I'd like to build up the largest bore, longest stroke SBC that can rev freely and safely to 7500-8000 RPM just like my 327.
Is this possible or are mechanical constraints (larger journal size/bearing overlap/rod to crank angle/etc/??) just not as favorable as with a small journal 327.
It would be cheaper with a BBC engine that's already a large bore/stroke. But getting ANY engine to run in that rpm range and do it reliably, and consistently, will not be cheap. What is your budget for building an engine like you want?
The issue is one of managing forces, NASCAR engines establish that large inch engines can and do rev very high 9000 RPM and more is not just touched but held is common.
It's not cheap this takes better than stock production parts from the block, crank, rods, pistons, bearings, rings, tricky pins all sorts of mechanical details and processes. This also is not wet sump territory, considerable effort and cost goes into oil management and lubrication system design.
my two favourite potential high rev engines
391 small block,,many reasons for not going bigger
and the monster 531 bb
I would say 13k or less for sbc
15k or less bbc
would aim at 700 hp sbc but be under
531 would be over 850 hp
these are race engines making 1.7 ish hp/cube and could be used on the street but that would be a short cruise at best. These engines would require valve springs each season , 200 passes on the rollers at most. 8,000 rpm builds a lot of heat,,,
not sure what kind of driveline parts you have that meet the stress levels these beasts will create.
I doubt there are any better sizes but there are other combos.
these combos are also build able with over the counter cylinder heads(not the cheap ones)
prices might be even higher with special balancing and very expensive heads
bb will make more power per cubes
1. Would look to fit engine to 1965 Corvette. Need advice on what I'd have to do to the driveline in order to prevent breakage. I already have a Kiesler 5 speed.
2. Engine would have to be streetable and worthy of everyday driving.
3. Don't need NASCAR technology, just something that will eagerly wind up to 7500 like my 327. No sustained high RPM use, simply would design with 7500 RPM shift point in mind (ie: power peak at around 6700). Drag race/street/hiway cruise use.
4. AND MOST IMPORTANT..............RIGHT NOW, FROM A MECHANICS STANDPOINT, WHAT WOULD BE THE STRONGEST BORE/STROKE RATIO AND JOURNAL SIZE AND ROD LENGTH TO COME CLOSE TO THE IDEAL DESIGN OF A 302 OR 327 SMALLBLOCK. THIS SAME QUESTION APPLIES TO A BIG BLOCK AS WELL.
5. A 600 HP small block or 750 HP big block are the goal.
6. No dry sump and no nitrous and no supercharging allowed.
In trying to answer my own question (#4), I would think that the largest bore either big or small block, would be a "given". The question is..............how long a stroke can I use before mechanics rules that reliability would be an issue without trick parts. Can someone help me understand journal overlap and how this applies to this discussion.
The question is..............how long a stroke can I use before mechanics rules that reliability would be an issue without trick parts. Can someone help me understand journal overlap and how this applies to this discussion.
Well, to try and answer your question here as best I can I'll just say with cast parts (cast cranks, rods and pistons) you wouldn't want to exceed a mean piston speed of 3,500 FPM (feet per minute) for a regular daily driver
The formula to figure mean piston speed is; RPM x stroke / 6.
So for a 350 Chevy at 6,000 RPM you get; 6000 x 3.48/6=3,480 FPM
If you use good quality forged components 4,000 FPM in a reliable engine is more than doable. In that case our 350 could be wound up to 6,900 RPM or so using this formula;
Mean Piston Speed x 6 / Stroke which for a 350 gives us;
4,000x6/3.48= 6,896 RPM.
Of course the higher the piston speed you get, the more exotic components you have to use. Going north of 4,500 FPM piston speed will require pretty expensive components but is doable. Approaching 5,000 FPM piston speed would require deep pockets and by this time your getting into the upper limit of off the shelf components....not to mention valve train components as well.....of course engines exceed these limits all the time. BUT what I'm trying to do is set a base line for a "reliable" engine.
The only number you need is 377.
400 block with 350 crank and 6" rods makes an inexpensive package that's sure to put a smile on your face. sprint cars have loved that setup for years. internally ballanced is also a plus in my book.
Agreed, but if I was building a 377 I'd run a 6.125 rod. While using the lightest pistons I could afford with AFR 195 Competition ported heads.
RPM brings on a whole host of issues that have to be managed, ignition, winadage, valve hamonics so to make the most power you're gonna be better served with a distributorless ignition, proper oil pan / windage tray and a timing belt drive.
peak power at 6700 rpm? thats a lot milder than I thought you wanted?The Horse power will be way down.pick a 427 and AFR 245 heads and make peak power around 7000 rpm and shift up to 7500 if needed on a track. My 434 makes peak power at 6500 and can easily rev past 7200,,
Its a bit scary at this rpm so I chip it to 6k on the street
If I was to do this I would start with a Cad 472 and wind it as hard as i can get it to go. Main thing would be the heads and valve train to allow it to turn big numbers on the tach. Some guys get stuck on a certain engine and cannot see that another solution is right around the corner.
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