My new recipe, opinions?

[cavaliers1323]

4cw 4.2 crank 3.895"
custom fordged rods 6.375"
custom fordged pistons .060" overbore 1.131" compression height ~30 cc dish
lunati voodoo cam 63503
head gasket .043"

quench .043"
scr ~9:1
dcr ~7.5:1

main question is am I loosing performance with such a low CR? I can put it where ever I want, just wanted to run pump gas as this is my DD.

[dwg86]

I would think you could bump the compression .5 and still be good. My stroker runs 7.75 DCR and 9.25 SCR, and I run 87 octane with a .043 quench with no ping.

Who makes the rods you are using, and how much do they cost?

[cavaliers1323]

They will be made by bulltear. They are not on the market yet, and nothing is set in stone. They are the next I6 part they are bringing to the market. Sounds like they will be offering a few different lengths. No idea on price as of now. We have been talking back and forth about the pistons/rods. If you have any questions I'd be glad to ask them, or you could contact them directly.

[6TIME]

The Lunati cam that you have listed pretty rowdy for a daily driver (2000-6000rpm). They are saying it has very rough idle quality, and advising 10:1 compression or more with that cam. You should consider the rpm range that the motor will see for most of it's life. Once you have determined this range, pick a camshaft that compliments it. Generally for a DD, milder camshaft profiles are the best way to go in terms of mileage, throttle response, and overall driveability.

[cavaliers1323]

That is a actually a very good point, however I don't mind the rough idle or the economy. What I do like is the long exhaust event. I will DD this vehicle, however it will see that rpm range often. (not 6k)

edit: where do you see the recommended CR?

I am after low end torque, maybe the mildest cam would be the best choice? Plugging in those numbers and dropping the piston dish to 27cc my SCR jumps to -9.27 and DCR -8.03 respectivly. @ 24cc SCR 9.54 DCR 8.27

[Bodo]

I hope you have alot of time to wait on that Lunati. I've been on the phone with them the past week regarding my order. They are having core issues. They don't have any.

I have to look for another cam supplier, but it's not looking good. Seems that many cam grinders are running low too.

[6TIME]

That long exhaust event increases overlap and kills low end torque production... Any cam with 200-215ish degrees of in/ex duration at .050 will perform well in a stroker motor. It sounds like you would like the power to start from idle on up? If so then try to find a profile that has a idle-1200rpm starting point for the operating range and you'll be fine.

[gradon]

or you could advance the cam and lower the range a couple hundred and increase the dcr by decreasing the overlap.

[cavaliers1323]

Thanks for the help guys! I'm now looking at 63500 rpm range 1000-5200 duration @ 250in/256ex. I have plenty of time, I'll be waiting for the rods for awhile as well. As far as advancing I'll have to play with the calc, is there anyway of knowing how much your dropping the rpm range?

So advancing reduces overlap and increases low end torque, thus lowering the rpm range but raises the DCR? The cam already has 4 degree "ground in," so is advancing 4 more degrees ok?

How much are people opening up the CC, I've seen as much as ~61 and it was a lot of work. Is it feasable for me to shoot for 60 CC?

When I enter the specs of the cam in the calc, the IVC number it gives me
is different than what lunati says. What am I missing here?

[cavaliers1323]

I could also use a recommendation on a set of rings. I'm looking at sealed power ze217k60, will these work?

[lafrad]

Advancing does nothing to change the overlap of the cam. All it changes is where the overlap happens in relation to the piston. When you "advance" the cam, there is less "exhaust" valve overlap on the intake stroke, the intake valve is open "fully", sooner, and it is finished closing earlier on the compression stroke.

At low rpm, this reduces the "internal EGR" from the exhaust, it also increases cyl filling and allows the engine to build more compression, more HP/TQ. At high RPM, the early intake valve closing event hurts airflow, reducing HP/TQ

In my build I went for a higher SCR and then a "striaght up" cam. I purchased a Crower cam with 4* of advance "ground in", but then used the keyed timing set to retard that 4*, so its set "straight up". This turned out well. I have a 10:1 static compression ratio and it seems to have ZERO problems with 89 octane. haven't tried 87 octane yet. Throttle response is AWESOME from and the engine has tons of torque.

[cavaliers1323]

Understood, so no need to advance on top of the "ground in" 4 degrees. Im going for low end so I think ill install it "straight up" and go with the "ground in" 4 degrees advance. What is your DCR? Thanks.

Any advice on any other issues?

[lafrad]

I would not go more than 4* of advance.... so install the cam straight up.

And, if you have a way to do it, i would take your DCR with 4* of advance, and increase the ACTUAL compression ratio until you get the same DCR with 0* of advance (retard the cam). that should give you all the torque and better throttle response...but not effect the knock potential in the lower RPM.

I have the "Power Compu-pro" cam "performance level 2". Buttery smooth idle, great off idle and midrange... falls off quite strong after 4750 rpm. BUT, I won't spin it that high, EVER> no reason in my eyes, I have TONS of torque and a stock converter. The smooth idle is AWESOME... way smoother than stock.


The Stroker Calculator tells me i have a 4.62L motor,
9.85:1 SCR,
8.21:1 DCR,
0.044" quench,
-52* Valve closing angle.


If I installed it "advanced" 4*, i would have had an 8.4:1 DCR, and the Rpm would have fallen offer at a LOWER rpm.

I WILL be trying 87 octane here soon... just only a half tank... just in case

[cavaliers1323]

i would take your DCR with 4* of advance, and increase the ACTUAL compression ratio until you get the same DCR with 0* of advance (retard the cam)

What exactly do you mean?

[lafrad]

take whatever DCR your were comfortable with before... and tweak the formula so that you have a higher static compression ratio, and a "straight up" cam. the compression ratio will add more than the advance of the cam... while still keeping the same Knock sensitivy as you had before.