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Discussion Starter #1
Thanks for the info on the heads and rockers questions, which however brings me to another question.

I would have to install my new cam, lifters, then put on the machined 2V heads and set them up with the rollerrockers, guideplates, and Then would be able to measure for correct length pushrods... By this time I am thinking that I would have to take the cam all back out in order to get it properly lubed for starting up the engine and break in, by the time I received the pushrods and was ready to start up...

So my question is would it be a bad idea to install my cam and break it in with the stock 4V heads I have so it is ready to go?... and then later put the machined heads on and the works to measure for correct length pushrods? (this would save some good and work) Or will the wear pattern be significantly different because the stock springs are not matched to the cam lift even though the rpms would be relatively low just breaking it in...?
 

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Discussion Starter #2
didn't say anything about it... but the above engine in question is a 351C
 

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You could break in your cam prior to assembling your final combination if you want to, but it really isn't necessary. If you do this, be ABSOLUTELY sure that you keep the same lifters on the same lobes when you reinstall it, or they will surely fail.

When you are trial-fitting your various new motor parts, you can do all of your pushrod measuring, cam degreeing, etc. with very light weight "checking" springs (like 3 lbs. of seat pressure instead of 125). They're faster and easier to work with, anyway. This avoids any excess "rubbing" of the lobes as you turn the engine over by hand. You just need one pair of light springs.

Only install the lifters for the particular cylinder you're working on at the moment, which avoids any friction on all the other cam lobes.

You should coat the cam journals with regular engine oil prior to installation. The cam lobes should be coated with the special moly assembly lube (a light grease) that is supplied and recommended by your cam maker. This cam lube is thick enough that it will not "run off" the lobes over time.

To be extra safe, on those lobes where you do checking activities with the light weight springs, remove the lifters when you're done and put an extra dab of assembly lube on the bottom (only) of the lifter, then replace it.

Finally, be sure to use a priming tool through the distributor hole with an electric drill to turn the oil pump for a minute or so and bring the engine up to full oil pressure just before replacing the distributor and starting the engine for the first time. This ensures oil to all the bearings, even if the engine's been sitting a long time since assembly.

For flat tappet cams, I prefer to install lighter seat pressure valve springs for the cam break-in. It's a pain, some would argue overkill, but if you ever wipe a new cam in a new motor you'll never start with the heavy springs again. If you do everything right, the odds are small that this will happen. But "small" isn't good enough for my limited wallet, so I up the odds in my favor with the lighter springs. Done many this way; never seen a failure.

If 125 lb. seat pressure is recommended, an 80-90 lb. seat pressure spring will allow you to break in the cam with minimal stress for 30 minutes at 2000-2500 rpm. DO NOT rev up the motor with these springs, not even once.

After the 30 minutes initial break-in, change the oil and filter. Then use a low-dollar air hose attachment that screws into the spark plug holes to put air pressure in the cylinder and hold the valves shut. Use a simple tool that compresses the valve spring retainer right on the head, and you can remove the stock-type light valve springs and install your final valve springs without having to remove anything other than the valve covers. Pretty easy.

Make sure the lighter pressure, "break-in" valve springs do not go into coil bind with your new, higher lift cam. Sometimes you can use the old, stock springs for break-in, but check for coil bind first or you'll break something. If you happen to run dual coil valve springs for your final combination, you can often remove the inner coil and dampener to reduce the pressure for break-in, then reinstall them to get your final running pressure. In all, it's a couple hours of extra work that is IMHO a cheap insurance policy against a new motor full of metal flakes and a bad case of personal indigestion.

If you choose a roller cam you can avoid all this trouble as well as increase your performance potential. Roller lifters do not require the special break-in procedure. Crane makes a conversion kit to put a roller cam in a flat tappet block. Very tempting.

Steve Amos
 
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