koondawg_74 roadrunner

So I was just curious to what the red line of the 318 in my Roadrunner would be. I read different things on the internet, from 4,000 RPM's to 6,000 RPM's. It is mainly stock. I bought it mostly assembled and put a double roller set up and Edelbrock Performer intake and 1406 carburetor on it. I'm not sure if it has ever been balanced. I've had it to 4,000 RPM's and it really sings but I don't know how much farther it would be able to take? I'm not talking about before it shifts, I'm asking what RPM's it would be safe to constantly run without it blowing up. I have 2.71 rear end gears. Thanks in advance!

TVLynn

4K-4.5K is probably all you want to go with a stock 318. Any more RPM is just counter productive

Chryco Psycho

I would guess the valves will start to float due to lack of spring pressure above 5000

Archer

koon - There are two factors involved. First is what can the engine physically handle (rotating assembly and valve springs, for example). Doubt a NEW 318 would have any valve float issues at 6K, but we're talking about a nearly 40 year old engine, springs do get weak. If the reciprocating system was in decent balance 40 years ago, that shouldn't change, but wear and carbon build up do factor in. The other issue is the cam's power band and ECU limits. If the factory was rated for 2k - 4k, going above that doesn't do any good. Since it's stock, the PB probably tapers off in the 4-5k range. If it's in a 74 car, IIRC the standard ECU is good for about 5 -6K. Going by memory here, and it's been a while since I played with a small block. In the late 70's/early 80's, my 318 with a stock bottom end, and HP heads, cam etc, didn't break a sweat at 6K. Safe extended running is always in the 2.5K range, with higher burst as necessary. That should be no issue with your gearing. Hope that helps. Archer

PK1

Max RPM = Mean Piston Speed (feet / min) x 6 divided by the stroke in inches.

Use 3750 ft/min for factory assembly.

6750 rpm plus or minus..

Good info in posts above, especially about 40 year old valve springs... High RPM use is not recommended.

6750 is NOT your redline. But it is the theoretical ending point rpm in the build design when planning it out IMO. Factory established rpm for your ride was a product or air / fuel and or mechanical limitations like float.

Example: Motor I'm doing now has a 7200 rpm end point. Cam peaks HP at 5700 and hold nice power to 6300. She is toast at 6400rpm. Its a budget build but in the right rpm for its use. 6300 will be redline. More rpm can be had but not without peak torque moving up in this build.

Take your car to a dyno shop and ask for a pull with air fuel and rpm. It can cost 50 buck to 75 bucks depending on where you are in the country. The motor will stop making power at a certain rpm and then you know how to set your redline.

Gorts 5th

my 318 had no problem going to 7000 rpm, did it once on accident but it never missed a tic.
right now i shift at 5500 rpm with that occasional 6000.
she pulls strong all the way, with a third of the throttle left. the air valve never gets fully opened she just keeps pulling and climbing in rpm.
i will say this my 318's have out lasted the 2 chevy 350's i ran in my early early day's of high screwl motor head.
even the motor i pulled for this new one was still running i could never get this type of abuse out of those chevy's!
And i abuse em... whats the use of having a hot rod if you cant ab-use it.
hel they always idle better after a good run.
it's good to blow the carbon out!:driving: