I'm just getting the details together for my winter-spring projects.I'm going to be doing a cam swap.I have found the cam I want,but it has a lobe separation of 106 deg.,now I know this will give a very choppy idle and low vacume,but I don't mind rough idle,car has no power brakes,so vacume is not a concern.What I am afraid of is that it will be TOO rough.I can have a custom ground one ordered for an extra $35 or so.Should I order one with same specs.,but with a 108-109 deg. lobe separation?Anybody run this tight of lobe sep?How rough is it?Do you foul out plugs at idle?Any input would be appreciated.This will be going into a 327,2.02-1.60 heads,edelbrock 600 carb and dual plane intake,MSD ignition,headers,2000 stall speed convertor.Also the cam in question has 218 deg. duration,.450 lift.THANKS IN ADVANCE!

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67 RS RAGTOP # matching, 4X4 CHEVY TRUCK

What kind of cam is this? 106 deg for a cam with that small of duration and lift seems a bit weird. I'm going to guess that the discription of this cam states that it has a strong mid range with good top end performance? I am going to speculate that given the small duration, the tight l/s is to try to make some top end without killing too much bottom and mid range. I don't think that you are giong to have all that choppy of an idle with it, but I could be wrong. These specs kind of sound like what Crane would do. Am I close? I think the rest of the combo looks good. Where are you giong to gear the car at? In my opinion, this sounds like a 3.42ish setup.

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Either you are a spy,or you know your stuff,Because this is a crane cam.Yes,it is supposed to make excellent low and mid-range torque and H.P.,which I think would work out well with a little 327.And is'nt supposed to lose any top end power.But it is said to have a "rough" idle.Also I have 3.42 gears in the car now,I was thinking of going to 3.73 or 3.90's after the cam swap,But the tech guys at crane said this cam will make a noticeable difference in my bottom end power,so I might be happy with the 3.42's.Like I said,I don't mind a rouge idle,but I don't want one that won't idle below 1200 RPM,and is a bear to drive.Thanks for the reply!

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67 RS RAGTOP # matching, 4X4 CHEVY TRUCK

I have to agree with 68RS on most everything but the idle. With that amount of valve overlap, it should have a rough idle and the idle will need to be set upwards of 900 - 1000 rpm. If your going to have an automatic, then vacuum will need to be a concern as the modulator valve requires vacuum. You should be able to overcome this aspect with a vacuum canister. Also your distributor, is it vacuum advance? My opinion, spend the extra $35 and have a custom cam ground. The grinder will want to know everything about the car and how you want to drive it.

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67 Camaro LS6 454/TH400/12bolt 3.73

Thanks cardude,I was going to have the car dyno'ed when finished,and have them re-curve the dist. if needed on thier dist. machine.I had this done already,but figured it would need to be tweaked in again after the swap.Yes it has vacume advance,it's a MSD distributer.I never thought that the cam would affect the trans. that much,I realize the vacume would be low at idle,but will it change much at full and part throttle,but I supposed this could be dealt with.I think a 1000 RPM minimum idle would be fine for me,but I would'nt want to go to much higher.Thanks for your reply also,these are the details I want to iron out now,not after the cam. is in!I have found the majority of tech guys know thier prouduct well, but can only guess on the more specific questions.

Well I finally ordered my cam today.Man,my head was spinning from all the info I read out here,articals,and tech lines that I called.Everyone has a different opinion on what to run.At one point I called a tech line and talked to three different tech guys,and got three totally different cam choices,from the same company!Thanks for the replies,I also posted my questions on chevelles.com and got some input.I put all the info together that I recieved and picked the cam I thought would work best all around IMO.I went with a Erson-HIGH FLOW E-110321.Specs. are Dur. @ .050=220 lift.472 lobe separation 108 deg.I chickened out on the 106 lobe sep. on the Crane I was considering.I think this cam (Erson)will still give a nice lope,but not be off the deep end.I think the bottom end power should be close to the Crane,but it should make power a few hundred RPM higher.I was also thinking of going with a 3.73-3.90 rear gear in the future,and this cam would work better with the gear change.

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67 RS RAGTOP # matching, 4X4 CHEVY TRUCK

Thanks for the E-mail John.Let me know how this cam turns out.It sounds like you must have a pretty healthy engine to put that in!One question though,does MM&S do this on line,over phone?How can I contact them.The above mentioned Erson cam was sent back to Summitt(see my post under "bench racing").It was ground wrong so I actually don't have a cam yet.Usually when I get burned I don't give second chances,so I would consider a different cam manufacturer.Thanks again

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67 RS RAGTOP # matching, 4X4 CHEVY TRUCK

Just remember if you are going to drive this on the street that the less the separation the smaller the rpm range.And where did you get this cam a circle track place.

67drake,

I just used MM&S for spec'ing a new cam. The program they use for determining the cam profiles has quite a bit of input from David Vizard (pronounced Vy-zard). It's $30 for the cam recommendation and free if you buy the cam from them. They do have competetive pricing. Denny is the man to talk to.

Carl

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Click here to see see my car and hear 5-speeds. http://www.geocities.com/casanoc

Sounds like just the place for an Isky 270 Mega cam. Whats everybody's opinion on it??. (270/221, 108/ wherever you want to put it). pdq67

I know this topic started awhile ago but I thought this info might be helpful to someone looking through past posts on lsa. The oct 94 Hot Rod tests a cam very similar to the one mentioned in the opening. It had 219 @ .050, .461 lift, and 106 deg lsa. They tested this cam back to back with another cam with same specs but 110 lsa. The 106 cam made less power under 2800 rpm but more from there on up. Peak power was up by 14hp, and there was a 25 hp gap at 5400 rpm, the highest rpm tested. They described the idle as noticeably choppier, but both cams produced 16 inches of vacuum at 950 rpm. It should be noted that the engine in this test was a 383, but I think it demonstrates that just having 106 lsa doesnt make a cam unstreetable.

Car Craft's Jan. 2001 issue on page 35 has two grafts titled "Lobe separation dependence on rod to stroke ratio" and "Lobe separation dependence on engine stroke".

And I need to ask what all this means?? I know that stroke plays a role in trapping more air in an engine for a given intake closing point. And I know that you can shift this point around using LDA(LCA) and ICA. But haven't put it all together, though.

I do have at least two old articles that graphically illustrate the tighter lobe centers do make more power down low. One of them was done by the Ed Isky's son. And I'm talking 30/40 lb-ft t increase at mid rpm here. Seems like the cams were 100, 110, and 120 degrees LCA's. The article went on to say that the 100 degree cam wasn't for sale nor even recommended to use, but rather ground for the test to illustrate the point.

THe other test if I remember right used three cams that had identical lobe intensities and LDA's and ICA's but ground on 108 and 112 centers. Something like a 194/5 cam, a 204 cam and a 212/214/216(?) cam were tested. It was real neat looking at what was going on.

Post back if anybody wants me to dig the mags out. pdq67

This may be an older article, but a good enough one that I saved it from the 1994 Hot Rod annual. It was written by a Dave Emanuel. This is my short version . . .

They tested six cams in a generic 9.5:1 comp 350 street combo with stocker type heads 1.94/1.5" valves and the following cams -

Test A = dur 205I/214E @.050, lift 430I/450E
Test B = dur 218I/228E @.050, lift 460I/480E

They switched to 2.02/1.6 valve heads with smaller chambers to increase the compression to 11:1 to better match the cam for test C.

Test C = dur 222I/222E @.050, lift 470I/470E

The bottom line -
Test A: Lobe sep at 108 produced more torque (about 10-15 FT/lbs) throughout the range plus 2 more horses at 5,000 RPM. The test engine did not run to the point where the torque curves crossed.
Test B: Lobe sep at 108 produced much more torque (like 25 - 35 ft/lbs) and five more HP until the torque curves crossed and the 112 degree cam took over at 5750 RPM.
Test C: The first cam was ground at 110 degrees and behaved like the tighter cams above except the torque curves crossed lower down around 5250 RPM. The second was ground for 114 degrees of lobe sep.

They also checked manifold vacuum and in all cases vac did not drop more than 1" with the tighter lobe sep. Now the interesting thing I noted in this article was that tighter lobe seperation did more for usable power than increasing duration with less impact on idle quality.

If you can make that 106 deg combo idle, let me know how it runs, it sounds like your on the right track.

Eric,

I'm looking at it. It's in the Feb. 1993 issue of Hot Rod on page 56.

I will try to dig out that other article that was done by Isky and the mag. It has about the same conclusion in terms of torque production using closer centers, too. pdq67