[Formulas]

ive never used weak springs for a flat tappet break in but this time i will because i have stuff laying around

so my 2 options are 88-200 or 95-240 1.8 / .600

obviously dont want to lose control under 4k rpm and i have no idea what the realm of usual pressures are for break in springage
old schoo e'heads
thanks

[25stevem]

I would use the weaker of the 2 for break in since your not going to need to top 2500 rpm.

[DOC]

Not sure of your setup, one cam I did a while back and at the recommendation of a well known successful engine builder, he told me to use just the outers to break it in, after breaking it in and driving gently for a few miles to add the 2nd spring. Had Zero issues with that and cam still doing great after 10years on the road. This was with CC 953 springs.

[mgarblik]

I will be breaking in a new cam for my 468 CU IN engine going in my 62 Catalina. Had it all assembled with 135-140 on the seat with double springs. Due to a recent flat tappet cam failure on a SBF on the dyno after a 30 minute break-in, I got nervous. Went in and removed the inner spring which took the seat pressure to 85 lbs. Going to run it in for about an hour before putting the inner spring back in. Typically, run the engine in on the dyno at 2200-2500 RPM, varying the load from 15%-25% for an hour. Occasionally, dropping the load and flashing the RPM's to 3000-3500 RPM's. If the cam is going to fail, it will almost always show up after that first hour. Drain the oil and cut open up the filter. If the camshaft ends up in the oil filter, it's a very bad day. We have had 3 engines chew up a cam on the dyno breaking them in since 2008. 2 Fords and one SBC. Also 2 other Fords chewed up their distributor gears during break-in, so don't forget to check the gear. Must be compatible with the cam used. Good luck with your engine.

BTW, also consider if the springs are new, after running the engine for an hour, the outer springs will lose 8-9 Lbs of seat pressure as well. (10%) is typical so when the inner is reinstalled in my case, the seat pressure will be 127-132 broken-in. Should be pretty easy on the cam.

[25stevem]

Number 9 here is Comp Cams recommendation for breaking in the springs themselves.
Fortunately this works in conjunction with the cam break in process other then if you remove a inner spring.
If so then another full heat up and cool down process is in order I guess.

[Steve C.]

"BTW, also consider if the springs are new, after running the engine for an hour, the outer springs will lose 8-9 Lbs of seat pressure as well. (10%) is typical so when the inner is reinstalled in my case, the seat pressure will be 127-132 broken-in."

Excellent point and a subject often overlooked. This being valvesprings losing pressure with run in and use.

Here the springs are set up at 135-140 on the seat, and expecting 127-132 after the dyno session. Another example, Ken Crocie did a build using a hydraulic flat tappet cam with the valvespring pressure set up at an initial setting of 130 on the seat. The actual pressure after a day on the dyno was 122 pounds.

And related, always check new springs at their intended installed height with their retainers on a calibrated spring tester. Never trust catalog specs ! I've had new springs that did not come anywhere close to their catalog rated specifications.


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[Formulas]

already have the 88-200 springs installed yesterday on one head
i have a tester thats how i know pressure @ 1.8 IH and .600 lift

using a new but old stock fat lobe 294 AH8 comp cam rhoads std lifter with external oil groove harland 1.65 round e'heads cleaned up a bit on a 433 11-1 compression
i may run this in front of a 4speed which is the reason for the lifters, more torque at clutch engagement