JBP

I believe base circle theory to be one of the most confusing things in relation to camshaft regrinding. Here, I'll dispell all rumor concerning regrinds with something that should be made a public somewhere on the internet. Because it seems as though no one understands it at all.

a) How can you gain more lift from removing material?
b) Why does the lift specifications change?
c) How can you gain more without adding/welding material?

I have a heavy mathematical/engineering background, I prefer to explain things this way. The only real way to prove base circle theory and how a trade off from removing material, adds lift, is to prove so with simple math and by pictorial reference. So I fired up autocad and here's the result:

STOCK CAM


Example: Stock camshaft with some nice round numbers to work with and comprehend. The stock camshaft has a lifter travel of 0.400" lift. (The rectangular piece sitting below the base circle on the LHS is the lifter). The LHS shows the lifter position at the cam heel. The RHS shows the lifter postion on the lobe tip (at full lift). The centerline of the base circle to the outer quadrant is indicated as 0.600". 0.600 + 0.400 = 1.000" (one inch) cam heel to lobe tip. Therefore, lifter travel is 0.400". Good so far?

MODIFIED CAM



Enter our modified camshaft: Presto chango, no material added, yet you can see already (pictorially), there's an extra 0.025" of lift. How? I'll explain. From the base circle of 0.600 we removed 0.050 of material. This results in a base circle of 0.550" and thereby giving us a cam heel radius reduction of 0.025" and the opposing quadrant losing the same amount (0.025") 0.025 + 0.025 = 0.050. Continuing, examine the LHS of the modified camshaft. See how the lifter has "up-jumped" the horizon reference of the stock camshaft by... 0.050"? Finally, the camshaft has rotated 180° and the lobe is now at the face of the lifter (full lift) and the lifter travel is now 0.425". (0.025" more than the original camshaft) No magic, no welding. Just plain simple physics.

JBP

Valve springs are priced on the website. We'll extend it at least until end of January.

BravoPuma6

simple physics my ass dude, any way u can dub that down? your taking metal off the stock cams and somehow the cams duration and lift profiles are better?

shabodah

The idea works, if and only if you compensate for it at with increased installed valve height. How are you doing that with this setup?

PS- For those of you who'd like to see this type of setup in Production use, the 2001 LS6 has a larger base circle and shorter valves than while the 2002 LS6 has a smaller base circle and larger valves, should be on those v8 sites somewhere.

BravoPuma6

ENGLISH dammit

shabodah

You can do what they suggest if you make other alterations at the same time. The cam either would need to sit closer to the valves to make up the .25 difference, or the valve would somehow have to made longer to take up the lash, or the rocker adjusted to, etc. Can be useful, just don't know how they would accomodate for it. If no lash adjustments were made, the profile would not open the valve when it should and would close the valve premature, and lift at the valve would be either the same as it started out or lessened.

BravoPuma6

i see, oh damn. so this is a bit more involving then just getting the GMPP cams.

JBP

First, You're dead wrong. You're complicating things beyond what need be. Also, you don't have a clue about a hydraulic valvetrain operates as lash does not need to be adjusted for take-up with the LSJ hydraulic lifter. The lobe heel is modified and not the entire base circle in a real-world scenario. The LSJ lifter is plenty accomodating for up to 0.090-0.100" base circle modification. First, to take up a 1/4" as you've indicated above is definatley coming from some magic hydraulic valvetrain. That distance of plunging action is impossible by any lifter in existance.

The number of cams that we've sold with regrinding done on them: LD9 (33 pairs), LN2 (48 singles), L61 (21 pairs), LSJ (6 pairs), LE5 (1 pair) 3.1L V6 (21 singles), 3400 V6 (8 singles) and not one return do to lash adjustment shows that hydraulic lifter can accomodate our specificaitons. Reguardless we still offer a 5-year warranty return on any manufacturing defect from our cams.

Secondly, for customers who are still hesitant about regrinding their stock cores. We offer the option of blank billets to keep the stock base circle dimensions and retain the TriFlow specifications as before. There's no need, but some customers are adamant about blanks for some reason.

Colt Cams and JBP have been doing this long enough to know whats right and whats wrong. We work hand in hand to bring cams that have results, proper fitment and testing.

NoRemorse

Exactly! I can see how altering the heel could increase lift as the height differance is all the matters in lift, but that assumes that the lifter CAN travel higher which would mean closing the valve.... farhter.. which is abviously not possible. So such a set up will not see such lift inless the lifters are modified to accomidate.

BravoPuma6

thats exactly what i was understanding, shab's comparison put it all into perspective.

Asphalt Assault

JBP you get all kinds of budding engineers on here who know more......

I am sure there is alot of us here who are just keeping quiet. There is nothing you can say that will change some peoples mind or ability to be educated. There will only be one way to help.... that is some will need their A$$ handed to them when they get smoked by someone with your reground cams. then in conversation they will then realize its produces more HP and they will want even if they dont understand it.

JBP I sorry you received some bashing about your idea here on this site (which as members we are not supposed to do). To me your explanations are understandable, make sense, and I know will work.

You will recieve a call from me to get the cams ground. thanks for being there to support this platform (ECOtec). I am sure you have fun! Later.

JBP

I could kiss you for that comment.

Nope, its not bashing. Its concern about a product with a lack of background and experience. I can understand the concern as reduced base circle is somewhat confusion concept. But believe me when I say Colt and JBP know what we're doing. We've been doing it for a long time, and there's nothing but positive results to back it up: Our LD9 camshafts, boast a 26WHP gain in a N/A config. Thats the biggest gain we've ever got out of a pair of 4 banger cams, and yes they are REGRINDS.

Your business is much appreciated.

shabodah

I missed typed. The number above was supposed to be .025, of course. I'm used to think of thousandth's of inches, and was on the way to bed when I posted. Yes, a hydraulic lifter can make up for that type of lash if it has to, but that doesn't make it a good idea. Considering you could have even more lift with a new blank ground with the smaller base circle, that would be the way to go for most people, and if they are going to be changing valvetrain components at that time anyway, it would make sense to compensate for the .025" I originally talked about. Making a lifter work harder than it needs to is a good way to mess with a valvetrain's high rpm stability.

JBP

0.025 fractional value is in the thousandths of an inch.

I'll let it slide this time!

Can you explain why?

Correct me if I'm reading this incorrectly. Take a billet cam, that comes with more material than stock on the lobe side and base circle side. Take base circle, grind down smaller than stock base circle. Keep lobe side as stock. Isn't that a regrind?

Basically, A lifter actuated by a regrind with 'x' amount lift compared to a billet cam with the same lift will work exactly the same. It only goes up and down in the bore, nothing else.

JMAc88

I don't really know too much about cams, but have been told that for high boost applications they are not necessarily the best idea. Is this true? and if so how much boost would you recommend on this set?

Also, I know cams can give a wicked exhaust note, would you happen to have a sound clip

shabodah

Well, more travel for the lash adjuster means more where on its seal, much like the rings of a piston where do to travel distance and speed.

I've never heard anyone refer to grinding a cam blank as a "re-grind" as the blank has not be ground before, lol. I am not suggesting leaving the lobe side as stock. The biggest issue with regrinding a cam, is unless you weld some more material on there, you can't alter duration as much as you'd like to. A cam blank gives you the ability to do this, and alter lift. In the example I am illustrating, we'll assume that the total radius of the cam is 25 thousandths more than the stock cam grind is at maximum lift. That's more lift there on it's own with the original base circle. No do as you suggest and reduce the base circle by 25 thousandths, and the total lift at the cam has been increased 75 thousandths instead of just 50.

The longer the distance it has to move, the quicker it will wear as stated above. When attempting to increase lift, a higher ratio rocker is almost always the best bet for valvetrain stability. You mentioned you will have a rocker available shortly. That looks like a good compliment to any valvetrain and cam upgrade.

NoRemorse

WTF? How am I wrong for not wanting a product unless I understand it??

As an engineer, I am not just going to buy a part because someone tells me it works, I have to know why and how. THe explainations givven are confusing quite a few people, so I just want a little more info before I make an opinion on if I think these are a worth while upgrade.

This is NOT bashing, this is wanting to be informed. So go crawl back to you hole and stop being an ass. And while your at it, buy one of those cyclose intake inserts becaus thye state more power and efficency!!

BravoPuma6

same hear man. im trying to understand this as well, lurking ftw i guess?

Asphalt Assault

I am not being an ass.... My statements were based on what you said.

I did not see questions, I saw statements. You were telling him how it does not work and it looked to me you were bashing a good idea that does works.... sorry but I understand it and know it does work. and it is simple physics. but you need to know how the components work to understand it. If you actually did ask questions for an understanding then I would have not made any comment. Whether you meant it that way or not that is how it sounded.

As for being an ASS I was actually providing shock value so you would think before you speak. that is all. but lets not get into an argument over it. lets just learn about how this works so you will get a set of ground cams and smoke who ever.

I will let you in on other things I have learned in my exhaust research. If you plan to go without turbo I have found out a good combination.

later fellow cobalt driver.

shabodah

I have no need to defend my statements and am not looking to shock people by them. That was not the first post questioning how things were being done here, so I also feel no need to restate those already asked. Hydraulics are not perfect, magic solutions. A lifter takes time to pump up properly and can have issues not bleeding of correctly. Under severe conditions it will loose its seal and not hold fluid at all, or even stick in position. It's there to help, but asking it to do 5x the job it was intended may go either way, depending on your luck. If it was such a great idea, there would be an OEM using it with no other mods on a stock engine. There isn't one doing so. See my example of the different versions of the LS6 above. I'm not suggesting it doesn't work whatsoever. That is obviously not the case.

JBP

Alright, everyone got what they wanted off their chest. You can only sway ppl so far, but if they are rooted in their beliefs, your attempts are fruitless nonetheless.


Continuing, Any other technical questions? (not related to how regrinds work)

shabodah

How much does the reduced overlap affect idle and fuel economy?

Asphalt Assault

Great question!

Asphalt Assault

I want to make as much HP with Stock S/C. I am planning other internal changes. If I do an engine build (pistons, rods, cam timing sprokets, valve springs, THE CAM REGRIND OF TOPIC HERE), and outside supporting modifications (Exhaust, intake, 60lbs injectors and HP Tuners). will this get me to 400 to 500HP? If not will a different cam regrind help?

Basically I am targeting the 400 to 500HP. I dont believe in spending money twice. will the cam regrind be enough to be useful to reach these power levels?

JBP

Idle quality is fine. Noticeablely different, with a lower pitch combines with a small, yet distinct lope.

Fuel economy is hard to measure as our customers who have them are very hard on their cars. Which makes it near impossible to find a decent number to deal with.