Flat tappet failure

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71Demon540

71Demon540

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Back in 2023, my mentor/step father and I rebuilt my father in law's BBC for his 69 Chevelle after the engine drank a nut from the carb air cleaner and punched a hole in the cylinder head. Anyway, the engine was rebuilt with speedmaster cylinder heads and a new hydraulic flat tappet cam from Comp cams. The cam was the same cam that came out of the engine (but new) and new lifters. The used lifters looked good but the camshaft had some spots that looked like the metal was beginning to "flake" off or deteriorate. Since my father in law didn't have the money for a hydraulic roller at the time, the new hydraulic flat tappet cam and lifters went in after we set up the heads for a hydraulic flat tappet cam. All the lifters spun when we built the engine and were barring it over. After I put the engine in the car, fired it up, immediately had very noisy valvetrain. It immediately went into failure. 30W Penn grade break in oil, proper break in procedure followed, (No idling). After recognizing we had an issue, we stopped. Pulled the valve covers, saw fine metal laying at the bottom of the heads by the valve cover rail. Pulled the intake, 5 lifters and cam lobes were totally trashed.

After my father in law saved up some money, I got his engine over to my house and tore it apart and began preparing for a rebuild. Wow did we get lucky. The 5 lifters and cam lobes didn't do as much damage as I was thinking. Luckily the skirts on the pistons were not destroyed and the cylinders had some minor scratches on them. Being a pure street cruiser, a dingleberry hone was utilized. New rings, new bearings, new oil pump, new cam and lifters, new gaskets, new valve springs, locators, and retainers for the new cam, and this will be going back together this week.

I have never ran a flat tappet as I was raised in the solid roller camshaft generation and I am generally against all flat tappets in this day and age. Not that there arent millions of people who run them with success, but Im not one of them. Especially a comp cams.

I just wanted to share this to show others more failures and hurdles we have to overcome in this sport.

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IMG_5040.jpg


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IMG_5038.jpg
 
Too much lifter preload? Wrong length pushrods? Adjustable rockers?

Any bent push rods? I lost a lobe once to the guides being too tall, it bent push rods then ate the lifter.
 
I own an engine dyno and starting right after the pandemic we started having lifter failures, lots of lifter/cam failures. This was on circle track engines, which, by rule, have to run a flat tappet. Most, not all, were comp cams. The solution, so far, has been to send brand-new lifters (or good used) out to be rebuilt and resurfaced.
 
looks like the lifters were soft.

That is some serious wear for what sounds like less than full break in time.
What was the cam grind?

Here’s one after 1/2hr run time on the dyno.
Hylift Johnson lifter, Melling cam, SBC
The other 15 were perfect.

IMG_3898.png


These days, FT cams in high rocker ratio big blocks seem to be particularly hard to get to live.
Slow, smooth lobe designs that will survive with pretty modest spring loads should help.
And you’ll more than likely need to break it in with very mild springs(solidly under 120/300).
I think solids with edm oiling have a better chance of surviving.
 
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I know of just short of half a dozen 396's that perpetually eat cams, My understanding is the lifter bores were machined skewed, B.H.J. has a fixture to guide/correct boring them to sleeve them....if I had one that would be job #1.....
 
Funny how these engines work perfectly for decades....& then suddenly the lifter bores need machining...

The BB Chev has two things that cause accelerated wear.....& nothing to do with the lifter bores:
- 1.7 rocker ratio...needs stronger springs to control the valve train
- large, heavy valves....need stronger springs to maintain control.
 
I've been building engines for the better part of 50 years and have never had a cam failure......until a Comp flat tappet about two years ago.......and also in a big block Chevy. A 1970 402. I did everything right by the book. There was damage to every single lobe and lifter. Now, it's been gone through again and is sitting on an engine dolly with a small, custom solid roller.
 
Bewy said:
Funny how these engines work perfectly for decades....& then suddenly the lifter bores need machining...

The BB Chev has two things that cause accelerated wear.....& nothing to do with the lifter bores:
- 1.7 rocker ratio...needs stronger springs to control the valve train
- large, heavy valves....need stronger springs to maintain control.
Click to expand...
Not to mention all the ridiculous angles not helping a single thing.
 
71Demon540 said:
Back in 2023, my mentor/step father and I rebuilt my father in law's BBC for his 69 Chevelle after the engine drank a nut from the carb air cleaner and punched a hole in the cylinder head. Anyway, the engine was rebuilt with speedmaster cylinder heads and a new hydraulic flat tappet cam from Comp cams. The cam was the same cam that came out of the engine (but new) and new lifters. The used lifters looked good but the camshaft had some spots that looked like the metal was beginning to "flake" off or deteriorate. Since my father in law didn't have the money for a hydraulic roller at the time, the new hydraulic flat tappet cam and lifters went in after we set up the heads for a hydraulic flat tappet cam. All the lifters spun when we built the engine and were barring it over. After I put the engine in the car, fired it up, immediately had very noisy valvetrain. It immediately went into failure. 30W Penn grade break in oil, proper break in procedure followed, (No idling). After recognizing we had an issue, we stopped. Pulled the valve covers, saw fine metal laying at the bottom of the heads by the valve cover rail. Pulled the intake, 5 lifters and cam lobes were totally trashed.

After my father in law saved up some money, I got his engine over to my house and tore it apart and began preparing for a rebuild. Wow did we get lucky. The 5 lifters and cam lobes didn't do as much damage as I was thinking. Luckily the skirts on the pistons were not destroyed and the cylinders had some minor scratches on them. Being a pure street cruiser, a dingleberry hone was utilized. New rings, new bearings, new oil pump, new cam and lifters, new gaskets, new valve springs, locators, and retainers for the new cam, and this will be going back together this week.

I have never ran a flat tappet as I was raised in the solid roller camshaft generation and I am generally against all flat tappets in this day and age. Not that there arent millions of people who run them with success, but Im not one of them. Especially a comp cams.

I just wanted to share this to show others more failures and hurdles we have to overcome in this sport.

View attachment 1716416474

View attachment 1716416475

View attachment 1716416476

View attachment 1716416477

View attachment 1716416478
Click to expand...
That'll just buff-out?
 
dano said:
Too much lifter preload? Wrong length pushrods? Adjustable rockers?

Any bent push rods? I lost a lobe once to the guides being too tall, it bent push rods then ate the lifter.
Click to expand...
Not too much preload
Pushrods were measured and purchased appropriately
Rockers are adjustable
No bent pushrods
 
Sr4440 said:
I own an engine dyno and starting right after the pandemic we started having lifter failures, lots of lifter/cam failures. This was on circle track engines, which, by rule, have to run a flat tappet. Most, not all, were comp cams. The solution, so far, has been to send brand-new lifters (or good used) out to be rebuilt and resurfaced.
Click to expand...
How much is that to get new lifters rebuilt and resurfaced? Is it cost effective?
 
PRH said:
looks like the lifters were soft.

That is some serious wear for what sounds like less than full break in time.
What was the cam grind?

Here’s one after 1/2hr run time on the dyno.
Hylift Johnson lifter, Melling cam, SBC
The other 15 were perfect.

View attachment 1716416662

These days, FT cams in high rocker ratio big blocks seem to be particularly hard to get to live.
Slow, smooth lobe designs that will survive with pretty modest spring loads should help.
And you’ll more than likely need to break it in with very mild springs(solidly under 120/300).
I think solids with edm oiling have a better chance of surviving.
Click to expand...
Dwayne, I cannot remember the spring pressures as they were set up 2 years ago and I cannot find the paper (my father in law has it somewhere) however I know they were set up appropriately for a hydraulic flat tappet cam. May have been less than 120 at the seat but again I cannot remember.

The cam grind was 240/246 @ .050
.574/.578 lift and 110 LSA

The new cam is 235/241 @ .050
.618/.618 lift and 112 LSA hydraulic roller by Howard’s
 

You do NOT get new lifters re-surfaced/refaced. You get lifters made pre -1995 re-faced; these are US made, correct metal & correct hardness.
 
Bewy said:
You do NOT get new lifters re-surfaced/refaced. You get lifters made pre -1995 re-faced; these are US made, correct metal & correct hardness.
Click to expand...
I would never use a flat tappet cam I was just curious what having them re faced would cost compared to going hydraulic roller and not worrying about these flat tappet failures.
 
Bewy said:
Funny how these engines work perfectly for decades....& then suddenly the lifter bores need machining...

The BB Chev has two things that cause accelerated wear.....& nothing to do with the lifter bores:
- 1.7 rocker ratio...needs stronger springs to control the valve train
- large, heavy valves....need stronger springs to maintain control.
Click to expand...
It's not funny, and these engines ate the cams 20+ years ago, not recently smartass. Go look the B.H.J. fixture up while You're at it. All of them ate the stock ones, the guys that changed them weren't newbies, & the "since it needs a new cam, I'll stick a better one in" replacements made the situation worse....one diehard Chebby bud killed 3 in a row & was bewildered, wanted Me to check it out, I started asking around those who knew those mills well & found out what I just shared.....accept it or not Dude......
 
Read post #8 smartarse & learn something.

Hemis were also hard on cams, same reason, strong v/springs.
 
I just checked comps website and the mopar dlc coated lifters are in stock now. I hope these flat tappet lifters are a solution for the problem with flat tappet failures. I have not tried them yet. They are priced reasonable. Comp seems to be all in on these lifters and it looks like they are available for most applications now. If anyone has any experience with the dlc coated lifters let us know please.

TAPPET, DLC HYDRAULIC FLAT TAPPET .904" DIA AMC & CHRYSLER APPLICATIONS SET 8 CYL - Set of 16 - COMP Cams® https://share.google/2awEYj2Af67SovNIC
 
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There is/was nothing wrong with Chrys lifters [ & aftermarket ], pre- 1995. You didn't see failures being reported like you see now. Get some pre-95 lifters & have them re-faced. When I was racing & testing different cams, I had lifters re-faced 2-3 times, never had a failure. FT lifters are the same hardness right through. Would a super hard lifter wear the lobe more?
 
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