Reliability of Lobes Designed for .904 Flat Tappet Lifters

[66Satellite47]

here

View attachment 1295692

Thanks

 

[JedIEG]

comp cams has a master catalog lobe profile too

Yeah I know, I have a copy, but the .904 lobe section is really limited from Comp. I would hope they have a lot more .904 lobes numbers than what is in the catalog but you probably have to call to get them.

Any issues with valve beat in with guys running the .904 lobe?
It seems like the .904 hydraulic flat lobes are almost the same rate and duration as a hydraulic roller with no need for the block machining or lifters so it seems like a great value for money. You just take the penalty in friction over a roller.

 

[moparedtn]

I was wondering how reliable flat tappet lobes that were designed for the .904 Mopar lifters are and if people have experience with them?

Well, they've been making them since the early 60's (factory and all), so I reckon the problem isn't "lobes that were designed
for the .904 Mopar lifters"...
The problems are typically these days with inferior quality parts rather - stuff made in China especially (looking at you, Comp
Cams).
Couple those with the misuse of synthetics that lack proper zinc and phosphates (mandatory for flat-tappet survival) and you
get the crapstorm of failures all too common in the hobby today.

 

[justcruisin]

I ran a synthetic oil (oil extreme) for 6 years with a XE275HL (904 lifter) cam, 120 seats, 295 open. Can't recall the zinc/phos content, something like 800PPM. The cam showed no sign of wear when I took it out.
There is plenty of thinking online that a good synthetic will provide the protection required for FT cams.
However, there is security in using what has worked in the past with a dino oil with 1500PPM+ zinc.

 

[moparedtn]

Amsoil's take on the whole ZDDP thing:
https://blog.amsoil.com/do-older-vehicles-need-high-zinc-motor-oil/
Their bottom line:
Break-in of flat tappet engines require LOTS (over 2000ppm) of zinc and accompanying additives.
After break-in, you still need to use oil that provides over 1000ppm ZDDP for the life of the engine.

 

[gtxrt]

i have the one in my 67 newport fresh rebuilt 440 with 2.76 gears till the 2.94 posi goes in. 217-221 @.050. on a 110 LSA with a 106 centerline but degree in at 107 centerline. it's right there off idle and still pulls to 5500 rpms. works for me for a nice cruiser. i ran Hughes engines cams they were very good kept pulling all the way but didn't turn on as fast down low, Hughes has more lift per duration but there not as fast ramp they have a wider spread between duration @ .050 and advertised duration.

 

[Master Gunner]

Hughes Engines does only Mopar parts and cams designed for the Mopar .904 lifter size, and has a very good tech line.

https://www.hughesengines.com/

Mark

 

[justcruisin]

Break-in of flat tappet engines require LOTS (over 2000ppm) of zinc and accompanying additives.
After break-in, you still need to use oil that provides over 1000ppm ZDDP for the life of the engine.

I'm sure that is sound advice, and what has been said for some time now and something that has worked - for the most part, FT cam failures still seem to happen regardless of oil, correct break in etc.
I could offer up examples of opinions in favor of synthetics, one from David Vizard, renowned automotive writer and all round petrolhead who is in favor of synthetics with FT cams but are these comments fact or advertising. Based on my experience I don't see that the use of a synthetic will deal a death blow to your engine and that a high zinc oil is the only way to go - although I have also use those oils (Brad Penn, Joe Gibbs) with good success.
The reason I tried a synthetic was I had too much oil pressure and wanted to switch to a thinner grade of oil. It has worked for me only thing I will say is it didn't help my rear main leak, but that may be contributed to the thinner oil.
I will be running spring pressures of 135/360 shortly with a SFT cam, hopefully all will be good.

 

[451Mopar]

I have been considering cams for my upcoming build. I am likely to go with a flat tappet due to the cost of a roller. I was wondering how reliable flat tappet lobes that were designed for the .904 Mopar lifters are and if people have experience with them? I dont see a lot of people suggesting them on threads.
The companies I see with mopar lobes are Hughes and Comp Cam's Extreme Energy HL series

For example these are basically the same duration but different lift accelerations and max lifts. I dont know why you would ever use the regular ramp rate unless there was a durability issue.
Regular ramp rate
https://www.compcams.com/xtreme-energy-230-236-hydraulic-flat-cam-for-chrysler-273-360.html
Mopar .904 tappet ramp rate
https://www.compcams.com/xtreme-energy-hi-lift-231-237-hydraulic-flat-cam-for-chrysler-273-360.html

Those lobe profiles are fine with the standard precautions for flat tappet cams.

 

[moparedtn]

I'm sure that is sound advice, and what has been said for some time now and something that has worked - for the most part, FT cam failures still seem to happen regardless of oil, correct break in etc.
I could offer up examples of opinions in favor of synthetics, one from David Vizard, renowned automotive writer and all round petrolhead who is in favor of synthetics with FT cams but are these comments fact or advertising. Based on my experience I don't see that the use of a synthetic will deal a death blow to your engine and that a high zinc oil is the only way to go - although I have also use those oils (Brad Penn, Joe Gibbs) with good success.
The reason I tried a synthetic was I had too much oil pressure and wanted to switch to a thinner grade of oil. It has worked for me only thing I will say is it didn't help my rear main leak, but that may be contributed to the thinner oil.
I will be running spring pressures of 135/360 shortly with a SFT cam, hopefully all will be good.

Nothing says using a synthetic with proper amounts of zinc and phosphorus made into the formula is necessarily
a bad thing here....
The two are not mutually exclusive.

 

[justcruisin]

Nothing says using a synthetic with proper amounts of zinc and phosphorus made into the formula is necessarily
a bad thing here....
The two are not mutually exclusive.

I don't know of any synthetics that have a high content of zinc and phosphorus, maybe there is but I haven't seen or used one. From what I have seen synthetics use other products such as moly and calcium in their HP package, mainly I imagine as high levels of zinc is not compatible with catalytic converters. What I am saying is ZDDP is not the only game in town as to protection for FT cams.

 

[PRHeads]

High zinc synthetic?
Not a problem

 

[justcruisin]

Thanks, good to know, what is your opinion on Dino vs synthetic for older engines. I know a lot of guys stick with what they have had good results with, what is your preference.

 

[Geoff 2]

Just,
You should be able to get Penrite in NZ. Their oils, syn & min, have the correct amount of Zn/Ph & it is not 2000 ppm.
I have been using Penrite for over 20 yrs in my 455. I also recommend it for the engines I build & AFAIK, the owners heed the advice. I always use Penrite break in oil [ 15w/40, a min oil ] for the initial start & then for 2000 miles
I use the 10w/60 TenTenths, expensive, but ultimate protection. NOT friction modified either like a lot of overseas oils...

 

[justcruisin]

Thanks for the heads up on the Penrite, and yes we have that here. matter of fact Supercheap has the 10w40 full syn on special for 29.99 for 4 liters, I ordered a couple of packs for my daily the other day.

 

[gtxrt]

any opinions on REV X says 3000 zinc

 

[Kern Dog]

As it has been stated numerous times, ADDITIVES are not recommended by most, if not ALL oil manufacturers.
The common reason given is that each oil is formulated with its own brand of chemicals and additives. Pouring in more additives is a huge gamble because the chemicals may not be compatible and could cancel each other out......leaving you worse off by a long shot.

 

[Geoff 2]

Exactly ^ right & well said!

 

[Geoff 2]

Just a comment on the origin of this thread: reliability of 904 lifters. No real difference between these & 842/875 lifters. Someone said you would need higher spring rate/more tension. Well maybe not, & if maybe, only by a small amount. 904 lobes can have higher lift, so the same spring will have more tension at max lift, compensating for the higher net lift.
The wear that the lifter/lobe sees is at this interface; governed by the radius of the lifter & the taper of the lobe. If both are the same on a 842 & 904 lifter/lobe, there is no change in the load seen at this interface; the only other factor is the spring tension, already covered above.

 

[66Satellite47]

In terms of reliability, the basic fact is, what is the quality of the lifter combined with the proper spring pressure for the cam lobe. Diameter makes no difference.