Let's spitball... 7.3 with shorter stroke?

Timmy · Feb 20, 2018

golfer said:
on our cylinder head flow bench, a 6.4L head flows about 60% more CFM than a 7.3L head...stock to stock

HEUI is definitely an issue wrt to performance...but unless you want to run a solid/no coolant (7.3L) head, going to common rail isn't a gain.

if you want to run coolant in your 7.3L heads (ie, our CNC ported), you'd still be short on CFM compared to a stock 6.0/6.4L

it's a real nut kicker.

How would a set of stage 2 ported heads from y'all compare to stock 6.4 heads?

elrodalexander73 · Feb 21, 2018

The guys who are using P-pump set-ups they have developed log style intakes, with individual runners, take a look at Smokin Addictions engine build.. Now that is way out of most individuals range of nature, but I've wonderered for quite some time what would some runner style intakes do for head flow and remote mount the turbo (much like the 6.5 diesel) and see what it does. I think some custom log style intakes would drastically improve head flow on a 7.3..

lincolnlocker · Feb 21, 2018

I wondered the same thing about how they achieve more flow for the mechanical setups.

live life full throttle

golfer · Feb 21, 2018

Timmy said:
How would a set of stage 2 ported heads from y'all compare to stock 6.4 heads?

very close. within 5CFM

C'roy78stroker · Feb 21, 2018

Funny you mention that elrodalexander, that's my plan is to remote mount the turbo to passenger fender well. Much like Duramax setups. Then try to come up with a large capacity intake manifold. I've just finished removing the manifolds today. I'll be ordering the flanges and tubing soon.

Timmy · Feb 21, 2018

golfer said:
very close. within 5CFM

Have y'all ever dyno tested the hp gain going from stock heads to your ported heads?

bluedge8 · Feb 25, 2018

elrodalexander73 said:
The guys who are using P-pump set-ups they have developed log style intakes, with individual runners, take a look at Smokin Addictions engine build.. Now that is way out of most individuals range of nature, but I've wonderered for quite some time what would some runner style intakes do for head flow and remote mount the turbo (much like the 6.5 diesel) and see what it does. I think some custom log style intakes would drastically improve head flow on a 7.3..

Technically, it won't change cfm in the head at all. But it may force more air through with boost, you would still have to clean up the flow IN the head.

C'roy78stroker · Jun 11, 2018

I'll be looking into this in case anyone was remotely interested in the original idea. If the stock crank rod journals can be destroked .250, a longer custom rod would be built, combine that with a .010 overbore, displacement would come out to a 6.9L ironically. I also ran numbers on the rod/stroke ratio (1.88) and bore/stroke ratio (1.04) with the altered setup. If the general ratio rules of thumb apply to any internal combustion engine then these numbers make it seem plausible. Plus with a longer rod, there would be more dwell time for the Piston near TDC which would also aid in the fuel injection window problem that we start to face with large fuel at higher rpm's. I'd like to get input about whether or not these calculations could be applied to diesel short block assemblies or not. Seems to me that rod ratio was a reason 6.7 Cummins crowd we're destroking down 6.4 liters.

emev0l · Jun 18, 2018

Timmy said:
Have y'all ever dyno tested the hp gain going from stock heads to your ported heads?

That’s the real question, I’m sure they have, they have their own engine dyno.

I’m 100% sure they make more power, I’ve just never seen any dyno results between 100% stock heads, a mild port job, and Swamps heads.

I’ve also not seen an insane rwhp gain between trucks with stock heads vs trucks with ported or Swamps/Crutchfield/Mondello heads.

There is a gain, but I don’t see it taking my breath away

golfer · Jun 18, 2018

emev0l said:
That’s the real question, I’m sure they have, they have their own engine dyno.

I’m 100% sure they make more power, I’ve just never seen any dyno results between 100% stock heads, a mild port job, and Swamps heads.

I’ve also not seen an insane rwhp gain between trucks with stock heads vs trucks with ported or Swamps/Crutchfield/Mondello heads.

There is a gain, but I don’t see it taking my breath away

117hp

back in 2013 we did 280 something dyno runs, changing from stock heads/manifolds to CNC heads and headers, and tested about 6(8?) different cam profiles (with each inj/head iteration) we worked on with our cam manufacturer.

emev0l · Jun 18, 2018

golfer said:
117hp

back in 2013 we did 280 something dyno runs, changing from stock heads/manifolds to CNC heads and headers, and tested about 6(8?) different cam profiles (with each inj/head iteration) we worked on with our cam manufacturer.

What was the setup that was teated with?

400/400’s a sledgehammer and a big cam?

That’s a solid jump, that’s deffinatly the last piece of the puzzle to make any more power on fuel

Would that be around an 85rwhp difference?

WHITExOBS · Apr 20, 2019

Reviving an old thread becuase i read it and didnt see anyone mention the increased dwell time and longer "slow down/speed up" period before and after tdc you could gain from destroking the engine and increasing rod length. Wouldnt this help to increase the injection window a little bit across the board at all rpm? Theoretically making it possible to squeeze some more rpm before your injection window becomes too narrow again for the heui to keep up.

Just thinking out loud i guess.

C'roy78stroker · Jul 12, 2023

WHITExOBS said:
Reviving an old thread becuase i read it and didnt see anyone mention the increased dwell time and longer "slow down/speed up" period before and after tdc you could gain from destroking the engine and increasing rod length. Wouldnt this help to increase the injection window a little bit across the board at all rpm? Theoretically making it possible to squeeze some more rpm before your injection window becomes too narrow again for the heui to keep up.

Just thinking out loud i guess.

I’m not the most experienced person with engines, but it makes since to me too. My thought was, if the heads already don’t flow enough air for 7.3 liters of displacement, then a de-stroke to smaller cubes would require less air. AND the longer piston dwell time would help with the injection window. I’m sure it’s fantasy land but I thought it could help two known set backs for the platform.

Powerstroke Cowboy · Jul 12, 2023

I would think the shorter the stroke, the less time you have at or before TDC.

But, how can it affect it at all? RPM is RPM and timing is just that timing.

So 4000 rpm and 25* BTDC is the same regardless of stroke length. But, a shorter stroke will have less distance to travel. So less dwell time.