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The Truth about Flat Tappet cam failure

TJ1978

TJ1978

I have MANY questions
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Great video.
This dude built my 350 in my blazer but I do have a flat tappet he stopped building flat pretty quickly afyer he finished mine because of failures. and im pretty sure that's my noise in the engine after oil change. Though the guys that installed fi messed it up...
Anyway
 
I only got about half way. Dude is unnecessarily long winded
He also contradicts himself several times, including the discussion of metallurgy after saying the brands they tested had no hardness issues.
Either there is a metallurgy issue or there isn't
Doesn't specify about "off brands or house brands" or no-name brands. Typically these are made by the ones he mentioned anyways

He also doesn't say which brands had cams that failed. Hard to tie up the lose ends for me



That said, I've advocated for roller cams for a long time
Part is wear/break-in/failure
Part is the fact that rollers generate a fairly significant power gain


I'd be curious to have the conversation with the NASCAR engine guys to find out what they were using for tappets in the race engines
I know what we were using for NHRA flat tappet classes, at $1000 a set. Failure rate on the cores and tappets was very low to non-existent
No break-in
 
One of the biggest contributors is incorrectly machined lifters. They are not supposed to be dead flat, rather be very slightly conical on the bottom. Along with the slight taper on the lobe this is what makes the lifters spin. No spin...flat cam. Definitely some heat treat problems too.

At any rate, this isn't news. Anyone gambling with a flat tappet cam today is crazy IMO. Foxin Russian roulette!

 
i am and have been told OCD ..... i have flattened a new cam before .

its a few items that do it . and most 2 i have noticed are lack of zink in oil and bad made parts .
 
Yeah, im thinking it may be worth it to convert from flat tappet to roller cam. I've seen some decently priced conversion kits. They are pricey but cheaper than a new engine
www.onallcylinders.com

Easy Roller: A Budget Small Block Chevy 355 V8 Hydraulic Roller Cam Conversion

Converting your older engine to a roller camshaft & valvetrain has a ton of upside—automotive expert Jeff Smith shows you how & why.
www.onallcylinders.com www.onallcylinders.com
 
Been running a zinc additive on my 1993 5.7 with a flat tappet cam for 20 years 240k miles. Everything is still in spec.

If you have a flat tappet, add zinc and problems become less.
 
Truth. The last flat tappet engine I built was in 2009 for my BBC in the Maiden. Comp Cams solid flat tappet cam w lobe face oriface lifters.
The SBC in the Vette was built in 1994, Crane solid cam and lifters.

I would only use GM Delphi or Johnsons lifters now for a flat tappet.
 
 
Yes you can, too much will cause corrosion and pitting, high zinc oil should be plenty once a cam is broken in. Ideally 1000-1100 ppm is plenty
 
Yeah if the metallurgy of the cam is right, that’s enough. It it’s not, it doesn’t matter

Also, the mention of the NasCar cars is almost irrelevant. Those cams were special made and also coated. The break-in/failure doesn’t apply to us peons
 
Most of the cam failures I’ve seen on FTs are on builds with junk cams or really high spring pressures, think of the amount of old junk still driving around, hell just 4.0 powered Jeeps alone….it’s nothing for those to go 250-300k miles and I’d bet less than a fraction of owners are running a high zinc oil, most are probably running the cheapest thing on the shelf.
 
While I still use Hi zinc oil, once the cam is properly broken in, and survives, the high zinc oil isn't as necessary.
Idk but what other engine makes are having high FT cam failures.
I am sure the bean counters didn't just skimp on Chevy flat tappets
 
On the "hamb" or the "jalopy forum" a lot of guys just go to synthetic oil after break in, some run regular oil with zddp additive, some run the Lucas or comprable hot rod high zinc oil. I guess it's just personal preference. Seems to be all over the place as to what is the "best" method. Most claim that after break in high zinc isn't absolutely necessary but most do it for piece of mind.

After cam break in dump oil and add fresh high zinc oil run it 300-500 miles, change oil and you should be good.

I do have a question, shocker I know. But why do you need to change the oil after the first 300-500 miles after break in? To get rid any metal that make work it's way loose from break in or? And even with that, some claim after break in they just run it and don't change the oil after 300-500 miles and have no problems.
 
It just makes sure you get that high concentration out of everything that wore at a mating surface.

I like pulling the oil to look
 
I have a GM Goodwrench crate engine in my square body that came with a flat tappet camshaft. So far it has been running good. I have known the proper break in procedure for these cams since the 70"s when there was nothing else available. It seems if you have to run a flat tappet cam, then you have to buy a couple of sets of lifters, and measure the taper on all of them to make sure you have a good set of liters. I will probably not build anymore engines with flat tappet cams because the risk of failure of a flat tappet out weights the cost of a roller cam.
 
If you want an entertaining read on what oil you should use try pirate4x4, Ilast I remember the thread was 1000 pages long. I haven't used Pirate since they got bought and sold out, may have archived that one lol.
 
Samba has a long thread too. I will only use dino high zinc oil in my air cooled vw. I think the dino oil removes heat better. Not tested, but my air cooled engine builder swore by it.
 
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