Nice cam. Slightly stouter than my streeter above it.
A SFT I assume.
A SFT I assume.
cam question
- Thread starter MattyP
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yellow rose
Overnight Sensation
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Your cam lists the Advertised already at .018 lash, so what you see is what you get
but check this out;
283/283/105+2/ 115.5 compression/111.5 extraction/ with an Ica of 64.5.. This is exactly what I was thinking about!, when I posted #40..
In your stock 340, this works out to
Static compression ratio of 11.02:1.
Ica of 64.5, and guessing at least 500 ft in Razor's Edge, 340 cubes
Effective stroke is 2.56 inches.
Your dynamic compression ratio is 8.74:1 .
Your dynamic cranking pressure is 180.79 PSI............................... 181
V/P (Volume to Pressure Index) is 142 .........................................142VP
This would be a dynomite anything engine, with waaay too much bottom end for the street, being very near to same as mine.
see below
AJs combo; corrected to 500ft
Static compression ratio of 10.95:1.
Ica of 64*, 500 ft elevation, 367 cubes
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.75:1 .
Your dynamic cranking pressure is 181.07 PSI. ............................. 181
V/P (Volume to Pressure Index) is 155 ......................................... 155VP
but the cam in mine is a hydro, and the advertised is at .008 tappet; and the spec on it is
276/286/110+4/61 overlap. but the actual valve closed to valve closed could be more like
288/298 ( could be even more, I never checked) and that changes the overlap to 78* where the valves are actually closed like yours are with the solids, and that moves the Ica to 70* and the new Wallace is;
Static compression ratio of 10.95:1.
367 cubes, Ica of 70*, still 500ft
Effective stroke is 2.64 inches.
Your dynamic compression ratio is 8.34:1 .
Your dynamic cranking pressure is 169.98 PSI. ................................. 170
V/P (Volume to Pressure Index) is 138 ............................................. 138
To compare the events then, my hydro;seat closed to seat closed, could be;
288/298/110+4/78 overlap /110 comp/102 extraction/Ica of 70*... compared to your solid at
283/283/105+2/73 overlap/ 115.5 comp/111.5 extraction/ Ica of 64.5*
Notice your effective stroke 2.56 compared to my 2.64; practically identical. And our bores are both 4.04. Also Notice your
115.5* compression, with the earlier Ica, is making 181psi/142 VP compared to mine at
110* compression, with just 4* later Ica is making 170psi/138 VP; the VPs, what counts on the street, being very similar.
But look at the extraction, yours is 111.5, compared to mine at 102. And I gotta tell-ya mine is a real pig for gas mileage.
I like your cam choice. It's everything mine is,and more, (we never talked about the tighter LSA) (nor your .620 lift compared to my .549/.571), BUT; without the horrendous (lol) fuel economy penalty.
I'm done with hydros.
I hope that makes sense
Hey AJ! Do mine! .030/360 @ 10.81-1 ratio.
(Oh, adjust valve lift for 1.6 rockers.)
Lunati cam card above.
(Oh, adjust valve lift for 1.6 rockers.)
Lunati cam card above.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Oh sure make me go hunt for it and slow me done yet more,lol.
OK, working on it
I made no compensation for the changed R-ratio
Ok so firstly the card doesn't say that the advertised is after lashing, but I assumed it was, cuz it sorta works out pretty close. So if that is true, them: I get
279/285/110+4/62 overlap/114.5 comp/103.5 extraction/ Ica of 65.5 compared to
YRs combo at
283/283/105+2/73 overlap/ 115.5 comp/111.5 extraction/ Ica of 64.5*
Notice YRs overlap is plus 11*, and that is power right there. Your compression is about the same, but again, the 110LSA has robbed degrees from the extraction, and your fuel-economy will be right down there with mine.
Ok lets install it
Static compression ratio of 10.81:1.
Ica of 65.5 and 500ft elevation,365 cubes
Effective stroke is 2.75 inches.
Your dynamic compression ratio is 8.54:1 .
Your dynamic cranking pressure is 175.38 PSI. ................... 175
V/P (Volume to Pressure Index) is 148 ............................... 148
Excellent street brawler
Now lets see what happens with the LSA closed up to 105; I get
279/285/105+1/72 overlap/116.5 comp/111.5 extraction/ Ica of 63.5, again compared to YRs
283/283/105+2/73 overlap/ 115.5 comp/111.5 extraction/ Ica of 64.5
and installed
Static compression ratio of 10.81:1.
Effective stroke is 2.80 inches.
Your dynamic compression ratio is 8.67:1 .
Your dynamic cranking pressure is 178.90 PSI. ........................ 179
V/P (Volume to Pressure Index) is 153 ................................... 153
Whoaa, that's a lotta lotta VP! but notice the extraction has picked back up, and perhaps more importantly, the Overlap has jumped up 10* bringing with it a nice power surprise, if the headers don't have to work into a restrictive exhaust.
Edited for clarity, and deleted unnecessary wordiness,lol
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Yup!
Thank you AJ! I appreciate it.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I share what I learn, correct me when I'm wrong. If you've seen me in the N&P you'll know my skin is thick.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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By the way....... My anti-pump ups are all clacking just a bit. You know what that means right?
Hyup they're acting like solids. And my cam has grown some duration below it's .008 spec, probably meaning-less to power, but not to idling. But Hughes did say it was a fast rate,lol. And I might be losing some lift to the lash.
In any case, it's still a wicked street brawler, and I can only imagine what a VP of 148 feels like,lol.
Hyup they're acting like solids. And my cam has grown some duration below it's .008 spec, probably meaning-less to power, but not to idling. But Hughes did say it was a fast rate,lol. And I might be losing some lift to the lash.
In any case, it's still a wicked street brawler, and I can only imagine what a VP of 148 feels like,lol.
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Oh! You edited the post. Almost missed it.
“Excellent Street Brawler” was the goal, thank you.
The exhaust is 1-3/4 Hooker Super Comps. It has a close to a zero loss exhaust system even though it is full length. It’s quite effective.
Backed by a 833 4 spd. & a 4.10 ratio.
“Excellent Street Brawler” was the goal, thank you.
The exhaust is 1-3/4 Hooker Super Comps. It has a close to a zero loss exhaust system even though it is full length. It’s quite effective.
Backed by a 833 4 spd. & a 4.10 ratio.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Bada boom
But I gotta ask; with a starter gear of 2.66x4.10=10.91,
Like my 3.09x3.55=10.97
How are you planning to make that killer VP stick?
Or, also like me, do you care,lol.
But I gotta ask; with a starter gear of 2.66x4.10=10.91,
Like my 3.09x3.55=10.97
How are you planning to make that killer VP stick?
Or, also like me, do you care,lol.
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This makes me wonder how it would change with a 410 stroker.
With a 6 pack, as wide and tall a tire as can be stuffed in an ‘73 Cuda and a smart application between clutch and pedal. In the street, as you know, you can’t but it like your at the track. A slightly lower launch rpm and a softer pressing of the pedal until your underway and from there it’s just foot to the floor and side step the clutch allowing it to slam up for the next 3 gears.
Previous engines were done this way without issue. It’s just getting to know the engine again. And brushing off the dust and rust on me.
This will be the most killer engine in THAT car I’ve had to date.
With a 6 pack, as wide and tall a tire as can be stuffed in an ‘73 Cuda and a smart application between clutch and pedal. In the street, as you know, you can’t but it like your at the track. A slightly lower launch rpm and a softer pressing of the pedal until your underway and from there it’s just foot to the floor and side step the clutch allowing it to slam up for the next 3 gears.
Previous engines were done this way without issue. It’s just getting to know the engine again. And brushing off the dust and rust on me.
This will be the most killer engine in THAT car I’ve had to date.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I'll be waiting to see those tires.
Staged outboards may just do it.
Otherwise, for me; there are no smarts in my feets; I just put her in gear, slam the gas, and whatever happens, happens; we'll deal with the surprises as they may appear,lol.
No not in traffic;
Staged outboards may just do it.
Otherwise, for me; there are no smarts in my feets; I just put her in gear, slam the gas, and whatever happens, happens; we'll deal with the surprises as they may appear,lol.
No not in traffic;
LMAO! Well, like I said, in the street, launch at a slightly lower rpm and apply the gas as fast as the tires can take it and let it rev to the shift point and then quickly, just start slamming gears like your bashing in a bears head in for your life.
yellow rose
Overnight Sensation
THANK YOU AJ.
Love the numbers, hate the math!!
It's good to see the numbers written out and to compare the numbers.
Cool stuff.
yellow rose
Overnight Sensation
Our stuff is very close. I have a 833 with a 4.56 and my box is a 3.09 low gear.
And I have 1.875 headers, Strip Dominator.
Agreed. I was entertaining the next larger Lunati SR but figure to error smaller. The car is heavy-ish @ 3465 as delivered. Besides aluminum on the engine, it has a AAR fiberglass hood. Also thought about 4.30’s but decided to skip the expense. The engine should rpm well even for a off the shelf cam. Nothing to hairy. The ported Edelbrock heads should carry the cams range a little further. I think it should be a good all around pump gas mill that can travel a bit.
Those 1.875 headers are Hookers? Outside diameter?
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Ported 6 pack on top.
yellow rose
Overnight Sensation
Do you think it has more to deal with people pick cams base on duration ?
I get most of us can’t pick on opening and closing points, so we go with duration lsa and overlap.
But most don’t even consider overlap except in a intuitive way.
Eg.. like if you picked a cam for a 3.23 geared 318 in a B body and went with 286 cause your eyes were bigger than your belly.
And knowing it’s probably too much went with a 114 lsa intuitively going with a 58 degrees of overlap.
Instead of deciding of starting with a decision of going with 58 degrees on something like a 105 lsa to give you 268 cam which is probably closer to acceptable ?
@273 I’d guess yes to a degree. To really science out a cam for YOUR particular build does require better than average understanding. Now luck (& the internet) is on your side. With the various calculators available and dyno sims available, you can putz about the internet entertaining yourself with the various cam manufacturers line of cams. Enter the values in the boxes of the dyno sims and get a reasonable read out of what you can expect. Of course, a well built and tuned engine is assumed by the sim and that is something to strive for.
The biggest problem occurs when people read up on current and past cam tech. They get confused. The old way worked well for that time. It will still work today. Unless you start changing the rest of the build with newer updates parts, that may not work as well as you think, the plan can fall apart.
On cams, the lobe lines from any one manufacturer can be a dizzying walk through a huge multitude of confusing numbers. In a general build, AKA A basic hop up that needs vacuum for brakes, your going to sacrifice somewhere. The quest for a smoother idle, sacrifice, mileage, sacrifice, etc.... kills power.
(OK, no duh there!)
I posted years back that this was the case each and every time to which end I wrote a little thing on picking a cam made simple. Which it is not in reality if your looking for every last inch of power.
In other words, generally speaking, the cam companies have 90% of this done for you already. Is not optimized or maxed out but generally pretty good.
The biggest problem occurs when people read up on current and past cam tech. They get confused. The old way worked well for that time. It will still work today. Unless you start changing the rest of the build with newer updates parts, that may not work as well as you think, the plan can fall apart.
On cams, the lobe lines from any one manufacturer can be a dizzying walk through a huge multitude of confusing numbers. In a general build, AKA A basic hop up that needs vacuum for brakes, your going to sacrifice somewhere. The quest for a smoother idle, sacrifice, mileage, sacrifice, etc.... kills power.
(OK, no duh there!)
I posted years back that this was the case each and every time to which end I wrote a little thing on picking a cam made simple. Which it is not in reality if your looking for every last inch of power.
In other words, generally speaking, the cam companies have 90% of this done for you already. Is not optimized or maxed out but generally pretty good.
In simple terms, for your basic hot rod on most levels, the cam manufacturers will most times list the parts and rpm band it will operate in. This will get you a good hot rod.
dirty white boy
50 yr old Juvenal delinquent
cause ya ant sposed to be trying to make power with a lowly 318 to start with!! sposed start with at least a 360 if not a 340 if you want that real mopar power! lololol
yellow rose
Overnight Sensation
Just from years of doing it, I can almost tell when someone has compromised their combo. The duration is low for displacement/RPM and the LSA looks too wide with a big spit between intake and exhaust.
They do that because they still want the RPM (moving the LSA wider to make the RPM hang on) because they didn't use enough duration. That's how you lose power. Every where.
If you look at my junk, I have a pretty fast lobe with what most consider a big at .050 timing for my displacement (340 CID/255 @ .050) and to keep the RPM down to a 6800 RPM shift speed the cam timing events are such that the LSA is 105. That keeps the lower and mid RPM power up there, and the narrow LSA keeps that duration from making the shift speed 7500.
With my combo and head flow, induction etc, it was decided that to get a shift RPM of 6800 I needed 255 at .050. If the timing was such that you end up with the de facto LSA of 110 it would have lost a ton in the lower and mid RPM's and needed to be turned much higher.
I'm not afraid of RPM's but I wanted to keep this one below 7000. Now, if I had used my W2 heads I probably could have used only 240ish at .050 and maybe a 108-109 LSA because the heads are so much better, and still kept my 6800 RPM shift speed.
I hope that makes sense and kind of shows the relationship between displacement/RPM/cylinder head/induction and cam timing events/LSA.
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