things worse. It doesn't matter if it's John Q Public or Steve Saleen building the engine, they all are dealing with the same issues. I would be very reluctant to push a stroker as hard as I would a stock stroke 4.6.

  14. #14
    The Shocker IUP99snake's Avatar
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    I'm not trying to make this a "to stroke or not to stroke" argument because it goes a little beyond the scope of the OP's questions..

    I can see where both of you are coming from. Ford chose the stroke in a 4.6 for a reason. There's probably a reason why they didn't go with a longer stroke, especially given how tempted the engineers must have been to stroke it to a 5.0.

    There are a lot of variables that go into successfully increasing the stroke besides simply "increasing the stroke". Piston design, ring locations, skirt length, rod length, rod ratio, counterweight balancing and the piston skirt-to-counterweight clearance are just some of the factors that go into a well designed stroker kit.

    With that being said, there are lots of people who have had great luck with a well engineered stroker kit. Similarly, a poor design warrants bad results. I saw a stroker kit for a 4.6 that was so poorly designed that the piston skirts were shaved off by the crank counterweights. *face palm*.

    When Ford decided to increase the stroke (and bore) in the Coyote motor, they put a great deal of engineering into it to ensure there would be no issues associated with many aftermarket stroker systems.

  15. #15
    SVT God SlowSVT's Avatar
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    Quote Originally Posted by IUP99snake View Post
    I'm not trying to make this a "to stroke or not to stroke" argument because it goes a little beyond the scope of the OP's questions..

    I can see where both of you are coming from. Ford chose the stroke in a 4.6 for a reason. There's probably a reason why they didn't go with a longer stroke, especially given how tempted the engineers must have been to stroke it to a 5.0.

    There are a lot of variables that go into successfully increasing the stroke besides simply "increasing the stroke". Piston design, ring locations, skirt length, rod length, rod ratio, counterweight balancing and the piston skirt-to-counterweight clearance are just some of the factors that go into a well designed stroker kit.

    With that being said, there are lots of people who have had great luck with a well engineered stroker kit. Similarly, a poor design warrants bad results. I saw a stroker kit for a 4.6 that was so poorly designed that the piston skirts were shaved off by the crank counterweights. *face palm*.

    When Ford decided to increase the stroke (and bore) in the Coyote motor, they put a great deal of engineering into it to ensure there would be no issues associated with many aftermarket stroker systems.
    The coyote motor design started from a clean sheet and takes into account the longer stroke. Pushing the 4.6 beyond the original design intent does not which puts the wrist pin into the oil ring, pulls .250" more of what precious little skirt is left in the cylinder and aggravates the rod/stroke ratio. To be honest even the Coyote motor is likely to have made compromises to maintain the same deck height with the 4.6. This motor is packaged very tight with the pistons just clearing the crank throws. As a design engineer I know when you're in that situation any change tends to have a ripple effect along a whole series of components and you end up "robbing Peter to pay Paul". There a compromises built into just about every motor ever made you just want to start with one which have the fewest.

    What I was getting at with the OP is a bigger bore is usually a better way to gain displacement which does not effect on the bottom end geometry. Lots of stroked 4.6 are running around without problems but they are certainly more susceptible to having them vs. a stock stroke mill.

  16. #16
    The Shocker IUP99snake's Avatar
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    Quote Originally Posted by SlowSVT View Post
    The coyote motor design started from a clean sheet and takes into account the longer stroke. Pushing the 4.6 beyond the original design intent does not which puts the wrist pin into the oil ring, pulls .250" more of what precious little skirt is left in the cylinder and aggravates the rod/stroke ratio. To be honest even the Coyote motor is likely to have made compromises to maintain the same deck height with the 4.6. This motor is packaged very tight with the pistons just clearing the crank throws. As a design engineer I know when you're in that situation any change tends to have a ripple effect along a whole series of components and you end up "robbing Peter to pay Paul". There a compromises built into just about every motor ever made you just want to start with one which have the fewest.

    What I was getting at with the OP is a bigger bore is usually a better way to gain displacement which does not effect on the bottom end geometry. Lots of stroked 4.6 are running around without problems but they are certainly more susceptible to having them vs. a stock stroke mill.
    I don't disagree with you. If I could choose one thing or another holding all else constant, I'd go with a larger bore as well. The larger bore helps un shroud the valves, an added benefit. But sometimes the circumstances don't always warrant it.

    If I had to choose between a Boss iron block vs. a stroker crank with my aluminum block, I'd choose to keep the aluminum block all day long. I wouldn't be willing to add 50-100 lbs to the front end just to go with a larger bore when I can add a stroker crank to achieve the same displacement without having to get an iron block.

    Sure, I could sleeve the factory block or go with a Boss aluminum block, but that's way out of my league.

    Here's an idea. It's expensive, but worth considering... The '13 GT500 aluminum 5.8 blocks are going to start coming down in price in the near future. That'll give you a lot of extra displacement without having to run an aftermarket stroker crank.

  17. #17
    SVT God SlowSVT's Avatar
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    Quote Originally Posted by IUP99snake View Post
    I don't disagree with you. If I could choose one thing or another holding all else constant, I'd go with a larger bore as well. The larger bore helps un shroud the valves, an added benefit. But sometimes the circumstances don't always warrant it.

    If I had to choose between a Boss iron block vs. a stroker crank with my aluminum block, I'd choose to keep the aluminum block all day long. I wouldn't be willing to add 50-100 lbs to the front end just to go with a larger bore when I can add a stroker crank to achieve the same displacement without having to get an iron block.

    Sure, I could sleeve the factory block or go with a Boss aluminum block, but that's way out of my league.

    Here's an idea. It's expensive, but worth considering... The '13 GT500 aluminum 5.8 blocks are going to start coming down in price in the near future. That'll give you a lot of extra displacement without having to run an aftermarket stroker crank.
    Unfortunately Ford stuck us with the 3 15/16" bore spacing which makes any thought of a short stroke/ big bore just that It appears the Coyote and 5.8 are saddled with the legacy of the mod motor dimensions. This might have stemmed from having to shoehorn the 4.6 into the FWD Lincoln Continental when the mod motors first arrived. Ford may have done this to minimize the cost of having to completely re-tool for the newer engines.

    They are really pushing the envelope with the new 5.8's 3.700 bore and resorted to nikesil over installing liners as not to remove too much material between the cylinders. A lean injector is going to cost you $5300 just for the block or you will need to get it sleeved which makes the walls paper thin. For me this is not a hot rodder's engine because of the expense involved having a supercharger connected to it. Looking over the 13 GT500 site it appears this fact has not gone unnoticed as very few of those guys are putting big blowers on them and seem to limit the mods to an exhaust and intake. At 650 hp its not worth screwing around and risking the warrantee.

    If one's main concern is weight then aluminum is the only logical choice. My priorities are a little different and place "durability" at #1 above everything else. In that regard iron has a clear advantage over aluminum which for me is worth the 74 lb hit on the Boss 5.0 block.

    Not sure if you've seen one in person but it's basically a Teksid cast in iron as it shares the same constant thickness main bearing bulkheads (the Romeo is webbed), same window venting, siamese bores, larger side bolts and NO JACKSCREWS!, a fatter pan rail and very similar water passages in the front of the engine. All the machine surfaces are "skim" passed and is made from a higher grade iron alloy over the production block. I would not hesitate to use this in a marine application



    This is without a doubt this is the most stout mod motor block available.
    Last edited by SlowSVT; 08-14-2013 at 03:28 AM.

  18. #18
    AKA 01yellerCobra slo984now's Avatar
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    Boss block+stroker crank=

    IMO of course.
    323 BB Stroker, 03 Heads, F1A at 19psi, Ford GT Cams, Bassani mids, catted X pipe, Borla Stingers, 80lb injectors, GT Pumps, CPR rails, -8 fuel line, T-56, 3.90's

  19. #19
    SVT God SlowSVT's Avatar
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    Quote Originally Posted by slo984now View Post
    Boss block+stroker crank=

    IMO of course.
    now there is "enthusiasm"


  20. #20
    SVT God shurur's Avatar
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    Ford seems to like square engines for matched bore/stroke as the new coyote is 3.6x3.6 for the fabled or not fabled equal HO/torque numbers and max rev.??

    I wondered why MMR offered a 3.7x3.6 BB/stroker..5.15L as well as the standard 5.3L BB stroker. And questioned if it was a reliability issue with the 3.7 stroke and these blocks. They claimed it was price points/marketing. Now I'm going to start thinking about it again. I have time, as a short block is Waaay down the road.

    The combos are increasing with 3.5, 3.6, 3.7 bores and 3.5, 3.6, 3,7 stroke so far....maybe someone else will start making modified designed blocks and other stuff in the near future.....

    Good stuff folks..

    OP, 2001SilvrGT, is building his 4.6L
    http://www.svtperformance.com/forums...uld-i-run.html

    Sorry for morphing your thread 2001SilvrGT....
    Last edited by shurur; 08-14-2013 at 08:51 AM.

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