snketr

iTrader: (3)

Is there a magic lift number or dur number? Or is it a combo of both?

Say I wanted to run the PP 226/581 cam with 1.8 rockers. That would give me a .619 lift. with the same duration on a 112

jermzz

iTrader: (18)

Valve events differ on cams... You can go to big for any one spot the valve is in, but it's really the events that determine when you get PTV issues.

Most of the cams the sponsors sell (unless specified for big cube motors) are made for stock headded ls1's. You run into problems when you start mixing the big cams with heads that have been milled. You need to check with the people who make your cam and ask them what head/rocker combos you can and can't use.

Eddie 70

iTrader: (3)

Great question. One I had been wondering about myself but had never asked. A question I did not think of when I ordered my cam. All I asked about was driveability and they told me I should be fine around town and on the interstate. So I was happy at that point.

brad8266

iTrader: (23)

There is no magic number. It is a combination of all aspects of the moving parts in the engine from pistons, head gaskets, valve angles, cam lift, duration, lobe seperation, and centerline.

In a stock block stock head LS1 though I would be checking PTVC with any of the larger cams. Anything in the 236 over range I would be at least measuring my clearances.

99blancoSS

iTrader: (115)

to be a smart ***: when the valve hits the piston the point to worry about it was right before..lol ok that doesnt help .... flame suit on

brad8266

iTrader: (23)

So true though.

bsf

iTrader: (7)

Hey, you stole my thunder. That is what I was going to say.

If you want to know for sure, measure. I am running a nominal 224/228 110lsa advanced ~2 degrees on install. If I remember correctly, I had like ~0.100” on intake and ~0.120 on exhaust. You can definitely run it tighter, but that is getting close for a cam everyone said “should” fit with no problem. Different heads and valves also affect PTV.

hammertime

iTrader: (1)

What heads? Any milling? What gaskets? When you are cutting it close, installed ICL and LSA will change the clearance between two otherwise identical setups.

I think most will agree that PTV clearance is 98% duration, and only 2% lift. Therefore, a 226 cam should clear just fine in a stock LS1. Milling the heads or running thinner gaskets will change the available clearance some, but moving the VE's with a tighter LSA or more duration, and things can change quickly.

02TransAm/Batmobile

iTrader: (32)

I was going to ask the same question because I am custom spec'ing for myself and don't know how big to go. I hate how these posts go because people reiterate the same **** over and over again.

"It has to do with valve duration more so than lift" - WE KNOW THAT ALREADY

" . . but it's really the events that determine when you get PTV issues. " - ISN'T THIS WHAT THE THREAD IS REFERRING TO ALREADY?

"I run this cam with no milling and worked for me" - Great. NOW BACK TO MY QUESTION . . . .

"I would check PTV clearance's on bigger cams, anything over 226" - NO **** SHERLOCK.

Again, instead of people adding insight or actual answers, they reiterate known knowledge or state what they run. I am not adding any answers to this post but would like to know also, if there is a formula we could use to figure out PTV clearances.

I downloaded J-Rods VE spreadsheet but I don't know exactly how to use it. I've got two cams here that I have questions about.

Custom Cam Number 1
IVO - 11
IVC - 43
EVO - 55
EVC - 7

Custom Cam Number 2
IVO - 7.5
IVC - 47.5
EVO - 55
EVC - 7

So, let's take a stock engine with a 66.67 combustion chamber and stock head gasket of 0.053", at what number do the valves collide?

What formula can someone use to figure out if their 64.45 combustion chamber with Felpro 0.040" will cause PTV issues?

What formula can someone use to figure out how much can a person safely mill their heads. I was considering milling my heads .030 to run a 11.1:1.

Not to be rude or anything but don't post up all over these boards unless you have something meaningful to the conversation. This applies to all opened threads.

02TransAm/Batmobile

iTrader: (32)

Snketr, here are your valve events if you line up your cam dot to dot. Of course it'll be subjected to change if you retard or advance the cam.

IVO - 1
IVC - 45
EVO - 45
EVC - 1

bsf

iTrader: (7)

But I think you are rude. People respond with what has already been said because people ask what has already been asked. People want some magic formula, but it does not exist, AFAIK. If you want some all encompassing formula, create it, and good luck. There are a lot of factors that determine whether PTVC will be sufficient. Look at the variables: cam lobe duration; cam lobe type; LSA; ICL/ECL; piston stick out; head gasket thickness; valve size; amount milled off heads; and maybe more. The only way to be absolutely certain is to measure after the fact. Short of that, run exactly what someone else is running who verified through careful measurement of PTVC.

02TransAm/Batmobile

iTrader: (32)

I don't want to open up a Dr. Phil session here but it's the truth.

I hope you don't vote for the next president under your "word of mouth" research methods instead of actual researching.

While their may not be an actual formula to figure out PTVC's (I don't know), it sounds like you condone the reiteration of known material. Sounds to me like you are not one to think outside of the box.

Two questions for you: AFAIK?

and . . .

"Short of that, run exactly what someone else is running who verified through careful measurement of PTVC." - The ****? Seriously? This is your advice?

brad8266

iTrader: (23)

If you arent adding answers to the thread yourself then STFU and go post your questions in your own thread. BTW your question about a PTVC formula has been answered before as well in previous threads. I will reiterate the same knowledge again like I always do for you people that cant use the search button, there is no PTVC formula.

You are being rude and you have not input anything meaningful to this thread. If you dont like how the forums are operated maybe you can go over to ls1.com and get some good insight there.

Have a good day.

99blancoSS

iTrader: (115)

What do you expect? You think you deserve to have only qualified individuals service you personaly?

This is an internet chat room. Your going to get people trying to help you with the best knowledge they have. Some are more qaulified than others obviously.

Try doing a search and figuring this one out for yourself or contact a damn sponsor. There is a formular to figure out what your asking. I didnt use it because I'm lazy and dont like math so I had Mamo do it for me. Before that it was LME and before that it was Thunder Racing.
Learn how to help yourself or learn who to call for the answers you dont want to take the time to learn for yourself. Pred Z, Patrick and others are experts in this area. I'd send pred z an email and ask him or have Patrick spec you a cam for $25.

Lashing out at responses from people trying to help isnt a good thing for you to do. Now me, I wasnt trying to help as I know I'm not good with duration and PTV.


Also 02transAm people who live in glass houses shouldnt throw stones

that was your helpful advice in a post. Do I need to read back to you what you just said about posting?>?>

NaSSty Nate

iTrader: (4)

Not to be rude but why don't you flycut the pistons and run the size cam you really want to run? If you are worried about PTV put a stock head on there not milled etc etc.

If you want to gain compression and run a good sized cam, mill the heads, flycut the pistons and throw the cam in there you want (still checking your PTV clearances before you fire it up)

hammertime

iTrader: (1)

I don't think your response was directed at me, but given the nature of the original poster's questions, I thought it was only fair to jump in.
02TransAm/Batmobile, I believe you know that its more about duration than lift, but you are not the person who started the thread. Those who posted before you are only trying to educate a fellow member of the forum. Those who chime in to agree further solidify that claim.

Sorry, but a blatant case of the pot calling the kettle black here. At least you bothered to follow up that post with something relevant to the original question. Too bad 'just lining it up dot to dot' is no guaranty that you will get those VE's. In order to do that, you'll have to degree the cam to check for any tolerance stacking in how the cam was ground, the timing set, keyways, etc.

I agree a formula would be helpful, but I can't imagine that would ever take the place of checking, when one variable (such as degreeing) could make all the difference.

02TransAm/Batmobile

iTrader: (32)

Brad 8266 - I know I am not adding answers but questions. Asking questions is a good thing, right? My questions still added to the original poster's questions so they were follow-up questions.

99BlancoSS - I replied to that thread saying that because the title of that thread was called, "Bigger is not always better!!!!" That title has a sexual inuendo that always has the response, "It's not the size of the boat but the motion of the ocean." I simply stated, "That's what people with small coc, . . I mean cams say," as a funny response. Also, that was NOT advice from me but a comment. Re-read it if you must.

NastyNateSS - Didn't take that offensively but that might be true. The cam that I was deciding to put in is close to a G5X3, or as PredatorZ put it, "G5X3 on steriods." I've heard of PTVC issues with G5X3's so I thought I would run into the same problem. I just prefer to not flycut as much as possible to obtain optimal compression.

Hammertime - True. Although, I thought my comment still pertained to the overall subject of the thread though.

NaSSty Nate

iTrader: (4)

I have some 5.3 heads milled 15 thousandths and a 40 thousandths cometic gasket with a ms3 (very close to X3). The reason I mention this is you can have whatever heads milled more...or run a thinner gasket to regain back that tiny bit of compression you have from flycutting your pistons. With stock pistons I think I was going to be around 11.7 with this chamber and gasket combo...my goal was to be around 11.5/6 ish so the flycutting put me where I wanted (could be off my math ain't perfect I know).

So my suggestion is to figure out what the CR you want is, then mill it the extra lil bit to go slightly above what it would need to be with the piston uncut and let the flycutting take that lil extra out. Someone with greater knowledge feel free to tell me why I'm wrong, but it makes some sense to me.

Get the heads ported and set how you want them, then get someone to design a cam to match what you want...I hear Patrick G is pretty good.

hammertime

iTrader: (1)

Are you trying to run a stock casting head, or looking aftermarket?

Do a search on here (sorry don't have the time to find it while I'm at work) for a thread in which Louis from LG Motorsports posted the valve drop (the distance from the valve seat to the deck surface) on stock castings vs. AFR 205 heads. AFR 205's milled to achieve a 59cc combustion chamber retain more valve drop than a stock, unmilled head.

In othe words, since the G5X3 cam was designed to clear a stock LS1, it will have a greater margin of safety with AFR 205's despite the milling, and a much better DCR for better all-around performance.

02TransAm/Batmobile

iTrader: (32)

I didn't know AFR heads allowed that additional clearance also. I knew ETP heads revised their rocker assembly differently to provide a shallower valve angle which, in return, means more PTV clearance. That's great to hear if I ever get AFR's in the future but right now my budget only has me stuck with my LS6 heads that I purchased from Patriot Performance. I plan on porting them just a tad. Mainly just blend in the valve bowls and remove any casting flash in combustion chamber and exhaust ports. Thanks!