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Old 02-14-2018, 05:25 AM
C'roy78stroker C'roy78stroker is offline
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Default Let's spitball... 7.3 with shorter stroke?

Just something that came across my mind. I was try to think of a negative to this hypothetical scenario. The ones I could think of would be a drop in torque, added expense for a longer rod, or block deck machining depending on the amount of de-stroking. What drew me this direction was if we had a smaller displacement engine but fed it the same fuel, for sake of max effort, 400/400's and then also ported the cylinder heads... Would the HP numbers go up any higher? Or would we still be breaking even do to fuel and air remaining constant? Just a thought, but I'd like to hear some speculation.
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Old 02-14-2018, 07:09 AM
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Quote:
Originally Posted by C'roy78stroker View Post
Just something that came across my mind. I was try to think of a negative to this hypothetical scenario. The ones I could think of would be a drop in torque, added expense for a longer rod, or block deck machining depending on the amount of de-stroking. What drew me this direction was if we had a smaller displacement engine but fed it the same fuel, for sake of max effort, 400/400's and then also ported the cylinder heads... Would the HP numbers go up any higher? Or would we still be breaking even do to fuel and air remaining constant? Just a thought, but I'd like to hear some speculation.
HP is a function of torque/RPM. I would think that unless you are getting significantly more RPM out of it, then you are taking a step backwards. I could be wrong in my assumption, but I feel like the RPM is limited more by how fast the injectors can operate than the stroke on the 7.3. Destroking it could improve rod to stroke ratio which would increase the longevity of the rods and less stress on the block too.
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Old 02-14-2018, 08:22 AM
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If less cubic inch was what you were after, I would think sleeving down the size of the cylinders would be a simpler way to go about it. I'm very curious to see where this discussion goes. Seems like I remember Morgan saying something about removing cubic inch from a 7.3 in a discussion a few years back. It was all hypothetical but I thought I remembered this conversation happening on here. Good topic by the way.
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Old 02-14-2018, 10:54 AM
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Quote:
Originally Posted by Petro View Post
If less cubic inch was what you were after, I would think sleeving down the size of the cylinders would be a simpler way to go about it. I'm very curious to see where this discussion goes. Seems like I remember Morgan saying something about removing cubic inch from a 7.3 in a discussion a few years back. It was all hypothetical but I thought I remembered this conversation happening on here. Good topic by the way.
I vaguely remember that discussion too. Sleeving down should strengthen the block due to thicker cylinder walls. Rotating assembly would be lighter too due to smaller/lighter slugs.

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Old 02-14-2018, 11:44 AM
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From what i remember somebody, Morgan or HotRodTractor I believe, said the best from a performance aspect would be a large bore and short stroke. The big bore allows for a larger valve area to get the most air in. I believe it was in a discussion on stroker kits for 6.4's and that for strictly adding cubic in. that adding bore was more effective than stroke because of headflow/valve area.

And I think that the 7.3's main issue is the injectors aren't fast enough for high rpm so to make horsepower they are forced to make gobs of torque.

I'd be curious to know if block weakness is more relative to cylinder pressure or from actual engine torque.
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Old 02-14-2018, 03:32 PM
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Increases in cylinder pressures will most likely track increases in torque or vise versa.

Good point about a large overbore and the ability to run larger valves. 7.3 could probably benefit from this, but not sure how it's open area scales from say a 6.0 or 6.4.

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Old 02-14-2018, 05:16 PM
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How about a Big bore short stroke engine with commonrail kit. Sounds expensive.
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Last edited by superpsd; 02-14-2018 at 05:19 PM.
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Old 02-14-2018, 05:40 PM
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Sounds fun!
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Old 02-14-2018, 05:55 PM
JDelaney JDelaney is offline
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Probably be cheaper to punch out a 6.7L to 7.3L.
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Old 02-14-2018, 06:10 PM
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I believe the discussion on removing cubic inch was strictly to deal with the limitations of heui injection system like the OP suggested. Basically making the most of the fuel the 7.3 is able to inject in the given window. With a common rail Injection system, I don't see any reason to eliminate cubic inch when you would have basically unlimited amounts of fuel flow. Head flow would be the biggest limitation after that. That's the way I see it, but I could be wrong.
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Last edited by Petro; 02-14-2018 at 06:12 PM.
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