I mull a lot of different ideas and the one I have had lately (for my project), is this:

VERY large, aluminum BBC, mild cam, mild compression, low RPM limit.

What I'm thinking is that if I have, say; a 4500-5000 rpm limit and 8.5:1 compression, I will have a very understressed motor that will make an @$$load of torque.

I'm also thinking that the block & heads, and to a lesser extent the crank, are the only high dollar items.

Block...? Who knows.
Heads...? Possibly the "as cast" AFR 305's. My mind is open.
Crank...? I'm open to suggestions.
Cam...? I'm thinking that something around .525 lift, 280-ish duration, probably around a 114 LSA. I'm just trying to ballpark this.
Induction...? 2 x 4 carbs. (I know it's not as efficient as a good single-4 setup, but I'm old enough to not care anymore. I just like the looks.)

I have never built an aluminum motor, but I have been given to understand that there are considerations involved that you don't have with iron blocks.


So here's the question portion:

1) In terms of, as much as practical, "off the shelf" parts, what am I looking at in terms of achievable displacement? I don't want to get into ultra high dollar "one-off" parts.

2) Realistically, what sort of expense am I looking at? I'm talking of both parts and labor. (machine shop time as well as assembly)

3) What are the additional considerations that you have to account for when building on an aluminum block? Specifically.

4) Money issues aside, is this a PRACTICAL notion in terms of mechanical feasibility, or am I getting into something so oddball in terms of street motors that I should stop NOW and never think of it again?


Finally, if I have erred and this should NOT be in this forum, I apologize.

 

3) What are the additional considerations that you have to account for when building on an aluminum block? Specifically.
=======================================

on the Aluminum Block => a lot of extra money to make LESS HP and Torque

Aluminum Block => big heat sink, with a small increase in Ring Blowby

 

Interesting topic. Not too long ago I did a "fantasy" BBC from easily available bolt on parts. Here's a description:

This design will be a sleeper, in spite of the obvious tunnel ram. It will idle like a stocker, pull enough vacuum for power brakes, but if our simulations are even close, it will be a 625lb-ft/650hp engine. Torque comes in by 2500 and power peaks about 6000.

The concept used to achieve this isn’t revolutionary; it has worked for others. Namely, high flowing heads with relatively small ports, like the Edelbrock/Chapman Victor Jr. CNC (P/N 60409), plenty of available airflow with the 7075 Tunnel Ram and a pair of 600/650 cfm airvalve carbs, and an out -of-the-box Comp 270HR hydraulic roller. If the rpm is limited to 6500 or less, life on the street isn’t a problem. A 6400 rpm rev limiter is strongly advised. A custom cam will do more, but this was to be a bolt-together engine.

This engine really needs a 4-bolt block, either a used MK IV (.030 over) or a new P/N 12550307 Gen VI block at stock size. Likewise, a 5140 forged crank, P/N 3963524 for the MK IV or the 1053 forged P/N 14096983 crank for the Gen VI and P/N 1249661 (set of 8) ‘Dimple’ rods are minimum requirements.

With the power potential of these heads, 2-1/8 primary diameter headers with 3-1/2 collectors are mandatory. Hooker Super Comp P/N 2227HKR for a ’55 Chevy, or P/N 2225HKR for a ’63-’82 Corvette. Anything smaller kills a bunch of power."


It's not exactly what you envisioned, but it's made from off-the-shelf available parts. I have the rest of the part numbers somewhere.

I disagree with your 8.5 C.R. Use as much compression as 92 octane will allow, which is a lot more than 8.5. There is almost no downside to this. All of the parts are easily up to the power/torque. You don't have to rev it past 5500, but you can. Piston speed is 4000 ft/min @ 6000.

Also, as Larry said, forget the aluminum block. I don't think you need to go beyond a .030 over 454 if you want to keep the bucks down.

My $.02

 

fantasy or fancy?

 

Damn, where's my spellchecker?

Good catch. I fixed it. "fantasy" defined sometimes as a "wild, visionary fancy"

 

This is one thing that I like about this forum...namely to get members in a mindset not to do overkill with mods that won't produce power for thier specific application. Why put a ton of $$$'s into something that will not really make you faster! Overkill seems to be the norm with most....

 

The reason I am consdering an aluminum block is for the weight savings.

Otherwise, I'd probably just get a GMPP 502 short block, put real rings in it and top it with AFR 305 "as casts".


All this daydreaming and you know...

At the end of the day I'll probably just take the lazy way out and buy that 502 RamJet for 10 grand. It's not a small amount of money, but it is pretty much complete, just add fuel and electricity.

 

Sigh...

 

FWIW,

The reason for the bad ring seal on a Aluminum motor is because the thermal expansion of aluminum is 3 times greater than iron. So when the motor heats up the variations in the cylinder bore become magnafied vs. the cast iron block. Hot honing is about the only way to solve this problem since it makes the bore round at operating temp. Bad thing is that the hot hone setup is around $25K!

Bret

 

Hey, I'm sorry...

I'm runnin' outta lifespan here!

 

I know the feeling. We were fighting the Germans and the Japanese when I was born.

I'm not a fan of "cookie cutter" or "bellybutton" cars or engines for rods. You're right that bolting in the 502 would be easy and powerful, but my "engine" was pretty much bolt together after boring/honing the block and balancing the rotating assy.

 

Well, the whole package, meaning the complete car, will be unique, because I have some non-mainstream ideas.

Hell, I'm a chopper freak from way back.
(Even used to write for The Horse, though i doubt you ever heard of that rag.)
Believe me...
My car isn't going to be cookie cutter, even if I DO buy a complete crate engine.

Frankly, that 572 from GMPP looks tempting too. And there's always Bill Mitchell...

 

The Horse with this cool misson statement?

"While other publications cater to the so-called "master builders," we here at The Horse recognize that the "real" master builders are not those rhinestone biker lites that build $50,000 static displays, but rather the average Joe who struggles to make ends meet. It's the guy who slaves away ten hours a day, then works until midnight in his garage, welding, cutting, and creating the bike of his dreams that inspires us to produce the best magazine that we can."

How about a few more details on the whole car?

 

Yeah...
THAT Horse.