What cam?

[mbaze]

Hey folks. I took my recently purchased '71 to a second mechanic this week to figure why the motor was still idling so rough and not performing well, even after Mechanic #1 replaced the ignition, distributor and carb, and tuned it to the best of his ability.

Turns out that I have a really tall cam in there (which Mechanic #1 missed!) that is not matched well with the rest of my components, including the 32/36 carb and aftermarket header. Without pulling the cam and measuring it, we can't tell its exact specs. But it's been ground significantly from original.

Mechanic #2 (well-respected as a top Bay Area BMW specialist) is recommending a stock cam and tii exhaust. I'm curious to know your experiences with various cams. My goal is a spirited daily driver. Not a hot-rod. But the point of owning a 2002 is to have fun, right? Having driven only one stock 2002 that was in mediocre condition, I don't really know what a mostly stock 2002 feels like. Mechanic #2 in convinced that the stock cam and tii exhaust will produce a very pleasant ride.

Thoughts from the daily drivers and tinkerers on this board? Is there much value in going with a slightly taller-than-stock cam? I know there are many choices out there.

(Please don't ask what he wants to charge to replace the cam and exhaust manifold. I weep just thinking about it.)

[wagnerf15]

There are at least 33 gazillion posts about this subject in the forum. Rather than waiting for our responses...do a thorough search and leisurely read what some fairly wise folks have to say about the subject. I did and couldn't believe the amount of info already out there....I decided on a 292 cam with my Weber 38. I'll let you know how it turns out....good luck

Cheers

[rogerspeed]

It is possible the cam is the problem, however, has a compression check been done and what are the numbers? Has anyone checked to see if the carb is leaking? (sucking air through the throttle shaft) that will produce symtoms you describe; or other carb problem. When I rebuilt my motor in the 69, 10:1 bathtub pistons & 284 cam it ran great and idled well, but the 32/36 carb (jetted per CD's recommendation) started leaking at the throttle shaft, got a brand new one, switched jets, problem solved. No need to replace the header, why was the dist replaced? unless the shaft is wobbly and/or if the vacum advance doesn't work (if fitted). Are they timing to the stainless ball in the flywheel? It would seem to me, unless the cam is completely radical, they should be able to get the motor to run right, (provided compression is right and timing correct) although the idle might be lumpy, I don't think its time to spend money on a new cam just yet. PS = valve clearence?

[scestes]

What cam do you have?

[mbaze]

Broke the cardinal rule of not searching the forums first.

It is a bit odd, at first blush, that Mechanic 2 is pinning the blame on the cam. However, the car had a major service and the new carb installed and tuned. (Don't know why I said it got a new distributor; I meant coil). Compression is relatively low across the board at 147. There was a single white smoke incident at start-up, but none since. And a pressure test on the cooling system produced no moisture in the chambers. So discovering the tall cam, Mechanic 2 is arguing that the car can't really be tuned right with a cam, carb and header that don't match.

[TobyB]

Don't go stock with the cam-

there are a lot of options that make better power with

a decent idle.

I ran a Delta 311 grind for a few years, and it was quite nice-

it takes lash caps, though.

Do tell us what cam's in there right now- I call dibs if you pull it!

heh

t

[rogerspeed]

Broke the cardinal rule of not searching the forums first.

It is a bit odd, at first blush, that Mechanic 2 is pinning the blame on the cam. However, the car had a major service and the new carb installed and tuned. (Don't know why I said it got a new distributor; I meant coil). Compression is relatively low across the board at 147. There was a single white smoke incident at start-up, but none since. And a pressure test on the cooling system produced no moisture in the chambers. So discovering the tall cam, Mechanic 2 is arguing that the car can't really be tuned right with a cam, carb and header that don't match.

I think the header is irrellevant, it should only improve the efficiency of the engine, any exhaust system leak however will make tuning difficult and adversely effect performance. It is somewhat unusual that all cylinder have the exact same compression. 147 psi would be indicate acceptable (fair to good) compression with stock pistons. With a 32/36 with proper jets and properly adjusted linkage is a progressive carb, the second throat doesn't start to open until the pedal is depressed beyond half-way down and usually doesn't come into play until 3000rpm, tuning is usually done below 3000rpm, depending on distributor and preference maxium advance is set between 1400 and 2400 rpm. Before getting into the cam, I'd go back to basics, valve adjust "cold", point gap, timing "hot" along with mixture and idle screws and carb jets,

[Guest Anonymous]

Unless the cam is huge there should be a way to make this work. A bigger cam will result in lower compression test numbers. 147 is ok. Can you see and id on the nose? Does the base circle look like it is smaller than stock? What is the timing set at? What jets are in the carb? What are the exact problems? In any case, I don't think changing the exhaust manifold is a cure.

[mbaze]

Thanks for all the feedback. Frankly, I'm more confused than ever. I mean, when the dean of Bay Area Bimmer mechanics says one thing, and you guys say another....

Truth to be told, though, he looked at all the past service records, saw the cam and stopped there. He hasn't laid hands on any other part of the car.

Lots to think about and check into.

[scestes]

One more time.... What cam do you have presently?

[bmdubracing]

One more time.... What cam do you have presently?

He does not know what cam he has in the car. I don't think the cam can cause that much of a bad idle with compression numbers like those. I would check jets if its a used carb, the po might have put larger idle jets in, I can see why but that could do it. Also if timing is retarded.

I ended up going with a mild 292 and solex 40 phh side drafts with a large self ported head and manifolds, up to 45% more cfm and idle is not a problem.

Good luck. If you have paper work for the cam being put in contact that company or person and ask for the duration or the LSA or just ask for a cam card most cams come with them.

[mbaze]

No record of the cam installation. And I don't know anything about the cam's specs/duration. But you can look at it and see that the lobes have been ground, as have the base of the lobes.

Thanks again, all.

[bmdubracing]

Does the cam have an IRE on it anywhere? If its a reground stock it may just be a 292 or 284.