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jamesnutter50

So confused !!!!

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As you might already know I was thinking of putting twin Weber 40dcoe on my 2002 and at the same time put a 292 cam on. the problem that I have is I keep getting so much conflicting advice some people say its the best thing since sliced bread and the others are telling me it will make the car "lumpy" and a bit of a pig at low rpm's. the people at piper cams say that a 292 cam is only really suitable if you always thrash the car otherwise its not really any good on the street. And they tell me the 268 cam would be better.

The question I really want to know is it a load of crap that they are telling me?

and the 292 is the one for the job?

Also do you loose a lot of torque?

My head is spinning with all the differing opinions.

HELP ME PLEASE !!!

JAMES

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I'm no expert mechanic, but if you plan on putting dual 40's then I think you'd be well-advised to go with a a 292 cam. The lumpiness people refer to is at idle, but when you're accelerating you'll be smiling. You won't lose any torque, but you'll gain high-end power, so it may seem like that. Also, the intake manifolds you elect to put on will impact the power curve. Shorter ones should give you more low-end grunt, while longer ones will give you more top-end. And no matter what the 40's will suck the gas like it's happy hour...I used to average 12mpg with mine! (But worth it)

Benzo '71 verona

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Guest Anonymous

Well the reason that you are confused is that on the internet you will find somone who "thinks" they know everything. The 292, in my view, is the best cam for the street as you still retain your torque so you can pull away from a light. Also you have to be conserned with where in the rev band you will make your power. the larger the cam the higher the rev band that is typicaly. the 292 keeps the power band where you can use it best (mid to high). there is just a HAIR of lump in the idle of the car and it will have to idle around 150rpm higher (typicaly) then with the stock cam. Any smaller cam like a 284 in my view is a waste of money. Going higher if your not racing and your going to need to pull away from a stop is a waste. there are people who love 300s on the street, I am not one of them.

the 40 carb can delever a lot of fuel, the key is it has to be jetted right so you dont put too much gas down the cylinders. I have 1 customer who is running one and loves it (street and tracks the car) but I prefer the 38/38. Remember with the bigger carb you will use more fuel, its like the old kid in a candy store if you have it mmmmm good.

Sam Schultz

merlin_m3_racing (a) yahoo.com NOTE the 2 underscores

LaValle's Import Restoration

Oak Ridge, NC

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Hi James.

I ran my 2002 with the Schrick 292 cam and dual 40 DCOEs for 5-6 years. With the 292 it had a slightly lumpy idle (no lumpyness above 1K though) - surely nothing that rocked the car, or made you think it was going to stall out though. Even when I kicked in my Behr AC (which roughened idle more), it was OK. With dual sidedrafts you need to run at least a 292 or hotter cam to take advantage of their abilities. The 292 Schrick cam is considered the best 'hot street' cam with that class of carburation due to it's nice compromise of low end and hi-end characteristics. It does hit it's power peak (much greater than stock) after 4000 rpms though, so if you never go there, it might be a poor choice. Note that Alpina made the only 'OEM' 2002 with dual Webers and they used a 300 deg Motorsport cam in their combo. (I ran this 300 cam before I went to the 292.)

I regularly got 21-24 miles per gallon with a 50-50 mix of street and highway daily driving on 91 octane pump gas. (210-230 miles/fill-up). I don't drive with a completely lead foot, but I get on the gas and rpms a good amount (it's too fun not to on the mountain roads I use everyday to/from work). FYI, I have the 5-speed OD in my car with a 3.91 diff - as they factor into mileage as well. I'm also running with 9.5:1 Mahle 'piano top' pistons and 4:2:1 headers into a custom BB TriFlo exhaust system.

Two of the biggest issues to take into account with this set-up are carb tuning and ignition. Most folks that diss on dual-Webers likely never had them set-up right - running way too large main venturis and the wrong mix of jets and such. These are performance carbs, that have infinite adjustability/scalability to work from small 4 cylinders to big block V8s, but V8 settings on a 4 cylinder will be all screwed up. I can vouch for the fact that they suck if the owner/mechanic doesn't know how to tune 'em - but if you set 'em up right they're extremely reliable (and satisfying). As I said, my 02 is a DD, and I wouldn't have to do anything with the carbs for more than a year at a time, running in sub-zero (w/ no choke) through hi-90 deg weather. On the ignition, I use a MSD ignition & coil through a Tii mech distributor with PerTronix. Again very reliable, and it makes sure I burn the fuel well at both low and high rpms. Outside of not having the carbs set-up well, not having a solid/superior ignition is the other main issue that can cause disappointments.

I'm not telling you what to buy - I don't know anything about how you drive and the rest of the mods you have or are considering making to your 02 - but it's tiring to hear laments that dual-sidedrafts don't work (or don't work well, or that they're tempermental, or don't get good mileage, yada-yada...). Or that only mild cams are OK for daily drivers or street cars or that hotter cams kill low-end driveability... The stout M10 is one motor that takes very well to these types of performance enhancements without suffering any reliability or significant disadvantage issues. (Maybe talk to Jeff or Jeremy at IE for some specific tips/advice on your planned set-up, they know their stuff.)

BTW, I've recently gone to the 304 Schrick in my motor, while still running the dual 40 DCOEs (but now retuned with larger chokes). I can say it's got an even lumpier idle and is much more top-end oriented than the 292 - but I'm still getting 20 mpg in this DD. (I also did an alum flywheel, clutch and Z3 shifter mod as part of my rebuild). Not to quote commercials or anything, but "I'm lovin' it". ;-)

HTH,

Tom (aka visionaut)

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just one correction from the first post...a longer runner intake will yield more low-end, while shorter will yield more top-end :)

Like I said, I'm certainly no expert. I'm curious though, as to why this would be the case. Can you explain?

Thanks.......Ben

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I noticed that too - didn't bother to point it out. The answer is 'effective intake length' - more is better for bottom end. (The distance between head inlet and very end of enclosed intake at opposite end of carbs). That's why longer stacks and a longer length intake manifold improve lower RPM performance, given the same motor with a short manifold and stubby or no stacks at all.

On my motor, I run the longer Warneford intake manifold, and I also run a pair of 'now-unobtanium' 90-degree Weber airhorn adapters to give me a very long effective air intake length to better balance out my 304 cam.

Pic of my set-up attached (sorry to modem users for image size...)

post-1565-13667570925498_thumb.jpg

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Hi James,

slightly off topic here but was it you who was interested in a lightened balanced flywheel?

Best wishes

Jon

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it was me. I got my stock flywheel loghtened in the end. I have a quick Question for you-

have you put your webber 40's on?

Are you running a 292 cam?

Also in you bits for 02's do you have an E12 cylinder head?

Regards James

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I drive any thing between 2000-6000 rpm. and I also drive round town alot.

With that in mind would you still go for it?

Also will the low down grunt be lost ?

Is it true the cam starts to make a differance from 2500rpm?

Thanks for your help

James

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it is highly advisable to bump you're compression ratio as well. I don't know if you are going that far with your project but I have "heard" that is one of the best things you can do while you have the engine apart. The overlap of a bigger cam effectively reduces your compression ratio. That's why guys running 316's or 328's are probably running at least 11:1 if not 12:1 ratios.

I went with about 10:1 on my rebuild (using dual 45's and a 292 regrind). The best knowledge that i gleaned from the collective here and elsewhere is to look at the engine systemically. everything from fuel/fuel delivery, ignition, internals to exhaust. If you tune the system to what you want anything is possible.

I use my car on the street no problem and also do driving schools. it really truly comes alive above 4000 rpm. At that point it is just singing a sweet harmony!

Mike

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True that on the compression ratio and cam overlap. I think the advice for a 292 is 9-9.5:1 to 10:1 (and not much higher if planning to use plain pump high-octane gas). Also concur on the need to look at it as a 'balanced/integrated system' - that's what I was trying to indicate in my responses.

My recall is the 292 doesn't start to 'kick in' until 3000-3200rpms or so, and more so after 3500-3700. If you rev to 6K, then it's all a rush of enjoyment after 4K ;-) Re: low end 'grunt' - off throttle it's probably not as good as with a milder cam, so you might have to put your foot into it more, or shift at higher revs, staying longer in each gear... You won't want to drive at rpms lower than 2500 in any gear.

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40's with 36 mm chokes don't idle well, and don't really start to pull until you hit 4k rpm.

40's with 28 or 30mm chokes can be quite docile around town. I have a set with 32's and they do alright.

Details are critical with 'em, like a linkage that stays adjusted and opens both carbs equally. As far as I've found, there are no good 'bolt-on' linkages for the 2002. But they're not hard to make. Or you can make the aftermarket ones work well.

A rolling road is well worth the money- find someone who understands that this is a street car, and who tunes Webers. They can help you get jetted for a mild motor that will still have lots of go when you open the throttle.

DCOE's are VERY flexible carbs- which means there are thousands of ways to fudge them up, but only a dozen or 2 that will work with your engine for your purpose.

fwiw,

t

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