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  #16 (permalink)  
Old 08-05-2010, 11:39 AM
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Quote:
Originally Posted by F-BIRD'88
The car did not perform cause the cam is too big.

I ran same exact combo with a crane/blueracer 214-224-.442-.465-112 13.00 flat @105.

Thats 375 gross dyno HP 300 to the wheels.

Bigger cams require higher 10:1+ cr 4.10's-4.56 and 3500-3800 stall to realise the top end gain.

got the T-shirt on this one.
The carb is too small and will hold the combo back. get a 750cfm carb if you want power.

The most common error people make is selecting the wrong (too big) cam for the combo and intended overall purpose.
The second is using too small a carb.
You seem hell bent to make both classic/common mistakes.
My Street Avenger 670 should be plenty of carb for what I want to do. A 750 would be overkill. Only place I could see a 750 benefiting me any is in the super high RPM's, and I don't plan to rev the motor any more than 5800-6000 RPM. When I get it together and jet the carb properly, I'll use my digital wideband to determine if I need more carb.

Again that Isky cam puts me too close to my highway RPM's, I also don't like the 108 LSA. I'd prefer a wider LSA in an attempt at a wider powerband.

I've already had a smaller cam in it. My cam specs were .420./.441 lift, 204/214 duration @.50, and a 107 LSA. It did it's purpose, and the car was quick for what it was, but not fast. Barely more cam than stock.

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  #17 (permalink)  
Old 08-05-2010, 11:50 AM
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You are lost in all factors in all respects. A wide band will not tell you what size carb is best.

Some people have to learn the hard way.
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Old 08-05-2010, 11:51 AM
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And PLEASE- do not concern yourself w/how the damn thing "sounds"!! That has not one thing to do w/anything- a cam sounds choppy because of its inefficiency at idle. It is a BAD thing, to be tolerated because it has to be, to get the performance needed at elevated RPM.

If you build it correctly for the use you have, it will sound one way- right.
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Old 08-05-2010, 12:08 PM
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Quote:
Originally Posted by F-BIRD'88
You are lost in all factors in all respects. A wide band will not tell you what size carb is best.

Some people have to learn the hard way.
A wide band tells me everything I need to know, and that's my A/F ratio in the higher RPM's. A slightly small carb has absolutely no negative effect on the engine until you're out flowing that carb. If I run lean at 6,000 RPM with the carburetor properly tuned, then I need a larger carburetor. Until that happens, I'm confident my 670 will do the job quite well for under 400hp.

I may be young, but I'm not stupid, and this isn't my first time turning a wrench.

Overdriv: I completely agree I made the wrong initial cam decision. Every cam I listed is recommended for the street, with a stock converter and gears. My converter isn't stock (stock is 1800 RPM stall, mine is a 2300-2500 stall), and my 3.42's coupled with the small tires would be similar to most street rods running 3.73's or 4.10's.

I don't want a super mild setup. I already had that. The reason I have the entire car apart and spending thousands of dollars is to make the car more aggressive, not to put a cam with almost exactly the same specs back in it.

Cobalt: The sound is important to me since this is my daily driver. I don't want a low choppy idle, I want a healthy, racy sounding idle with good off idle response. I also don't want a stock sounding idle which is what I had before.

Now that's not saying that's at the top of the list, but normally the "right way" sounds good!
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Old 08-05-2010, 12:25 PM
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It appears you are not considering the .7 ratio of the 700R4 and the lockup converter. Stall speed means nothing when you are in lockup. If you want all that to be usable you might want to think about some changes.

Quote:
Originally Posted by Jr. Mechanic
A wide band tells me everything I need to know, and that's my A/F ratio in the higher RPM's. A slightly small carb has absolutely no negative effect on the engine until you're out flowing that carb. If I run lean at 6,000 RPM with the carburetor properly tuned, then I need a larger carburetor. Until that happens, I'm confident my 670 will do the job quite well for under 400hp.

I may be young, but I'm not stupid, and this isn't my first time turning a wrench.

Overdriv: I completely agree I made the wrong initial cam decision. Every cam I listed is recommended for the street, with a stock converter and gears. My converter isn't stock (stock is 1800 RPM stall, mine is a 2300-2500 stall), and my 3.42's coupled with the small tires would be similar to most street rods running 3.73's or 4.10's.

I don't want a super mild setup. I already had that. The reason I have the entire car apart and spending thousands of dollars is to make the car more aggressive, not to put a cam with almost exactly the same specs back in it.

Cobalt: The sound is important to me since this is my daily driver. I don't want a low choppy idle, I want a healthy, racy sounding idle with good off idle response. I also don't want a stock sounding idle which is what I had before.

Now that's not saying that's at the top of the list, but normally the "right way" sounds good!

Last edited by Overdriv; 08-05-2010 at 12:32 PM.
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  #21 (permalink)  
Old 08-05-2010, 12:30 PM
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Quote:
Originally Posted by Overdriv
It appears you are not considering the .7 ratio of the 700R4 and the lockup converter. Stall speed means nothing when you are lockup. If you want all that to be usable you might want to think about some changes.
Could you elaborate please? I don't plan on running the TC locked at WOT, the only time the TC will be locked is on the interstate at 65-75 MPH.
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Old 08-05-2010, 12:53 PM
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an AF gauge will tell you NOTHING about properly sizing a carb. Quick rule of thumb is to take hpX2. in other words your typical 350hp chevy will work with a 700cfm carb. The smaller the carb the easier it will be tune at low RPM though.

And you're thinking of your gearing all wrong. you're 3,42's are more like 2.73's when comparing it to the normal hot rod crowd is is running a th350 or something similar.

If you want a hot cam then get hot cam gears and a hot cam converter. 4.10's minimum and a 3,000 stall, as already stated several times.
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  #23 (permalink)  
Old 08-05-2010, 12:56 PM
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Understood. The converter lockup means about 200 RPM off the engine. That combined with the .7 ratio of the 700R4 in OD will determine your cruise RPM. Reread my other comments.

Being young doesn't make you stupid, it might mean you lack a bit of experience. But understand when you ask questions and share specs for others to consider, you will get their opinions and suggestions.

Quote:
Originally Posted by Jr. Mechanic
Could you elaborate please? I don't plan on running the TC locked at WOT, the only time the TC will be locked is on the interstate at 65-75 MPH.
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Old 08-05-2010, 01:04 PM
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You are so wrong on so many fronts.
Your 350 vortec engine will only consume about 550-575 cfm of air at max output.
But the 750cfm carb will allow that engine to draw the 550cfm it wants and needs, with less work.

The air fuel ratio does not taper off when a smaller carb get size limited.
It just restricts top end airflow makeing the motor work harder to pull in the air.
Resulting in less net power to drive the wheels.

The 750 carb is the best overall carb for this combo. It will be 10hp+++
and more torque better than the 650-670carb at 4500 and up. With no loss on the low end.

Your preconceived notions on cams and how they work and effect the power curve and driving impression in general and specificly with this car/engine combo is false.
You are so way off when it comes to understanding carbs.

Yes you are young and lack in experience.

As I said you are just looking for validation of your shots in the dark choices.

If you were to call a cam company tech help line and do that, they will agree with you and hang up.

Why don"t you call one or a few of these cam companies and keep your trap shut as to what you think is the right cam. DO not tell them what specs you want etc etc Just tell them exactly what you got and shut up and listen.
Then, take their advice or don't.......
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  #25 (permalink)  
Old 08-05-2010, 01:18 PM
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I don't want a low choppy idle, I want a healthy, racy sounding idle with good off idle response. I also don't want a stock sounding idle which is what I had before.

The Isky cam is the one that will do this , best, in your car with your combo.
It will do it better than all the other cams you have considered.
Its got the idle and the quick torky power you want in a street machine without getting carried away.

If you want a cam that cruises a little more efficiently on the hiway in OD
Then you got to give up something. A cam cannot be a "racey idle cam" and a "Hiway cruiser" cam at the same time.
The Crane HMV272-2 is the cam for this. You will hear the idle. It is a good bit bigger and more power full than the cam you are replaciing.
Really good with a 1.6 intake rocker for increased intake lift.
272-284-216-228 112 .484" in .480" ex with a 1.6 1.5 rocker set.
You'll like this one for cruising/overall power and the Isky 270 magnum for the idle. and explosive mid range power.
Both cams pull to 5800-6000. Both are best with a 750cfm carb.
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  #26 (permalink)  
Old 08-05-2010, 02:22 PM
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I'd go for the 270 Isky cam F-Bird suggested. I think you'll be happy with it. Popcorn machine idle, great midrange performance, and you'll be pretty close to the 400 marker.

I'd also possibly consider this Howards Max Torque camshaft.

220/220 @ .050, 284/284, .470/.470, 108 lsa. 1,700-5,700.
http://www.summitracing.com/parts/HRS-110991/
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  #27 (permalink)  
Old 08-05-2010, 03:07 PM
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Quote:
Originally Posted by Jr. Mechanic
I've already matched the heads to this cam, I'm around .520-.530 max lift on them.

For the record, this is my nice daily driver, not a project car, weekend toy, or track car. However, my goal is to have a well streetable car that I can run at the track a few weekends a year, then jump on the interstate and drive home. I feel dumb, but up until now OD is the only thing I didn't take into account when choosing the cam. I knew I was a little low on the stall speed as well as the CR, but I figured I would make it work.

Fuel mileage isn't my biggest concern. With my old cam and heads I could pull 22mpg at 75mph, but anything between 15 and 20mpg in OD with lockup engaged, I'll be happy with.

Rear gears aren't going to get changed unless I break something. I love my 3.42's, the car was always hot off the line and cruises really well with a 26" tall tire, even back when it had the 305.

The torque converter is a B&M Tork Master with a 2300-2500RPM stall. It's what B&M recommends for a medium weight car with 350-450tq. Remember this isn't an all out drag car, I don't need to get every ounce of performance out of the cam.

The cam doesn't have to be a Crane, I would actually prefer to go with Lunati or Comp this time around unless someone can recommend the perfect cam. I would much rather squeeze the setup for all I can as I would rather be closer to the 400hp mark than 375.

Also keep in mind, I don't need to use lock up or overdrive around town, so the lowest RPM's I'll see are maybe 2000 at 55MPH. If I'm cruising any slower than that I can disengage lock up or take it out of OD.

Here's what I'm considering:

Comp Cams Magnum 270H: .470 lift, 270 advertised duration, 1800-5800 operating range

Comp Cams XE268H: .477/.480 lift, 268/280 advertised duration, 1600-5800 operating range

Comp Cams XE274H: .490 lift, 274/286 advertised duration, 1800-6000 operating range

Lunati 60102: .468/.489 lift, 262/268 duration, 1400-5800 operating range

All have a 110 LSA, except for the Lunati which has a 112 LSA. All of them are largest cam for stock converter/gears or require slightly higher stall than stock according to Comp and Lunati. I'm actually leaning towards the Lunati or the XE268.

Any opinions?
If I were you, I'd move to Texas. There isn't anything in your choice of components that's going to end up with a year around daily driver in Ohio that won't be downright miserable, if not impossible, for at least half the year. Or at least put a stick gear box in the thing so when it chokes up on icy air and unburnable fuel you can kick the clutch in to free up the crank then tinker with the throttle position to clean it out and get it running again for a few minutes.

Your selection of parts will make a great summer runner. You've among other things, hit the great hot rodder's/racer's conundrum that "what's good for the track, isn't good on the street", at least if you don't live in a place with a warm year around climate.

Your choices for parts would be great if you lived in LA, DFW, Houston, St Pete but for Cleveland, Chicago, Indy, etc. this just won't make a year around hot rod commuter car that's much fun, if not dangerous.

Bogie
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  #28 (permalink)  
Old 08-05-2010, 03:28 PM
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Quote:
Originally Posted by oldbogie
If I were you, I'd move to Texas. There isn't anything in your choice of components that's going to end up with a year around daily driver in Ohio that won't be downright miserable, if not impossible, for at least half the year. Or at least put a stick gear box in the thing so when it chokes up on icy air and unburnable fuel you can kick the clutch in to free up the crank then tinker with the throttle position to clean it out and get it running again for a few minutes.

Your selection of parts will make a great summer runner. You've among other things, hit the great hot rodder's/racer's conundrum that "what's good for the track, isn't good on the street", at least if you don't live in a place with a warm year around climate.

Your choices for parts would be great if you lived in LA, DFW, Houston, St Pete but for Cleveland, Chicago, Indy, etc. this just won't make a year around hot rod commuter car that's much fun, if not dangerous.

Bogie
No sir, not worried about that. She gets driven up until early November when the lowest temperatures are in the 30's-40's. It's a warm weather DD, not to mention she's never seen snow. Although I did drive it right up until the first snow this last winter and she always fired right up with the choke set. I have a Jeep that gets driven in the winter and in bad weather.
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  #29 (permalink)  
Old 08-05-2010, 03:47 PM
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When I was your age I turned my daily driver GTO into what you're looking for. By the next fall I had purchased a cheap beater car to drive back and forth to work. I did end up driving it year round but it wasn't near as much fun as I let on.

If you can't give up having to have the choppy idle and want to be able to cruise in OD then you better plan on sticking more gear in it. I'd put something on the order of a 4.56 in it, that gives you a FDR of 3.19 to 1 with the 700R4. Cruise RPM @ 55 with a tire having a true loaded rolling diameter of 25" will be about 2360. Here's a link to calculate tire loaded diameters....

Gear Ratio and Tire Dia. Calculators

You've been given some great advice from guys that have "been there done that" and have already made the same mistakes. None of us think you're dumb but you sure are stubborn.
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Old 08-05-2010, 06:19 PM
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Well I guess I will throw my 2 cents in here. First of all you don't want to over cam your engine. Yes we all love that lopey sound at idle but it does you no good if you plain on driving this thing every day. I went with to big of a cam in a couple several builds in the past and I had to learn the hard way and lose out on lots of money.

I am running a 350 sbc, crane 284/292 222/230 @50 with 509/527 lift, 9 to 1 compression, edelbrock rpm dual plane intake, world 2 sportsman heads, turbo 350 transmission with a 2200 rpm stall with 3.42 rear end gears.

I had this motor built last summer to put into my 96 chevy s10 and this is my truck I drive everyday back and forth to work and I had done everything to tune this thing and have various things over the last couple of months to get this thing to run efficient and have come to the conclusion that my cam is a little too big for everyday driving in my opinion for my setup.

Yes I like the lopey idle and I have plenty of vacuum with 15 inches but keeping the plugs clean and keeping the carburetor working really good and trying to get excellent street manners with stop and go traffic stops everyday has taken its toll on me. You can't have your cake and eat it too as the old expression goes. I would go with a smaller cam as to what was suggested by the guys who posted here.

In a couple of weeks I am going to a 260/270 212/218 @ 50 510/510 lift roller cam to replace the bigger crane cam in my motor. Yes I will lose some power on the very top end but I will have way much better torque and response on the bottom end and midrange where my rpms are the most. I cruise at 2200 rpm at 55 and my motor is decent wise but its still at the bottom end of the power band and it is kind of soggy with my current stall.

With this being your everyday ride you want something that will cruise around all day long and be withing a good rpm range for what you got. I did a bigger to smaller cam swap in my more decked out ride that I only drive on the occasion too cause of too many headaches and having over camed my engine.

You can do what you want but if you want to be honest with your self like I had to do then you will have to try to make the best decision on what will be best for your vehicle overall and what will make it run the best with what you have. I love the big racy cams but I won't ever go that radical of a route in any future builds ever again.

That type of setup requires a lot more maintenance over the long haul and is more and more in my experience not worth it just for the ultimate power and sound. I just want to have something nice and still be able to drive it around Good luck on your build I am sure you will make a good choice hopefully.

Eric
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