Phreakish
Well-Known Member
You've confused LSA with intake centerline.
LSA will not change IVC, it changes exhaust valve opening and closing if the ICL is kept the same.
Wallace Racing - Cam Degree Calculator
LSA Question
- Thread starter Dan the man
- Start date
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You've confused LSA with intake centerline.
LSA will not change IVC, it changes exhaust valve opening and closing if the ICL is kept the same.
Wallace Racing - Cam Degree Calculator
Dan the man
Well-Known Member
Then why does every inv closing calculator ask for the lsa and if the cam has been advanced? I've used this same formula to check against cams that include the inv closing point and it gives the same answer as the cam company showed for their cam
Phreakish
Well-Known Member
Because they're calculating all of the valve events. LSA itself won't change IVC, ICL does.
Dan the man
Well-Known Member
Is the ICL changed when the cam is advanced ?
Phreakish
Well-Known Member
Yes. Advance is used to alter the ICL to influence the IVC.
LSA and ICL are only related if trying to center the overlap to TDC - there's reasons to do this, and there's reasons not to.
Dan the man
Well-Known Member
Phreakish, I have another question if I may, I went back over the calculator's for figuring inv closing point and not one asked for the ICL except the one that you showed. They asked for the advertised duration divided by 2 then add the LSA then subtract the amount of advance of the cam if any then subtract 180 equals the inv closing point. Why don't they ask for the ICL? If I don't have a cam card how can I find out the ICL of a cam? I'm going to use the Wallace calculator. I'm not saying that what you're saying is wrong I simply wanted to say what I read. I thank you very much for your help on this.
Phreakish
Well-Known Member
ICL is on every cam card for a reason. If a calculator doesn't use it, that's on whoever made the calculator.
Their calculators are assuming the overlap is evenly split at TDC. Few people install cams there because it's rarely where best performance is found. The physics of that are complicated.
You can find cam cards or built-in advance from most vendors. Comp for example builds in 4 degrees into just about everything, but the ICL listed is just a starting point.
Dan the man
Well-Known Member
Thanks for the information. I'll use the Wallace calculator. When Howard and I think it's lunati show 112 / 108 on their website are they giving the LSA/ ICL numbers?
Phreakish
Well-Known Member
Correct. You can play with ICL to get the IVC where you want it. It's not uncommon for many builders to run more than the typical 4 degrees advance, and the window for advance/retard is larger than most assume. P-V clearance is usually a non issue with off the shelf cams, but should always be checked anyway. I'm running ~300 adv duration and ~.600 lift and still have well over .140" p-v clearance.
Dan the man
Well-Known Member
Thanks. That's a awesome cam
Dale Davies
Well-Known Member
Wellll, LSA and the advance or retard of any given cam WILL affect IVC. Grind another cam with otherwise identical specs but a different LSA and the IVC will change by 1/2 the LSA change. If a person is stuck on attaining a particular IVC point the cam advance or retard can be adjusted.
Dan, I know many are talking about valve events and particularly IVC. IMHO you would be best off studying David Vizard's Powertec 10 videos on camshaft selection and/or get a copy of his How to Build Horsepower book which also mentions his cam selection method. For a race engine this is a good starting point with other LSA's tested on a dyno. For a snappy and strong running street engine that wojld be overkill. Dyno time can be used to dial in cam advance or retard but is again a little over the top for a street engine. If you so desire a dyno test, use the time for proper breakin and tuning the ignition curve and carb or EFI.
I know those statements will ruffle crap out of the hardcore crowd on here, but you are learning and need to get the right cam now. That is what DV's 128 forula will give for LSA. After that you can chose duration looking to port flow. IMHO and Reic Weingartner's, get as much lift as the heads and springs will allow. For a street engine look to 0.500" to 0.550" lift. Street engines work well with about 4° cam advance and most cams will have that taken into account during the grinding process.
Before installing the heads, dial the cam to ensure it is correct according to the cam card. Install light checking springs on #1 cylnder.Then drop the head on without the gasket and just snug a few bolts to hold the head in place. With modelling clay in strips accross the valve reliefs adjust the valves. Now you can rotate the engine two revolutions. The head can nnow be removed to measure valve to piston clearance. When a gasket is installed for final assembly valve to piston clearance will be increased by the gasket thickness when compressed which is not an issue.
Remember the KISS principal and put the noise behind you. When selecting a cam grinder, talk to a few. Keep the 128 formula indicated LSA but probably not wise to go tighter than 108° or 106°. Also remember that as you increase duration you will get more overlap which will cause a rougher idle. This is what Comp does with their Thumper cam line. If you want the long duration cam you will probably need to increase LSA a degree or two and accept the rougher idle. Have fun with building a good engine but do not fuss over at what timing point your IVC is at.
If your head is hurting by all this email DV and he can spec a cam for your build and desired driving for a small fee. You can rest assured you will get a strong running engine that way.
Dan the man
Well-Known Member
All very good information. Doesn't the IVC affect the cylinder pressure? I did read that too much cylinder pressure can cause detention and to little causes power loss? Am I understand this correctly? I'm going to invest in some good books on cam selection and engine building. One cam company did say that for what I'm wanting to do that I would want a cam with like .500" lift and a short duration something in the 262* advertised duration. I'm not looking to build a race car, just something that has good throttle response and low to midrange torque. I've been told that I may want to look into a custom ground cam like you said.
Dale Davies
Well-Known Member
I again recommend David Vizard's How to Build Horsepower book and his cam selection videos at Powertec 10 on youtube.
For my 289 I am trying to get the money to finish, I have the cam I put in a 351W. It is single pattern, 210° @ 0.050", 256 seat to seat, 0.472" lift with the Ford 1.6:1 rockers and 109° LSA. This worked well in the 351. The formula using 127 for Ford heads indicates the LSA is a ° or so wide, but the cam is fairly quick off the seat and I am going to use 1.72:1 roller rockers at least on the intake. I will have the exhaust seats cut to 40° to aid low lift blowdown.
Witb the 1.72:1 rockers, my lift should be right around 0.500".
Dan, what are your heads, LA or Magnum?
Regarding your question about IVC, yes it does have an effect on cylinder pressure. You are in Missouri so do not experience the cold we get. To a point high cylinder pressure is your friend and is easy to deal with. You can install a water injection system which cools the combustion temperature without the hassels of EGR. A vacuum switch turns it on when vacuum drops to a preset value. At small throttle openings and high vacuum, detonation is not a problem. Run distilled water and add maybe 2% water soluable oil to lubricate things. DV has a video on this to run 14:1CR on 87 octane fuel. You can lean the mixture out benefiting fuel economy without affe ting power.
I recommend to subscribe to his videos.
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Dan the man
Well-Known Member
LA heads. I'm going to get his book on how to make horsepower
Dale Davies
Well-Known Member
You can upgrade the heads with Magnum or Chev LS valves. 1.88" Magnum or the 1.9" LS. You need to have the guides replaced with 5/16" bronze guides honed to fit the valve stems. These valves come with 5/16" and 8mm stems so they are considerably lighter. With the LS valves, inexpensive LS beehive springs, retainers and locks can be utilised. This can reduce valve weight by 30 grams or more. For this to work the installed height needs to be 1.8".
I wanted to go this way but my 1966 289 heads installed height is 1.64". This necessitated compatible springs by PAC sourced through Summit. Then I needed compatible retainers and locks, also through Summit. Different year 302 and 351 heads are 1.8". Yours should be simpler.
Dan the man
Well-Known Member
Sounds like a awesome modification and not expensive either
Probably the most important one line sentence in DVs books is the one below....& very few people take any notice of it [ I am one who does....]
'If you want a smoother idle, do NOT widen the LSA, shorten the duration'.
'If you want a smoother idle, do NOT widen the LSA, shorten the duration'.
Dan,
IVC is useless for calculating cyl pressure. I just do not know why people put so much 'faith' in it. The CP is going to be influenced by a host of OTHER factors that control cyl filling, such as port flow etc.
IVC is useless for calculating cyl pressure. I just do not know why people put so much 'faith' in it. The CP is going to be influenced by a host of OTHER factors that control cyl filling, such as port flow etc.
Dale Davies
Well-Known Member
Mine is starting to add up. Non GM valve springs and retainers. Then I got 1.72:1 Scorpion roller rockers, 7/16" rocker studs with guide plates and hardened pushrods to be compatible with the guide plates. I also will be paying the machine shop to drill and tap for the studs and mill the casting to lower the height for rocker clearance with the roller rockers. Then there is cutting the seats about 0.100" larger diameter for the bigger valves. Our problem in Canada is the about 1.35 exchange rate on the money.
You do not have the exchange issue and should be able to use springs from the General. If you could find a low mileage LS at a wrecker and they have a head sale, just grab the heads. Then strip the valves, springs, retainers and keepers out. The LS are not hard on valves. Many 6.0l engines have 400k km or 250k miles on them and the heads have never been off. That makes those parts very inexpensive. Then just seats as required and the valve guides. The General uses press in cast iron guides that seem to last and may be less expensive, but the reports I hear say the bronze are better.
Just a few thoughts to ponder.
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Dan the man
Well-Known Member
I'm thinking about either picking a cam off or the shelf or having a custom cam ground. IVC has to be of some importance as everything that I've read on it is the cylinder will either have to much or to little cp, and everything points to the ivc point. I'm not saying that your wrong. I'm saying that it might be getting way too complicated for what I'm looking for doing with the car. I'm not going racing, towing, etc. I just want a decent running fun to drive street car.
Seriously Dan, you don't even have a car... let alone an engine!
Dan the man
Well-Known Member
I know that. I'm trying to get a idea of what I may want to do with it. And who knows, I might leave it as is. I've seen way too many people jump into a project without having a game plan and that results in either disappointments or money wasted. I have to get what I can from every dollar that I spend. I don't want to buy something twice
The further you move away from stock mainly duration and lsa wise the more of an issue it becomes picking the right cam and designing the overall drivetrain combo, especially if you stay with stock gears stall cr etc.. , but depending on the person cause a lot of it comes personal preferences and compromises, you can generally can go up 10-15 degrees over a stock non performance cam and tighten the lsa a few degrees before more stall becomes a must and deeper gears are needed. Some might like less and some may even find bigger acceptable.
Dale Davies
Well-Known Member
Bewy is talking straight. For your mild build take the indication from the 128 formula. You are not considering a radical cam, and I expect you are looking for about 10:1 compression. One or two degrees on IVC is not going to make a huge difference.
Like I previously stated, if you do find a detonation problem you can not tune out except by backing off timing a bunch, just get a water injection system. The octane of water is essentially infinite. In the conversion from its liquid state to steam or vapour state, water expands 1,600 × and absorbs a huge quantity of heat to accomplish that.
Don't fret, despite how some make it out this is not rocket science. Building a race engine for say Prostock, NASCAR or F1 is a different issue not to be worried about here. For any of those engines the cost of entry is 100k and up. For F1, just one piston is $5k and up. Just a bit of perspective.
Dan the man
Well-Known Member
I thought about this Howard cam, .479 / .494 x 255* / 261* duration at 0.050 is 204*/ 214* 112* LSA 108* IVC. They have one that's a little hotter than this one is. If I need a different converter and gears that's fine. Maybe I've figured this out wrong but for good throttle response and low to midrange torque i don't need a cam that's going to pull much over 4800 rpm's on the street
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