I think the .921” was a leftover idea from the 394?

as far as going away from the 45 bank I think it was to accommodate future big bores like the 403.

The lifter banks needed to be moved inboard to clear the bores. It’s still very close in the 403 now , it wouldn’t work if they didn’t move them inboard

 

I’m told shortly after the first of the year.

 

Cutlassefi, thank you. Thats an explanation I was asking about.

 

At what point do larger lifters become advantageous? Then, at what point are they a disadvantage? I say it's a moot point because the window is so narrow and applies to even fewer applications.
How aggressive of a cam do you want?

 

The 394 did use the .921 lifters and could very well be the reason,don't really know.

 

I don't want any cam,I'm retired. If large diameter lifters are not better for some applications why were mushroom lifters developed?

 

Mushroom lifters had nothing to do with diameter really. They were developed to make the best use of the diameter you had to work with. The mushroom shape essentially extended the contact patch so you got more effective duration.

 

If they helped the cam,isn't that the purpose of them? I'm confused by your reasoning.

 

They helped the cam BECAUSE of the increased contact patch. Obviously they had limited resources so this was sort of a band aid.

 

Lifter diameter had nothing to do with contact patch. Increased lifter diameter has more to do with lift, specifically, rate of lift. The higher the rate of lift causes the load on the lifter to move to the outside. A flat tappet can be so aggressive the contact point can move pass the outside diameter of the lifter causing the edge of the lifter to gall into the cam lobe. A mushroom lifter has a larger face than the body allowing for more aggressive ramps. In the case of the roller it has to do with side loading the lifter once again the larger the wheel the more aggressive it can be.

 

That has always been my thoughts on a larger diameter lifters. The larger the more aggressive you can be with the cam. I remember mushroom lifters from way back in the day.. What is the reasoning behind Mopar cam grinds used in GM cams? I've seen some Olds guys say they use Mopar profiles.

 

The Mopar 904 lobes can be more aggressive than a GM 842. You can always use a larger diameter but never smaller. So a 921 can be used with a 904 lobe.

 

That sounds about right, from what I recall. Thank you for providing the details.

You had the correct idea about the mushroom lifters and DUH filled in the missing details.

The "Hemi grind" profile can be put on any cam blank with enough material to grind. My step brother has a "Hemi grind" cam in his wedge head 383 Mopar. I believe I have either seen or heard someone putting an "LS" profile on an Olds cam.

Valve lifters are generally ground using a 40 inch radius on the bottom. One cam grinder will "resurface" lifters using a 36 inch radius on the bottom. This would allow faster opening ramps without scuffing the cam with the edge of the lifter.
Now come the comments.......

 

its not really lift. even a low lift cam lobe can be so aggressive on the opening ramp , it can go off the edge of the lifter. Like the stock cheater cams which have minimal lift.

the opening ramp is where a big dia lifter has an advantage, once past approx .170” to .200 lifter rise, there is no advantage, the lifter diameter becomes irrelevant past that point.

the quicker you can open the valve is a benefit because it can delay the reversion back into the intact tract. That hurts power at all rpm’s.

as rpm’s rise, it gets more difficult to control aggressive ramp lobes , so they tend to be less aggressive as rpm’s rise. On the bb Olds when you want to make as much power as you can with a flat tappet, bigger diameter lifters and aggressive ramp rates are always better.

You also have to pay attention to lifter face chamfer. Some lifters come with very large edge chamfers which reduces the diameter .

.017” is the distance I’ve been told is how close the lobe can come to the edge.

 

the lobes have no idea which engine they are in. If I put a Chevy duntov 30/30 lobe on my Olds cam, will the rear main seal start leaking? 😁

lifter crown does not dictate opening ramp profile.

 

I wasn't thinking it would affect the opening or closing ramp profile. I was wondering if they would use a smaller radius to make the lifter edge higher and not scuff the cam. What are your thoughts ?

Yes, the lobes don't care what engine they are in. That was the point I was trying to make.

 

lobes are ground with a taper to match the lifter crown to promote rotation. Changing the crown can screw that up .

mixing and matching cam and lifter manufacturers sometimes can lead to wiped out lobes because of minor differences in lobe taper and lifter crown between manufacturers.

When the lifter crown, lobe taper and lifter bore offset to lobe centreline is all correct…big aggressive lobes with .921” lifters can last a very long time

one other thing that causes issues in Olds is using a bronze aftermarket cam thrust washer without back cutting the cam to compensate for the added washer thickness.

what that does is it moves the cam forward in the block while simultaneously taking away the offset to rotate the lifter

 

Very interesting to know. Thank you.

 

Or you can machine the cam face on the block, which I prefer and do on everything. That also cleans up what can sometimes be a area that is worn to begin with.

 

Did you use larger than 0.842" lifters in any of your EMC entries?

 

yes. Although you have to go off the cam tunnel centerline for that way to be accurate. Sitting in on a mill with either the bell housing as the reference or the timing cover face isn’t a good idea. I know they are not spot on with the cam tunnel.

i can have the cam back cut on its thrust face in 15 minutes. It’s takes longer than that to get block set up on a mill.

 

On the flat tappet , yes. With the .904” MM series Comp lobes. That was one of the main reasons for using a .921” lifter block

 

Is it possible to increase lifter bore diameter on a 0.842 455 block?

 

Correct. We locate off the cam face beyond the wear. It won’t necessarily correct any potential misalignment of the block face vs the cam tunnel but machining the cam won’t either.

 

.842”? Yes, with thin wall liners. And no core shift of the lifter boss casting. I have some blocks here that have some awful core shift,, they would be a bad one to start with

 

He has previously said that lifter diameter is irrelevant.

 

I meant to type 0.842.
Why are liners required when increasing lifter bore diameter?
would the larger lifter also not aid in spreading the load out especially with performance high pressure valve springs?

 

I don't recall Dale saying that lifter bore diameter was irrelevant?

 

Why are you trying to start trouble? That's not what he said.

 

I said the discussion is irrelevant because 98% of people building serious Olds engines aren't going to do it. I can see Chad and Dale trying to squeeze every last drop out, but most won't. Those are also dyno and race engines. How is the durability on the street?
It's just like the 4/7 firing order swap. The cams are on the market, but if it's so great, why isn't it common place?
AND, it's a sidebar to Mark's thread about bringing another hydraulic roller lifter to market.

 

Weren't mushroom lifters used for class or racing with cam restrictions? It was just another way to squeeze out every last HP in those situations. If that's true, then no need for a "no rules" engine like a street motor.

 

In jr stock and stock factory lifter size lifter had to be used in the early days they had to be OEM.
Super stock might have been allowed mushroom lifters?

 

Bernhard wrote:
Your right 98% will not go to this level of detail. But I find it interesting to see how detail oriented and creative performance minded engine builders are.

 

I didn't say he did,the other guy made that statement. Keep up man.

 

It's very relevent to a guy building a low budget engine and trying to get the most out of the build. Everybody is not building all pout engines.

 

I don't know all the pricing, but it doesn't seem like an economical solution by the time you get the bores bushed, find suitable lifters, and have a cam ground to take advantage.

 

Yes it cost to modify the block to accept larger lifters for sure. My point is/was that a larger diameter lifter was advantagous when using a more aggressive cam. I guess the best way to put it is you can use a more aggressive cam with a .921 lifter versus a .842. I know @ one time finding roller lifters for a .921 bore was very limited and only certain lift cams could be used. They why I said lifter diameter matters when selecting a cam.

 

Not sure I would agree with the above ststement! As with this engine platform, there is nothing a cam can't do with .842 that a bigger lifter can. HARD TO PUT THIS INTO WORDS THAT WON'T OFFENED PEOPLE. But for a 900Hp OLDS engine, there more in the cam and pushrods then there is in a lifter. 99% of the info about the lifter is just advertisement and upselling.

I run .842 roller lifter over 10,000RPM on a 55mm cam core and 1/2" double taper pushrods. I had a very good and long discussion with MR. Gene FULTON about using a larger lifter in one of my big motors for the street. Is it a better deal? YES Gene said, but HE wasn't sure it was worth the $$$ for a 70% street motor. As Gene said, "we have used .842s for years with success!"

 

So you're saying there is no advantage in using a larger diameter lifter ever?

 

Popcorn's done!


Have at it. I've said my piece.