Kfxguy

iTrader: (1)

The summit stage 1 ghost cam has negative overlap and makes phenomenal power for a small cam.

grubinski

And an IVC event of 43 ABDC, which according to the discussion above, is waaayyy too early for an engine this big.

Kfxguy

iTrader: (1)

Can you explain why?

grubinski

The discussion above shows that this engine wants more like 50 ABDC IVC event.

As far as *why*, it's because the action of the piston going down 4 inches in the same time the stock piston goes down 3.622 inches will get the intake charge moving into the cylinder with a lot more velocity, and thus inertia. In any engine, the intake charge will continue to flow into the cylinder after the piston starts coming back up, because of inertia ... that's why any camshaft, even the mild stock camshaft, closes the intake after BDC.

Since the stroker motor we're discussing here pulls the air into the cylinder with more velocity, that incoming charge will be more willing to fight the piston to get into the cylinder even as the piston is coming up. Thus we can hold the intake valve open a touch longer past BDC in order to fill the cylinder more effectively.

I found timing online for the stock LS7 cam of 211/230 120-3 ... that closes the intake valve at 48.5 degrees ABDC, and that's a mild stock cam with ~ -20 degrees overlap. It's done that way because the engine has a 4 inch stroke.

Kfxguy

iTrader: (1)

you are over complicating things.

What experience do you have with designing, cutting, grinding cams, building engines and porting heads and intake manifolds? How many have you done? I’m interested in your total experience.....

old motorhead

iTrader: (10)

Here's mine. Hell yes, stroke it. An LS2 intake manifold is ****. It's even shittier trying to feed a 408. You can go Fast intake mani for a lot of bucks + it's not going to appear stock. Or, upgrade to ported LS3 heads and a ported and rod modded stock LS3 intake manifold....and it will appear stock. By the time you sell your ported 243's, you're not out a whole hell of a lot of money vs the FAST intake and you have a much better top end. You can get your stock LS3 heads CNC ported, cleaned and assembled with the valve springs of your choice, multi angle valve job, and milled to your spec for around $800 from Tx Speed.

A full C6 Z06 exhaust system is a bolt on for you. It appears stock and is a nice upgrade over stock. Not as good as long tubes, but at least you should pass a visual inspection. They come up for sale quite often on the Vette forum.

On a 408, flat top pistons with valve reliefs gives you a little over 11:1 CR with LS9 head gaskets and 70 cc heads if memory serves. Combine that with a 0 overlap cam as others have mentioned and you'll make some decent power and shouldn't raise a whole lot of attention. I have a 0 overlap 226/234 115+4 cam in my SBE LS3 that's set up similar to the above. It will idle in 6th gear smoothly at a little under 40mph. Something like that in a 408 wouldn't be noticeable.

grubinski

LOL, sorry, I thought you were asking a question, not looking for a pissing match. Have a nice day.

spanks13

iTrader: (5)

What stroker engines have you built? Yes I've done it I had a 211/218 on 116 cam in my 402.

Not over thinking things. IVC at 43* with 11.5:1 compression on 91 octane will almost certainly detonate at low rpm high load and probably at full power too. 43* IVC will peak at 5800-6000 rpm and fall off fast. At 11:1 it didn't detonate on 91 on the street, but I did need to run octane booster at the drag strip or it was inconsistent.

IVC not only sets the cylinder pressure, but also optimizes the high rpm tuning of the entire intake tract.

Kfxguy

iTrader: (1)

most of the engines I’ve built are stroker engines.

it’ll detonate at low rpm high load? What? Lol. At what timing? That’s why you have adjustable ignition timing. Is this the rookie camshaft thread I stumbled upon? I gotta get outta here, I’m losing IQ numbers by the second reading this. Lmao.

Kfxguy

iTrader: (1)

that’s a decent little cam too. The one I recommended is 222/233 and would idle like stock in a stroker and still make a really good improvement in hp over the stock cam. Mavn had this cam in his trans am and made 455rwhp with ported heads in an ls1. So with big rectangle port heads and a stroker it’ll probably make around 500rear and have some serious tq and should pass the sniffer because it has negative overlap. If he didn’t have to contend with emissions I’d recommend something totally different. Matter of fact, I wouldn’t have even chimed in except for the fact that he wants a decent cam that has 0 to negative overlap. You ask a cam question, you gonna get a different answer from everyone. Everyone is a cam expert these days. But can’t install one to save their life. Lol.

spanks13

iTrader: (5)

Lol you put 243/799 heads on any engine at 11.5:1 on 91 octane with a small cam it is going to rattle itself to pieces. My bone stock c5z ls6 rattled like a bitch on 91 octane with a stock calibration.

Get on with your bad self man. Enjoy life. Wouldn't want you to lose any more IQ numbers you might not be able to find your way back here to tell us how wrong we are.

Kfxguy

iTrader: (1)

lmao. Are you serious? You are comparing your stock ls6 with stock calibration to this guy building a stroker motor? Do you really think he’s going to build a stroker motor with heads and cam and run it on a STOCK CALIBRATION? I think you should refrain from giving ANY advice.

im not sure you realize how many different things come into play when it comes to detonation resistance and sensitivity. I’ll name a few:

vehicle weight
fuel octane (of course)
combustion chamber quench
combustion chamber smoothness and no sharp edges
ignition Timing (this is a big one right here, not sure you realize but it is variable)
gearing
stall if it’s an auto, lockup rpm/mph also

I’ve tuned quite a few vehicles and I never send them out rattling. I just tuned a 418 with 12:1 compression in a truck. Pump gas. Does not rattle. Know why? Engine was built paying attention to the details and I didn’t give it excessive timing that would make it rattle. Yours rattled probably because it was recommended to run 93 and you were running 91. Easy fix, take a couple degrees of timing out. Not sure what’s so complicated about that. I also didn’t realize I was going to have to explain such trivial and stupid **** when recommending a mild cam for the op, which I know will work just fine. And you try to throw in some **** about your stock calibration rattling when not using the recommended fuel. Like what? How does that even fit in here? Smh.

grubinski

The ignore list is a wonderful thing.

spanks13

iTrader: (5)

I'm not sure why this has been such a heated discussion lol. I agree there are a million ways to skin a cat. For a stealthy cam in a corvette with a manual and 11.5:1 compression I don't think the summit ghost cam is the best choice. My experience with my 402 with three different sizes of camshafts - one being smaller than a stock ls7 cam - means I will never agree with you about the summit ghost cam in this application. I think it is a great option for an otherwise stock ls3 or mild bolt-ons.

Yes you can pull timing out to keep it from pinging, but if you're having to pull a bunch of timing you're likely worse off than reducing cylinder pressure somehow else.

Yes - pinging below torque peak in 4th to 6th gear when someone pushes the gas down instead of downshifting is a serious concern in a street car. Do you disagree?

Yes I'd hope that the engine is blueprint, put together and tuned properly with correct quench and no sharp edges in the combustion chamber. LS6 corvettes are notoriously bad in stock form on 91 octane when it comes to pinging and the cylinder heads are most of the issue. I replaced the 243 heads with AFR205's without changing the cam, bumped compression almost half a point and the car never rattled again even with more timing. The point of the story was saying that I would not recommend 799 heads with an early IVC and 11.5:1 compression to be run on 91 octane.

Kfxguy

iTrader: (1)

the thing guy, that you are misunderstanding is timing can be reduced because the engine does not necessarily NEED or WANT it. I’ve built some way above everage engines with higher compression and lower timing and they made more power than the next guy. When you turn compression up, you don’t need all that timing. If you increase octane, you can add timing. Higher octane burns slower so you have to start the burn rate sooner. Less octane, faster burn, less timing. You know this. I’ll bet you money that two engines built identical but one with less compression and more timing will be slower and make less power than one with higher compress and less timing. Also when you run higher octane and increase timing, you’ll have a LONGER burn which usually equates to more power, of course if everything it dialed in correctly.

I had an old third gen back in the day that I built a 383, 11.8:1 compression and I could run 87 octane with no clatter. Why? I had a haltech (snazzy for back then) and it had a rotary dial (super high tech lol) that I could turn to dial back the timing when I ran 87. Put it back to straight up when I ran 93. That thing was faster than any other car around at that time. Everyone else was running lower compression. You know what heads I had? Fast burns. They have the same shape combustion chamber as a 243. It liked only 26-27 degrees on high octane. Made 450rwhp and 480tq. Car ran low 11’s at 124mph on street tires. That’s an old scoop sbc mind you. None of the new tech we have now. Small cam too. 230/244 @ .050. On a 114 lobe sep.

one of the drag bikes I built ran 12.5:1 compression on pump 93. 28 degrees timing.

so what if you have to pull a little timing out. That’s an advantage, throw some higher octane in, add timing, more power. I could discuss this stuff with you guys for hours.

Che70velle

iTrader: (6)

What does static compression have to do with anything? Engine never sees it or has any idea what it’s set up for. Dynamic compression is what dictates what fuel can be ran and timing tables to be used. Grubinski tried to explain this in previous post, but got shot down. Dynamic compression is established by camshaft events. I could build you a 16:1 engine and run it on cow **** with enough cylinder bleed off from cam events, and the timing set low enough.

bortous

If a referee is needed, let me know.

Kfxguy

iTrader: (1)

I give up. I'm wasting my time. Do whatever the flock you wanna do.

Mickyinks

Che70velle is spot on, Dynamic compression is where its at, use cam durations and lsa to get dynamic where you want, . learn new things everyday if you take the time to listen.
I think my ivc is 81.9 lol 12.4 static 8.7 dynamic, had to go e85 as weather is warming and near detonation

Kfxguy

iTrader: (1)

I had this same discussion with people years ago on a 4 wheeler forum when I was building a drag motor. They tried to tell me the same **** coupled with the fact that the stroke and rpm would exceed the maximum piston speed. I did not listen and went ahead and built my motor. It held a Dyno record for years and was faster than just about everything I raced including street bike engine equipped quads. So look, you guys can over think it all you like. Matters not to me. OP, sorry that you are gonna have to sift through the bullshit. Any time you ask a cam question, be prepared to get numerous different answers. Whether it be from experienced people, who actually do and have done what they give advice on and then the ones who answer and act like they know so much but yet they pay to have all their stuff done. They can tell you how to do it, but they can’t do it. And I’m not directing this at any person in particular, but if the shoe fits.....you know who you are.