Maximizing flow limited combos?

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Mean416

Mean416

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Hey fellas. This is a different spin on a common theme here, relating to power potential vs. flow capabilities of the cyl head.

My particular challenge, at present is I have an OOTB set of aftermarket heads that are flow limited. These are slated for attachment to a 4" stroker combo. (In my case it's a 340 based, not that it matters much). Combo has flat top pistons with valve reliefs and will be around 11.5:1 compression with my gaskets and deck. I have hedman hussler 1-7/8 headers, and (right now) an M1 single plane. I do plan on a head upgrade at some point but it's not in the cards now.

So I totally understand that this combo is very flow limited and from what I've seen pretty much everywhere it'll do good to make in the range of somewhere between 450-500 crank HP, and will probably top out sub 6000 rpm.

My question is, what "tricks" can someone employ to get the most out of a combo like this? For example, I could consider valve job, valve sizing, cam, rocker arm, intake, carburetor, ignition, some exhaust changes etc. It would be nice if said parts would also play well in the future with an upgraded set of heads but not absolutely necessary.

What would you guys do to max out a set of heads? What would a "stock port" class engine do?
 
Different valves of the same size can flow surprisingly different amounts, maybe one the flow bench guys can tell ya the best ones.
 
If I wanted to be sure I went over the 500hp mark, I’d be at least in the mid-250’s.
The particular lobe family used would be a factor.
(Although, if it were going in a bracket car, at 11.5 CR it could be noticeably more…….depending on various vehicle related considerations)

All the heads would really need is a once over to correct any potential “issues”, and a spring/retainer/lock upgrade.
 
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@PRH thanks. That's what I'm looking for.

What would you consider noticably more?

Anything different under consideration relating to other valve events?
 
Mean416 said:
Ohh I'll definitely hit it with nitrous shot anyway but I won't stop at 100 HP lol
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I'm limiting my nitrous set up to 100hp, cast crank, hypereutectic pistons. 50 HP under each plate

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Mean416 said:
@PRH thanks. That's what I'm looking for.

What would you consider noticably more?

Anything different under consideration relating to other valve events?
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The application would dictate the basic duration numbers.
But, in the right application I don’t think low-270’s would be “too much”, but that would be something like a light weight dedicated race car with plenty of stall and a narrow operating window.

If you’re going to spray it anyway, I wouldn’t get too worked up about maximizing the N/A power.
 
Why not just send out the heads to someone with a CNC program. Which are they? Seems like you have the budget to say change other pieces of the puzzle. Why not port and have the heads checked out. Or is this together already and you don’t want to pull the heads. Just read it is not together. I personally would not consider that VERY flow limited.
 
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furrystump said:
Why not just send out the heads to someone with a CNC program. Which are they? Seems like you have the budget to say change other pieces of the puzzle. Why not port and have the heads checked out. Or is this together already and you don’t want to pull the heads. Just read it is not together. I personally would not consider that VERY flow limited.
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Well, I already have most all of the parts and pieces. So if I can tweak a couple things and get another 50hp or whatever....I'd definitely consider it.

Sending for porting, including necessary valve changes, etc. That's gonna end up costing a couple grand.

I could manage a cam change, maybe some valve job, different valve sizes etc. something along those lines is still gonna be a lot less costly.

When I do end up getting new heads they'll likely be Bloomers.
 
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