How to raise rpm redline on SBC?

Please list the procedure(s) in great detail and approximate cost(s) to raise the rpm redline on a small block chevy to, say, 8000rpm. 10,000rpm? Higher?


Initial(but changeable)constraints:

1) For now, lets work with 305-350 cubic inches. If, however, under 300cid----i.e., 282 or even smaller would be better we can explore that as well.

 

Simple answer..... to do that reliably you need better EVERYTHING.

 

go to nascar and buy a engine

 

If it isn't balanced I don't care how good the parts are.

 

A real THICK wallet, that will be empty when your done.

 

Yup, or you could just stand on the gas pedal until it goes boom. Serious money just to make it go 8k.

 

To simplify this $$$$$ Cubic money

 

shorter stroke is the best way- one of the reasons 283s and 327s perform so well for a small engine-

titanium or otherwise lightened valves- thinner valve stems, ovate wire behive springs, smaller retainers made of titanium (getting less spendy these days), maybe a rev kit to put under the heads.

Roller cam, lightened lifters, spendy pushrods that are light yet still stiff, lightest rockers you can find to withstand the valve springs you'll need. You'll need good flowing heads, portmatched intake, good ignition.

Machine work and balancing- DONT SKIMP, you'll need to pay attention to the details.

Dry sump to keep the crank from swimming in oil is great, but a quality windage tray, baffled pan is mandatory if you dont.

oil shedding coatings, and friction reducing coatings would be beneficial.

Put a baffle on top of the cam valley to keep cam windage down, oil feed restrictors to keep the heads from flooding-smooth and paint the inside of the valley for oil drainback.

just do everything,lol..

rick.

 

Low friction and balance are your friend as well as truck loads of money.

 

There is no simple recipe for what you want to do. Costs will vary greatly depending on your skill level including negotiating skills.

First - buy a couple good SBC build books - Amazon.com comes to mind, as you may need to learn more of the basics. The HAMB can't do all your homework. I spent about $3000 in 1972 to build a 336" that spun to 7500 with ease. Lots better stuff available now but the process isn't much different.

Charlie

 

i got one that works all the way to 8 grand, at least twice a lap, for 100 laps, and it lasted 23 races and still runs.......probably about 7500 in parts, it is limited in a few areas for rules......but made 425 on a chassis dyno.......

 

An engine is just an AIR PUMP !! Lots in and lots out !! >>>>.

 

Reply..........I don't no IF he's Still in Business R' not, BUTT, I had Balanced , .040 over....two fours, etc., w/ Racer Brown Roller Set-up in tha'
'60's..........That turned 8500 rpms.......idle SMOOTH!

That's When U did'nt Tell ENYBODY!, what?, U wes Runnin'..........
Turned 12.90's in Quarter!
____________________________________

Smokem', Smokey!!!
(That was w/ ATLAS BUCRONS on REAR!)

 

You pull the airfilter off and drive another engine under it.

 

Well, had to read down a ways to get to some good info that 69fury posted. In addition to the items he posted, lightweight pistons hung on the end of good rods will go along ways towards making whatever combo you come up with be more reliable. When you get into those high RPM's the effective weight of those pistons and rods skyrockets as they start and stop moving in two directions every crankshaft rotation. That causes a lot of torsional vibration in the crank, so you need a good crank, and a decent damper as well. Good main caps or a girdle will help the main bearings live. Breathing, crunching the mixture, lighting the fire, exhausting. There's always going to be a "weakest link", so spend as much as you can afford.......

 

Lets not forget aluminum rods, Floating pins, Ignition upgrades, Reduced ratio accessory drives and 47 other things I can't think of right now..

 

I ran a 327 in a dirt car that was made up of parts from four different engines. we balanced the parts and ran a HP chevy cam. the telltale was always at 7800 to 8,000 when it came back in from a race.
small journal forged crank, 350/350 cam, BB oil pump, 461x heads SS valves, 11.0 pistons, Canadian 2bbl intake with a highly modified 500 CFM Holley 2bbl.

Details on your build: run a matched cam, lifters, springs retainers with an RPM range you want to use and HOW you are going to use it, (drag, oval, road course)
DO NOT GUESS OR USE A CAM SOME ONE ELSE USED OR SUGGESTED.
Call a cam maker and talk to them ......
true double roller timing chain
relief grind the block at the rear to open the oil passage.
run a big block oil pump and custom make a pickup.
run restrictors in the upper end oil passages.
use SS or titanium valves 2.05 / 1.65
forged crank, pink or carillo rods.
Raduis cut your bearings or undercut your crank journals (this will reduce drag)
When you put in the crank on lubed bearings it should spin VERY freely.
Run light tension piston rings, which will require you to run a large capacity vent system to the headers. light weight Venola pistons, custom made
port match your intake and heads.
open up the bowls under the valve seats
Stud the block
on a 327 I would use a predator carb 830
on a 350 you could get away with a dominator
small blocks like around 10.50 to 11.75 compression.
MSD ignition system
run a small diameter clutch with a flex plate, less mass
Balance crank, harmonic balancer and flexplate together and tell
the machine shop that you want a high end balance (most will not know)

I have only built two engines similar to this that were run on the street, both were 302 chevy engines, one in a Camaro (full road race suspension) the other was in a El camino (street racer) Both would turn well over 8K.

$10k to 18k depending on what parts you have and how well you know your machinist and how much of the work you can trust to do your self.

 

valve train and ignition will cost the most, high rpms are like rain tires. just allows you to break shit faster.

 

It will take having the lightest components you can find (or have made) balanced to each other and everything that holds them together reinforced.

The buckets of money don't hurt either!!!

 

why? there is no logical reason to spin a street motor that fast. you can go as fast as you want and be under 6000rpm. just a big waste of money for little bragging rights

 

Build a 302 sbc, 350 After market block, 3" lightweight knife edged crank, aluminum or titanium rods, the best 18 degree or lower angle heads you can buy and you will get there , a good starting point would be $10,000-15,000

 

1969 z28 302!!!!

 

There are such things as cubic inch limits... with a class limit of 305 or 306 inches, would you pull a 305 out of an 86 station wagon? If you're racing me, I sure hope you do...

Me? I'd grab a low deckheight block, destroke it to 303 inches. 6 inch rod-3 inch stroke for a 2:1 rod/stroke ratio- 10,000rpm nice and compact.

-rick

 

I wouldn't destroke, it's not really about stroke at all.

First off a motor that you can run to 10,000 rpms routinely will cost more than some folk's car.

I'd go for 8000-8500 rpms. I'd run a solid roller cam. You need heads/ intake/ cam that makes some power up there.

 

'69 z28 302

 

Our dirt modified race motors would bump the 8k chip twice a lap, and live all season long.

406 CID, stock 400 two bolt block modified to take splayed bolt steel caps, Callies super light crank, Manley super light 6" H-Beam rods, JE super light hollow dome two ring pistons, Bodix 11x heads, stainless valves, GOOD oversized valve springs, Comp Cams solid roller cam, Clevite bearings, oil restrictors, large od hollow push rods, shaft mount roller rockers, wet sump 7 qt pan with two kickouts, everything balanced, and nothing but ARP fasteners throughout. I use an MSD Pro Billet distributor, and an MSD 6AL ignition box. HEI's are not reliable in this RPM range (IMO), not even MSD's version.

A few notes:

1) At these speeds, you will not be able to stop some blowby and/or foaming in the crank case with a wet sump pan. It's not an insurmountable problem up to 8k, but above that you're gonna be forced into dry sump (and all the expense and complexity that entails).

2) Everything matters when you spin one this fast. All the clearances are critical, all the bolt torques matter. The rod and crank studs should be tightened according to stretch, not torque. Piston to valve clearance is a big F'n deal at these RPM's. Give yourself a little more room on the exhaust side ('cause the piston is chasing that one).

3) Expect to spend at least $12k to put one like this together. Probably closer to $15k now.

4) Change the oil and lash the valves religiously and on very short intervals (we did it every other race). Cut open the used filter, and look for metal. You will usually get a very little bit of metal in the oil with every change, nature of the beast. When the volume of metal you're finding increases, pull the motor and freshen it up ('cause it's fixin' to force you anyway). We would get a full season (23 races) out of an engine with little trouble, but I have no idea what that means in street mileage.

5) This combo on methanol will yield ~700 HP and some change.

 

Longer rods..........

 

Well lets see first you need a steel insert for your right shoe and second a sack full of $100.00 bills for starters then add all new hi dollar internal parts.

 

it would be easier just to flush 10k down the toilet

 

Folks are talking about manuals for this kind of thing, the one I reach for is the Chevrolet Power Manual that used to be sold over the counter at Chevy dealerships.

Anyway, they specify that after a complete competition build using GM parts that an engine should be redlined at 7600 for circle track and 8000 for drag racing. This would be the specs for a DZ 302 AFTER you completely went though it. A lot of Z-28's were turned this tight off the show room floor, but back in the 70's I saw quite a few Z-28's for sale with blown up engines or no engine at all in them. Just a WAG, but if you had a good core to start with now days, it would probably cost in the $5000.00 range to build one of these.

Next step up would be with light weight aftermarket components (pistons/crank/etc.), better rods, upgraded oil system to get the engine to live. And then better heads, valve train, induction, etc. to make horsepower. This is where you get into the "speed costs money, how fast do you want to go?" range.

As far as cubic inches, seems like the big bore/short stroke combo's seem to be the way to go. Revs quicker and keeps piston speed down. With small blocks, 4" bore and keep shorting the stroke til you get to the size right for the class seems like a good way to go. I've heard of quite a few engines smaller than 300 cubic inches built this way.
And as a big bore/short stroke footnote, I looked at an older 500" pro stock engine that had a 3.50" stroke crank in it. Seems like the pistons were somewhere around 4.8" diameter. It took a special block with larger bore spacing than stock and everything else that went with it to make it work. VERY expensive way to build an engine, but as a buddy of mine once said, "It costs to be boss!"
Off to work,
Larry T