Build suggestions for 340?

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Effective stroke has to do with cam timing evens IIRC & got this right. AJ will splain it good!

That cam, in the right setting, is indeed an outstanding cam. (I run something very similar in a Hydraulic roller) In the wrong setting, it’s pathetic. This is why AJ runs to the calculators. They can realllllly bell dial in what your looking for even if you don’t know what you need.

If you have all of the other information about the car& engine but are missing the best possible (or as close as possible) cam timing events (cam size included) the calculators point the way. IF! You follow the calc exactly, I will be a custom grind and may have a grinder scratching there head. LOL!!!

Also beware that what technically or scientifically works out as the best cam may not be what you like to drive around in. The engine may not idle nicely, drive around in idle well, drive nice below the point where the torque picks up and becomes nice to drive in... etc.....

This is why there are a bunch of cams that look very similar but react unbelievably different. And also why every time someone asks for advice on a cam, there is a different answer for almost every reply.

Go on and fill out the on line forms for a cam recommendation to 10 cam grinders and receive 10 different suggestions.

I have a good understanding of cams, not a great one. I’ve been knee deep in conversations with grinders and racers. I’ve come to the conclusion that knowing everything for everyone is impossible and it is not possible to get the right scientifically or via calculators the right cam but for only one person. Myself.

No matter how you explain your decision to another, they will more than likely tell you that you screwed up.
Some will tell you that you don’t care about HP (to small of a cam) because of your choice, then next guy will ridicule you for the lack of torque it’ll make. (To big of a cam) or the lack of midrange torque. (Wrong timing evens)

Make the best educated choice possible, stab it and run it. If you like it, enjoy! If not, there easy to swap out.
 
Jim64 said:
So thanks, Rusty, for that cam recommendation - I think it does a good job of fitting my realistic parameters!

AJ - I got the spec from Lunati about that cam, and based on that, I attempted to fill out the formula, and here's what I entered and what it calculated:
Number of Cylinders : 8
Bore in Inches : 4.08
Stroke in Inches : 3.31
Rod Length in Inches : 6.123
Static Compression Ratio : 10 :1
Inlet Valve Closes ABDC : 39°
Boost Pressure in PSI : 0
Target Altitude : 800 (Feet)
Results:
Static compression ratio of 10:1.
Effective stroke is 3.03 inches.
Your dynamic compression ratio is 9.24:1 .
Your dynamic cranking pressure is 192.80 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.08 :1.
V/P (Volume to Pressure Index) is 183

Either there is something off in my input, or this is an outstanding cam. Please correct me if I've entered something incorrectly...
-Jim
Click to expand...

Using the united Engine calculator I get 8.5 dynamic. I think that's closer.
 
Jim64 said:
So thanks, Rusty, for that cam recommendation - I think it does a good job of fitting my realistic parameters!

AJ - I got the spec from Lunati about that cam, and based on that, I attempted to fill out the formula, and here's what I entered and what it calculated:
Number of Cylinders : 8
Bore in Inches : 4.08
Stroke in Inches : 3.31
Rod Length in Inches : 6.123
Static Compression Ratio : 10 :1
Inlet Valve Closes ABDC : 39°
Boost Pressure in PSI : 0
Target Altitude : 800 (Feet)
Results:
Static compression ratio of 10:1.
Effective stroke is 3.03 inches.
Your dynamic compression ratio is 9.24:1 .
Your dynamic cranking pressure is 192.80 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.08 :1.
V/P (Volume to Pressure Index) is 183

Either there is something off in my input, or this is an outstanding cam. Please correct me if I've entered something incorrectly...
-Jim
Click to expand...
That 39 degrees intake closing is measured @.050” You should be entering 60 degrees for that cam if I’m not mistaken.
362D4F03-1942-4B04-A01C-037D3749ED15.png
 
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12many said:
That 39 degrees intake closing is measured @.050” isn’t it? You should be entering 60 degrees for that cam if I’m not mistaken.View attachment 1715664015
Click to expand...

Depends on which calculator you use. The United Engine calculator says to add 15* to the .050" ICV. So using their formula that would be 54*.
 
Jim64 said:
Either there is something off in my input, or this is an outstanding cam. Please correct me if I've entered something incorrectly...
-Jim
Click to expand...

Yeah; you inputed the wrong numbers. the first timer often does that.
if you look at the very top of the calculator it says;

Dynamic Compression Ratio Calculator
(Use seat to seat or advertised specs for Intake spec for best results)
Click to expand...

You inputed the .050 numbers, and the calculator is not set up for that.
The .050 numbers are a throw-back to the earlier years when there was no consistent way to compare cams. You could take five 268 cams each from a different grinder, and have five different running engines, yet all were the same rated 268. Somebody got smart and said, we gotta level the playing field; so after that day,the cams had to be rated at .050. This still does not mean that every grinders [email protected] cam is gonna perform the same in your engine! it just narrows the choices a whole bunch.
Anyway; the Wallace is all about being able to compare LOW RPM performance, and the .050 numbers have nothing to do with low-rpm. So you cannot use them. And you cannot even use them to fudge the calculator by adding an arbitrary number, like is done with some other calculators.
So
You have to use the advertised numbers. Which, in the case of the 271H10 are 271/279/110+4.
And you have to generate all the missing numbers from those, and it can be done.
Ok,so;, I'll work it out for you, then show you how to do it. The numbers are;
271/279/110+4/55overlap/119 comp/106 power/ Ica of 61*
There is your magic Ica of 61*; but
Notice the PowerExtraction is only106*. That's just ducky at WOT and 5000 plus rpm. But the rest of the time it is gonna cost you fuel usage.
Furthermore, the checking tappet lift is .006 inch, so the cam measures bigger than it would when compared to the same cam when the checking tappet lift is .008, like Hughes and Mopars are measured. No big deal, but you just cannot compare it to those other cams.
Furthermore, that 61* on this .006 rated cam
IS NOT
gonna be 61* when remeasured at .008 tappet rise; even tho it is the exact same cam! This is how guys get screwed.
Ok so here is how you can generate all the numbers from just the four given numbers, in blue above.
Overlap first;
Take the average of the given durations and subtract double the LSA; easy-peasy. So
(271+279/2) - (2 x 110) =275-220 =55*overlap
Next we have to figure out where the intake installed centerline is. the spec is +4 so; so
110 less 4=106 Icl easy peasy.
Next; We need to figure out how much of the overlap to give to the intake stroke and how much to the exhaust stroke. One would think, we could just divide it in half, and sometimes you can; but usually the vendor wants to give a lil extra to the intake, to get a lil extra compression degrees. In this case; take half the intake duration and subtract the installed centerline, and so
271/2 -106= ~30*.. leaving 25* for the exhaust.
Next; now we can figure out how many degrees are allocated to the compression stroke; Here's how; The four stroke cycle is two revolutions, right? On the first revolution the engine does intake and compression and on the second it does compression and exhaust. There is a short period of time where both valves are open, one is closing and the other is opening; and they call that overlap,cuz,well the cycles are overlapping, go figure,lol.
Ok so for the first two strokes, we have in this case 360degrees plus the 30*of overlap, that we earlier allocated to the intake stroke, and from that we subtract just the intake duration. That which is left is the compression duration. So that looks like
(360+30) -271=119 compression.
Finally, we need to calculate the ICA. The theoretical compression stroke is 180*, but in our case it is physically, just 119, so we subtract the smaller from the larger and out pops the Ica, like so
180-119=61*= Ica

Of all these numbers, the only one that the Wallace wants is that 61* Ica
done
 
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AJ, that was a great post. This type of calculation is roughly in my head but only used at the drag engine or heavy hitting street engine level.

(Really at this level, it’s easy, the mantra is more the merry and then add some more!)

You can see some of this at work IF you get the full knowledge of the engine being dyno’d on you tube. Richard Holdner has a good channel and a lot of dyno videos.
 
Jim64 said:
I thought the same thing, but AJ has examples of 2.5, 2.6, 2.7...so I don't know where it comes from or how to calculate it. (I'm thinking it does have something to do with the timing of the intake valve closure after BDC.)
Click to expand...
Effective stroke is what is left over after the Intake valve is at it's advertised closed position, which you have to input as Ica. This is a computer-generated number and not the real world number cuz; the number that you input as Ica is the fall-out from using advertised numbers in which the valve is not yet closed! At .008tappet rise, and with 1.5 rocker ratio, the valve could still be open up to;
.008 x 1.5 = .012inch
But the calculator consistently generates that number from whatever you input, so it is still a useful tool.
 
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AJ/FormS said:
Yeah; ...
Of all these numbers, the only one that the Wallace wants is that 61* Ica
done
Click to expand...
So with that new number:
Number of Cylinders : 8
Bore in Inches : 4.08
Stroke in Inches : 3.31
Rod Length in Inches : 6.123
Static Compression Ratio : 10 :1
Inlet Valve Closes ABDC : 61 °
Boost Pressure in PSI : 0
Target Altitude : 800 (Feet)

Static compression ratio of 10:1.
Effective stroke is 2.63 inches.
Your dynamic compression ratio is 8.15:1 .
Your dynamic cranking pressure is 163.28 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.99 :1.
V/P (Volume to Pressure Index) is 135

-Jim
 
Jim64 said:
So with that new number:
Number of Cylinders : 8
Bore in Inches : 4.08
Stroke in Inches : 3.31
Rod Length in Inches : 6.123
Static Compression Ratio : 10 :1
Inlet Valve Closes ABDC : 61 °
Boost Pressure in PSI : 0
Target Altitude : 800 (Feet)

Static compression ratio of 10:1.
Effective stroke is 2.63 inches.
Your dynamic compression ratio is 8.15:1 .
Your dynamic cranking pressure is 163.28 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.99 :1.
V/P (Volume to Pressure Index) is 135

-Jim
Click to expand...

That's better.
 
I guessed at your elevation.
I guessed at your Scr
Do not order a cam until you have the proper numbers because 164 psi is borderline too much pressure for open-chamber, factory iron heads, on best pump gas. You will loose more power if you cannot run full timing, than what you will gain with a few psi pressure.
And remember, full power means almost nothing in a 340 powered 1965 Barracuda with 225/70-15 street tires, with a clutch and 3.23s. Even a 318 can smoke those tires in that combo. How do I know?
Because my bone-stock long-block, 1973 318 winter-motor could..... with a 4bbl and my full-length, dual 3-inch pipes, in my 3650 pound tank of a 68 Barracuda..You know what the VP is on a 1973 318?
>at 930 ft;How about
Static compression ratio of 8:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.10:1 .
Your dynamic cranking pressure is 134.82 PSI.
V/P (Volume to Pressure Index) is 112
Remember the Ludicrous Factor?
3650/112=32.6 decidedly NOT Ludicrous

In your 65 guessing at 3100, I get 3100/112=27.68, Not Ludicrous yet, but; not too shabby either
 
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Jim64 said:
So with that new number:
Number of Cylinders : 8
Bore in Inches : 4.08
Stroke in Inches : 3.31
Rod Length in Inches : 6.123
Static Compression Ratio : 10 :1
Inlet Valve Closes ABDC : 61 °
Boost Pressure in PSI : 0
Target Altitude : 800 (Feet)

Static compression ratio of 10:1.
Effective stroke is 2.63 inches.
Your dynamic compression ratio is 8.15:1 .
Your dynamic cranking pressure is 163.28 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.99 :1.
V/P (Volume to Pressure Index) is 135

-Jim
Click to expand...
Has anyone actually used this foromula of figures (as above) bulit that exact engine then physically measured the cranking pressure to see how close it comes to the pre build calculations?
 
How do I find more info about this cam? From some handwritten notes I inherited from the previous owner, I think it might be a "TQ20 450-268". That's the cam I just took out of my 340.

20210106_133125.jpg


20210105_173414.jpg
 
Jim64 said:
How do I find more info about this cam? From some handwritten notes I inherited from the previous owner, I think it might be a "TQ20 450-268". That's the cam I just took out of my 340.

View attachment 1715665088

View attachment 1715665089
Click to expand...

CC = CompCams, H = hydraulic, 8 most likely means 108 LSA. You might send the numbers to Comp. Sometimes they can help.

TQ 20 indicates an Erson grind, but that cam pictured is clearly Comp.
 
HAHAHAHA - "CC" - I was, for some unknown reason, reading that sideways, thinking it was two odd circles. Thanks, Rusty! This is a great forum.
 
RustyRatRod said:
I would build a stock 69 340 short block. Use the Lunati 268 VooDoo cam. Have the heads professionally ported. Then put it together.
Click to expand...
I totally agree with you combo. The only thing I would do on the rebuild is buy some rods (eagles ?) because of the cost to rebuild the stock rods and you still end up with the small bolts. And I really, really like to crank mine up. Don't get me wrong as I've taken stock rods wayyy up there but it's a great upgrade for little overall cost. By the way. you rock Rusty!
 
LO23M8B said:
I totally agree with you combo. The only thing I would do on the rebuild is buy some rods (eagles ?) because of the cost to rebuild the stock rods and you still end up with the small bolts. And I really, really like to crank mine up. Don't get me wrong as I've taken stock rods wayyy up there but it's a great upgrade for little overall cost. By the way. you rock Rusty!
Click to expand...

I'm totally on board with that, because by the time you rework and upgrade the stock rods, you've spent more than enough to get new ones. But I'm like you, I do like the stock rods, too.
 
Agree stock rods are fine , buy if you have to have them worked on to run , cheaper to buy new
 
Use Scat I beam rods ....not the Eagle SIR rods.
 
Jim64 said:
Two more questions: is there any reason to buy new cylinder head bolts? Mine seem fine; every bolt came out smoothly.

And - is this a decent harmonic balancer? Mine seems fine, but is 50 years old...
Pro Race Products Pro Sport Harmonic Balancer

Jim
Click to expand...

It may SEEM fine, but would you trust a 50 year old rubber if you were 18 again? Yeah, me neither.
The harmonic damper I pulled off my 91 360LA , after I bead blasted it just to clean it up convinced me to shitcan it.
If you're constrained by size, the Fluidampr is 1/4" greater diameter. Note it is for an internal balance engine, so you're good there.

I just ordered this for my 360 build with part of my stimulus check.
Fluidampr 720301 Fluidampr Harmonic Dampers | Summit Racing

flu-720301_nk_xl.jpg
FLU-720301_xl.jpg
FLU-720301_GM.jpg
FLU-720301_GJ.jpg

Fluidampr Harmonic Dampers 720301
296.gif

Fluidampr Harmonic Dampers

Brand:Fluidampr

Manufacturer's Part Number:720301

Part Type:Harmonic Balancers

Product Line:Fluidampr Harmonic Dampers

Summit Racing Part Number:FLU-720301


UPC:815293001036

Engine Balance:Internal

SFI Rating:SFI 18.1

Degree Markings:Yes

Degree Marking Range:50 BTDC to 10 ATDC

Outside Diameter (in):7.250 in.

Keyway Quantity:One

Harmonic Balancer Material:Steel

Harmonic Balancer Construction:Fluid

Harmonic Balancer Finish:Black zinc chromate

Mounting Hardware Included:No

Quantity:Sold individually.

Notes:Additional timing/degree marks at 90, 180, and 270 degrees. This damper is designed to be used with a 1971 and later timing cover with the pointer on the driver side. If it is used with the passenger side pointer, it will be 90 degrees off
 
Jim64 said:
Two more questions: is there any reason to buy new cylinder head bolts? Mine seem fine; every bolt came out smoothly.

And - is this a decent harmonic balancer? Mine seems fine, but is 50 years old...
Pro Race Products Pro Sport Harmonic Balancer

Jim
Click to expand...
that is the balancer i'm using on my 426 stroker seems fine have not had a problem in 5,000 miles , good for the price as for rods I used Molnar h beams on my stroker molnar i neams on my 340 a bit more expensive than eagle or scat i just think they are betteqhality m just my opinion which ain't worth much
 
Jim64 said:
Thanks for all the detailed information - now I need to go learn about VP!
-Jim
Click to expand...

Here's a great article on 340 HP numbers. I have a 69 340 X head, just getting ready to break the cam in. Factory iron heads, steel rockers, steel crank. I currently don't have specs on internals- see story in "340 break in question"
After reading this article, I understood that getting to 400 HP was much more attainable than I imagined. HR dynoed a stock 340 with headers and a factory 6 pack and I believe an Edelbrock intake at 363 HP.Choose your headers carefully, I recommend Doug's for overall fit. They're 3x the cost of cheaper headers but worth it, they don't hang low and the only mod I needed was at P/S box, 1 small dimple.
How Bad Did Mopar’s 340 beat Ford & Chevy? Shocking New Data!
 
Great thread.., but has anyone used the Lunati version of the 340 Hi Po cam part # 10201002...considering it for my build.
Lunati says: 298/308 duration @ 50 232/242, 462 intake lift / 473 exhaust lift LSA 112 /112. 2500-6500 RPM range. Also using J heads, with 2.02's. 68-70 exh, mans. Thinking about 2 1/2" head pipes with 3" H pipe exhaust dumping at rear axle, any feedback.?

Car is 72 Scamp 3.91's, 245/60/15 drag radials, 2500 convertor, 904 with low 1st gear. S/S springs, snubber.
Building for wife for weekend drag strip duty with the female gearhead club.:)
HotRod20
 
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