Valve Spring Seat Pressure - Cam Break-In

[bobs66440]

I'm getting ready to break in my rebuilt 440 with a Summit 6401 .465 .488 /.282 .292 flat tappet cam and Stealth heads with 130lb closed seat pressure (330 lb @ .600) single spring with dampers. They, and Summit tech said that they will be fine for break-in, but I've been reading that 80-100lb would be better. I only want to do this once.

Anyone have experience with this cam & spring combo during break-in? Opinions?

Thanks.

[Challenger340]

I'm getting ready to break in my rebuilt 440 with a Summit 6401 .465 .488 /.282 .292 flat tappet cam and Stealth heads with 130lb closed seat pressure (330 lb @ .600) single spring with dampers. They, and Summit tech said that they will be fine for break-in, but I've been reading that 80-100lb would be better. I only want to do this once.

Anyone have experience with this cam & spring combo during break-in? Opinions?

Thanks.

It ain't the seat /closed spring pressure, but rather the "over the nose" pressure at peak lift that kills flat tappet Camshafts during break-in.
Thats why I use low ratio 1.2 rockers for my Cam run-in's, keeps me from the higher Cam Lift/Spring pressures.

I'm not understanding your specs ??
Do you mean that your current springs are INSTALLED(closed) at 130#, and excert 330# at .600" Valve lift ??
If the above is true,
then you have 330Lb/Inch rate springs....which means at roughly .490" lift you are still 291lbs Spring Pressure "over the nose".
Getting close.....but still should be OK

Use lotsa Zinc in the Oil
Fire it immediately, less cranking the better, directly to 1800-2000rpm while setting timing, 20 minutes minimum, NO idling at all !
anything goes wrong while running it in, KILL it, NO idling.
Doesn't hurt to vary the rpm a couple hundred rpm periodically during the 20 minute run-in , splashes Oil different places on the lobes. 

Bob out.

[bobs66440]

I'm getting ready to break in my rebuilt 440 with a Summit 6401 .465 .488 /.282 .292 flat tappet cam and Stealth heads with 130lb closed seat pressure (330 lb @ .600) single spring with dampers. They, and Summit tech said that they will be fine for break-in, but I've been reading that 80-100lb would be better. I only want to do this once.

Anyone have experience with this cam & spring combo during break-in? Opinions?

Thanks.

It ain't the seat /closed spring pressure, but rather the "over the nose" pressure at peak lift that kills flat tappet Camshafts during break-in.
Thats why I use low ratio 1.2 rockers for my Cam run-in's, keeps me from the higher Cam Lift/Spring pressures.

I'm not understanding your specs ??
Do you mean that your current springs are INSTALLED(closed) at 130#, and excert 330# at .600" Valve lift ??
If the above is true,
then you have 330Lb/Inch rate springs....which means at roughly .490" lift you are still 291lbs Spring Pressure "over the nose".
Getting close.....but still should be OK

Use lotsa Zinc in the Oil
Fire it immediately, less cranking the better, directly to 1800-2000rpm while setting timing, 20 minutes minimum, NO idling at all !
anything goes wrong while running it in, KILL it, NO idling.
Doesn't hurt to vary the rpm a couple hundred rpm periodically during the 20 minute run-in , splashes Oil different places on the lobes. 

Bob out.

Hi, thanks. Yes, I estimated 291lbs also. I'm very nervous about this after all the trouble I've been through with it. I'm using Brad Penn 30WT break-in oil with a bottle of the Comp cam break in additive. I am using the original carbs and distribuitor as I know they work well. I have the distributor phased in at approx 10deg BTDC. I'm not going to hook up the ps pump or anything unnecessary. I'm going to run straight water with no thermostat.

What do you think I should set the total timing at (vac adv disconnected)?

[Challenger340]

IMO,
That Camshaft has somewhere late 230's to 240's @ .050 duration, 30-32* Total should be fine.
Don't wanna go blowing too much unburnt out the exhaust on break-in, just pushes the EGT's higher with lower timing than that.

it should break-in just fine.

[GPULLER]

That's good news to here Bob.  Now get out there and break it in!  We'll be waiting for results.   
Nothing better than the smell of fresh paint and gasket sealer in the morning....except for maybe...

[firefighter3931]

IMO,
That Camshaft has somewhere late 230's to 240's @ .050 duration, 30-32* Total should be fine.
Don't wanna go blowing too much unburnt out the exhaust on break-in, just pushes the EGT's higher with lower timing than that.

it should break-in just fine.

Those Summit Cams have slow/gentle ramp speeds and you don't have high spring pressures so like Bob said ; use good oil with a breakin additive and get it up to 2000rpm immediately and keep it there for 20 minutes. Set the timing at 30* and readjust the throttle speed if necessary. Make sure you have enough fuel in the tank to run it for the full breakin period. A Big fan blowing air in the rad will help to keep things cool. 

Bob's advice is spot on...as usual 


Ron

[bobs66440]

That's good news to here Bob.  Now get out there and break it in!  We'll be waiting for results.  
Nothing better than the smell of fresh paint and gasket sealer in the morning....except for maybe...

Gotcha  

I called Summit and the spring they recommend for that cam is the Comp-911, which actually has a higher rate and open seat pressure (305lbs  over the nose vs 291lbs for mine - @ .488 lift) than the ones I'm using, so hopefully I'll be in good shape...