347 advice

CRonaldo773 · Jan 27, 2026

I am currently building a 347, it did have a f303 cam but am looking at upgrading. I have 185cc AFR heads. I would like to make 400-450 whp. I have read that most stock blocks crack near the lifter valley when around 400whp. Just looking for recommendations on better cams as well as other parts while the engine is out.

2000xp8 · Jan 27, 2026

The block will be fine if you don't delete the rev limiter, which is 6250.
Custom cam for sure.
When it comes to a NA engine, 400rwhp and 450rwhp are miles apart.

AeroCoupe · Jan 27, 2026

Custom cam is the way to go. What intake are you looking at? I would think the exhaust would need to be 3” and some good headers to make the 450 rwhp as that is putting you in the 525 to 550 fwhp range.

CRonaldo773 · Jan 27, 2026

AeroCoupe said:
Custom cam is the way to go. What intake are you looking at? I would think the exhaust would need to be 3” and some good headers to make the 450 rwhp as that is putting you in the 525 to 550 fwhp range.

I was looking at the Holley systemax, and long tubes but am trying to find some from other brands other than bbk. Currently I am with the stock intake manifold and short tubes headers and catless xpipe. Another thing that would determine which intake manifold is whether i decide to build for boost or keep it NA

CRonaldo773 · Jan 27, 2026

2000xp8 said:
The block will be fine if you don't delete the rev limiter, which is 6250.
Custom cam for sure.
When it comes to a NA engine, 400rwhp and 450rwhp are miles apart.

Do you recommend NA or boost?

2000xp8 · Jan 28, 2026

NA or supercharged is a pretty loaded question.
I think NA is more reliable.
I also think SC is better to drive.
I'd also say it's debatable on spending the money to build a 347 then adding the supercharger when the blocks limit is already 500rwhp. Personally, i'd be more comfortable with 450rwhp. The finances just don't make sense for the minimal extra gain.

IMO, one of the best driving setups is a 302 with good h/c/i and a low boost vortech. The problem is that everyone gets greedy.

Keep in mind, i would do NONE of this, without building out the suspension and brakes first, maybe even the trans too.

347 advice

CRonaldo773

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2000xp8

AeroCoupe

lube between the nut and the face. I know my lubes

CRonaldo773

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CRonaldo773

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2000xp8

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347 advice

CRonaldo773

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2000xp8

AeroCoupe

lube between the nut and the face. I know my lubes

CRonaldo773

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CRonaldo773

New Member

2000xp8

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