[71SportRagtop]

My buddy has a 71 Chevelle. This winter I helped him swap out his tired old 307 for a 383 stroker. When he built the motor he installed the heads with the inner springs removed for cam break in. He fired up the motor to break in the cam with only the outer springs. I assumed that he went back in at a later time and re-installed the inner springs.

It turns out that he didn't do that. Last night we were at a cruise night with a group of guys and of course we were talking cars and since we both put new motors in this year we talked a lot about that. My buddy mentioned that next winter he was going to go back in and re-do the inner springs. I asked if he felt it was OK to run his motor with just the outer springs and he said it is fine since he's not taking the RPM's very high. His claim is that he's OK running the motor that way for about 1000 miles then in the fall he'll swap in the inner springs.

I told him that didn't sound right. I told him that cam companies recommend dual springs for a reason, but he feels it will be OK since his driving it light. Is he OK running like this for say 500-1000 light cruise miles??

[67gtospud]

Sounds like a bad idea to me since the inner valve springs help to give the proper spring pressure. Also I'd imagine it wouldn't take much to float the valves with just the outer springs installed depending on the outer spring's valve pressure.

[b-man]

Could lead to some valve seat pounding as the valves will tend to bounce off the seats with reduced spring pressure.

This will lead to valve seat recession.

There's always going to be a time where your buddy won't be able to resist getting on it, the springs won't be up to the task.

Tell him he needs to get in the garage and finish up.

[71SportRagtop]

Originally Posted by b-man

Could lead to some valve seat pounding as the valves will tend to bounce off the seats with reduced spring pressure.

This will lead to valve seat recession.

There's always going to be a time where your buddy won't be able to resist getting on it, the springs won't be up to the task.

Tell him he needs to get in the garage and finish up.

That's kind of what I thought but he felt it would be OK to get through the cruise season. I think I'm gonna suggest that we do it together. I know Jegs sells an adapter to use compressed air to hold the valves in place while you do the job. He's go a compressor and I think the two of us can do this job without any issues. I've never done it before so I'm going to help just to say I've done it.

[b-man]

Keep each piston at TDC as you do the work.

Even using compressed air to hold the valves closed won't guarantee that the valves won't drop into the cylinder.

[ronstory]

Another option is to use the 'rope method' to avoid dropping the valve into the cylinder. I've only used it fix a broken spring on a single cylinder... not trying to do all 8. It certainly is possible, but will take time/patience.

[bluebandit]

Ive used the rope method several times to change valve seals without any problems. Used a real soft nylon rope. If you do this,be sure to turn the engine by hand to compress the rope. My brother-in-law did this one time and bumped the starter to compress the rope. He wound up cracking the skirt off one of his pistons.

[70pontiaction]

I bought the fitting to use air pressure (not used it yet) but still have done the rope thing about a dozen times. It worked well, no need for a compressor and IMPOSSIBLE for the valve to drop if it's done like this:

First disconnect the battery, take off the valve covers and back-off and remove ALL the spark plugs, rocker arms and pushrods.

Next bring the first piston up BY HAND towards TDC until you can see it through the spark plug hole, stopping about 1 1/2" down.

Feed in several (3 or 4) feet of 5/16" nylon rope, leaving another foot or so hanging out of the plug hole. Basically, you fill up the cylinder with soft nylon rope. I usually tie a big knot in the end so it can't accidentally fall into the cylinder.

Now SLOWLY bring the piston up BY HAND until there is resistance and it stops. DON'T force it with a breaker or long ratchet anything like that. I've done this via the fan blade on a flex fan, wearing a pair of leather gloves and also via the big bolt in the harmonic balancer.

Next use a spring compressor to compress the spring, remove the locks and retainer and outer spring and then reassemble and install the pair of springs back over the valve stem. Reinstall the retainer and locks and loosen the spring compressor, making sure the locks are retained in the groove(s) in the valve and the retainer is straight and level on top of the spring. I normally give the retainer a few raps with a rubber mallet to make sure something isn't going to pop loose later.

Next, turn the crank backwards from the direction which crushed the rope a bit to allow some clearance and pull the rope back out and move on to the next cylinder in the rotation.

When you've done all sixteen springs (and it takes a little while), reinstall the pushrods and rockers and run through the preliminary, pre-start valve adjustment. Install the plugs, fire it up, run until fully warmed up and readjust the valves.

[steve25]

Most inner non-race type springs only add some 30% more total spring pressure. In this light as along has your buddy keeps his revs under 3500, I can see a issue with valve floating, but 3500 rpm only would drive me nuts in short order!

[71SportRagtop]

We talked more about it last night. His theory is that he removed the inner springs to break in the cam. Then he was going to put about 500 easy miles on the motor to make sure that there were no issues, and then go back in and install the inner springs. Since we really only use our cars for short trips to local cruise nights, they don't get hammered. He says he's done it this way in the past and never had an issue. I just always heard guys say that they broke in the cam and then immediately installed the inner springs.

I guess time will tell.

[steve25]

Well once the cam has 1 hour of run time on it it's as broke in as it's ever gonna get, so he's being more than a bit anal with the 500 mile thing!

[ronstory]

And the first 20ish mins of life on cam / lifter is the most critical. Cam companies will give you a *minimum* RPM to run for the that period of time. Most will be 1500rpm, but my engine builder always recommend just running at 2k for 20, which makes it easy to remember.

[paul s.]

I consider the cam break-in procedure a two step process and ALWAYS run it with the outers only, and then the inners included. I have NEVER had a customer call back with a problem. I suspect some of the guys having problems with their cams going flat may be skipping this step. Granted, it's a pain when you have to do it with the engine in the car but, whatever. Better to do it ONCE!

I agree with Steve25, the 500 mile thing is unnecessary.

Something else to consider; is he using spring cups to locate the outers? Many times, a dual spring set up is located via the inner spring's I.D. Without the bottom of the spring being positively located, it can slide around and the valvetrain can become chaotic and go into valve float sooner... then the springs become weaker, the seats are pounded out, etc.