Hi All,
I am in an awfull position at the moment where I have rebuilt a SBC 25 years ago, used an old cam with mismatched lifters, should have gone new.
I eventually found the cam needed solid lifters and have struggled on with a nice sounding but not a happy engine which has been loosing power by the year!
Due to my stupidity recently, ruining my flywheel after servicing the carb by dumping excess fuel into the bore before starting up, not only do I need a new gearbox package due to various reasons, I now have to have the whole engine rebuilt due to a worn cam as well, no point in going that deep and leaving old stuff below!
I have never heard of needing Zinc additive on flat tappet cams until now??
Lead replacement for valves, Octane for fuel, Yes, but never Zinc?
I was always recommended a good thick oil like Castrol GTX or a 20w 50 oil, but again no mention of Zinc?
If you have a Flat tappet cam, START using it now!
The worrying thing, I was still told by a mechanic today, its not needed???
I've included a link for some more info.
https://rislone.com/blog/engine-oil/the-effects-of-zinc-oil-additives-on-older-engines/
You Decide, is it worth the risk!
From what I've read and learnt so far, it's needed when breaking in a new cam and followers.
It's use as has better impact resistance which prevents the initial harsh wear on the cam and lifters when breaking them in.
For non roller lifters the engine should be broken in by running at approx 2000rpm for 30 mins continuously.
I'll caveat this with I'm not an engine builder but have built mine from scratch and did a lot of reading before doing so.
So I'd say yes to running high zinc oil, but you can also get a zinc additive. I bought my first batch from real steel. I'll be running mine in for 500miles then flush and another 500 with zinc additive.
For ref mine is a 1973 Chevy 350, that's got a 383 stroker kit with hydraulic roller cam and followers.
I have always ran a zinc additive in my SBC since rebuild.
As mentioned above i use a break in oil which has the zinc contents needed for the engine, and i now mix it with a good mineral grade oil, VR1 normally.
Oil flush and change is on my winter list also!
Thanks for replying!
I must confess, it seems to be very easy to get things wrong, there's so many little things that some don't get to hear about and learn the hard way!
When my engine is rebuilt, I will treat it like it's lined with Gold for a while!
I'm going to use a Zinc additive/oil from now on.
Is there anything else I wonder thats easily missed by the average person?
As Tommy says the answer is absolutely. Zinc is vital for a flat tappet cam and not only during break in but all the time. However, you should not run a high zinc content oil if you are using cats as the zinc coats the cat plates and stops them working. If you have a roller cam then you should not really need the zinc. Lucas oils do a hot rod and classic oil that has all the zinc that a flat tappet needs without any additional additives. I know this is an older thread but thought this might be useful.
I concur, Real Steel advised me to add a slug of "running in additive" with every oil change....cheap insurance!
Simon