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Discussion Starter #1
Basically how much does cylinder head flow affect turbo sizing?

I have an intake plenum bolt hole that broke off a while back and it’s been held together with a jimmy rigged fix for now with a long all thread and two nylock nuts. Long story short I haven’t had the time or desire to pull the head to fix it my either welding a new ear and tapping or just replacing the head till recently. I started looking at junkyard heads and then aftermarket and then ported heads and it got me to thinking about how head flow effects turbo size.

For example, the D&J machine stage 1 head flows 220cfm vs 155 cfm for the stock head. The generally held consensus is that the HE351 runs out of its efficiency at about 425hp. Dollars per HP concerns aside, could you slap a higher flowing head like that D&J on and extend the efficiency of the HE351 up to say 475hp (just picking a theoretical number)?

I would imagine cam selection would also make some difference here as well. Just some thoughts and questions for the experts. I know it wouldn’t make sense for most as slapping a bigger turbo on is easy and relatively cheap, but for someone who was thinking about compounds maybe it allows using the high flow head and a smaller single turbo and gets to a similar place as compounds but doesn’t have to redo exhaust brake, the complication of an extra turbo in the engine bay for around the same cost?


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I don't think it's as simple as having more CFM allowing the stock turbo to work better. The problem is a turbos efficency at moving the air, which dictates how dense it will be.

This is why a bigger turbo at a lower CFM can move more air than a smaller turbo at a higher CFM. The smaller turbo starts introducing heat and the density of the air being moved drops. There is also the restriction in flow on the turbo itself.

From what I remember anyway, the stock turbo is a 60lb/min turbo. So 810 cfm or so. Head already outflows the stock turbo, as it's flowing 930cfm total. Stock turbo issue is heat brought on by attempting to push CFM which = a lower density.

Hopefully that made sense.
 

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Adding a ported head will of course add efficiency, meaning you will need less boost to achieve the same power, but if you're talking about milling off the intake manifold and adding a side draft, and porting/polishing both intake and exhaust then your talking big bucks...like 5k minimum. However you can simply get a good valve job done which seems to be a great gain by itself and add some exhaust porting and be done for not much more than a stock replacement. If you aren't wanting to go up over 700hp don't waste your money buddy, it is a waste imo. People have pushed over 1k on a stock head. Yes it will help, but simply adding more boost does the same thing up to a certain point. If you need a stock replacement I recommend the fleece street cylinder head, I just bought one myself. They add thread in freeze plugs, add over sized valve seats and its about what a stock head costs. You can shop for a core on EBay and get it machined yourself and add the valve job.

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From what I remember anyway, the stock turbo is a 60lb/min turbo. So 810 cfm or so. Head already outflows the stock turbo, as it's flowing 930cfm total. Stock turbo issue is heat brought on by attempting to push CFM which = a lower density.
Do you remember where you found that information? I've always seen the head flow in the 150-170 CFM range. Or is the total 930 CFM and the 150-170 is per cylinder?
 

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Do you remember where you found that information? I've always seen the head flow in the 150-170 CFM range. Or is the total 930 CFM and the 150-170 is per cylinder?
Yeah that rating is usually per cylinder, I've always kind of heard it's around 155 like OP said, but never anything exact.
 
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Discussion Starter #6
All interesting thoughts. Absolutely correct that the side draft full she-bang heads are around $5k and at that point probably doesn't make sense.

What I was thinking was more along the lines of the D&J stage 1 head that flows 220cfm that runs $2600 and change. When you add say an SXE362 for $1300, you're at $3900. Depending on the kit you use, that's squarely in the ballpark of a compound setup. Consider someone like me with the MOPAR elbow mounted exhaust and Thuren shock towers- a new exhaust brake is another $1,000 and maybe ditching the nice fancy shocks, maybe a larger single with a ported head starts making some sense and gets you in a similar ballpark performance as compounds.

I guess the real question is where does a ported head really benefit you? Is it only at really high HP levels or can a much more efficient head extend the efficiency of a smaller turbo significantly?
 

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Discussion Starter #7
If you need a stock replacement I recommend the fleece street cylinder head, I just bought one myself. They add thread in freeze plugs, add over sized valve seats and its about what a stock head costs. You can shop for a core on EBay and get it machined yourself and add the valve job.

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That Fleece head looks really nice. Did you consider getting a core head and having work done to it? I'd be curious to know how the costs compare. Also, what did shipping cost on the head and core return?

I live about an hour and a half from Mountain high Performance, who seem to have a really good rep on common rail heads. Been thinking about talking to them about some lower end options. I really don't want to have my current head worked on because I don't want my truck to be down for weeks, would prefer having parts in hand and swap 'em over a weekend.
 

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My stock head was still in great shape but being in the state I am and literally hours away from any decent machine shop I had to bite the bullet and order what I needed. If I had a good shop near me like you it's a no brainer lol go get yours done. You can save money with shipping. I paid around 2k delivered. The head was 1700, then with core of 500 it was 2550 I think but obviously I got 500 back. You can get a nice valve job done with freeze plugs tapped for cheaper than I paid for sure. But this is all assuming you're head isn't cracked which they are known to do.
 

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My head got to me within a week through xdp I highly recommend them or pure diesel power they both have excellent customer service and ship fast.
 

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My stock head was still in great shape but being in the state I am and literally hours away from any decent machine shop I had to bite the bullet and order what I needed. If I had a good shop near me like you it's a no brainer lol go get yours done. You can save money with shipping. I paid around 2k delivered. The head was 1700, then with core of 500 it was 2550 I think but obviously I got 500 back. You can get a nice valve job done with freeze plugs tapped for cheaper than I paid for sure. But this is all assuming you're head isn't cracked which they are known to do.
I’ll have to get a new head since mine having the broken intake plenum bolt hole probably makes it a good candidate for a side draft and that’s about it. It leaks boost noticeably at 25psi and higher. Welding new material in there and re-tapping it just doesn’t seem like the greatest idea and that’s what it would take to fix.


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Discussion Starter #11
There's a rebuilt head on fb marketplace in my area right now for $1200: "Fully rebuilt 5.9 common rail head with new fire rings and new head gasket. Had new guides professionally installed, valve job, resurface, cut for fire rings, stem height and recession set and assembled by a professional machine shop. " and at least looks pretty nice.

Fire rings seem way overkill for my need but that seems like a really good price for a head considering a stock reman from cummins is about $1400 from most vendors, not including shipping and core charge. Thoughts on a Fire ring head on a do-it-all daily driver type truck like mine?

If I bought a $400ish used head, what could I expect to pay to have it rebuilt at a machine shop- decked, new valves, seats and springs (stock level)?
 
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