DAPSUPRSLO

iTrader: (14)

I am pretty sure Tim's car was not through a twelve bolt. Can you confirm this? Was it through exhaust or a cutout?

Well when I was there you ended up with 362 ish rwhp on that car because I remember you asking me what I thought. If you dynoed it another day locked then fine. Plus, was that through a twelve bolt, NO.

Also, what did Tim's car run at the track?

The fact is comparing dynoes just doesn't work unless it is the same dyno on the same day. Just like comparing tracks doesn't work unless it is the same track on the same day.

The only reason Burbanman got me was I missed a gear, don't get your story wrong. With the Jennings stage 1 box on the way this should be a thing of the past.

I have no idea what you are trying to say with the 106 number. He was talking about lobe separation angle, not intake center line. I think you are very confused of what the original poster is aking.

RoyO

The cam was ground with 4* of advance in it by the recommendation of the guy at Comp Cams. Im about to remove it and go another direction with the car anyway, but thanks for the tip.

DAPSUPRSLO

iTrader: (14)

First off talk to thunder about an agressive ramp rate lobe without excessive lift. This is what I did. I am assuming you are concerned about valve spring failures, not p/v issues as a result of peak lift numbers. Peak lift occurs when the piston is more then far enough away to prevent any p/v issues.

As far as a 106 lsa cam goes here is what I would try. Use the same 108 icl as thunder does for the TRex and do the following. Use the same intake duration and use a 232 exhaust lobe. What will this do? This will close the exhaust valve in the same exact place the TRex cam does and give you the same amount of overlap; however, it will open the exhaust valve way later (56 degrees before bottom dead center for TRex, 40 degrees before bottom dead center for my cam) for more peak torque and less rpm.

Normally I am not an advocate of reverse split cams but I think this cam could be really killer given an excellent exhaust system. When you drop the pipes look out. There is plenty more options out there also.

FASTONE

Tommy are you good and confused yet???

DAPSUPRSLO

iTrader: (14)

If you or anyone else is confused ask a question. This is the only way to gain knowledge.

Tommy Tucker

This is great! You can't know everything in life, so I like to ask (doesn't mean I'll agree!).
I'm not too confused

My immediate thoughts are:
1. I thought that lift was a P/V issue with long duration.
2. Do fast ramps make P/V tighter?
3. With the tight LSA should I be (ideally) thinking about increasing static compression by milling? (already have 10.9-1)
4. Reducing the LSA increases the power by the increased scavenge effect, but unless we increase the duration at the same time the intake will open later and the exhaust will close earlier...yes? That's why we need a 240 type duration preferably on fast ramps.
5. So should I then simply limit my lift to what the intake/heads/exhaust can flow and maximise my duration and ramps on the lowest LSA I can live with?

I hope I'm on the right lines here.
Great board
T.

GrannySShifting

iTrader: (10)

Nick I wasnt commenting on you racing burbanman at all but of the car that was at the dyno that day and burbanman. dont get your panties wadded, you are being kinda defensive. Just about Crystals car put a hurtin with 18 inch wheels and 2.73 gears vs burbans car with 3.73s, ET streets, and no interior from a dig, just an off comment thats all. Cant talk abotu cars on LS1Tech?

Yes Tims numbers were thru a 10 bolt. loss of 6-12 hp from what Ive seen on this dyno, its not as much as everyone makes it out to be. On that dyno most decent cams make 390-405 thur 10 bolt, and similair stuff makes 385-395 thru 4.30/4.56 geared 12 bolts. I think comparing the numbers is reasnable, it was dynoed within two days of yours, and with the same correction factor used to correct to SAE, on the same dyno.

Im vary aware of what Tommy was asking. He said "How far can I go considering p/v with a 106 LSA" This doesnt have to be a pissing match really. He, assuming a 106 installed centerline with the LSA of 106 he was talking about, is opening the intake 2 degrees earlier then a TRex. That means he needs 4 degrees less intake duration with a Trex style intake lobe given those specs, depending. I personally wouldnt retard any cam of the size we're talking about, but thats just an opinion. Nick be careful about recommending that cam your talking about

GrannySShifting

iTrader: (10)

The more overlap you have, low speed characteristics of the motor will improve with more compression. If your putting more cylinder pressure into play, it helps keep the spent charge going the right way, out the cylinder not back in. If youve noticed some cams in a stock compression car, sound tamer in a car with 11.0+ compression. Likely why MTI had people complaining about the Stealth II Id say colonels car had some compression with his heads and some are putting it in cars with stock heads.

lift is by product of lobe design, it can indicate ramp speed comparing it to duration, but its arbitrary in reality. I can have a 242 .530 lift cam thats a much faster ramp then a 242/.600. It can be really fast off the seat, up the ramp, and just lay over the nose of the lobe. You can have a lobe thats slow off the seat, fast up the ramp, easy over the nose and the same on the closing side. Theres not a fast or slow lobe really, they can be different in different parts. Id lok at the lobes, and go with what ever the lift may bee as long as it doesnt place springs into coil bind or have excessive lift, or not enough to get it where the head peaks at.

GrannySShifting

iTrader: (10)

For example of LSA changes a 114 vs a 110.

a 114 +0 (no advance) cam has its intake centerline at 114. Center of the exhaust lobe is 114 degrees later. Changing that to a 110 straight up/no advance, it will be on a intake centerlien of 110, the intake would open close 4 degrees earlier, and the exhaust 8 degrees earlier.

Generally, Id say if a cam needs to be advanced or retarded its not usually the optimal cam

To get the intake lobe in the same spot, youd need a 110 LSA or a 114+4 everything else being equal

GrannySShifting

iTrader: (10)

if the lobe centerlines are the same an aggressive 242 lobe vs a lazy 242 lobe in most cases id say the lazy lobe hits piston first. Intake valve hits on the opening ramp, exhaust hits on the closing ramp. if they are very slow closing ramps Id say they hit first. Now if you ran an aggressive eexhaust ramp, and the valve bounced, then thats a wash out

GrannySShifting

iTrader: (10)

The TR 230 lobe isnt so aggressive Id shy way from using it at all, Im pretty sure I know which lobe it is from. it actually looks to be slower opening/closing the valve right off the seat then their 224 lobe. 10 degrees more duration at .006, 7/8 more at .050 and 6 more at .200

DAPSUPRSLO

iTrader: (14)

My PMS was flairing this morning Jeff. It has been a bit nasty at work so I appologize for my defensiveness.

You are correct in saying that if he installed at 106 icl he would have to make the intake lobe 4 degrees smaller then the TRex. I wouldn't run that cam at 106icl though I would retard it two degrees for a 108icl as the TRex Sits. I think it would be interesting to see what similar intake events and similar exhaus closing events would bring with the only difference being the much later opening of the exhaust valve. My guess, as stated before, would be much less rpm ability but much more peak torque in the areas that matter. Ofcourse this cam would have to be in front of an excellent exhaust system and would really shine with open headers.

I don't understand why I should be carefull recommending that cam. It is just a suggestions. Personally, I think it would make great power but I could also be wrong.

If you're heads are milled or if you have bigger then stock valves checking the p/v clearence is a must however.

GrannySShifting

iTrader: (10)

Very true. I beleive I know a little bit, but just now starting to scratch the surface in the last year. Some dont know. <-No problem. Some claim to know. <-big problem Some say what they know, and not much else. <-smart. Those that really know, wont tell <- smartest

DAPSUPRSLO

iTrader: (14)

Actually, moving the lobe separation angle and icl at the same time in the manner you speak of would cause the exhaust valve to open and close at the same exact time. Why? Because you have advanced the cam 4 degrees but pulled the exhaust lobe 4 degrees closer to the intake essentially retarding the exhaust valve 4 degrees. What you have done though is added more time in which the intake valve and exhaust valve are open simultaneously (overlap). Remember, the camshaft rotates in a manor which makes the exhaust lobe the first lobe to break the plane at any part of the 360 degree circle. In other words the cam rotates clockwise with the exhaust lobe being in the 3 oclock position (not exact just relative to the intake lobe) and the intake lobe being in the 12 oclock position.

If you disagree let me know. I'm starting to get a headache.

DAPSUPRSLO

iTrader: (14)

Remember though, if you never discuss then you will never learn from your mistakes and get others opinions.

I believe some really do know and talk. I don't proclaim to know all either. Trust me, I have way more questions unanswered then questions I can answer when it comes to this stuff. Even Mr. Massingil will tell you the same thing and this man knows more about valve timing events then I will probably ever know. Not everyone is out to beat the world. Some are just out to help others because they enjoy doing so and like variety.

HumpinSS

iTrader: (1)

If all the "smart" ones stayed quiet we wouldnt be where we are now...

FASTONE

Even if someone post something they did to their car and it didn"t work too good we all learn from their mishap.When someone post things that worked good we benefit from that too.If only the uninformed posted on here we would all be uninformed!Lot of smart post on this site!!

J-Rod

Here are a couple of bits and pieces a I scavenged from a few threads...

Your valve isn't completely open when the piston is at TDC. You can have a cam with 1" lift as long as the timing and durration doesn't put the valve at max opening while the piston is at TDC... Last time I checked, in most cases the intake valve is just BEGINNING to open (nowhere near max lift) slightly before the piston reaches TDC and isn't completely open until the piston is near BDC. It's simple folks, MAX LIFT DOESN'T MEAN JACK ANYTHING WHEN TALKING ABOUT PTV CLEARANCE! If you don't believe me on the timing sequence, take a look at this webpage

<http://auto.howstuffworks.com/engine.htm>

pay close attention to when the valve reaches it's max opening. Then you will see why PTV isn't necessarily determined by lift. I know it's a DOHC in the illustration but the concept is the same.

An LS1 motor isn't ANY different than any other 4-stroke, internal combustion engine?? If PtV was an issue at max valve lift, all we would do is check for clearance at that point and call it good. This would lead to many engine failures as it would show you have a MILE of room. PtV becomes an issue during the overlap cycle, where the exhaust valve is closing and the intake valve is just opening. Your tighest clearance is going to be roughly 10* BTDC for the exhaust valve and 10* ATDC for the intake valve.

Duration, intake centerline, ramp rates, etc. play a MUCH more important role than max valve lift. It is ALL in the timing events.

If you have too much durration then your exhaust valves will be too far open for too long and the piston will tappy tap on them on their way up on the exhaust stroke. If there is too much advance ground into the cam and you have too high of a ramp rate then the intake valves will be too far open too soon and again mr. piston and mr. valve will kiss. These are just two examples of many that could cause problems, and they didn't even take into account many other factors. You only have to worry about PTV when the piston is nearing it's TDC, at TDC, and slightly after TDC, not when the valve is at full lift. And once again, "Duration, intake centerline, ramp rates, etc. play a MUCH more important role than max valve lift. It is ALL in the timing events." Picking a cam for a motor isn't as simple as putting a round peg in a round hole and when it fits, patting yourself on the back and calling it a job well done.


Basically you wont have a problem at max lift. piston to valve problems happens when the valves are opening and closing not at max lift!

GrannySShifting

iTrader: (10)

Its cool Nick, I can bit a bit abrasive when I say things too, I dont mean anything by it (usually ) Im just for effecient communication not English editing lol


Thast what I meant by careful he has oversize valves, and milled heads.

Tommy Tucker

Now I think I am clear on PtoV. I was just about there but now I am much happier about the lift aspect.
So do the cam grinding sponsors on this board do much R&D or is it up to me to do the donkey work? Do they know what combos work?

I am not sure about what dropping the LSA as far as 106 will offer as opposed to a 110
J-ROD...apparently you are familiar with driving these cams. Could you give me an analysis on the performance/behavioural thing please?
A 110 won't pass emmisions so that's not the reason folks don't go all the way to a 106.