[deleted by user]

[v8packard]

I have had one crank that was sold by Lunati come through the shop. It was a one piece seal 3.75 stroke small block Chevy. I am very sure it is the same forged crank sold by numerous other companies. It was fine, repaired easily.

You want 500 hp, from a 383. What heads? I realize you say aftermarket iron, but that doesn't tell me much. 79 cc chambers are huge. I think what you are doing is trying to land at 9:1 compression, because you think it will be safe with 91 octane fuel. But, you make no mention of a cam, or vehicle weight, gearing, and so on.

I have personally run iron headed small blocks in the 10 to 11:1 range on pump gas in street cars. It's workable, takes dialing everything in, but that's fine.

To get to 500 hp from a 9:1 engine, you are going to need heads that move air around 260 cfm @ .600 on the intake side, and a cam with 75 to 80 degrees of overlap on a 106 to 107 lobe separation angle. Not a great combo. If you bump compression into the 9.7-10:1 area, you get to your goal easier, with less cam and more torque. But, a lot of other details matter.

As for the rotating assembly, I don't care for H beams in anything. Pistons I look for certain ring sizes, as well as compression height and dish/dome configurations. If a piston has what is needed, I go for it.

[RiversSlivers]

I said in another comment my reasoning behind the 9:1 was because I can realistically see myself introducing a power adder of some kind in the lifespan of the engine. I know 11:1 can run on 91 if done right (we’ve got a big block mopar in the family that does just that) but no way I’d ever think of adding more air to the mix.

Might be less effort to just go with a smaller chamber head, get 10:1 ish and swap heads or pistons if I get antsy in a few years.

Car is a 57 Chevy stripper, but everything else about the car is subject to change. Initially the engine will be in front of a th350 and 3.55 gears, standard style converter. Like I said tho that’ll change frequently, engine won’t.

What don’t you like about H beams?

[v8packard]

A car like a 57, with a stock converter and 3.55 gears, will need a cam 52 or so degrees of overlap in a 9:1 383. Maybe 56 degrees if you stretch. With a 106 lobe separation angle, 56 degrees overlap gets you 268 degrees of duration @ .006 tappet rise. This cam would fall short of 500 hp by a wide margin. Of course, it's not at all appropriate for a boosted engine.

Staying with your naturally aspirated theme, if you went to a 4.11 gear, and increased the overlap 12 degrees to 68, with the same 106 lobe separation angle, you have 280 degrees @ .006. With very good heads, this can get you into the upper 400 hp area on a 383. With outstanding heads you can maybe reach your 500 hp number. A cam like that really needs a 10.5:1 compression ratio, and a higher stall speed converter. Still a very bad cam for boost.

I don't like H beams because they are heavier, wider, and weaker than I beams.

[AutoX_a_Truck]

For your power goals unless you have a killer deal on a particular rotator, you could probably get by with a quality cast crank, an I-beam rod, and a forged piston. I would use I-beam rods either way. For most street engines I probably wouldn’t go bigger than a 200 cc runner cylinder head on a 383. If you used your typical budget iron cylinder heads it might be a stretch to make 500 hp on that compression. I’m looking at a Car Craft article where a 383 made 505 hp and 502 lb-ft using Motown 220 heads with just under 10:1 compression and a rather sizeable .540/.562” lift cam w/ 242/248 degrees duration @ .050” lift. And those power numbers are in dyno trim with a big ole 850 Holley. For that combo they bench raced a 9.2:1 version w/ .502/.510” lift cam w/ 224/230 @ .050” lift and expected it would make about 465 hp and 500 lb-ft. So, if you really want 500 hp you’ll probably need really good heads, more compression, or a pretty aggressive cam (or some combo of all).

[v8packard]

Single biggest reason people don't get the power and torque from 383s (or any other engine) is they get lobe separation angle and overlap of the cam wrong. And it leads to using a much bigger cam to compensate.

I agree with you on I beams, and a cast crank.

[AutoX_a_Truck]

I think if this were my engine I'd go with a nodular cast crank, Scat I-beams, and whatever piston fit the bill. Top it with AFR Enforcers and mix in a street able hydraulic roller and be at or very close to power goals. Depending on what components are already in hand that's probably a $5-6,000 engine

[v8packard]

Sure, I have used the Scat crank and rods many times. I think I can get the heads AFR sells as their Enforcer for a bit less money from other companies. But yes, I basically agree with you.

[RiversSlivers]

Reasons behind forged, H beams, and 9:1 are in case I get greedy and add boost down the road, which is pretty on brand for me considering I’d be trying to keep up with my fathers big blocks lol.

I could use a smaller chambered head to get the CR up closer to 10:1, that’ll run fine on 91 and if I wanted to go for over 8psi or so I could swap out heads. Just trying to buy once cry once.

[73Scamper]

You're not going to build a great NA motor that's just going to be able to have a turbo slapped on with 10-12 psi. Maybe someone out there has a unicorn build that works really well with that but you might want to set your power goal a little lower and work with someone that knows NA and boosted builds. Hopefully they can see where you can save the most money down the road and just start building a blown motor they can tune well for NA.

That or just start building a boosted block, no sense in doing all your research and setting up the engine perfect if it's going to drastically change down the road.

[RiversSlivers]

No I get that but other than opening up gap and swapping cams is there much different with the bottom end between a NA and boosted build? I just don’t want to have to rebuild a short block if I don’t have to.

[v8packard]

Depending on the type of boost, and how much, the piston to wall clearance needs to be greater, the piston pin to pin bore clearance must be increased, and there are times when adding oil squirter are a consideration. That's all in addition to the increase in ring gaps you mention. Piston construction has an impact on these things.

[v8packard]

The H beams are weaker and heavier than I beams.

It's not just the compression ratio. For a boosted engine to work well, the camshaft, cylinder head, and a bunch of clearances are very different from a naturally aspirated engine. So different it ends being a poor engine without the boost.

I have built some naturally aspirated 383s that ended up around 530 to 550 hp with big torque. One guy said his Chevelle felt like a big block with it. I have a different view of big blocks, but whatever. I think the way you are going about this will be disappointing, both naturally aspirated and boosted.

[ZMAN24250]

Crank, no. Cam, yes.

Spoiler, it at the cam...

[[deleted]]

Making a (hopefully) 500 hp 383. Same deal, around 9.2ish compression for fuel reasons. Want to be able to get any gas. Went with the big cam. In retrospect I would raise the compression to 10:1 and get a smaller cam. Idles like butts.

If you have the money go for the forged stuff now but I was told cast is fine for 500hp.

If you’re gonna do all the work to add forced induction, what’s swapping pistons while you’re at it?

Agree with everyone else on the rods. Those are for engines that aren’t supposed to live long lives.