Cam lift
#11
Originally Posted by 82306
If my cam is 268 @50 will you guarantee it will work with .512 lift?
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance.
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance.
#14
Originally Posted by 82306
If my cam is 268 @50 will you guarantee it will work with .512 lift?
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance. Flycutting the stock pistons isn't just for clearing a bigger cam it is also to add radial clearance for the larger valves that come standard on most aftermarket heads these days.
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance. Flycutting the stock pistons isn't just for clearing a bigger cam it is also to add radial clearance for the larger valves that come standard on most aftermarket heads these days.
Couldn't have said it better myself, thank you very much!!!!
Example.
My custom cam, on my GT40's is .552/.544 lift with 1.7 ratio peds. It would have been ~.600 but I didn't want to convert to stud-mount, and .550 is about the safe limit for ped's. Duration is ~222/230 and it should clear.
My current cam (that is coming out) is a TFS #1 also being run with 1.7's, its .530/.544 221/225 (if my memory isn't too foggy) and clears no problem, and the GT40's have larger than stock valves obviously.
Duration has far more to do with P2VC than lift does, as peak lift doesn't occur until the piston is well down the bore. Its the valve events when the valve is chasing the piston, piston chasing the valve that cause issue. Radial clearance is another, often overlooked issue as well, and is a very common one with large-valve heads.
#15
Originally Posted by 82306
If my cam is 268 @50 will you guarantee it will work with .512 lift?
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance. Flycutting the stock pistons isn't just for clearing a bigger cam it is also to add radial clearance for the larger valves that come standard on most aftermarket heads these days.
On the other hand I will bet you I can get a 220 lobe @50 with just over .600" lift to work. It wouldn't be with the stock installed height nor the stock valve spring but realistically if you care about your engine you wouldn't be re-using the stock springs with any cam swap - hell I don't keep them when using the stock cam!
Duration is the more important factor when dealing with piston to valve clearance. Flycutting the stock pistons isn't just for clearing a bigger cam it is also to add radial clearance for the larger valves that come standard on most aftermarket heads these days.
Last edited by Ponyryd; 08-09-2006 at 09:25 PM.
#16
Stock long block can handle .512" lift, more if you have the pistons fly-cut to accept more lift
#17
On that note do you know if he's had any worked done to his heads in the past? For example lets say a new set of springs were installed and someone never set/checked the proper installed height.
What happens if his springs go into coil bind at .500 lift now? Maybe the heads were milled .040â⌠or there has been 10 valve jobs done to them unbeknownst to the current owner? Bottom line is there are no guarantees and you must check your stuff and not hold a few tips from an internet forum as gospel.
Good point here. If you use the clay method always check for radial clearance. You must cover the entire relief and not just merely fill it full of clay. Too many times I have heard of individuals checking the p to v only for depth, finding it's within spec and all therefore should be wellâŚ.
Once the engine is run a valve gets tweaked and the builder cannot figure out how this could have possibly happened with all the âclearanceâ they initially though was there. I guess itâs a good thing witness marks usually confirm where they forgot to check.
What happens if his springs go into coil bind at .500 lift now? Maybe the heads were milled .040â⌠or there has been 10 valve jobs done to them unbeknownst to the current owner? Bottom line is there are no guarantees and you must check your stuff and not hold a few tips from an internet forum as gospel.
Radial clearance is another, often overlooked issue as well, and is a very common one with large-valve heads.
Once the engine is run a valve gets tweaked and the builder cannot figure out how this could have possibly happened with all the âclearanceâ they initially though was there. I guess itâs a good thing witness marks usually confirm where they forgot to check.
Last edited by 82306; 08-10-2006 at 12:14 AM.
#18
I am not afraid of my tech guru status being threatened, yes, I said that a stock long block can handle .512" lift because I know it can, fabs was not asking about duration and did not give cam specs, he merely asked what stock heads can handle...which I answered-adding that a stock long block could handle it, if anyone else was interested.
Now, I could stay here and give out scenerios of what happens if this..what happens if that, but it has nothing to do with the question being asked, question has been answered, I'll move on. I will add that it sounds like you know what you're talking about, but it seems to be over and above said question.
Originally Posted by fabs_4000
Hey there, does anyone know how much lift the stock heads can handle? :2:
#20
I wasnât trying to roast you, as I am sure your help is much appreciated on this forum. I took a somewhat vague answer and tried to paint a clearer picture. Also I was stressing the importance of checking your parts vs. relying on general internet insight to avoid it.
For sure? And youâre going to guarantee this? Ever heard of an 1986 H.O⌠Maybe with your engine, but what exactly does he have here? Again you never know and canât be sure until it is verified. Lets say his heads have been milled to china by a previous owner and the I.H is wrong, when he fires up his engine with a new cam and it hits, whose fixing it?
You HAVE to give out scenarios because thatâs the reality of life. I see 50+ engines a season and let me tell you wouldnât believe whatâs actually out there. Especially when it comes to valvetrain. Truth is you never actually asked him any more details before âconfirmingâ what will work. SPEEDTOSPARE answered it dead nuts on and went on to even ask about his combination. See below
Stock heads can handle more lift if set up correctly. The question is how much do you need and have they been properly ported to utilize it. If the head is unported or the port job is terrible then it wonât matter much anyways.
Too much information is better then not enough. Hell even G.I Joe knew knowing was half the battle!
I said that a stock long block can handle .512" lift because I know it can
Now, I could stay here and give out scenerios of what happens if this..what happens if that, but it has nothing to do with the question being asked, question has been answered, I'll move on.
keep it under .500 lift with a 1.6 rocker and you should be safe. Keep in mind theres no guarantee that they duration is going to be too big. Puddy the heads just to be safe - SPEEDTOSPARE
I will add that it sounds like you know what you're talking about, but it seems to be over and above said question.
Last edited by 82306; 08-10-2006 at 10:52 AM.