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I have a 1970 LT1, just rebuilt the engine rings, bearings, heads & cam. Replaced the solid cam with a hydraulic Comp Cams CL12-214 with ~525 lift. Properly prep’d the cam lifters and components with assembly lube. Valves were done and springs were checked. Primed the oil pump and ensured oil was distributed through to the rockers.
Pre-adjusted the lifters to zero lash plus about half a turn. Started right up and got it to 2000-2500 RPM immediately and ran it for about 15 minutes. Turned it off and pulled the valve covers to check the rockers.
Turns out several of the cam lobes got eaten during the break in.
Two thoughts.
1: I always smeared moly paste on the bottom of the lifters and the cam lobes.
2: I would invest in a hydraulic roller cam.
Sounds like u put forth a good effort for Cam break in. Only additional task I might do if u insist on a flat tippet cam, install lighter valve springs till the cam is polished up
A new cam going flat really sucks. A lot of work to fix it.
From: At my Bar drinking and wrenching in Lafayette Colorado
What valve springs are you running and what's the on-seat pressure? Are they double springs? If so, did you remove the inner spring for break-in? Running a thin synthetic oil for flat-tappet break-in may not be the best idea...
2 things come to mind. 1. Did you make certain you didn't get moly paste on the side of the lifters? 2. Are you certain all lifters were spinning freely?
Are they double springs? If so, did you remove the inner spring for break-in?
Cams come with a listed max open spring pressure for break-in, and double springs are usually too stiff and require removing the inner spring as Lars pointed out. There are also specific break-in oils for cams, like PennGrade 1 break-in oil. They want you to run that oil 500 miles before you change it.
You need to break-in with non-detergent oil like from Driven Oils Break-in oil, detergents wash away the moly paste you just smeared on the lobes, you also need to remove the inner spring during break-in and maybe next time go with the tool steel lifters or the diamond like coating (DLC) lifters, you can also buy 1.3 ratio rocker arms that cut down spring load during break-in buy reducing the total amount of lift and the extra spring loads from the higher lift
That is the biggest Hyd FT cam Comp has and I seriously recommend going back one to the 292 Magnum....244/244@.050 and .501/.501 110lsa.....
The other thing is are you physically spinning the lifters one you drop them in? You should be able to raise them and they should all fall down by themselves....free with no "crunchies" feeling with fingers when you spin them....
What is your pushrod length at?
I am building one right now with an Isky 292 Mega (similar to the Comp) and I measured 7.825....if you are way longer or shorter...that can be an issue...
As was noted I was careful with the moly lube to ensure it was not on the non-contact areas and that they weren’t “sticky”. Push rod length was standard 7.8”.
Had the springs tested and they were in spec for the cam but seems like for start up I should have taken out the inner.
I’ve built several LT1s with the same springs and startup process but this cam is a bit higher in lift than the others that were closer the to “”nostalgia” grind below 0.500”.
As suggested I should probably go back to the smaller cam or if I want the bigger spec - use a retrofit roller.
As mentioned above...the lifters MUST spin as the cam rotates. Drop lifters in place and mark them on the top edge. Turn cam by hand and verify they rotate (usually as they drop down) as the cam turns.
Physically inspect each lifter for "crown". Should be .0015-.002" difference between outer edge and center. Then look at each cam lobe. It must taper to one side.
Need to ck lifter to bore clearances to make sure there's not something really worn weird there.
There's some funky machining happening these days on cams and lifters that cause lots of issues.
And the light spring pressure on start up is a good thing for sure.
If you do Not thoroughly wash out entire long block of Any of those cast iron fines that were wiped from failed lifters & lobes; any subsequent repair attempt's successes are in jeopardy.
If, IF you revisit solid flat tappet lifters; suggest the extra cost of upgrade to direct lube option; solids with a tiny EDM hole thru lifter face (hole offset even better). Direct lube option Not available (Nor feasible) for hydraulic lifters (although having a pro machinist groove your lifter bores can be a functional alternative).
Sbc-BBC Flat tappet lifters Must rotate in their bores; or else they will soon fail.
Do ensure there is NO moly paste (Nor other heavy assembly lube) adhered to sides of lifters or adhered to walls of lifter bores. That can cause temporary stiction; preventing rotation during critical first moments of break-in.
With manifold REMOVED: and as you rotate crank thru several revs, Verify all 16 lifters are rotating in their bores.
Also, typically you can verify lifters are rotating while motor is running, via pulling valve covers And Observing ALL 16 Pushrods Spinning (a dot of bright paint can help to see it).
Suggest NO synthetic motor oil during assembly Nor during Entire break-in period.
As was noted I was careful with the moly lube to ensure it was not on the non-contact areas and that they weren’t “sticky”. Push rod length was standard 7.8”.
Had the springs tested and they were in spec for the cam but seems like for start up I should have taken out the inner.
I’ve built several LT1s with the same springs and startup process but this cam is a bit higher in lift than the others that were closer the to “”nostalgia” grind below 0.500”.
As suggested I should probably go back to the smaller cam or if I want the bigger spec - use a retrofit roller.
If this were me, it would get a 292MEGA Isky cam, use mineral oil, and if it is actually a double spring (not spring with damper as some think the damper is a spring and it isn't) remove the center spring.....if it is a flat wound coil leave it, that is the damper..
..What are the springs and what pressure are they, I do not care if they are rated for the cam, what are they....? 110-120 on the seat and 310-320 over the nose are the right numbers....
I had my cam ground by a small grinder that does all his own work. Been in business a very long time.
Was your "assembly lube" actual moly lube? I don't understand a hydraulic cam in a LT-1 the sound is what set them apart.
Oh and comp doesnt grind their own hydraulic flat tappet cams. I've heard of people having problems. I suspect they don't care because they get a chance of selling 2 cams.
That's pretty close to my same situation. 1970 LT1 just ate a cam lobe and lifter not long after a complete rebuild. Just pulled the engine yesterday. I can see through the face of the lifter. Used break in oil and was flowing through all the rockers arms without issue.
Would never use synthetic oil in these engines having said that their seems to be so many problems with cams anymore probably because of heat treating process not being sufficient making it kind of a crap shoot as well as the quality of the material used.
1970 LT1 Eating Cams
