big hammer

Yeah I have "big" tires and and have been working on my suspension. I can get half assed traction in 2nd but she's squirrely all the way.

I'd think 17.5* of overlap will tune pretty easy

spanks13

iTrader: (5)

Is that at zero valve lash or including .010" lash for the LLSR?

Hydraulic equivalent would be ~233/246?

speedtigger

iTrader: (16)

It would be the equivalent of a 234/248.

NAVYBLUE210

Daniel,
I included my Cam Motion Cam Specs Below, for comparison
with BigHammer's.
(HR ~ 237*/243*) +~2* with larger diameter lifters.

Did I see somewhere that you acquired a FAST W/ Mid Length Runners?
Did you flow your SPS Heads?
Dan

64post

iTrader: (5)

I'd like to use a LLSR cam similar to yours for a high compression 416 using AFR 260's and either a Holley Hi Ram 105 or a FAST 102 with mid or short runners. Track only car, no street and likely e85 used, what would you think the right cam for me would look like on a spec card, Dan?

Darth_V8r

iTrader: (4)

I know you directed this at Dan and not me, but hammers cam might be a bit better choice. For higher RPM and avoiding a heavily intake biased overlap. And I'd run the hi ram.

64post

iTrader: (5)

239/253? Too small imo. I'll be leaving on a trans brake @5500-6000 and looking to shift @7200+

NAVYBLUE210

Pete
Not a Cam Guru, only play one on tech LOL!
So something like 248*/258* 112*+3* .680"/.663".
This is closer to speedtigger's cam in his 403" with a 4.0" stroke.
The AFR Head is 20 CCs smaller in port size VS
the Dart Heads but flows better intake and has a better
E/I Ratio, being NA only, 10* is plenty for split,
maybe even 8* shifting @ 7200 RPM. Keeping
lift under .700" means much less expensive
valve springs, and longer life.
Overlap is about 25*, significantly
more than my 17.5* and more than Hammers
22*. I would run the FAST and test both Mid &
Short Runners, but the short would probably
need a 7800 RPM shift and maybe just a little
more lift & duration to separate significantly.
I am confident 720+ FWHP and 600+ RWHP
is likely with 13.5:1 Comp, E85, and your
attention to detail.
Looking forward to your results!
Anyway thanks for asking I'm sure Jake and
Steve would spec larger LOL.

big hammer

I shift this cam in the 7500-7800 range. Don't let the duration fool you

NAVYBLUE210

Remember its a 4.00" stroke 416", automatic with a
5500-7500 RPM range with a 5500-6000 RPM converter.
Track only. Speedtiggers "Little Beast" cam 247*/259*

big hammer

Yes 4" stroke will change it some.

big hammer

Ls3 heads and a mid runner fast goes together like peas and carrots

NAVYBLUE210

Throw in the LLSR and that's like adding mashed potatoes.

big hammer

Sounds like a boner inspiring combo right there

spanks13

iTrader: (5)

Hey Dan.

Just saw your post! Thanks for the cam card. When accounting for the hot lash both your cam and Big Hammer's are surprisingly small for the RPM range and size of the engine. The stock-ish stroke length makes a big difference vs a 4" arm.

An equivalent hydraulic would only have 11 and 17* of duration for your two cams. My drag LS3 with a Victor Jr. has 25* of overlap - 239/251 110+2. It has a flat peak from 7000-7400. It is actually very mild to drive around, but is carbureted and has a 5800 stall converter and a glide lol.

I did let it slip in the other thread that I picked up a mid length Fast. I drove out to Tony's shop and picked up an already Mamofied one he had on the shelf. Super nice guy! Had a fun chat bs-ing about stuff for about an hour and of course left with a gorgeous intake!! That does mean I spent my solid roller budget on induction though...I'll be using short travel hydraulic Johnson lifters.

I have nottttt received the SPS heads yet. Nothing against Gavin. Ran into some delays getting the custom sized hollow stem valves - he got a little screwed over by the mfg'ers. I was part of the initial batch of heads that were going out and the valve delays ran into his planned shop expansion/move...so got a little backed up. He started working on my head and noticed something odd...the CNC wasn't done properly and instead of hand blend fudging it he's starting with a fresh casting.

I wish I had the money to slide a few different cams into my engine when I finally get to build it. I've been kind of obsessively playing with the cam timer to try and nail the best compromise. Your guy's builds are making me think I can go smaller, but then again I do have a 4" crank which will need more duration to achieve the same rpm range given the higher piston speed at the same rpm.

I do think I want to get a 243 (hydraulic) intake lobe in mine, but that starts getting real big. 243/258 112+3 seems real good if I could stomach the 26.5* overlap. Looking at your cam a smaller split 243/250 110+2 is also pretty enticing with the same overlap. 239/246 111+2 would also probably run great at 20.5* overlap.

I think the short runners will really run well with a tight center - IVO at least 10* BTDC - preferably 12*+.

speedtigger

iTrader: (16)

This thread makes me happy.
It is awesome how you all are considering your valve events, runner lengths and displacement. Better yet, you all are trying your ideas and sharing results. Very cool.

spanks13

iTrader: (5)

It's a lot of fun for me. I'm just the loser with the 4" crank and small bore :'(

Tigger I'm curious - I've been thinking since this morning about the EVO event and how it would relate to stroke and piston speed.

Since the exhaust event is largely completed by blowdown and not by the piston pushing the exhaust out - does the stroke of the crank have anything to do with the EVO event?

Normal logic with a longer stroke states that you need to advance your valve events a bit to compensate for the increased piston speed, but with EVO I can't see how it is going to impact it much.

64post

iTrader: (5)

Why the insecure thoughts about a 4" stroke? it'll work in your advantage. Adding 3/8" stroke to a stock stroke creates a 1.53 rod ration assuming you're using 6.125" rods, this added "arm" adds leverage, compression and piston speed not allowing the piston to dwell at the top and bottom of strokes much if at all, you get a better cyl. fill and peak power/torque in a lower rpm, this works well for moving a car.

Darth_V8r

iTrader: (4)

FWIW, I tend to see the EVO position as much associated with compression ratio as anything else. Higher CR = earlier EVO. With larger strokes, I tend to see the exhaust duration increased by adding to the EVC event and creating more overlap.

That's just "observating" through many cam spec threads in general. Fun discussions for sure

CAMMOTION PERF

Lets consider the parameters for choosing the EVO. Stating the obvious, the exhaust valve's job is to evacuate spent gasses. When to open the exhaust valve is influenced by how much exhaust gasses it has to get out and how long it has to do it right?

First consideration is the volume of exhaust gases after a power stroke. The more power an engine makes, the more exhaust gas volume it will generate. So, the EVO has a direct relationship with power levels. The more volume of spent gasses, the sooner you must open the exhaust valve.

Second consideration is the RPMs. At high RPM, the exhaust cycle happens faster than at low RPM. So, as RPMs increase, the exhaust valve must open sooner to have enough time to expel the gasses.

Lastly we must consider the engine and vehicles exhaust flow. Obviously exhaust valve size, port size/port flow, exhaust header size/flow characteristics and the exhaust system after the headers flow.

One thing I see people say repeatedly is; "This head or that head needs duration spread of x amount of degrees. Yes, the head does influence the valve events, but that thinking does not take into consideration RPM, power levels or the vehicles exhaust system. So, it is a failed generalization.

As for the stroke, rod ratio etc., the exhaust cycles dynamic is not the same as the intake. On the intake, the signal from the piston creates the pressure differential and the signal that creates flow. On the exhaust side, you merely have a very high amount of pressure in the cylinder that is providing the impetus for flow. So, once the valve opens, the pressure differential exists already and is not influence by the bore/stroke/rod ratio to any significant amount.

~Steven