exhaust setup during break-in and valve springs

[ToiletDuck]

Hi, we are just about ready to get my bro's 360 goin (been sitting in big pile of parts and boxes all summer long) and just had a few questions.


When doing the initial break-in, would it be ok to run just headers? We were thinking about getting a couple feet of exhaust tubing and glasspacks for backpressure and our hearing.


Also the heads are stock and im guessing the valve springs are the original ones. Should we replace those before we fire it up? I think we should but he wants to hold off on it.

[dwc43]

Change the springs. They are a major power robber as the get weaker. I lost 500 rpm one weekend in my race car and another 500 by the next race. The springs were failing real quick. Don't think they'll fall off that bad on a stocker, but the will loose power. If you put in a new cam and lifters it's a must. You have to have the whole package to make good power.
As for open headers it will be o.k. on everything but your ears.
Our race cars run nothing but open headers and a short adjustable pipe after the collector for tunning purposses.

[72Challenger]

You don't mention what sort of mods this engine has, but if you're talking about initial break-in, obviously at least some of the parts will be new. It is common practice to use light valve springs while beaking in a high lift cam. The high pressures of the springs used during normal running will wipe the lobes pretty quick.

Since you won't be going over 2500 RPM during initial break-in, the old springs will be fine. But definitely replace them before you twist it up tight, if you float a valve at high RPM, you'll be starting all over again! And even if you don't hurt anything, you will certainly be giving away HP with the old ones, as dwc43 pointed out.

[ToiletDuck]

Thanks for the info.

We will wait till after breaking in the cam to replace the springs.


I dont remember the specs but its a compcams 268H.



Ill post pics once we get the thing runnin

[451Mopar]

The weak springs should be ok for cam break-in, but check them for coil bind. I think with the mild cam it should not be a problem.
Replace the springs before reving the engine to the higher RPM's.

Open headers shouldn't hurt the engine (might laen out the air/fuel mixture), but the noise might have your neighbors calling the cops?