Is it possible to build an hi-revving sb (8K or more)
If so what would you put inside ?
(no plans, just wondering)

 

all day; there's lotsa bb's turning those rpms too.
forged internal balance

 

Good forged crank, arp fasteners, good rods, solid cam with strong valve springs, it's very possible.

 

3.25" stroke would help to keep it together. Longer than that will make the cost go up a lot. Shaft mount rockers would be good too.

A wheelbarrow full of money makes anything possible.

-Mark.

 

Keep in mind that a motor that makes good power to 8,000 rpm will be a dog below 4,000. (read track only)

 

for the right amount of money anythings possible, so long as you don't turn the rods past 700fpm, then you window the block.

-alex

 

That assumption is to easy. There are a lott more variables involved.

My combo is :
- 400 sbc
- 3.250" stroke steel crank
-6.250" steel oliver rods
- je pistons with 10/1 CR
- dart pro 1 aluminum 215
- crane mech. roller cam (278/288 + 246/256 @0.05 and 0.63" lift
- normal 1 3/4" headers
- soon to be fitted with an 8 tb manifold and efi.
- valve springs 1.550" with 220 closed and 500 open
- revkit
- stud girdle.

If you take care in selecting the right parts for the combo, you can have relatively good low power and still can go higher in the rpm's. A lott depends on the airflow through the engine.

I feel that 7000 rpm is a critical limit in cam selection.Going higher would require longer duration and would mean a higher CR an loosing a lott of bottom end. These heads would be on the way out at 7500.

However, bottom end torque can be enhanced with the right selection of gear ratio's. However you would loose top speed to gain low down. Overall it will be faster accelerating with higher gears.

My engine is planned for a 8000 rpm limit. Camshaft says it will rev to 7200 in a normal 350 so I would be able to get there I guess. I haven't had the chance to test.

 

buy an SB2 or SB2.2

-alex

 

As noted, all forged internals, HUGE heads, solid roller cam, BIG single plane, BIG carb. Studs throughout...might consider taking the block 1/2 solid with fill on the bottom. Definitely an aftermarket block.

I'm rambling but interested I've turned a couple of SBC's I've built to 7000, but have no personal experience with an engine that lives in this RPM range.

 

You definatly need to make a strong bottom end and combine the right parts. However, the use dictates what parts that you will have to use. If this is for all out racing at constant high rpm, you would definatly have to go all the way. Otherwise a standard block is good.

 

I honestly can't see a stock block holding up to this RPM in stock form. Cast caps are definitely out, even with studs. Figure by the time you put on steel caps and align bore/hone you've spent $1000...so why not go with a far stronger aftermarket block? Figure this is a 15K+ engine in any case by the time it's all together.

I'd be interested seeing a cast cap stock block turn 8K...but only from a suitable distance and someone elses' funding

I agree usage is part of it, i.e. 8K on a circle track vs. 8K for 10 seconds...but I think in either case you'd be hard-pressed to keep that forged or billet crank in the block at those speeds.

It'd be fun to build one up and see

 

I want one of those F1 V8's that turn 20,000 RPM...but I know I couldn't afford one...

 

To keep money down 360 ci sprint cars are not allowed to run fancy splayed billet cap bottom ends. They just use studded 4 bolt billet caps on stock blocks with 3.500 inch strokes. They generally turn @8600 RPM twice each lap. I've turned my 358 ci 9000 at the drag strip with conventional Stud girdle type valve train. But to make it really reliable for 9000+ you need shaft rockers or better yet the actual overhead cams.

Piston speed is not the problem - Valve train is.

 

Ran a 302 Camaro to 8000 rpm many times. Stock bottom end, balanced and all, and the optional Chevy 140 cam and Bow Tie Iron Phase 6 heads. Stock rocker arms and good valve springs. Pretty cool to hear it buzzing at 8000 rpm.

 

I used to run Nascar short track. 358 in limit w 10 to 1 comp. I used an 010 block with all the best components, it ran 8000+ lap after lap !! I still have it if you are interested.
Pops

 

Man, I stand corrected. Just goes to show I've either been captured by the aftermarket marketing machine or I'm just paranoid ;-)

 

Those high nickle, high tin '010 blocks are getting pretty hard to come by. I used to get about 1:1 usable cores, over the last few years it's become about 4:1 - 3 end up in scrap. Lately I've been buying the new GM 350 ("Targetmaster") blocks - they're not great, but in the end cheaper :/

 

302 with a solid lifter cam will spin that high repeatedly and hold together.

 

I had a LS-7 468 external balance with srp 10-2 pistons, 680 lift roller cam, and would do 7000rpm all day. The motor was carefully put together but was done using much stock stuff. 580hp to the wheels EASY! I did it for under $8000.
For 8 G you can do quite a bit if you don't buy into "if its shiny it must be fast" stuff.

 

My 302 went about 3500 up. It was fairly flat, kind of like an old Harley engine, just kept going faster and faster.

Would you guys believe you can do it with a mostly stock 2 bolt SBC bottom end? No concrete in the lower water jackets, as that just screws up the cooling. No billet caps or splayed caps or whatever.

And actually, much higher than 8000 rpm. Try 9500.


Bingo! These guys have it. My 302 was built to run about 9500 rpm. It would. gkull is right, the valve train HAS to be perfect. This involves balancing the valvetrain, something most engine builders can't comprehend.

The bottom end was a steel crank small journal with 2 bolt mains, with .004 inch clearance which all say is too much. It is for a 5000 - 6000 street engine, but at this speed, anything less wiped the bearings regularly. The crank floated on 85 psi oil pressure.

This was a road race engine and lasted for a lot longer than 10 seconds at a time. Once the bottom end was working, it went several weekends (a few hundred miles) before a valve dropped. Like gkull said, the valvetrain is the critical problem.

A header had cracked, it sucked cold air, and the valve went the last weekend before we knew something was wrong.

The main issue with 9500 is trying to convince a forever Chevy driver that 9500 is acceptable. I was always leery above 8000. Had it been a Mazda, I would have had no qualms with 12,000 or so, but that SBC at 9500 was nerve-wracking. (Strange is driving a car that when the 12,000 RPM tach pegs, you shift.)

My builder will do one for you. I still have most of the parts. Need a good SJ block that is solid at .020 over.

Send money.