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Old 07-03-2021, 05:00 PM   #1
martijn266
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Default First engine build, valve options?

Hello,

Im starting my first proper engine build and i'm looking for some advice.
I'm thinking about upgrading my valves to the 46/38 combo but the shop has steel and stainless valves. What would be the right choice and why?


Setup will be:
100k miles b230fk with new bearings and
Mildly ported 530 with 46/38 valves
Upgraded valve springs
H-beams
Holset hx35
3 inch exhaust
6 puck clutch with 850r pressure plate
Megasquirt

Aiming for a 'reliable' 350hp
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Old 07-03-2021, 05:49 PM   #2
cwdodson88
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Either would have trade offs. With stainless you might want do some research into different seat materials to aid in heat transfer. But really, I think steel would be good for your goals and not require as much thought into seat materials and machining.
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Old 07-03-2021, 06:00 PM   #3
culberro
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I’d personally just keep the stock valve size and spend money on getting the ports sorted.

Slapping 46/38 valves into a 530 without substantial port work is spending money without a lot of return in performance.
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Old 07-04-2021, 05:06 AM   #4
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I guess that big valves and stock manifolds(?) are combo where money can be spent more effective.

300 hp with stock B230F is just a walk in a park. Well at least with Re85 fuel.
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Old 07-04-2021, 06:02 AM   #5
martijn266
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Quote:
Originally Posted by cwdodson88 View Post
Either would have trade offs. With stainless you might want do some research into different seat materials to aid in heat transfer. But really, I think steel would be good for your goals and not require as much thought into seat materials and machining.
Do I need to get the seats machined with steel valves? I read in the groupbuy for 46/38 that they are drop in replacements.
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Old 07-04-2021, 06:04 AM   #6
martijn266
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Quote:
Originally Posted by culberro View Post
I’d personally just keep the stock valve size and spend money on getting the ports sorted.

Slapping 46/38 valves into a 530 without substantial port work is spending money without a lot of return in performance.
Would it be worth it with a 531 head? I can get my hands on a decent 531 for not to high of a price
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Old 07-04-2021, 10:03 AM   #7
cwdodson88
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Quote:
Originally Posted by martijn266 View Post
Do I need to get the seats machined with steel valves? I read in the groupbuy for 46/38 that they are drop in replacements.
Sizewise, the might be “drop in” with some massaging done at the machine shop. Like culberro points out, going bigger might not really be better without more work elsewhere.

Here’s a place to start off if you wanted to go down the rabbit hole. There are great write ups and information out there on the subject. And if you haven’t done anything like this before, it might be worth something to spend time on the research before pulling the trigger on parts.

https://www.enginebuildermag.com/201...and-selection/

HP Academy has some good courses on engine building, part selection and information on the “why” you would want to research things further if you select certain parts.

https://www.hpacademy.com/
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Old 07-04-2021, 12:11 PM   #8
culberro
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Quote:
Originally Posted by martijn266 View Post
Do I need to get the seats machined with steel valves? I read in the groupbuy for 46/38 that they are drop in replacements.
46/38 valves will just fit on the factory valve seats. The OEM seat material is of very high quality, so I would not recommend changing it.

Quote:
Originally Posted by martijn266 View Post
Would it be worth it with a 531 head? I can get my hands on a decent 531 for not to high of a price
The issue with flow on the 530 and 531 heads is in the exhaust and intake ports, and the intake manifold. Then the chamber needs to be opened up on the exhaust side because the valve is very shrouded.

Using larger exhaust valves can be an upgrade, but the exhaust port must be ported. This is the same with the intake. The major restriction in the exhaust is not the valve, but the sharp turn and sharp corner that the exhaust gasses must take in the port.

The intake valve size is good for lots of HP (both NA and boosted). The port needs some work, and a better intake manifold to really take advantage of everything.

The 531 will make more power because it does have a better intake port and chamber shape, but it has the same low-flow exhaust port.
I recommend that people just use what head they have and have it mildly ported for those power levels.
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