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Mushroom lifter cams
https://www.slantsix.org/forum/viewtopic.php?t=39618		 Page 2 of 3
Author:  Charrlie_S [ Wed Apr 07, 2010 6:19 pm ]
Post subject: 
Quote:
The big question is what would you gain when you have a head that dies at .600" lift anyway?

In all honesty, I saw a damn fast all motor car at MATS that is running way less camshaft than what I run in my junk. :shock:
That was my thinking on the mushroom cam. I really(my opinion) don't think roller cams are cost effective. Was thinking a mushroom would be much cheaper, but still allow a faster lift rate then a "regular" flat tappet.
Author:  emsvitil [ Wed Apr 07, 2010 9:46 pm ]
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A faster lift rate will allow more time with the valve fully open.............
Author:  Charrlie_S [ Thu Apr 08, 2010 4:24 am ]
Post subject: 
Quote:
A faster lift rate will allow more time with the valve fully open.............
exactly
Author:  Doc [ Thu Apr 08, 2010 8:56 am ]
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And that is the "right answer" to the roller / mushroom lifter question... most all SL6 engines I build and use don't really need the aggressive lift rates and corrosponding long open valve times these parts are designed to allow.

Let's face it... the .904 lifter already designed into the SL6 can handle pretty steep cam lobe lift rates... bigger cam numbers then I want to run.

The only application where I see a possible need for the special lifters is land speed, boat or aircraft situations where you run the engine in the higher RPM ranges, for long periods and you really don't care about mid-range and low speed operation.

I will agree in concept that a roller lifter application has less friction and therefore "robs" less HP... keeping the oil cooler as a result but I don't have any real data to back-up that claim.
DD
Author:  Aggressive Ted [ Thu Apr 08, 2010 11:56 am ]
Post subject: 
Doc,
Quote:
most all SL6 engines I build and use don't really need the aggressive lift rates and corresponding long open valve times these parts are designed to allow.
What is the tallest lift cam (which cam) that you like to run for the street and occasional track duty?
What cam would you suggest for my not so light 74 Swinger and 2.76 ratio 8 3/4 Sure Grip?
I have been running the E254.....or should I stick with the cam?

I have my good engine apart at the moment getting a few up grades for this year at the track.....
1. Just recieved the Engine Builder valves
2. Found a new MOPAR double roller chain
3. Picked up a HV oil pump which I need to send to you
4. Have a Weiand four barrel manifold
5. Thinking of ordering the crank scraper next.....
Author:  Doc [ Thu Apr 08, 2010 1:47 pm ]
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Do you know the current "redline" RPM with your current 254 cam?
Do you want to push the current "redline" (power falls-off) higher-up the RPM scale? (and loose some low RPM responce)

My gut feel is that you should stay with the small cam for you high geared, heavy car.
DD
Author:  Aggressive Ted [ Thu Apr 08, 2010 4:25 pm ]
Post subject: 
Doc,

Yes, the tach slows down about 4300 rpm or so but, I thought that was do to max flow of the 1920 one barrel. It is real good to 4000 rpm but doesn't gain allot very quickly after that. The acceleration starts to peter out like there is a limiter on the engine. Under that it is real spunky. I was thinking a two barrel or 4 barrel would allow more air flow and the cam might rev a little higher or at least make more power along the way up.
Author:  Joshie225 [ Thu Apr 08, 2010 6:06 pm ]
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I'm with Doc; stay with the small cam. I'd work on intake flow improvements myself.
Author:  66aCUDA [ Fri Apr 09, 2010 7:07 am ]
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Ted do your testing with the current cam. Then if you want/need to go bigger you can. I think I agree with you that the 1920 is all done by 4K and going 2 bbl or 4 bbl would get you more with the 254.
Frank
Author:  DusterIdiot [ Fri Apr 09, 2010 7:35 am ]
Post subject:  Yep...
I was able to wind the Comp Cam 252 up to about 5K on the clock with a BBD, but then it would go flat...once the Hyperpak went on even with a little 390...the engine would now be free to wind up to 6200 rpm for launches, and the nice fat torque band that the hpak and "Torque" cam provided, meant acceleration all the way through the gears (the last "back roads speed test" on that engine left me with a heavy car at 5000rpm on the clock in overdrive still pulling hard...too bad I ran out of road and my 120 speedo was at the end of it's dial too...)

So definately step up to a carb and intake with more flow and see what happens...

Just as an FYI...in an attempt to get "more" out of a torque cam I had one custom ground with more lift, but kept the same duration and LSA...what I found was there is a solid relationship with our particular motor that it enjoys more duration than lift...the high lift short duration camshaft seems to enjoy the revs, does not like low RPMs, and stops short on the power at about the same spot the stock cam falls flat...

-D.Idiot
Author:  Doc [ Fri Apr 09, 2010 8:33 am ]
Post subject: 
Yes... I have seen the same results when increasing lift without other changes, low speed response and mid range power falls off and you don't get it all back at the higher RPMs.

It all about a good combination of parts and settings and in this case, fine-tuning an already good combo.

For this analysis, take a look at intake port velocity and how the velocity thru the intake track impacts overall engine volumetric efficiency.
One simple tool to look at is the mach index of the air flow at different RPMs and valve sizes / lifts.

Here is a basic calculator that will show how your current combo already has pretty good velocity numbers and that going to a bigger valve size will push the VE "sweet spot" higher, in terms of RPMs. Higher lift rates also moves the the sweet spot (.5 mach) higher in the RPM range.

It is important to be realistic about the RPM you drive at and where you want to "set" the max VE in the RPM range.

Use your back button with this calculator so you can change one value at a time. (play with valve size, lift and RPM)
DD
http://www.wallaceracing.com/machcalc.php
Author:  Dart270 [ Fri Apr 09, 2010 9:59 am ]
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Tilley experimented with high-rate cams with higher lift and they were worse than his lower lift designs. Duration/LSA and centerline are most important, from my searches and experience.

Lou
Author:  Aggressive Ted [ Fri Apr 09, 2010 10:36 am ]
Post subject: 
Doc, Lou, DI, Frank and Josh,

I ran the numbers with stock valves and the Engine builder valves and I see what you mean about choking the flow You really run into trouble at 5000 rpm on up.

The information from your cam experiences is excellent and very valuable! Thanks...I will take heed and leave the E254 in and up grade the head some more and bolt on the Weiand four barrel and see what it will do. Not sure what the best carb would be, but leaning towards the 625 cfm Barry Grant Road Demon.
Author:  Joshie225 [ Fri Apr 09, 2010 11:06 am ]
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625CFM is too much. I'd do an electric choke Edelbrock 500 or a 390 CFM Holley. If you must have Barry Grant get a 525 CFM model.
Author:  Dart270 [ Fri Apr 09, 2010 12:29 pm ]
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Yes, definitely do not be tempted by big CFM. Been there, no gain for a motor like yours.

I like the Edelbrock 500 performer and the 500 AVS Thunder even more since I just bought one of those and tuned it in on Slantkota. Holley 350 2bbl or probably better yet 390 4bbl would be other decent choices, as Josh said. Even a BBD would be a solid step up from a 1920.

Lou
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