raz0rblade654

Hey, anyone got thoughts on a set of heads and cam that will help a 489 make peak power ~7400 rpm? Want to be around 11.5-12:1 compression. I was looking at Lunati’s 40110926. 272 @.050”... and for heads, AFR-2001 with 335cc intake runners. Would this combo create a bottleneck anywhere? Any ideas? Thanks!

gkull

I used to spend lots of time researching on engine dyno simulation software. It is amazing how accurate they have become and how inexpensive. The cost is small compared to the engine. This is just one example that I think is easier to use. Version 5 is less than 50 bucks now


You need to input accurate data

https://www.jegs.com/i/COMP+Cams/249...4aAsMvEALw_wcB

leigh1322

My best friend's son has a 588 that peaks at less than that, 7000, and he makes 840HP.
For a combo like that you need to talk to a race engine builder.
Everything needs to work well together at that level.
PM me if you want a referral.

Jebbysan

Those heads are way to big for a 489.......
If I were to build this.....I would you the Brodix Race Oval CNC and a shelf Comp .748/.714 "bracket" cam.......this would make over 700 horsepower under 7000 rpm. It has the potential to make closer to 750 depending on the intake and carb package.....
I feel the minimum cubic inch for a 335/345 cc head is 540 cubic inches.......even then it is a little large, better suited for the 555/565's larger bore (4.560/4.600 as opposed to 4.500).
That 4.280 bore will not work the head hard enough......
The Brodix race oval is an amazing head.......AFR has a 290cc oval I believe as well.......it flows so well, and the velocity is so high.....the VE (Volumetric Efficiency) is at 100% which negates having to rev the crap out of it.......7400 rpm is spinning a 4.250 crankshaft, although not out of the question.....it is just not necessary.
I built a 12 to1 477 (4.500 bore-3.760 stroke) for a Nostagia race GTO in Canada years ago......it had the heads and cam I mentioned......it Made 840 horsepower and 680 ft/lbs. torque as flat as Kansas.....the owner wanted the short stroke deal to save breaking chassis parts and it did anyway! It used a Dart Intake and a Pro Systems 1050 Dominator.
You may find cams that make more ultimate power......but the 748/714 is very easy on Valvesprings.....

Jebby

7T1vette

I'm still trying to get my head around "7400 rpm from a 489 cu. in. engine"

I doubt that any stock Chevy block casting could hold up to that for very long....

427Hotrod

Getting true HP peak to 7400 RPM on a conventional headed BBC is really tough. They'll rev up there...but peak HP RPM will be lower. Now it will likely "hang on" well after peak...but now we're talking shift points and trap RPM of near 8000 RPM.

Way back when I over cammed my 540 and it peaked at 7400...but was a pig down low. Dropped cam down and picked up 7 MPH the next weekend at the track since I was operating it in the RPM range I was geared to. This was with an incredible set of professionally ported Brodix heads measuring 377cc. Later when tested on the dyno the combo peaked at 6800 or so and actually made more power.

11.5 will run on 93 octane...12.0 is pushing it. If you're going to buy race gas, then go for 13.5-14.0 compression.

Can you give us any more info on plans for it and the car combination?

JIM

roscobbc

Following careful selection some 8/10 years ago I used stock RR Ovals on my 489 manual for the totally opposite reason to the OP. I wanted a head that featured ports with a higher velocity port velocity across a wider rev band than perhaps some of the other heads on the market. I wanted to retain the 3.08 rear and M21 with perhaps a wider power band at (1500 to 6100 rpm with peak 571 hp at higher figure) using a 234/240 .544/.536 lift hyd flat tappet cam. Mild enough for urban street use but better than stock fuel economy using Edlebrock RPM air gap inlet and 950 dp. Super wide torque band with 450 ft/lbs at 2500 rpm and 606 ft/lbs at 3850 rpm.

427Hotrod

What you've built is a fun/simple torquey street motor. With 3.08 gears and a close ratio. it would be insane to go any other way. I like screaming them to the moon...but what you've got is a blast too.

One of my favorites was a buddy who had a 540 with a tight converter and 2.73 gears. That thing was a heck of a lot of fun on the street and the gearing made all those cubes WORK.

JIM

jkippin

I used to run a 496 with a 6500 stall converter.. It would launch off the transbrake 6500rpm. Shift point was set at 7800. and yes this was a factory block. Joe Jocono who ran the "Rollin Stoned" funny car asked one time how many rpms I turned. When I said 10k he didn't believe me so before the run we set the recall on the tach to zero and made a run. When we returned he hit the recall and said "NO ****". Made a cool $100.00 bet with him on that.
8500rpm I was still making over 1000 hp

Vette5311

I've run several GM block engines to 7200 / 7500 with main studs and a steel crank. I think about 315 on the intake port is about as big as you want to go. Camshaft, well you can write books on that, as the selection is never ending and everyone has their favorite. A good oval port from Brodix will get the job done also.

roscobbc

Hi Jim - how are you doing? haven't spoken for some time. Funny you mention a 2.73 - buddy of mine mentioned he has a 2.73 gear set - made me wonder..........

centuryoldracer

Seconding the race gas scenario remember that each point of compression is worth about 4% more horsepower NA with no other changes, so if you are going to have to run race gas you might as well get some free horsepower with higher compression.

centuryoldracer

I run tall gears in all of my BB builds too, usually 3.08s although I do have a 69 Camaro with 2.73s. Makes them able to be driven on the highway at 70 reasonably

roscobbc

With 27.5" tall rear rubber 70 mph cruise for me with 3.08 is about 2550 rpm I think. Not to sure how to calculate rpm drop with 2.73 gears - any idea what the rev drop would be please? - I was always concerned about being possibly past the hp/tq limit of what stock drive shafts and other drive line components would take before going bang. Would lower gear set increase that risk?

Jebbysan

No, slicks increase the risk, especially with a 4-5 speed manual.
A lower numerical ratio only increases the load on the trans and driveshaft.....but with street tires, none of it is a concern assuming everything is well sorted.

Jebby

Vortecpro

Jim

Remember this:

leigh1322

I built a gear excell spreadsheet to play with gear & tranny ratios. Feel free to use it. Math says a 3.08 would put you at 2726 at 70 and a 2.73 would be 2416.
I am going 5 spd OD to get down to 1950 at 70.

Your rear tire is a little taller, so that changes it a bit. Just change the rear tire size. 2337 & 2637.

centuryoldracer

Nice!

roscobbc

Thanks for the calc - guess my oem rev counter reads a hundred or so rpm low......2,73's would cut about 300 rpm off cruise.......interesting