Musi Pump gas 555
 

Musi sells a crate Chevy 555 touted as big power at 676 -723hp runs on 91 octane.

This seems very doable on a 555 Pontiac with 350 cfm e-heads.

What do you guys think?

Musi sells a Pontiac crate engine? Or are you referring to his Chevy 555?

You will get the same hp but more torque from a street build 535 Pontiac than his Chevy 555.

Sounds like it has the potential to be an underperformer.

Butler has a pump gas 535 that is 700hp x 700ftlbs:

https://butlerperformance.com/g-2128...-pump-gas.html

Over 541ci pretty sure you need a 4.75 stroke crank, which would be billet, and requires considerable machine work. Lead time on those cranks are like 2 years, too.

I know there are a couple on here that have done 571ci builds. Formulajones' dad's build is a 571.

You might be able to do a 555ci with a 4.50 crank, would take like a 4.43 bore, not sure the aftermarket blocks' max bore is. Pretty sure the IA2 goes to 4.35 bore, forget what the MR1 goes to.

535 should be plenty though, that's what I did, pretty sure I'm in that range (700x700), think I run a bigger grind than the Bulter 7x7 build.

Spotts guess-timated the build at @670hp with the 315cfm heads and am now at the 340cfm heads. He commented I would be easy over 700 with the 340 heads. It's pump gas and streetable, that's what I built it for. Have AC and power brakes.

What are you trying to do?


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Interesting, Edelbrock has Musi 555s on their' website:

https://www.edelbrock.com/musi-racing

It's rated at 732hp & 652ftlbs with the Edelbrock EFI setup.


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Yes, the 555 is offered as a partnership with Edelbrock.

there's quite a few guys who made that much HP with a Pontiac in the past 45 years....you can make 675-700 on the stock block, with a 3" main, and a cast 455 4.21" stroke crank, with those heads. but you'll need a tunnel ram and 2-4's, or a big aszed Dominator.
i.e. 2-660's or 2-750's or ? a 1350 Dominator

My '67 had a 535 with 340E-heads, 10.3 SCR and SD's road paver which is not a huge cam for those cubes. 650hp and 667Tq with a TorkerII....91-92 octane.....wouldn't have taken much more to get it over 700hp, but was strictly a street-driven car.

Road paver cam specs?

IIRC - 246/252 on 114LSA .600/.600 with 1.5s, but I ran 1.65s and a 4-7 swap in addition believe they are CC magnum lobes....I think Dave had trouble with the dyno holding the torque below 4000, and we didn't know where it actually peaked because of it.....AND SD's dyno specs were known for being conservative.

At what RPM did it make peak HP?

Stan

I don't remember.

700 hp from a 555 BBC is an extremely mild build. Typically BBC's that size and pump gas can easily top 800 or more with a pretty decent cylinder head and a hydraulic roller and be pretty maintenance free. Hell I just bought a 598 BBC from blueprint that made 786 hp 772 tq with a very small 258 @ .050 hydraulic roller and marginal heads that only flow 350 cfm, for their size I can put a better set of afr's on it and bump the cam up a smidge and make 850+ with this engine and still drive it everywhere.

Dad made 724 HP 764 TQ with his 571 Pontiac on pump with a 261 @ .050 hydraulic roller using an old set of Eddy round ports heads, and he drives that thing every place, very docile. Bischoff who built that engine would have liked to put a better head on it and see it make another 75-100 HP but the budget wouldn't allow it. When is it enough anyway.

Much easier and much more docile to make these numbers with a larger engine. Trying to do it with a 455 is going to be on the radical side and knowing how most guys are in this forum they won't like driving it much.

I actually like the 505-535 sized Pontiac builds that are in the 650 HP range. I know quite a few of those done. Still more power than most can put down efficiently, docile enough to drive everywhere, and fast enough to scare your wife and run with anything on the street. The torque curve is what I like best about the larger inch engines.

Cam card attached. It's a custom Comp solid roller, Hi Tech lobes, 260/267 @ .050, conservative .631 lift, 112 LSA. Believe it's 10.55 SCR but would have to check. Idles at @850. I ordered a matching intake when I got the heads, super victor efi. All light weight valvetrain, PAC springs, titanium retainers. It revs to the moon.

I was considering going bigger but was talked out of it, because of the heads it was built with. Steve C. had input on the selection. I will have it on a chassis dyno for tuning this summer, should have a closer number from that. I may switch to 1.65 rockers, will have to see.

I have a conservative 2.5 exhaust on it now, but will be switching to 3" tapered head pipes to the mufflers, should remove one of the last restrictions.

Someone could probably run the numbers and get a good idea too if they wanted to. I honestly don't care what the numbers are, it's basically only good for bragging rights, but the dyno would give an idea of what the level of efficiency is. That I am interested in.


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I mentioned that 571 build above, curious, what's the bore & stroke on that?

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Definitely 3" exhaust, preferably mandrel. But you already know that. You should easily get 700 H/P out of that combo.Engine will want 2" headers though and dominator carb like a 1050.

It's got the 2" Doug's on there now, problem is, the collectors are all in different directions. That screws up the whole exhaust, and getting the tailpipe tips to line up is a challenge, at best. With the splitters coming out the valance, it's a dance to make them look right.

With the Pypes exhaust, the one part of the X pipe is very close to the crossmember cutout, and under certain conditions it rubs.

The 1 7/8" headers are much better in fit & finish, guess they sell the most of those, and tighten the QA over the 'race' 2" ones. The oil filter is also much easier to R&R.

I'll take the hit for dropping back to the 1 7/8" ones, exhaust drives me crazy, it's like a crooked picture hanging on the wall.



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You'll still do really good with the 1-7/8" headers. These exhaust systems have to be all custom installed so they fit properly. I had my Son help me with ours as he's a welder. I did both cars at the time with all 3" mandrel and full 3" Trans am tips. Came out beautiful. There was lots of fabricating to get the tips installed with 3" though. Wish you were closer as I'd love to help with exhaust. It's a fun project in my opinion. Work of art when done.